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Author name code: pallavicini
ADS astronomy entries on 2022-09-14
author:"Pallavicini, Roberto" 

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Title: A new arrival at the VLT: the commissioning of the X-shooter
    spectrograph .
Authors: Di Marcantonio, P.; Santin, P.; Zacchei, A.; De Caprio, V.;
   Riva, M.; Spanò, P.; Zerbi, F. M.; de Ugarte Postigo, A.; Pallavicini,
   R.; Vernet, J.; Dekker, H.; D'Odorico, S.; X-shooter Team
2010MSAIS..14..230D    Altcode:
  Starting from October 2009 a new ESO/VLT instrument will be offered to
  the astronomical community worldwide: the X-shooter spectrograph. This
  first second-generation VLT instrument is being built as a collaborative
  effort of several European Institutes (with INAF playing a prominent
  role, co-PI R. Pallavicini) and ESO. <P />The main features of X-shooter
  are high efficiency and the unique capability to cover in one "shot"
  a very broad spectral range, from U to K band, making the Instrument
  appealing for cutting-edge science. The present paper reports on the
  commissioning periods just held in Paranal and on the efforts made to
  meet all foreseen stringent requirements.

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Title: TW Hya: A Simultaneous Optical and X-Ray Campaign
Authors: Dupree, Andrea K.; Brickhouse, N. S.; Cranmer, S. R.; Irwin,
   J.; Bessell, M. S.; Crause, L. A.; Lawson, W. A.; Luna, J.; Mallik,
   S. V.; Pallavicini, R.; Schuler, S. C.
2010AAS...21542904D    Altcode: 2010BAAS...42..350D
  A world-wide campaign of spectroscopy and photometry was carried out
  for 17 days in February- March 2007 (JD 2454147 - 2454164) in support
  of an extended CHANDRA HETG observation of the nearby accreting T
  Tauri star: TW Hya (CD -34 7151).This program included photometry from
  Super WASP-South and SAAO. Spectroscopy was obtained from TNG/SARG,
  Vainu Bappu Observatory, SAAO, MSSO, Magellan/MIKE, Pico do Dios,
  and Gemini-S. The photometric period of the star derived from the
  periodogram of WASP-S photometry during this time was 4.76+/-0.01
  d. Hα fluxes do not appear to correlate well with the photometric
  period nor the total X-ray flux, perhaps influenced by flaring that
  occurred in both optical and X-ray sequences during this time. Hα
  profiles from TW Hya can change dramatically during a night, with
  substantial systematic changes in the wind opacity signaled both in Hα
  and the He I 10830 Å transition. Related posters by Schneider et al.,
  and Wolk et al. address the optical veiling and X-ray spectrum of TW
  Hya from this program. <P />Research supported in part by NASA and
  the Smithsonian Astrophysical Observatory.

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Title: Metallicity of low-mass stars in Orion
Authors: D'Orazi, V.; Randich, S.; Flaccomio, E.; Palla, F.; Sacco,
   G. G.; Pallavicini, R.
2009A&A...501..973D    Altcode: 2009arXiv0905.1840D
  Context: Determining the metal content of low-mass members of young
  associations provides a tool that addresses different issues, such as
  triggered star formation or the link between the metal-rich nature
  of planet-host stars and the early phases of planet formation. The
  Orion complex is a well known example of possible triggered star
  formation and is known to host a rich variety of proto-planetary disks
  around its low-mass stars. Available metallicity measurements yield
  discrepant results. <BR />Aims: We analyzed FLAMES/UVES and Giraffe
  spectra of low-mass members of three groups/clusters belonging to the
  Orion association. Our goal is the homogeneous determination of the
  metallicity of the sample stars, which allows us to look for [Fe/H]
  differences between the three regions and for the possible presence
  of metal-rich stars. <BR />Methods: Nine members of the ONC and one
  star each in the λ Ori cluster and OB1b subgroup were analyzed. After
  the veiling determination, we retrieved the metallicity by means of
  equivalent widths and/or spectral synthesis using MOOG. <BR />Results:
  We obtain an average metallicity for the ONC [{Fe/H}] =-0.01± 0.04. No
  metal-rich stars were detected and the dispersion within our sample
  is consistent with measurement uncertainties. The metallicity of
  the λ Ori member is also solar, while the OB1b star has an [Fe/H]
  significantly below the ONC average. If confirmed by additional [Fe/H]
  determinations in the OB1b subgroup, this result would support the
  triggered star formation and the self-enrichment scenario for the Orion
  complex. <P />Based on observations collected at Paranal Observatory,
  ESO (Chile). Programs 072.D-0019, 074.C-0757, 076.D-0136, 076.C-0145.

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Title: X-ray properties of the young open cluster around λ Orionis
Authors: Franciosini, E.; Sacco, G. G.; Pallavicini, R.
2009AIPC.1094..592F    Altcode: 2009csss...15..592F
  We present XMM-Newton observations of the young (~1-8 Myr) cluster
  around the hot (O8 III) star λ Orionis. We have obtained both EPIC
  imaging data of the cluster and a high-resolution RGS spectrum of
  the hot star. We have detected 167 X-ray sources, of which 56 are
  identified with cluster members, and 24 are identified with new
  photometric candidates. We present the results of the EPIC spatial
  and spectral analysis of the cluster sources, and compare them with
  those obtained for the “twin” σ Ori cluster.

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Title: X-Shooter: A Medium-resolution, Wide-Band Spectrograph for
    the VLT
Authors: Kaper, L.; D'Odorico, S.; Hammer, F.; Pallavicini, R.;
   Kjaergaard Rasmussen, P.; Dekker, H.; Francois, P.; Goldoni, P.;
   Guinouard, I.; Groot, P. J.; Hjorth, J.; Horrobin, M.; Navarro, R.;
   Royer, F.; Santin, P.; Vernet, J.; Zerbi, F.
2009ASSP....9..319K    Altcode: 2008arXiv0803.0609K; 2009svlt.conf..319K
  X-shooter is the first second-generation instrument for the ESO Very
  Large Telescope, and will be installed in 2008. It is intended to
  become the most powerful optical &amp; near-infrared medium-resolution
  spectrograph in the world, with a unique spectral coverage from 300 to
  2500 nm in one shot. The X-shooter consortium members are from Denmark,
  France, Italy, The Netherlands and ESO.

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Title: X-SHOOTER: a unique opportunity for the Italian community .
Authors: Spanò, P.; Zerbi, F. M.; Santin, P.; Pallavicini, R.;
   De Caprio, V.; Riva, M.; Tintori, M.; Di Marcantonio, P.; Zacchei,
   A.; Molinari, E.; Riva, A.; Cosentino, R.; Bruno, P.; Dekker, H.;
   D'Odorico, S.
2009MmSAI..80...44S    Altcode:
  X-Shooter is a high-efficiency, wide band (U to K), intermediate
  resolution (4,000-14,000), single-object spectrograph for the Very
  Large Telescope (VLT). To optimize efficiency and increase wavelength
  coverage, light is split by dichroics into three arms: UV-Blue, Visible,
  and Near Infrared. It will be the first second generation instrument of
  the VLT instrument suite. Currently in the last phase of integration,
  X-Shooter will see first light in the last quarter of 2008. This paper
  highlights first results obtained in our facilities.

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Title: FLAMES spectroscopy of low-mass stars in the young clusters
    σ Ori and λ Ori
Authors: Sacco, G. G.; Franciosini, E.; Randich, S.; Pallavicini, R.
2008A&A...488..167S    Altcode: 2008arXiv0805.2914S
  Aims: We performed a detailed membership selection and studied
  the accretion properties of low-mass stars in the two apparently
  very similar young (1-10 Myr) clusters <ASTROBJ>σ Ori</ASTROBJ>
  and <ASTROBJ>λ Ori</ASTROBJ>. <BR />Methods: We observed 98 and 49
  low-mass (0.2-1.0 M<SUB>⊙</SUB>) stars in <ASTROBJ>σ Ori</ASTROBJ>
  and <ASTROBJ>λ Ori</ASTROBJ> respectively, using the multi-object
  optical spectrograph FLAMES at the VLT, with the high-resolution (R∼
  17 000) HR15N grating (6470-6790 Å). We used radial velocities, Li and
  Hα to establish cluster membership and Hα and other optical emission
  lines to analyze the accretion properties of members. <BR />Results:
  We identified 65 and 45 members of the <ASTROBJ>σ Ori</ASTROBJ> and
  <ASTROBJ>λ Ori</ASTROBJ> clusters, respectively, and discovered 16
  new candidate binary systems. We also measured rotational broadening
  for 20 stars and estimated the mass accretion rates in 25 stars
  of the <ASTROBJ>σ Ori</ASTROBJ> cluster, finding values between
  10<SUP>-11</SUP> and 10<SUP>-7.7</SUP>~M<SUB>⊙</SUB> yr<SUP>-1</SUP>
  and in 4 stars of the <ASTROBJ>λ Ori</ASTROBJ> cluster, finding
  values between 10<SUP>-11</SUP> and 10<SUP>-10.1</SUP>~M<SUB>⊙</SUB>
  yr<SUP>-1</SUP>. Comparing our results with the infrared photometry
  obtained by the Spitzer satellite, we find that the fraction of
  stars with disks and the fraction of active disks is larger in
  the <ASTROBJ>σ Ori</ASTROBJ> cluster (52±9% and 78±16%) than in
  <ASTROBJ>λ Ori</ASTROBJ> (28±8% and 40±20%). <BR />Conclusions:
  The different disk and accretion properties of the two clusters could
  be due either to the effect of the high-mass stars and the supernova
  explosion in the <ASTROBJ>λ Ori</ASTROBJ> cluster or to different ages
  of the cluster populations. Further observations are required to draw
  a definitive conclusion. <P />Based on Data collected at the ESO Very
  Large Telescope, Paranal Observatory, Chile [programs 074.D-0136(A)
  and 076.C-0125(A)]. <P />Tables 1, 2 and 4-7 are only available in
  electronic form at http://www.aanda.org

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Title: Open clusters as key tracers of Galactic chemical
    evolution. III. Element abundances in Berkeley 20, Berkeley 29,
    Collinder 261 and Melotte 66
Authors: Sestito, P.; Bragaglia, A.; Randich, S.; Pallavicini, R.;
   Andrievsky, S. M.; Korotin, S. A.
2008A&A...488..943S    Altcode: 2008arXiv0807.2313S
  Context: Galactic open clusters are since long recognized as one of the
  best tools for investigating the radial distribution of iron and other
  metals. <BR />Aims: We employed FLAMES at VLT to collect UVES spectra
  of bright giant stars in a large sample of open clusters, spanning
  a wide range of Galactocentric distances, ages, and metallicities. We
  present here the results for four clusters: Berkeley 20 and Berkeley 29,
  the two most distant clusters in the sample; Collinder 261, the oldest
  and the one with the minimum Galactocentric distance; Melotte 66. <BR
  />Methods: Equivalent width analysis was carried out using the spectral
  code MOOG and Kurucz model atmospheres to derive abundances of Fe,
  Al, Mg, Si, Ca, Ti, Cr, Ni, Ba; non-LTE Na abundances were derived
  by direct line-profile fitting. <BR />Results: We obtain subsolar
  metallicities for the two anticenter clusters Be 20 ([Fe/H] = -0.30,
  rms = 0.02) and Be 29 ([Fe/H] = -0.31, rms = 0.03), and for Mel 66
  ([Fe/H] = -0.33, rms = 0.03), located in the third Galactic quadrant,
  while Cr 261, located toward the Galactic center, has higher metallicity
  ([Fe/H] = +0.13, rms = 0.05 dex). The α-elements Si, Ca and Ti, and the
  Fe-peak elements Cr and Ni are in general close to solar; the s-process
  element Ba is enhanced. Non-LTE computations of Na abundances indicate
  solar scaled values, suggesting that the enhancement in Na previously
  determined in giants in open clusters could be due to neglected non-LTE
  effects. <BR />Conclusions: Our results support the presence of a steep
  negative slope of the Fe radial gradient up to about 10-11 kpc from the
  Galactic center, while in the outer disk the [Fe/H] distribution seems
  flat. All the elemental ratios measured are in very good agreement with
  those found for disk stars of similar metallicity and no trend with
  Galactocentric distance seems to be present. <P />Based on observations
  collected at ESO telescopes under GTO programmes 71.D-0065, 072.D-0019,
  and GO programme 076.D-0220. Tables 4-7 are only available in electronic
  form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
  or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/488/943

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Title: VizieR Online Data Catalog: Low-mass stars in {sigma} Ori
    and {lambda} Ori (Sacco+, 2008)
Authors: Sacco, G. G.; Franciosini, E.; Randich, S.; Pallavicini, R.
2008yCat..34880167S    Altcode:
  Observations were carried out using the fiber-fed multi-object
  spectrograph FLAMES (Fiber Large Array Multi Element Spectrograph),
  mounted on the UT2 telescope at the VLT and operated in the MEDUSA
  mode (132 fibers, each with an aperture of 1.2" on the sky). <P
  />Observations were performed in service mode and were divided into
  separate runs of 1h duration each, including instrument overheads. The
  {sigma} Ori cluster was observed in 6 runs in October and December
  2004, while {lambda} Ori was observed in 8 runs in October and November
  2005. <P />(5 data files).

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Title: Building up a database of spectro-photometric standard stars
from the UV to the near-IR: a status report
Authors: Vernet, J.; Kerber, F.; Saitta, F.; Mainieri, V.; D'Odorico,
   S.; Lidman, C.; Mason, E.; Bohlin, R. C.; Rauch, T.; Ivanov, V. D.;
   Smette, A.; Walsh, J. R.; Fosbury, R. A. E.; Goldoni, P.; Groot,
   P.; Hammer, F.; Horrobin, M.; Kaper, L.; Kjaergaard-Rasmussen, P.;
   Pallavicini, R.; Royer, F.
2008SPIE.7016E..1GV    Altcode: 2008SPIE.7016E..46V
  We present a project aimed at establishing a set of 12
  spectro-photometric standards over a wide wavelength range from 320
  to 2500 nm. Currently no such set of standard stars covering the
  near-IR is available. Our strategy is to extend the useful range of
  existing well-established optical flux standards into the near-IR by
  means of integral field spectroscopy with SINFONI at the VLT combined
  with state-of-the-art white dwarf stellar atmospheric models. As a
  solid reference, we use two primary HST standard white dwarfs. This
  ESO "Observatory Programme" has been collecting data since February
  2007. The analysis of the data obtained in the first year of the
  project shows that a careful selection of the atmospheric windows
  used to measure fluxes and the stability of SINFONI make it possible
  to achieve an accuracy of 3- 6% depending on the wavelength band and
  stellar magnitude, well within our original goal of 10% accuracy. While
  this project was originally tailored to the needs of the wide wavelength
  range (320-2500 nm) of X-shooter on the VLT, it will also benefit any
  other near-IR spectrographs, providing a huge improvement over existing
  flux calibration methods.

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Title: VizieR Online Data Catalog: Abundances of giants in four
    Galactic clusters (Sestito+, 2008)
Authors: Sestito, P.; Bragaglia, A.; Randich, S.; Pallavicini, R.;
   Andrievsky, S. M.; Korotin, S. A.
2008yCat..34880943S    Altcode:
  Spectra for 2 to 6 giant stars in Be 20, Be 29, Cr 261, and Mel 66 were
  obtained with FLAMES@VLT using the fiber link to UVES. Abundances of
  Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba were derived using equivalent
  widths (and synthesis for Na), model atmospheres and input atmospheric
  parameters based on photometry. <P />For each member star in the four
  clusters we give the measured EWs. <P />(2 data files).

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Title: Building-Up a Database of Spectro-Photometric Standard Stars
    from the Ultraviolet to the Near-Infrared
Authors: Vernet, J.; Kerber, F.; D'Odorico, S.; Bohlin, R.; Ivanov,
   V.; Lidman, C.; Mason, E.; Rauch, T.; Saitta, F.; Smette, A.; Walsh,
   J.; Fosbury, R.; Goldoni, P.; Groot, P.; Hammer, F.; Horrobin, M.;
   Kaper, L.; Kjaergaard-Rasmussen, P.; Pallavicini, R.; Royer, F.
2008eic..work..153V    Altcode:
  No abstract at ADS

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Title: Chemical abundances of T Tauri stars in star forming regions
Authors: D'Orazi, V.; Randich, S.; Palla, F.; Flaccomio, E.;
   Pallavicini, R.; Sacco, G. G.
2008MmSAI..79..695D    Altcode:
  Accretion disks of T Tauri stars are commonly assumed to be the site
  where planets form. At the same time, surveys of old planet-host stars
  -the end product of planet formation- have shown that gas giant planets
  preferentially form around metal-rich stars. A critical question,
  with important implications for our understanding of planet formation,
  is therefore whether metal-rich T Tauri stars exist. In this context,
  we have started a project aimed at the determination of the metallicity
  of T Tauri stars in different star forming regions (SFRs): we present
  the results of a pilot study focusing on a few members of the Orion
  Nebula Cluster (ONC) and Sigma and Lambda Orionis clusters.

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Title: Coming Soon on Stage: X-shooter
Authors: Vernet, Joel; Dekker, Hans; D'Odorico, Sandro; Pallavicini,
   Roberto; Kjörgaard Rasmussen, Per; Kaper, Lex; Hammer, François;
   Groot, Paul; X-Shooter Team
2007Msngr.130....5V    Altcode:
  X-shooter is a single-target, intermediate-resolution,
  wide-wavelength-range (UV- to K-band) spectrograph. It will be the first
  of the second-generation VLT instruments to go to the telescope. First
  light is planned in the second half of 2008. Here we give an update
  on the integration status and on the expected performance.

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Title: XMM-Newton observation of the classical T Tauri star SU
    Aurigae and the surrounding field
Authors: Franciosini, E.; Scelsi, L.; Pallavicini, R.; Audard, M.
2007A&A...471..951F    Altcode:
  Aims: We investigate the properties of the X-ray emitting plasma of the
  classical T Tauri star SU Aurigae and of other sources in the field of
  view. <BR />Methods: We use XMM-Newton to obtain a high-resolution RGS
  spectrum of SU Aur as well as EPIC imaging data and low-resolution
  spectra of the star and of other X-ray sources in the surrounding
  field. We reconstruct the emission measure distribution of SU Aur
  from the RGS spectrum using a line-based method, and we perform
  multi-temperature fits of the MOS spectra of the strongest sources both
  for the full observation and for selected time intervals to study their
  spectral variability. <BR />Results: The emission from SU Aur is highly
  variable, showing three flares during the observation. The MOS spectra
  indicate a very hot corona, with significant emissivity up to ~40 MK in
  quiescence, and temperatures up to 140 MK during flares. The emission
  measure distribution derived from the RGS spectrum peaks at log T =
  7.0; any contribution to the X-ray luminosity from cool plasma (T∼
  2 MK) cannot exceed 5% of the total emission. Abundances are ~0.3-0.6
  solar with the exception of Mg and Ne that are solar. Spatial analysis
  of the full EPIC field results in the detection of 104 X-ray sources,
  6 of which are associated with the known Taurus-Auriga members in the
  field of view (including SU Aur). <BR />Conclusions: The characteristics
  of the X-ray emission of SU Aur are very similar to those of young
  active late-type stars, with a very hot corona and flares, suggesting
  magnetic activity as the origin of most of the X-ray emission, rather
  than accretion. <P />Table 2 is only available in electronic form
  at http://www.aanda.org

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Title: Tracing mixing in stars: new beryllium observations of the
    open clusters NGC 2516, Hyades, and M 67
Authors: Randich, S.; Primas, F.; Pasquini, L.; Sestito, P.;
   Pallavicini, R.
2007A&A...469..163R    Altcode: 2007arXiv0705.2330R
  Context: Determinations of beryllium abundance in stars, together
  with lithium, provide a key tool to investigate the so far poorly
  understood extra-mixing processes at work in stellar interiors. <BR
  />Aims: We measured Be in three open clusters, complementing existing
  Be surveys, and aiming at gathering a more complete empirical
  scenario of the evolution of Be as a function of stellar age and
  temperature. <BR />Methods: We analyzed VLT/UVES spectra of members
  of <ASTROBJ>NGC 2516</ASTROBJ>, the <ASTROBJ>Hyades</ASTROBJ>, and
  <ASTROBJ>M 67</ASTROBJ> to determine their Be and Li abundances. In
  the first two clusters we focused on stars cooler than 5400 K, while
  the M 67 sample includes stars warmer than 6150 K, as well as two
  subgiants and two blue stragglers. We also computed the evolution
  of Be for a 0.9 M<SUB>⊙</SUB> star based on standard evolutionary
  models. <BR />Results: We find different behaviours for stars in
  different temperature bins and ages. Stars warmer than 6150 K show Be
  depletion and follow a Be vs. Li correlation, while Be is undepleted
  in stars in the 6150{-}5600 K range. NGC 2516 members cooler than 5400
  K have not depleted any Be, while older Hyades of similar temperature
  show some depletion. Be is severely depleted in the subgiants and
  blue stragglers. <BR />Conclusions: The results for warm stars are in
  agreement with those of previous studies, supporting the hypothesis that
  mixing in this temperature regime is driven by rotation. The same holds
  for the two subgiants that have evolved from the “Li gap”. This
  mechanism is instead not the dominant one for solar-type stars. We
  show that Be depletion of cool Hyades cannot simply be explained by
  the effect of increasing depth of the convective zone. Finally, the
  different Be content of the two blue stragglers suggests that they
  have formed by two different processes (i.e., collisions vs. binary
  merging). <P />Based on observations collected at ESO-VLT, Paranal
  Observatory, Chile, Programme numbers 65.L-0427, 68.D-0491, 69.D-0454.

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Title: Old Stars in Young Clusters: Lithium-depleted Low-Mass Stars
    of the Orion Nebula Cluster
Authors: Palla, F.; Randich, S.; Pavlenko, Ya. V.; Flaccomio, E.;
   Pallavicini, R.
2007ApJ...659L..41P    Altcode:
  We measured lithium in a sample of low-mass stars (~0.1-0.3
  M<SUB>solar</SUB>) of the Orion Nebula cluster. We find evidence for
  significant Li depletion in four high-probability members, corresponding
  to nuclear ages between ~15 and 30 Myr. In two cases, there is excellent
  agreement between the mass and age based on models of Li burning and
  those derived from the H-R diagram, reinforcing our early findings. For
  the two other stars, the nuclear age is significantly larger than the
  isochronal one. Several Li-depleted stars display accretion activity,
  veiling, and emission lines. We discuss empirical evidence in favor of
  the old nuclear age and the implications on the star formation history
  of the Orion cluster. <P />Based on data collected at ESO-VLT, Paranal
  Observatory, Chile [ID 074.C-0757(A)].

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Title: Lithium-depleted stars in the young σ Orionis cluster
Authors: Sacco, G. G.; Randich, S.; Franciosini, E.; Pallavicini,
   R.; Palla, F.
2007A&A...462L..23S    Altcode: 2006astro.ph.11880S
  Context: Knowledge of the age distribution of stars in young clusters
  and associations is crucial to constrain models of star formation. HR
  diagrams of different young clusters and associations suggest the
  presence of age spreads, but the influence of errors on the derived
  ages is still largely debated. Determination of lithium abundances
  in low-mass stars represents an alternative and robust way to infer
  stellar ages. <BR />Aims: We measured lithium in a sample of low mass
  members of the young (4-5 Myr) σ Ori cluster with the main goal of
  investigating its star formation history. <BR />Methods: Using the
  FLAMES multi-object spectrograph on VLT/UT2, we obtained spectra of 98
  candidate cluster members. The spectra were used to determine radial
  velocities, to infer the presence of Hα emission, and to measure the
  strength of the Li i 670.8 nm absorption line. <BR />Results: Using
  radial velocities, Hα and Li, together with information on X-ray
  emission, we identified 59 high probability cluster members. Three
  of them show severe Li depletion. The nuclear ages inferred for these
  highly depleted stars exceed 10-15 Myr; for two of them these values
  are in good agreement with the isochronal age, while for the third
  star the nuclear age exceeds the isochronal one. <P />Based on data
  collected at the ESO Very Large Telescope, Paranal Observatory, Chile
  [program 074.D-0136(A)].

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Title: Metallicity of low-mass members of the Orion Nebula Cluster.
Authors: D'Orazi, V.; Randich, S.; Palla, F.; Flaccomio, E.;
   Pallavicini, R.
2007MmSAI..78..656D    Altcode:
  We present the results of a pilot study aimed at measuring the
  metallicity of seven low mass members of the Orion Nebula Cluster
  (ONC). We find a very close to solar metallicity for six of the sample
  stars, while one star might have an over-solar metallicity, with [Fe/H]
  = 0.3 ±0.07.

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Title: The X-shooter Spectrograph: A Second Generation Instrument
    for the VLT
Authors: Covino, Stefano; Zerbi, Filippo Maria; Pallavicini, Roberto;
   Conconi, Paolo; Cosentino, Rosario; DeCaprio, Vincenzo; de Ugarte
   Postigo, Antonio; Di Marcantonio, Paolo; Riva, Marco; Santin, Paolo;
   Spanó, Paolo; Zacchei, A.
2006ChJAS...6a.361C    Altcode: 2006ChJAA...6S.361C; 2006ChJAS...6..361C
  X-shooter is a spectrograph designed to feed the Cassegrain
  focus of the VLT. It may cover in a single exposure the spectral
  range from the UV to the H band with possible extension to the K
  band. The instrument is constituted by three arms, blue, visible and
  near-infarred, with optimized optics, coatings, dispersive elements and
  detectors. It operates at intermediate resolution (R = 4000-14 000),
  sufficient to address quantitatively a vast number of astrophysical
  applications. Approved as second generation instrument for the VLT,
  X-shooter is expected to be available to the community in the first
  part of the year 2008.

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Title: VizieR Online Data Catalog: XMM observations of sigma Ori
    cluster (Franciosini+, 2006)
Authors: Franciosini, E.; Pallavicini, R.; Sanz-Forcada, J.
2006yCat..34460501F    Altcode:
  XMM-Newton observations of the sigma Ori cluster, centered on the hot
  star sigma Ori AB, were carried out as part of the Guaranteed Time of
  one of us (R.P.) using both the EPIC MOS and PN cameras and the RGS
  instrument. The observation (ID 0101440301) started at 21:47 UT on
  March 23, 2002 and ended at 9:58 UT on March 24, 2002, for a total
  duration of 43ks. The EPIC cameras were operated in Full Frame mode
  using the thick filter. <P />(3 data files).

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Title: X-shooter UV- to K-band intermediate-resolution high-efficiency
spectrograph for the VLT: status report at the final design review
Authors: D'Odorico, Sandro; Dekker, Hans; Mazzoleni, Ruben; Vernet,
   Joel; Guinouard, Isabelle; Groot, Paul; Hammer, Francois; Rasmussen,
   Per Kjaergaard; Kaper, Lex; Navarro, Ramon; Pallavicini, Roberto;
   Peroux, Celine; Zerbi, Filippo Maria
2006SPIE.6269E..33D    Altcode: 2006SPIE.6269E..98D
  X-shooter is a single target spectrograph for the Cassegrain focus
  of one of the VLT UTs where it will start to operate in 2008. The
  instrument covers in a single exposure the spectral range from the UV
  to the K' band. It is designed to maximize the sensitivity in this
  spectral range through the splitting in three arms with optimized
  optics, coatings, dispersive elements and detectors. It operates at
  intermediate resolutions (R=4000-14000, depending on wavelength and slit
  width) with fixed echelle spectral format (with prism cross-dispersers)
  in the three arms. The project has completed the Final Design Review
  in June 2006. In this status report, the overall concept is summarized
  and new results on the dichroics, the active flexure compensation
  system, the operation modes and the expected performance are given. The
  instrument is being built by a Consortium of Institutes from Denmark,
  France, Italy and the Netherlands in collaboration with ESO. When in
  operation, its wide spectral range observing capability will be unique
  at very large telescopes.

---------------------------------------------------------
Title: Element abundances of unevolved stars in the open cluster M 67
Authors: Randich, S.; Sestito, P.; Primas, F.; Pallavicini, R.;
   Pasquini, L.
2006A&A...450..557R    Altcode: 2006astro.ph..1239R
  Context: .The star-to-star scatter in lithium abundances observed
  among otherwise similar stars in the solar-age open cluster M 67
  is one of the most puzzling results in the context of the so called
  "lithium problem". Among other explanations, the hypothesis has been
  proposed that the dispersion in Li is due to star-to-star differences
  in Fe or other element abundances which are predicted to affect
  Li depletion. <BR /> Aims: .The primary goal of this study is the
  determination of the metallicity ([Fe/H]), α- and Fe-peak abundances
  in a sample of Li-poor and Li-rich stars belonging to M 67, in order to
  test this hypothesis. By comparison with previous studies, the present
  investigation also allows us to check for intrinsic differences in the
  abundances of evolved and unevolved cluster stars and to draw more
  secure conclusions on the abundance pattern of this cluster.<BR />
  Methods: .We have carried out an analysis of high resolution UVES/VLT
  spectra of eight unevolved and two slightly evolved cluster members
  using MOOG and measured equivalent widths. For all the stars we have
  determined [Fe/H] and element abundances for O, Na, Mg, Al, Si, Ca,
  Ti, Cr and Ni.<BR /> Results: .We find an average metallicity [Fe/H]
  = 0.03±0.01, in very good agreement with previous determinations. All
  the [ X/Fe] abundance ratios are very close to solar. The star-to-star
  scatter in [Fe/H] and [ X/Fe] ratios for all elements, including
  oxygen, is lower than 0.05 dex, implying that the large dispersion in
  lithium among cluster stars is not due to differences in these element
  abundances. We also find that, when using a homogeneous scale, the
  abundance pattern of unevolved stars in our sample is very similar to
  that of evolved stars, suggesting that, at least in this cluster, RGB
  and clump stars have not undergone any chemical processing. Finally, our
  results show that M 67 has a chemical composition that is representative
  of the solar neighborhood.<BR />

---------------------------------------------------------
Title: XMM-Newton observations of the σ Orionis cluster. II. Spatial
    and spectral analysis of the full EPIC field
Authors: Franciosini, E.; Pallavicini, R.; Sanz-Forcada, J.
2006A&A...446..501F    Altcode: 2005astro.ph.10209F
  We present the results of an XMM-Newton observation of the young (∼
  2{-}4 Myr) cluster around the hot star σ Orionis. In a previous paper
  we presented the analysis of the RGS spectrum of the central hot star;
  here we discuss the results of the analysis of the full EPIC field. We
  have detected 175 X-ray sources, 88 of which have been identified with
  cluster members, including very low-mass stars down to the substellar
  limit. We detected eleven new possible candidate members from the 2MASS
  catalogue. We find that late-type stars have a median log L_X/L_bol ∼
  -3.3, i.e. very close to the saturation limit. We detected significant
  variability in ∼ 40% of late-type members or candidates, including
  10 flaring sources; rotational modulation is detected in one K-type
  star and possibly in another 3 or 4 stars. Spectral analysis of the
  brightest sources shows typical quiescent temperatures in the range
  T_1∼ 0.3{-}0.8 keV and T_2∼ 1{-}3 keV, with subsolar abundances
  Z∼ 0.1{-}0.3 Z_⊙, similar to what is found in other star-forming
  regions and associations. We find no significant difference in the
  spectral properties of classical and weak-lined T Tauri stars, although
  classical T Tauri stars tend to be less X-ray luminous than weak-lined
  T Tauri stars.

---------------------------------------------------------
Title: Current problems of stellar astrophysics in optical
    spectroscopy .
Authors: Pallavicini, R.; Randich, S.
2006MSAIS...9..189P    Altcode:
  We present the highlights of current programs in stellar optical
  spectroscopy carried out with 8-10m class telescopes as well as with
  smaller telescopes. Topics briefly discussed here include: 1. light
  element abundances and their cosmological implications; 2. search for
  Population III stars and spectroscopy of extremely metal deficient
  stars; 3. abundances of different stellar populations in the Galaxy;
  4. spectroscopy of resolved stars in Local Group galaxies; 5. Li and Be
  abundances and internal mixing in stars; 6. spectroscopy of very-low
  mass stars and brown dwarfs; 7. radial velocity search of extrasolar
  planets; 8. stellar oscillations and asteroseismology; 9. stellar
  magnetic activity and Doppler imaging of stellar surface features.

---------------------------------------------------------
Title: Multi-Object Spectroscopy of Open Clusters with FLAMES:
    Preliminary GTO Results
Authors: Pallavicini, R.; Spanò, P.; Prisinzano, L.; Randich, S.;
   Sestito, P.
2006cams.book..181P    Altcode:
  We report on preliminary results of VLT/FLAMES observations of the
  old open clusters NGC 2506, Mel 66 and Cr 261, obtained as part of our
  Guaranteed Time on this instrument. We focus in particular on the very
  old cluster Cr 261, one of the oldest open clusters in the Galaxy. We
  compare the derived Li abundances with those of other old clusters,
  and we discuss briefly Li depletion on the main-sequence from the age
  of the Hyades to ~8 Gyr.

---------------------------------------------------------
Title: XMM-Newton spectroscopy of stars in open clusters and star
    forming regions
Authors: Pallavicini, R.; Franciosini, E.; Maggio, A.; Scelsi, L.;
   Sanz-Forcada, J.
2006AdSpR..38.1509P    Altcode:
  We discuss observations of open clusters and star forming regions
  obtained with the RGS and EPIC instruments on board XMM-Newton. These
  observations provide a powerful tool to investigate the temperature
  structure, emission measure distribution and elemental abundances
  of stars from the pre-main sequence phase to post-main sequence
  evolution. We report in particular on EPIC and RGS spectroscopy of
  hot and cool stars in the very young cluster around σ Orionis, of
  two stars in the Hyades (the main-sequence star VB 50 and the clump
  giant VB 71) and of two pre-main sequence stars in Taurus Auriga
  (the classical T Tauri star SU Aur and the weak-lined T Tauri star HD
  283572). The implications of these observations for models of magnetic
  activity in late-type stars, of wind emission in early-type stars,
  and of X-ray production in the early stages of stellar evolution are
  briefly discussed.

---------------------------------------------------------
Title: XMM-Newton Observations of the Taurus-Auriga Star-Forming
Region: the Fields around SU Aur
Authors: Franciosini, E.; Pallavicini, R.; Scelsi, L.
2006ESASP.604...77F    Altcode: 2006xru..conf...77F
  No abstract at ADS

---------------------------------------------------------
Title: The X-shooter Spectrograph for the VLT .
Authors: Zerbi, F. M.; Pallavicini, R.; Conconi, P.; Cosentino, R.;
   De Caprio, V.; de Ugarte Postigo, A.; Di Marcantonio, P.; Riva, M.;
   Santin, P.; Spanó, P.; Zacchei, A.
2006MSAIS...9..419Z    Altcode:
  X-shooter is a single target spectrograph for the Cassegrain focus of
  one of the VLT UTs. It covers in a single exposure the spectral range
  from the UV to the H band with a possible extension into part of the
  K band. In order to maximize the sensitivity in this spectral range
  the beam is splitted in three arms with optimized optics, coatings,
  dispersive elements and detectors. It operates at intermediate
  resolution (R=4000-14000) sufficient to address quantitatively a vast
  number of astrophysical applications. Approved as second generation
  instrument for the VLT, X-shooter will be available to the community
  in the first part of the year 2008

---------------------------------------------------------
Title: Lithium and Metallicity in the Intermediate Age Open Cluster
    NGC 752
Authors: Sestito, P.; Randich, S.; Pallavicini, R.
2006cams.book..179S    Altcode:
  We have determined Li abundances (log n(Li)) and metallicity ([Fe/H])
  in the ~2 Gyr old open cluster NGC 752. The cluster turned out to
  have a nearly solar Fe content, at variance with previous reports of
  sub-solar metallicity. The Li distribution vs. effective temperature
  (T <SUB>eff</SUB>) of NGC 752 is very similar to those of IC 4651
  and NGC 3680, which have similar age but dierent [Fe/H]. Moreover,
  similarly to the other two clusters, NGC 752 does not show a Li scatter
  as large as that observed in the solar age cluster M 67. In general,
  the Li vs. T <SUB>eff</SUB> distribution does not appear to depend
  significantly on metallicity, as shown by the comparison of NGC 752
  with IC 4651 and NGC 3680; however, a weak dependence on metallicity
  might be present when comparing the three clusters in the [log n(Li),
  mass] plane.

---------------------------------------------------------
Title: FLAMES Observations of Old Open Clusters: Constraints on the
    Evolution of the Galactic Disc and Mixing Processes in Stars
Authors: Randich, Sofia; Bragaglia, Angela; Pastori, Livio; Prisinzano,
   Loredana; Sestito, Paola; Spano, Paolo; Villanova, Sandro; Carraro,
   Giovanni; Carretta, Eugenio; Romano, Donatella; Zaggia, Simone;
   Pallavicini, Roberto; Pasquini, Luca; Primas, Francesca; Tagliaferri,
   Gianpiero; Tosi, Monica
2005Msngr.121...18R    Altcode:
  Open clusters are populous groups of stars whose members have the
  same age, chemical composition, and distance from the Sun. Hence,
  they provide homogeneous samples to investigate several important
  issues related to stellar and Galactic evolution. We present here an
  overview and preliminary results of a VLT/FLAMES programme aimed at
  a detailed study of seven old clusters. Our two main goals are the
  determination of the radial abundance gradients in the Galactic disc
  and their evolution with age, and the investigation of internal mixing
  processes in stars similar to our Sun.

---------------------------------------------------------
Title: Age Spreads in Star-forming Regions: The Lithium Test in the
    Orion Nebula Cluster
Authors: Palla, Francesco; Randich, Sofia; Flaccomio, Ettore;
   Pallavicini, Roberto
2005ApJ...626L..49P    Altcode: 2005astro.ph..5162P
  We present the initial results of a study of the surface lithium
  abundance in a sample of low-mass members (M<SUB>*</SUB>~0.4-1.0
  M<SUB>solar</SUB>) of the Orion Nebula Cluster (ONC) that provide an
  independent clock to estimate stellar ages. We report the discovery
  of a significant depletion of lithium in four stars with estimated
  masses of ~0.4 M<SUB>solar</SUB> and ages ~10 Myr. Comparison with
  the predictions of numerical and analytical models shows excellent
  agreement between the isochronal age and lithium depletion timescale
  for two objects, the first such case for lithium-poor pre-main-sequence
  stars. Our results bear on the issue of the real age spread in the
  ONC and hence on the overall duration of the star formation process,
  indicating that the stellar population did not come into existence in
  a single, rapid burst. <P />Based on data collected at the ESO Very
  Large Telescope, Paranal Observatory, Chile [program 072.D-0019(B)].

---------------------------------------------------------
Title: The σ Orionis open cluster observed with XMM-Newton: source
    detection and spectral properties
Authors: Franciosini, E.; Pallavicini, R.; Sanz-Forcada, J.
2005ESASP.560..551F    Altcode: 2005csss...13..551F
  No abstract at ADS

---------------------------------------------------------
Title: Spot the differences: the X-ray spectrum of SU Aur compared
    to TW Hya
Authors: Smith, K.; Audard, M.; Güdel, M.; Skinner, S.; Pallavicini,
   R.
2005ESASP.560..971S    Altcode: 2005csss...13..971S; 2005astro.ph..4562S
  We present high-resolution Chandra HETGS X-ray spectra of the classical
  T Tauri star SU Aur. The quiescent X-ray emission is dominated by a
  20-40 MK plasma, which contrasts strongly with the cool 3 MK plasma
  dominating the X-ray emission of the CTTS TW Hya. A large flare
  occurred during the first half of our 100 ks observation, and we have
  modelled the emitting plasma both during this flare and during the
  apparently quiescent periods. During the flare, an extremely high
  temperature plasma component (at least 60 MK) accounts for the bulk
  of the emission. There is an indication of the presence of Fe XXVI
  emission at 1.78 Angstrom, which is maximally formed at 130 MK.

---------------------------------------------------------
Title: Lithium abundances in intermediate age and old clusters
Authors: Pallavicini, R.; Randich, S.; Sestito, P.
2005ESASP.560..867P    Altcode: 2005csss...13..867P
  No abstract at ADS

---------------------------------------------------------
Title: Coronal properties of active G-type stars in different
    evolutionary phases
Authors: Scelsi, L.; Maggio, A.; Peres, G.; Pallavicini, R.
2005ESASP.560..939S    Altcode: 2005csss...13..939S
  No abstract at ADS

---------------------------------------------------------
Title: High energy processes in young stars: Chandra X-Ray
    spectroscopy of HDE 283572, RY Tau, and LkCa 21
Authors: Audard, M.; Skinner, S. L.; Smith, K. W.; Güdel, M.;
   Pallavicini, R.
2005ESASP.560..411A    Altcode: 2005csss...13..411A; 2004astro.ph..9309A
  Weak-lined T Tauri stars (WTTS) represent the important stage of
  stellar evolution between the accretion phase and the zero-age main
  sequence. At this stage, the star decouples from its accretion disk,
  and spins up to a higher rotation rate than in the preceding classical
  T Tauri phase. Consequently, dynamo processes can be expected to
  become even stronger at this stage. High energy processes can have
  effects on the remaining circumstellar material, possibly including
  protoplanets and planetesimals, and these effects may account for
  certain observable properties of asteroids in the current solar
  system. Chandra observed for 100 ks the WTTS HDE 283572 which probes
  the PMS stage of massive A-type stars. We present first results of
  the analysis of its high-resolution X-ray spectrum obtained with the
  High-Energy Transmission Grating Spectrometer. A wide range of Fe
  lines of high ionization states are observed, indicating a continuous
  emission measure distribution. No significant signal is detected
  longward of the O \textsc{viii} Ly$\alpha$ line because of the high
  photoelectric absorption. We also report on the preliminary analysis
  of the zeroth order spectra of RY Tau and LkCa21. In particular,
  we show evidence of an emission line in RY Tau at 6.4 keV that we
  identify as fluorescent emission by neutral Fe caused by a strong
  X-ray flare which illuminated some structure in (or surrounding)
  the CTTS. A comparison of X-ray spectra of classical T Tau stars,
  other WTTS, and young main-sequence stars is made.

---------------------------------------------------------
Title: Coronal properties of G-type stars in different evolutionary
    phases
Authors: Scelsi, L.; Maggio, A.; Peres, G.; Pallavicini, R.
2005A&A...432..671S    Altcode: 2005astro.ph..1631S
  We report on the analysis of XMM-Newton observations of three G-type
  stars in very different evolutionary phases: the weak-lined T Tauri
  star <ASTROBJ>HD 283572</ASTROBJ>, the Zero Age Main Sequence star
  <ASTROBJ>EK Dra</ASTROBJ> and the Hertzsprung-gap giant star <ASTROBJ>31
  Com</ASTROBJ>. They all have high X-ray luminosity (~10<SUP>31</SUP>
  erg s<SUP>-1</SUP> for HD 283572 and 31 Com and ~10<SUP>30</SUP>
  erg s<SUP>-1</SUP> for EK Dra). We compare the Emission Measure
  Distributions (EMDs) of these active coronal sources, derived from
  high-resolution XMM-Newton grating spectra, as well as the pattern
  of elemental abundances vs. First Ionzation Potential (FIP). We also
  perform time-resolved spectroscopy of a flare detected by XMM from
  EK Dra. We interpret the observed EMDs as the result of the emission
  of ensembles of magnetically confined loop-like structures with
  different apex temperatures. Our analysis indicates that the coronae
  of HD 283572 and 31 Com are very similar in terms of dominant coronal
  magnetic structures, in spite of differences in the evolutionary phase,
  surface gravity and metallicity. In the case of EK Dra the distribution
  appears to be slightly flatter than in the previous two cases, although
  the peak temperature is similar.

---------------------------------------------------------
Title: VLT/FLAMES observations of Collinder 261
Authors: Spanò, P.; Pallavicini, R.; Randic, S.
2005IAUS..228..111S    Altcode:
  We report on results of VLT/FLAMES observations of the very old cluster
  Cr 261. We compare the results with those of other clusters older than
  the Hyades.

---------------------------------------------------------
Title: Some Like It Hot: The X-Ray Emission of the Giant Star
    YY Mensae
Authors: Audard, Marc; Telleschi, Alessandra; Güdel, Manuel; Skinner,
   Stephen L.; Pallavicini, Roberto; Mitra-Kraev, Urmila
2004ApJ...617..531A    Altcode: 2004astro.ph..8345A
  We present an analysis of the X-ray emission of the rapidly rotating
  giant star YY Mensae observed by Chandra HETGS and XMM-Newton. The
  high-resolution spectra display numerous emission lines of highly
  ionized species; Fe XVII to Fe XXV lines are detected, together
  with H-like and He-like transitions of lower Z elements. Although no
  obvious flare was detected, the X-ray luminosity changed by a factor
  of 2 between the XMM-Newton and Chandra observations taken 4 months
  apart (from logL<SUB>X</SUB>~32.2 to 32.5 ergs s<SUP>-1</SUP>,
  respectively). The coronal abundances and the emission measure
  distribution have been derived from three different methods using
  optically thin collisional ionization equilibrium models, which is
  justified by the absence of opacity effects in YY Men as measured from
  line ratios of Fe XVII transitions. The abundances show a distinct
  pattern as a function of the first ionization potential (FIP),
  suggestive of an inverse FIP effect as seen in several active RS CVn
  binaries. The low-FIP elements (&lt;10 eV) are depleted relative to
  the high-FIP elements; when compared to its photospheric abundance,
  the coronal Fe abundance also appears depleted. We find a high N
  abundance in YY Men's corona, which we interpret as a signature
  of material processed in the CNO cycle and dredged up in the giant
  phase. The corona is dominated by a very high temperature (20-40 MK)
  plasma, which places YY Men among the magnetically active stars with
  the hottest coronae. Lower temperature plasma also coexists, albeit
  with much lower emission measure. Line broadening is reported in
  some lines, with a particularly strong significance in Ne X Lyα. We
  interpret such broadening as Doppler thermal broadening, although
  rotational broadening due to X-ray-emitting material high above the
  surface could be present as well. We use two different formalisms to
  discuss the shape of the emission measure distribution. The first one
  infers the properties of coronal loops, whereas the second formalism
  uses flares as a statistical ensemble. We find that most of the loops
  in the corona of YY Men have their maximum temperature equal to or
  slightly larger than about 30 MK. We also find that small flares could
  contribute significantly to the coronal heating in YY Men. Although
  there is no evidence of flare variability in the X-ray light curves,
  we argue that YY Men's distance and X-ray brightness do not allow us to
  detect flares with peak luminosities L<SUB>X</SUB>&lt;=10<SUP>31</SUP>
  ergs s<SUP>-1</SUP> with current detectors.

---------------------------------------------------------
Title: Lithium evolution in intermediate age and old open clusters:
    NGC 752 revisited
Authors: Sestito, P.; Randich, S.; Pallavicini, R.
2004A&A...426..809S    Altcode: 2004astro.ph..7305S
  We present new high resolution spectroscopic observations of the
  intermediate age (∼2 Gyr) open cluster <ASTROBJ>NGC 752</ASTROBJ>. We
  investigate the Li vs. T<SUB>eff</SUB> distribution and we obtain
  a new accurate determination of the cluster metallicity. We compare
  the results for NGC 752 with other intermediate age and old clusters
  spanning the age range from the <ASTROBJ>Hyades</ASTROBJ> (∼0.6
  Gyr) to <ASTROBJ>NGC 188</ASTROBJ> (∼6-8 Gyr). We find that NGC
  752 has a solar iron content ([Fe/H]=+0.01±0.04), at variance
  with early reports of sub-solar metallicity. We find that NGC 752
  is only slightly more Li depleted than the younger Hyades and has
  a Li pattern almost identical to that observed in the ∼2 Gyr old
  <ASTROBJ>IC 4651</ASTROBJ> and <ASTROBJ>NGC 3680</ASTROBJ>. As for
  the latter clusters, we find that NGC 752 is characterized by a tight
  Li vs. T<SUB>eff</SUB> distribution for solar-type stars, with no
  evidence for a Li spread as large as the one observed in the solar age
  solar metallicity <ASTROBJ>M 67</ASTROBJ>. We discuss these results
  in the framework of mixing mechanisms and Li depletion on the main
  sequence (MS). We conclude that the development of a large scatter in
  Li abundances in old open clusters might be an exception rather than
  the rule (additional observations of old clusters are required), and
  that metallicity variations of the order of ∼±0.2 dex do not affect
  Li depletion after the age of the Hyades. <P />Based on observations
  collected at Telescopio Nazionale Galileo, La Palma, Canary Islands.

---------------------------------------------------------
Title: XMM-Newton Proposal 03006901
Authors: Pallavicini, Roberto
2004xmm..prop...25P    Altcode:
  We propose to observe the open cluster NGC 6475 (age ~220 Myr, [Fe/H]
  = 0.14 +- 0.06) to investigate the activity-rotation-age relationship
  of low-mass stars in the crucial age interval between the Pleiades and
  the Hyades. We will use XMM-Newton observations of the proposed cluster
  to go a factor of 10 deeper than ROSAT (to detect new faint candidate
  members) and to obtain spectral information on the brightest cluster
  members (to derive coronal temperatures and metallicities). These
  observations will provide strong constraints on the universality
  (or lack of) of the activity-rotation-age relationship, and hence on
  dynamo models of stellar coronal activity.

---------------------------------------------------------
Title: Can we use adaptive optics for UHR spectroscopy with PEPSI
    at the LBT?
Authors: Sacco, Germano G.; Pallavicini, Roberto; Spano, Paolo;
   Andersen, Michael; Woche, Manfred F.; Strassmeier, Klaus G.
2004SPIE.5490..398S    Altcode:
  We investigate the potential of using adaptive optics (AO) in the V,
  R, and I bands to reach ultra-high resolution (UHR, R &gt;= 200,000)
  in echelle spectrographs at 8-10m telescopes. In particular, we
  investigate the possibility of implementing an UHR mode for the
  fiber-fed spectrograph PEPSI (Potsdam Echelle Polarimetric and
  Spectrographic Instrument) being developed for the Large Binocular
  Telescope (LBT). By simulating the performances of the advanced AO
  system that will be available at first light at the LBT, and by using
  first-order estimates of the spectrograph performances, we calculate
  the total efficiency and signal to noise ratio (SNR) of PEPSI in the
  AO mode for stars of different magnitudes, different fiber core sizes,
  and different fractions of incident light diverted to the wavefront
  sensor. We conclude that AO can provide a significant advantage, of
  up to a factor ~2 in the V, R and I bands, for stars brighter than
  m<SUB>R</SUB> ~ 12 - 13. However, if these stars are observed at UHR
  in non-AO mode, slit losses caused by the need to use a very narrow
  slit can be compensated more effectively by the use of image slicers.

---------------------------------------------------------
Title: Unsolved problems in observational astronomy. I. Focus on
    stellar spectroscopy
Authors: Pallavicini, R.; Randich, S.
2004AN....325..462P    Altcode:
  We present the highlights of current observational programs in stellar
  optical spectroscopy carried out with 8-10 m class telescopes as
  well as with smaller telescopes. Topics discussed include: 1. light
  elements abundances and their cosmological implications; 2. search
  for Population III stars and spectroscopy of extremely metal deficient
  stars; 3. abundances of different stellar populations in the Galaxy;
  4. spectroscopy of resolved stars in Local Group galaxies; 5. Li
  and Be abundances and internal mixing in stars; 6. spectroscopy of
  very-low mass stars and brown dwarfs; 7. radial velocity search of
  extrasolar planets; 8. stellar oscillations and asteroseismology;
  9. stellar magnetic activity and Doppler imaging of stellar surface
  features. We also highlight the role that dedicated 1-2 m automatic
  telescopes with spectroscopic capabilities can play in several fields
  of stellar optical spectroscopy.

---------------------------------------------------------
Title: X-shooter: UV-to-IR intermediate-resolution high-efficiency
    spectrograph for the ESO VLT
Authors: D'Odorico, Sandro; Andersen, Michael I.; Conconi, Paolo; De
   Caprio, Vincenzo; Delabre, Bernard; Di Marcantonio, Paolo; Dekker,
   Hans; Downing, Mark D.; Finger, Gert; Groot, Paul; Hanenburg,
   Hiddo H.; Hammer, Francois; Horville, David; Hjorth, Jens; Kaper,
   Lex; Klougart, Jens; Kjaergaard-Rasmussen, Per; Lizon, Jean-Louis;
   Marteaud, Michel; Mazzoleni, Ruben; Michaelsen, Niels; Pallavicini,
   Roberto; Rigal, Florence; Santin, Paolo; Norup Soerensen, Anton;
   Spano, Paolo; Venema, Lars; Vola, Pascal; Zerbi, Filippo M.
2004SPIE.5492..220D    Altcode:
  X-shooter is a single target spectrograph for the Cassegrain focus
  of one of the VLT UTs. It covers in a single exposure the spectral
  range from the UV to the H band with a possible extension into part
  of the K band. It is designed to maximize the sensitivity in this
  spectral range through the splitting in three arms with optimized
  optics, coatings, dispersive elements and detectors. It operates at
  intermediate resolutions (R=4000-14000, depending on wavelength and
  slit width) sufficient to address quantitatively a vast number of
  astrophysical applications while working in a background-limited S/N
  regime in the regions of the spectrum free from strong atmospheric
  emission and absorption lines. The small number of moving functions
  (and therefore instrument modes) and fixed spectral format make it easy
  to operate and permit a fast response. A mini-IFU unit (1.8" x 4") can
  be inserted in the telescope focal plane and is reformatted in a slit
  of 0.6"x 12" .The instrument includes atmospheric dispersion correctors
  in the UV and visual arms. The project foresees the development of a
  fully automatic data reduction package. The name of the instrument
  has been inspired by its capability to observe in a single shot a
  source of unknown flux distribution and redshift. The instrument is
  being built by a Consortium of Institutes from Denmark, France, Italy
  and the Netherlands in collaboration with ESO. When it operation,
  its observing capability will be unique at very large telescopes.

---------------------------------------------------------
Title: A Multiwavelength Perspective of Flares on HR 1099: 4 Years
    of Coordinated Campaigns
Authors: Osten, Rachel A.; Brown, Alexander; Ayres, Thomas R.; Drake,
   Stephen A.; Franciosini, Elena; Pallavicini, Roberto; Tagliaferri,
   Gianpiero; Stewart, Ron T.; Skinner, Stephen L.; Linsky, Jeffrey L.
2004ApJS..153..317O    Altcode: 2004astro.ph..2613O
  We report on four years of multiple wavelength observations of the RS
  CVn system V711 Tau (HR 1099) from 1993, 1994, 1996, and 1998. This
  combination of radio, ultraviolet, extreme ultraviolet, and X-ray
  observations allows us to view, in the most comprehensive manner
  currently possible, the coronal and upper atmospheric variability of
  this active binary system. We report on the changing activity state
  of the system as recorded in the EUV and radio across the four years
  of the observations, and study the high energy variability using an
  assemblage of X-ray telescopes. (Longer abstract in paper).

---------------------------------------------------------
Title: XMM-Newton observations of the σ Ori cluster. I. The complex
    RGS spectrum of the hot star σ Ori AB
Authors: Sanz-Forcada, J.; Franciosini, E.; Pallavicini, R.
2004A&A...421..715S    Altcode: 2004astro.ph..4078S
  We present XMM-Newton observations of the young ({∼} 2{-}5 Myr)
  cluster around the hot (O9.5V) star σ Orionis AB, aimed at obtaining
  a high resolution RGS spectrum of the hot star as well as EPIC imaging
  data for the whole field. We show that the RGS spectrum of σ Ori
  AB may be contaminated by weaker nearby sources which required the
  development of a suitable procedure to extract a clean RGS spectrum
  and to determine the thermal structure and wind properties of the hot
  star. We also report on the detection of a flare from the B2Vp star σ
  Ori E and we discuss whether the flare originated from the hot star
  itself or rather from an unseen late-type companion. Other results
  of this observation include: the detection of 174 X-ray sources in
  the field of σ Ori of which 76 are identified as cluster members,
  including very low-mass stars down to the substellar limit; the
  discovery of rotational modulation in a late-type star near σ Ori AB;
  no detectable line broadenings and shifts (⪉ 800 km s<SUP>-1</SUP>)
  in the spectrum of σ Ori AB together with a remarkable low value of
  the O VII forbidden to intercombination line ratio and unusually high
  coronal abundances of CNO elements.

---------------------------------------------------------
Title: The science case of the PEPSI high-resolution echelle
    spectrograph and polarimeter for the LBT
Authors: Strassmeier, K. G.; Pallavicini, R.; Rice, J. B.; Andersen,
   M. I.
2004AN....325..278S    Altcode:
  We lay out the scientific rationale for and present the instrumental
  requirements of a high-resolution adaptive-optics Echelle spectrograph
  with two full-Stokes polarimeters for the Large Binocular Telescope
  (LBT) in Arizona. Magnetic processes just like those seen on the Sun
  and in the space environment of the Earth are now well recognized in
  many astrophysical areas. The application to other stars opened up a
  new field of research that became widely known as the solar-stellar
  connection. Late-type stars with convective envelopes are all affected
  by magnetic processes which give rise to a rich variety of phenomena on
  their surface and are largely responsible for the heating of their outer
  atmospheres. Magnetic fields are likely to play a crucial role in the
  accretion process of T-Tauri stars as well as in the acceleration and
  collimation of jet-like flows in young stellar objects (YSOs). Another
  area is the physics of active galactic nucleii (AGNs) , where the
  magnetic activity of the accreting black hole is now believed to be
  responsible for most of the behavior of these objects, including their
  X-ray spectrum, their notoriously dramatic variability, and the powerful
  relativistic jets they produce. Another is the physics of the central
  engines of cosmic gamma-ray bursts, the most powerful explosions
  in the universe, for which the extreme apparent energy release are
  explained through the collimation of the released energy by magnetic
  fields. Virtually all the physics of magnetic fields exploited in
  astrophysics is somehow linked to our understanding of the Sun's and
  the star's magnetic fields.

---------------------------------------------------------
Title: Coronal and photospheric metal abundances in Gl 355 (LQ Hya)
Authors: Covino, S.; Audard, M.; Tagliaferri, G.; Randich, S.; Gudel,
   M.; Pallavicini, R.
2004cosp...35.2997C    Altcode: 2004cosp.meet.2997C
  One of the most interesting topics in the field of coronal emission from
  late--type stars concerns the discrepancy seen for some stars between
  the metal abundances measured in the corona with respect to the values
  obtained for the photosphere. However, for only few objects, the quality
  of available data allow us to properly address the problem. First of
  all, there is a lack of optical spectra with S/N adequate for abundance
  determination. For most of the stars in this category only global
  metallicity is available. Regarding the X--ray spectra, it is only with
  the combination of high resolution gratings and high throughput provided
  by the Chandra and XMM--Newton missions that single element abundances
  in coronal plasmas can be effectively retrieved in active stars. To
  this aim we performed XMM--Newton observations and high-resolution
  optical spectroscopy of Gl355 to derive a reliable set of abundances
  both in the corona and in the photosphere. The XMM--Newton observation,
  EPIC pn and MOS, RGS and the ESO-1.5m FEROS data allowed us to derive
  abundances for a set of elements (i.e. C, N, O, Fe, Si, etc.). We now
  discuss the results of our analyses and draw some conclusions.

---------------------------------------------------------
Title: High resolution spectroscopy of open clusters with SARG
Authors: Sestito, P.; Randich, S.; Pallavicini, R.
2004MmSAI..75...24S    Altcode:
  We present high resolution spectroscopic observations of open clusters
  of different ages and metallicities obtained with SARG at TNG. We
  derived lithium abundances for solar-type stars in NGC 752 (∼2 Gyr)
  and NGC 188 (∼6-8 Gyr) and for early-K stars in Praesepe (∼600
  Myr). We found that (i) Li depletion in solar-type stars might stop
  at an age of ∼2 Gyr; (ii) the spread in Li abundances observed in
  M 67 seems to be an exception rather than the rule in old clusters;
  (iii) Li evolution does not seem to be affected by small variations
  in metallicity. <P />Based on observations collected at TNG

---------------------------------------------------------
Title: XMM-Newton spectroscopy of stars in open clusters and star
    forming regions
Authors: Pallavicini, R.; Franciosini, E.; Maggio, A.; Sanz-Forcada,
   J.; Scelsi, L.
2004cosp...35..195P    Altcode: 2004cosp.meet..195P
  We present XMM-Newton RGS and EPIC spectra of stars in open clusters
  and star forming regions obtained as part of the Mission Scientist
  Guaranteed Time. The objects discussed include the hot star sigma
  Ori AB in the sigma Ori cluster, the late-type stars VB 50 and VB
  71 in the Hyades (respectively a main-sequence star and a giant),
  and the pre-main sequence stars HD 283572 (a weak-line T-Tari star)
  and SU Aur (a classical T Tauri star) in the star forming region
  Taurus-Auriga. All stars were observed with the RGS at high-resolution
  and with EPIC at low-resolution. We investigate the thermal structure
  and chemical abundances of these stars and we put constraints on wind
  velocities (for the hot star) and densities (from He-like triplets). We
  discuss the implications of these observations for the understanding
  of coronal emission and winds in stars of different activity levels
  and in different evolutionary phases.

---------------------------------------------------------
Title: XMM-Newton EPIC observations of stellar clusters and star
    forming regions
Authors: Pallavicini, R.; Franciosini, E.; Randich, S.
2004MmSAI..75..434P    Altcode:
  We report on observations of open clusters (OCs) and star forming
  regions (SFRs) obtained with the EPIC camera as part of the Mission
  Scientist Guaranteed Time on XMM-Newton. These observations provide
  a powerful tool to investigate the evolution of coronal activity
  in late-type convective stars and its dependence on magnetic field
  generation by dynamo processes. We discuss the motivations for this
  program and present some results for the SFRs sigma Orionis (∼2-5
  Myr) and Taurus-Auriga (∼1-10 Myr) as well as for the OCs IC 2602
  (∼30 Myr), alpha Persei (∼50 Myr), Praesepe (∼600 Myr) and the
  Hyades (∼600 Myr). We discuss imaging and spectral data provided by
  the EPIC MOS and PN detectors focussing on the determination of the
  cluster X-ray luminosity function and of the temperature structure,
  chemical abundances and time variability of cluster stars. <P />Based
  on observations collected with the ESA mission XMM-Newton as part of
  the Mission Scientist (R. Pallavicini) Guaranteed Time

---------------------------------------------------------
Title: Coronae of Cool Stars
Authors: Audard, M.; Drake, S. A.; Güdel, M.; Mewe, R.; Pallavicini,
   R.; Simon, T.; Singh, K. P.; Skinner, S. L.; White, N.
2004IAUS..219..243A    Altcode: 2003IAUS..219E.188A; 2003astro.ph.10032A
  We present preliminary results of grating observations of YY Mensae and
  V824 Arae by Chandra and XMM-Newton. Spectral features are presented
  in the context of the emission measure distributions, the coronal
  abundances, and plasma electron densities. In particular, we observe a
  coronal N/C enhancement in YY Men believed to reflect the photospheric
  composition (CN cycle). Finally, we interpret line broadening in YY
  Men as Doppler thermal broadening in its very hot corona.

---------------------------------------------------------
Title: Future Capabilities for Solar/Stellar Observations
Authors: Carpenter, K.; Hassler, D.; Berger, T.; Bastian, T.;
   Pallavicini, R.; Balachandran, S.
2003csss...12..359C    Altcode:
  This session outlines the potential instrumental capabilities for the
  observation of cool stars and the Sun. The individual contributions
  cover space-based solar missions (Hassler), ground-based solar
  optical/IR instruments (Berger), solar-stellar radio capabilities
  (Bastian), space-based stellar missions (Carpenter), ground-based
  optical (Pallavicini) and infrared facilities (Balachandran) for
  stellar observations.

---------------------------------------------------------
Title: XMM- Newton observations of open clusters
Authors: Franciosini, E.; Randich, S.; Pallavicini, R.
2003AdSpR..32.1143F    Altcode:
  We present observations of stellar clusters obtained with XMM-
  Newton as part of the Guaranteed Time program. We have obtained EPIC
  observations of the open clusters Praesepe, a Per, o Ori and Hyades and
  of the Taurus-Auriga star-forming region. The results of the analysis
  are presented and discussed, with emphasis on the imaging data. In all
  clusters a large number of new X-ray sources with no known catalogued
  optical counterpart has been detected. In σ Ori three X-ray sources
  coincide with very-low mass members of the cluster, including a brown
  dwarf candidate. The Praesepe observation does not show the discrepancy
  with the Hyades found by ROSAT, supporting the suggestion that this
  cluster may be formed by two merged clusters of different ages.

---------------------------------------------------------
Title: New modelling of a large long-duration X-ray flare on UX Ari
Authors: Livshits, I. M.; Livshits, M. A.; Pallavicini, R.
2003AdSpR..32.1181L    Altcode:
  We have carried out a new gas-dynamic simulation of the physical
  processes occurring in a fixed amount of plasma confined in coronal
  loops heated in the top. We chose the solution which explains both
  the time behaviour of the temperature and the energetics of the
  X-ray emission of a long-duration X-ray flare observed by BeppoSAX
  on UX Ari. This analysis makes it possible to obtain the length of
  the loop and the distribution of the temperature and 'density along
  the loop (with T<SUB>max</SUB> ≈ 100 MK and n<SUB>e</SUB> = (1 -
  3) · 10 <SUP>11</SUP> cm <SUP>-3</SUP>), as well as to estimate the
  X-ray flare area S ≈ 1022 cm <SUP>2</SUP>. Franciosini et al. (2001)
  have developed a time-dependent model of magnetic reconnection for the
  decay phase of the same flare. Our gas-dynamic solution corresponds
  to reconnection of middle-scale magnetic fields which in the model by
  Franciosini et al. (2001) corresponds to a degree n of the Legendre
  polynomial close to 5. The magnetic field strength is estimated to
  be about 100 G near the loop top. We argue that the shrinkage-effect
  plays a more important role during large long-duration X-ray stellar
  flares than in solar two-ribbon flares.

---------------------------------------------------------
Title: Why solar astronomers should be interested in stars
Authors: Pallavicini, R.
2003AdSpR..32..885P    Altcode:
  I discuss the scientific reasons why solar astronomers should be
  interested in other stars and why Solar Physics should be put in the
  broader context of Stellar Astrophysics. Selected topics include stellar
  interiors and helioseismology, dynamo action and activity cycles,
  stellar surface activity, stellar chromospheres, coronae and winds,
  and the study of the Sun in time.

---------------------------------------------------------
Title: The evolution of lithium depletion  in young open clusters:
    NGC 6475.
Authors: Sestito, P.; Randich, S.; Mermilliod, J. -C.; Pallavicini, R.
2003A&A...407..289S    Altcode: 2003astro.ph..5394S
  We have carried out a high resolution spectroscopic survey of the
  220-250 Myr old cluster <ASTROBJ>NGC 6475</ASTROBJ>: our main purpose
  is to investigate Li evolution during the early stages of the Main
  Sequence. We have determined Li abundances for 33 late F to K-type X-ray
  selected cluster candidates, extending the samples already available in
  the literature; for part of the stars we obtained radial and rotational
  velocities, allowing us to confirm the membership and to check for
  binarity. We also estimated the cluster metallicity which turned out to
  be over-solar ([Fe/H]=+0.14 +/- 0.06). Our Li analysis evidenced that
  (i) late F-type stars (T<SUB>eff</SUB> &gt;≈ 6000 K) undergo a very
  small amount of Li depletion during the early phases on the ZAMS; (ii)
  G-type stars (6000 &gt;≈ T<SUB>eff</SUB> &gt;≈ 5500 K) instead do
  deplete lithium soon after arrival on the ZAMS. Whereas this result is
  not new, we show that the time scale for Li depletion in these stars
  is almost constant between 100 and 600 Myr; (iii) we confirm that the
  spread observed in early K-type stars in younger clusters has converged
  by 220 Myr. No constraints can be put on later-type stars. (iv) Finally,
  we investigate the effect of metallicity on Li depletion by comparing
  NGC 6475 with the similar age cluster M 34, but we show that the issue
  remains open, given the uncertain metallicity of the latter cluster. By
  using the combined NGC 6475+M 34 sample together with the Hyades and
  the Pleiades, we compare quantitatively Li evolution from the ZAMS to
  600 Myr with theoretical predictions of standard models. <P />Based
  on observations collected at the European Southern Observatory.

---------------------------------------------------------
Title: Is Praesepe really different from the coeval Hyades cluster?
    The XMM-Newton view
Authors: Franciosini, E.; Randich, S.; Pallavicini, R.
2003A&A...405..551F    Altcode: 2003astro.ph..4519F
  The Praesepe open cluster represents a puzzle since it has about the
  same age as the Hyades, and only slightly different metallicity, yet
  previous ROSAT observations resulted in a detection rate of cluster
  sources significantly lower than for the Hyades. We present a new 50
  ksec observation of Praesepe performed with the EPIC instrument on
  board XMM-Newton, which resulted in the detection of ~ 200 sources,
  including 48 cluster members. We detected all solar-type (F-G) stars in
  the field of view, ~ 90% of the K stars and ~ 70% of the M stars. We
  find that the distribution of X-ray luminosities of solar-type
  Praesepe members is comparable to that of the Hyades, in contrast
  with the previous ROSAT results; however, the disagreement between
  the ROSAT and XMM-Newton results appears to be mostly due to X-ray
  faint Praesepe members falling outside the XMM-Newton field of view,
  while it is considerably reduced when considering only the subsample of
  stars in the ROSAT survey in common with the present observation. The
  finding supports an earlier suggestion that Praesepe may be formed by
  two merged clusters of different age.

---------------------------------------------------------
Title: The ICE spectrograph for PEPSI at the LBT: preliminary
    optical design
Authors: Pallavicini, Roberto; Zerbi, Filippo M.; Spano, Paolo;
   Conconi, Paolo; Mazzoleni, Ruben; Molinari, Emilio; Strassmeier,
   Klaus G.
2003SPIE.4841.1345P    Altcode:
  We present a preliminary design study for a high-resolution echelle
  spectrograph (ICE) to be used with the spectropolarimeter PEPSI under
  development at the LBT. In order to meet the scientific requirements
  and take full advantage of the peculiarities of the LBT (i.e. the
  binocular nature and the adaptive optics capabilities), we have designed
  a fiber-fed bench mounted instrument for both high resolution (R ≍
  100,000; non-AO polarimetric and integral light modes) and ultra-high
  resolution (R ≍ 300,000; AO integral light mode). In both cases,
  4 spectra per order (two for each primary mirror) shall be accomodated
  in a 2-dimensional cross dispersed echelle format. In order to obtain a
  resolution-slit product of ≍ 100,000 as required by the science case,
  we have considered two alternative designs, one with two R4 echelles
  in series and the other with a sigle R4 echelle and fiber slicing. A
  white-pupil design, VPH cross-dispersers and two cameras of different
  focal length for the AO and non-AO modes are adopted in both cases. It
  is concluded that the single-echelle fiber-slicer solution has to be
  preferred in terms of performances, complexity and cost. It can be
  implemented at the LBT in two phases, with the long-camera AO mode
  added in a second phase depending on the availability of funds and
  the time-scale for implementation of the AO system.

---------------------------------------------------------
Title: XMM-Newton Proposal 02002101
Authors: Pallavicini, Roberto
2003xmm..prop...11P    Altcode:
  We propose to observe the open cluster NGC 6475 (age ~200 Myr) to
  investigate the activity-rotation-age relationship of low-mass stars
  emerged from ROSAT observations. We will use XMM observations of the
  proposed cluster to go a factor of 10 deeper than ROSAT (to detect
  possible previously unseen low-luminosity populations) and to obtain
  spectral information on the brightest cluster members. We will compare
  the X-ray luminosity function of the cluster with the similar age
  cluster NGC 1039 and with younger and older clusters already observed
  by us with XMM. This comparison will provide strong constraints on the
  universality (or lack of) of the activity-rotation-age relationship
  in the crucial age interval between the Pleiades and the Hyades.

---------------------------------------------------------
Title: The Hot Corona of the Giant YY Mensae with Chandra and
    XMM-Newton
Authors: Audard, M.; Güdel, M.; Skinner, S. L.; Pallavicini, R.;
   Drake, S. A.; Mewe, R.
2003HEAD....7.1202A    Altcode: 2003BAAS...35..616A
  We present Chandra and XMM-Newton high-resolution X-ray spectra of
  the rapidly rotating giant YY Mensae. It belongs to the class of “FK
  Com stars”, i.e. single cool giant stars with projected equatorial
  velocities measured up to 110 km/s. Chandra and XMM-Newton provide
  excellent high-resolution X-ray spectra to study the properties of this
  extreme coronal source. The X-ray spectrum is dominated by a strong
  continuum component with bright emission lines, mostly from H-like
  transitions and highly ionized Fe lines (up to Fe XXV), indicative of
  a very high coronal temperature (≈ 3 keV). The Chandra High-Energy
  Transmission Grating Spectrometer data are ideal to study at very high
  resolution this hot coronal source. The Reflection Grating Spectrometer
  onboard XMM-Newton however provides better information on the cool
  coronal plasma, and on the carbon and nitrogen abundances. Although
  no obvious flare was detected in the light curves, YY Men's X-ray
  luminosity varied by a factor of two between the Chandra and XMM-Newton
  observations (log L<SUB>X</SUB> ≈ 32.16 - 32.42). We derive the
  coronal emission measure distribution, elemental abundances, and
  density estimates. <P />We acknowledge support by SAO grant GO2-3016X.

---------------------------------------------------------
Title: The AVES adaptive optics spectrograph for the VLT: status
    report
Authors: Pallavicini, Roberto; Delabre, Bernard; Pasquini, Luca;
   Zerbi, Filippo M.; Bonanno, Giovanni; Comari, Maurizio; Conconi, Paolo;
   Mazzoleni, Ruben; Santin, Paolo; Damiani, Francesco; Di Marcantonio,
   Paolo; Franchini, Mariagrazia; Spano, Paolo; Bonifacio, P.; Catalano,
   Santo; Molaro, Paolo P.; Randich, S.; Rodono, Marcello
2003SPIE.4841..715P    Altcode:
  We report on the status of AVES, the Adaptive-optics Visual
  Echelle Spectrograph proposed for the secondary port of the Nasmyth
  Adaptive Optics System (NAOS) recently installed at the VLT. AVES
  is an intermediate resolution (R ≍ 16,000) high-efficiency fixed-
  format echelle spectrograph which operates in the spectral band 500
  - 1,000 nm. In addition to a high intrinsic efficiency, comparable
  to that of ESI at Keck II, it takes advantage of the adaptive optics
  correction provided by NAOS to reduce the sky and detector contribution
  in background-limited observations of weak sources, thus allowing a
  further magnitude gain with respect to comparable non-adaptive optics
  spectrographs. Simulations show that the instrument will be capable
  of reaching a magnitude V = 22.5 at S/N &gt; 10 in two hours, two
  magnitudes weaker than GIRAFFE at the same resolution and 3 magnitudes
  weaker than the higher resolution UVES spectrograph. Imaging and
  coronographic functions have also been implemented in the design. We
  present the results of the final design study and we dicuss the
  technical and operational issues related to its implementation at the
  VLT as a visitor instrument. We also discuss the possibility of using a
  scaled-up non-adaptive optics version of the same design as an element
  of a double- or triple-arm intermediate-resolution spectrograph for the
  VLT. Such an option looks attractive in the context of a high-efficiency
  large-bandwidth (320 - 1,500 nm) spectrograph ("fast-shooter") being
  considered by ESO as a 2nd-generation VLT instrument.

---------------------------------------------------------
Title: BeppoSAX observations of CF Tucanae and TY Pyxidis
Authors: Franciosini, E.; Pallavicini, R.; Tagliaferri, G.
2003A&A...399..279F    Altcode:
  We present the results of BeppoSAX observations of the RS CVn binary
  systems CF Tuc and TY Pyx. A long-duration flare was detected on CF
  Tuc just at the beginning of the observation; a second smaller flare
  occurred about half a period later. The light curve of TY Pyx shows a
  significant orbital modulation of the quiescent emission with possible
  evidence for eclipses, and strong flares. We find that the coronae of
  the two stars are very similar: both systems have quiescent temperatures
  of ~ 10 and 20-25 MK, with only a factor of two difference in the
  emission measures. During the flares, temperatures of ~ 30-40 MK are
  reached; these temperatures are not high enough to give detectable
  hard X-ray emission in the PDS. Both stars have subsolar coronal
  metallicities: we confirm the very low coronal abundance of CF Tuc
  (Z ~ 0.1-0.2 Z<SUB>sun</SUB>), while for TY Pyx we find Z ~ 0.5-0.6
  Z<SUB>sun</SUB>. For both stars the coronal metallicities are in good
  agreement with their measured photospheric abundances.

---------------------------------------------------------
Title: PEPSI spectro-polarimeter for the LBT
Authors: Strassmeier, Klaus G.; Hofmann, Axel; Woche, Manfred F.; Rice,
   John B.; Keller, Christoph U.; Piskunov, N. E.; Pallavicini, Roberto
2003SPIE.4843..180S    Altcode:
  PEPSI (Postham Echelle Polarimetric and Spectroscopic Instrument) is
  to use the unique feature of the LBT and its powerful double mirror
  configuration to provide high and extremely high spectral resolution
  full-Stokes four-vector spectra in the wavelength range 450-1100nm. For
  the given aperture of 8.4m in single mirror mode and 11.8m in double
  mirror mode, and at a spectral resolution of 40,000-300,000 as designed
  for the fiber-fed Echelle spectrograph, a polarimetric accuracy between
  10<SUP>-4</SUP> and 10<SUP>-2</SUP> can be reached for targets with
  visual magnitudes of up to 17th magnitude. A polarimetric accuracy
  better than 10<SUP>-4</SUP> can only be reached for either targets
  brighter than approximately 10th magnitude together wiht a substantial
  trade-off wiht the spectral resolution or with spectrum deconvolution
  techniques. At 10<SUP>-2</SUP>, however, we will be able to observe
  the brightest AGNs down to 17th magnitude.

---------------------------------------------------------
Title: Evolution of lithium beyond the solar age: A Li survey of
    the old open cluster NGC 188
Authors: Randich, S.; Sestito, P.; Pallavicini, R.
2003A&A...399..133R    Altcode: 2002astro.ph.12098R
  We have determined Li abundances for 11 G-type stars in the 6-8 Gyr
  old open cluster <ASTROBJ>NGC 188</ASTROBJ>. These data significantly
  enlarge the number of cluster stars with Li measurements, allowing
  us to extend the investigation of Li depletion in open clusters to
  ages well beyond the age of the Sun. We have also inferred the cluster
  metallicity which turns out to be solar. We find that solar-type stars
  in NGC 188 are only slightly more Li depleted than the much younger
  <ASTROBJ>Hyades</ASTROBJ> and no more Li depleted than stars of similar
  temperature in the 2-4 Gyr younger cluster <ASTROBJ>M 67</ASTROBJ>. At
  variance with M 67, NGC 188 members show virtually no scatter in
  their Li abundances. Surprisingly, no solar-type star in NGC 188
  appears as Li depleted as the Sun or as the most Li depleted stars in
  M 67. We discuss the implications of these results for mechanisms of
  internal mixing and Li depletion in main sequence stars. <P />Based
  on observations collected at the Italian National Telescope Galileo.

---------------------------------------------------------
Title: Galactic open clusters: key tracers of stellar structure
    and evolution
Authors: Pallavicini, R.
2003MSAIS...3...74P    Altcode:
  Galactic open clusters are homogeneous samples of stars with
  approximately the same age and chemical composition but different
  masses, effective temperatures, rotation rates and magnetic
  activity. They provide a fundamental tool to test models of stellar
  structure and evolution and to investigate the formation and chemical
  evolution of the galactic disk. Recent advances in the study of open
  clusters are reviewed with emphasis on the determination of lithium and
  berillium abundances as tracers of internal mixing mechanisms and on the
  investigation of coronal activity and evolution from the X-ray emission
  of cluster stars. <P />Based on ground-based observations collected
  at ESO and TNG and on space observations collected with XMM-Newton

---------------------------------------------------------
Title: The complex XMM-RGS spectrum of the hot star sigma Orionis
Authors: Pallavicini, R.; Sanz-Forcada, J.; Franciosini, E.
2002hrxs.confE..29P    Altcode:
  We present a preliminary analysis of an XMM-Newton observation of the
  sigma Orionis cluster centered on the O9.5V star sigma Ori. In addition
  to the EPIC image, which shows the presence of about 240 sources, mostly
  low-mass PMS stars belonging to the cluster, a high statistics RGS
  spectrum is obtained for the central source. The EPIC image shows the
  presence of nearby sources, including a flaring one, which, although
  weaker, may contaminate the RGS spectrum of the central star. We
  present an analysis of the RGS and EPIC spectra of sigma Ori and of
  the EPIC spectra of the nearby sources and we discuss the possible
  contamination of the hot star RGS spectrum by the other sources.

---------------------------------------------------------
Title: XMM-Newton Observations of X-ray Luminous G-type Stellar
    Coronae
Authors: Scelsi, L.; Maggio, A.; Peres, G.; Sanz-Forcada, J.; Gondoin,
   Ph.; Pallavicini, R.
2002hrxs.confE..22S    Altcode:
  We present results obtained from the analysis of XMM-Newton spectra
  of the Hertzsprung-gap giant 31 Com and of the pre-main-sequence star
  HD 283572, two G-type stars in very different evolutionary phases,
  but having similar high X-ray luminosities. We discuss methodological
  issues related to the data analysis, as well as the results on the
  inferred properties of the stellar coronae.

---------------------------------------------------------
Title: XMM-Newton Spectroscopy of Two Hyades Stars
Authors: Franciosini, E.; Sanz-Forcada, J.; Maggio, A.; Pallavicini, R.
2002hrxs.confE..15F    Altcode:
  We present the results of XMM-Newton observations of two Hyades stars:
  the giant theta1 Tau and the solar-type star VB 50. From the analysis
  of RGS and EPIC spectra we derive the temperature structure and chemical
  abundances of the coronae of the two stars.

---------------------------------------------------------
Title: Chandra and XMM-Newton X-Ray Spectroscopy of the Hot Corona
    of YY Mensae
Authors: Audard, M.; Güdel, M.; Skinner, S. L.; Pallavicini, R.;
   Drake, S. A.; Mewe, R.
2002AAS...201.3307A    Altcode: 2002BAAS...34.1156A
  We present Chandra and XMM-Newton X-ray spectra of the rapidly rotating
  K giant YY Mensae (d = 290 pc). YY Men is a member of a loosely-defined
  class of rapidly rotating single cool giant stars (“FK Com stars”),
  whose outstanding property is a projected equatorial velocity measured
  up to 110 km/s, in contrast with the expected maximum of 6 km/s for
  giants. One of the leading theories to explain the extreme properties of
  FK Com stars suggests that they were formed by coalescence of a contact
  binary when one of the components entered into the giant stage. Previous
  observations have shown that its corona displays plasma with a very
  hot temperature of about 3 keV, with probably no or very little plasma
  at temperatures below 1 keV. The new X-ray observatories now provide
  excellent high-resolution X-ray spectra to study the coronal properties
  of this extreme coronal source. The X-ray spectrum is dominated by
  a strong continuum and by bright emission lines, mostly from H-like
  transitions and Fe XXIV lines. Thanks to its wavelength range and its
  sensitivity, the Reflection Grating Spectrometer onboard XMM-Newton
  provides important information on the presence of cool coronal plasma,
  mostly seen at wavelengths between 20 and 40 Å. Simultaneous EPIC
  CCD spectra also constrain the high-temperature component of the
  emission measure distribution. The Chandra High-Energy Transmission
  Grating Spectrometer data are ideal to study at very high resolution
  the short wavelength range of this hot coronal source. We derive
  the coronal emission measure distribution, elemental abundances,
  and density estimates. We acknowledge support by SAO grant GO2-3016X.

---------------------------------------------------------
Title: Multiwavelength analysis of Gl 355 (LQ Hya)
Authors: Covino, S.; Tagliaferri, G.; Bertone, E.; Cutispoto, G.;
   Messina, S.; Panzera, M. R.; Pasquini, L.; Pallavicini, R.; Randich,
   S.; Rodonò, M.; Setiawan, J.
2002ASPC..277..357C    Altcode: 2002sccx.conf..357C
  No abstract at ADS

---------------------------------------------------------
Title: BeppoSAX observations of CF Tuc and TY Pyx
Authors: Franciosini, E.; Pallavicini, R.; Maggio, A.; Tagliaferri,
   G.; Covino, S.
2002ASPC..277..473F    Altcode: 2002sccx.conf..473F
  No abstract at ADS

---------------------------------------------------------
Title: High-resolution ground-based spectroscopy: where and how ?
Authors: Pallavicini, R.
2002AN....323..288P    Altcode:
  An overview is presented of high-resolution optical spectrographs in
  operation or under development at large telescopes, with emphasis on
  those facilities best suited for the study of late-type stars and
  stellar surface inhomogeneities. Plans for the development of new
  high-resolution spectroscopic instruments are discussed with emphasis
  on the ICE spectrograph for the PEPSI spectropolarimeter at the LBT.

---------------------------------------------------------
Title: A new concept and a preliminary design for a high resolution
    (HR) and very-high resolution (VHR) spectrograph for the LBT
Authors: Zerbi, F. M.; Spanò, P.; Conconi, P.; Molinari, E.;
   Mazzoleni, R.; Pallavicini, R.; Strassmeier, K. G.
2002AN....323..499Z    Altcode: 2002astro.ph..3039Z
  A way to fully exploit the large collecting area of modern 8-10m
  class telescopes is high resolution spectroscopy. Many astrophysical
  problems from planetary science to cosmology benefit from spectroscopic
  observations at the highest resolution currently achievable and
  would benefit from even higher resolutions. Indeed in the era of
  8-10m class telescopes no longer the telescope collecting area but
  the size of the beam - which is related to the maximum size in which
  reflection gratings are manufactured - is what mainly limits the
  resolution. A resolution-slit product Rvarphi =~ 40,000 is the maximum
  currently provided by a beam of 20 cm illuminating the largest grating
  mosaics. We present a conceptual design for a spectrograph with Rvarphi
  =~ 80,000, i.e. twice as large as that of existing instruments. Examples
  of the possible exploitation of such a high Rvarphi value, including
  spectropolarimetry and very high resolution (R ~ 300,000), are discussed
  in detail. The new concept is illustrated through the specific case of
  a high resolution spectropolarimeter for the Large Binocular Telescope.

---------------------------------------------------------
Title: UVES Be observations of early-G dwarfs in old clusters
Authors: Randich, S.; Primas, F.; Pasquini, L.; Pallavicini, R.
2002A&A...387..222R    Altcode: 2002astro.ph..3155R
  We have obtained the first beryllium measurements of late F/early
  G-type stars in the old open cluster <ASTROBJ>M 67</ASTROBJ> (4.5 Gyr)
  and in the intermediate age cluster <ASTROBJ>IC 4651</ASTROBJ> (1.7
  Gyr). One member of the young cluster <ASTROBJ>IC 2391</ASTROBJ> ( ~
  50 Myr) was also observed. Our sample stars have effective temperatures
  within a range of +30-+380 K from the solar temperature. All our sample
  stars, including the Sun and the young cluster star have, within the
  errors, the same Be abundance. This result implies that late F/early
  G-type stars undergo very little (if any) Be depletion during their
  main-sequence life-time. Since these stars have undergone some Li
  depletion, our finding is indicative of shallow mixing, i.e. of a
  mixing process that can transport surface material deep enough for
  Li burning to occur, but not deep enough for Be burning. As shown in
  previous studies, the Li vs. Be diagram is a powerful diagnostic of
  stellar interiors. In this context, we do not find any evidence of
  correlated Li and Be depletion; furthermore, a comparison with various
  models shows that the Be pattern of our sample stars is compatible only
  with models including gravity waves. This class of models, however,
  cannot reproduce the Li observations of M 67. Based on observations
  collected at European Southern Observatory, Chile (65.L-0427). Part
  of the data were obtained as part of an ESO Service Mode run.

---------------------------------------------------------
Title: Beryllium abundances in old open clusters
Authors: Randich, S.; Primas, F.; Pasquini, L.; Pallavicini, R.
2002ASPC..274..240R    Altcode: 2002ohds.conf..240R
  No abstract at ADS

---------------------------------------------------------
Title: Observations of stellar coronae with XMM-Newton
Authors: Franciosini, E.; Sanz-Forcada, J.; Maggio, A.; Pallavicini, R.
2002cosp...34E.457F    Altcode: 2002cosp.meetE.457F
  We present observations of stars and stellar clusters obtained with
  XMM-Newton as part of the Guaranteed Time program. We have performed
  EPIC observations of the open clusters Praesepe,Per and Hyades and of
  the Taurus-Aurigae star-forming region. RGS spectra have been obtained
  for two stars in the Hyades (1 Tau = VB 71 and VB 50) and two stars
  in Taurus-Aurigae (HD 283572 and SU Aur). The results of the spatial
  and spectral analysis will be presented and discussed.

---------------------------------------------------------
Title: High-energy radiation from outer stellar atmospheres
Authors: Pallavicini, R.
2002css1.book..875P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Scientific Objectives and Design Study of an Adaptive Optics
    Visual Echelle Spectrograph and Imager Coronograph (AVES-IMCO)
    for the NAOS Visitor Focus at the VLT
Authors: Pallavicini, Roberto; Zerbi, Filippo; Beuzit, Jean-Luc;
   Bonanno, Giovanni; Bonifacio, Piercarlo; Comari, Maurizio; Conconi,
   Paolo; Delabre, Bernard; Franchini, Mariagrazia; di Marcantonio,
   Paolo; Lagrange, Anne-Marie; Mazzoleni, Ruben; Molaro, Paolo; Pasquini,
   Luca; Santin, Paolo
2002sdef.conf..205P    Altcode:
  We present the scientific case for an Adaptive Optics Visual Echelle
  Spectrograph and Imager Coronograph (AVES-IMCO) that we propose as a
  visitor instrument for the secondary port of NAOS at the VLT. We show
  that such an instrument would be ideal for intermediate resolution
  (R=16,000) spectroscopy of faint sky-limited objects down to a magnitude
  of V=24.0 and will complement very effectively the near-IR imaging
  capabilities of CONICA. We present examples of science programmes
  that could be carried out with such an instrument and which cannot be
  addressed with existing VLT instruments. We also report on the result
  of a two-year design study of the instrument, with specific reference
  to its use as parallel instrument of NAOS.

---------------------------------------------------------
Title: Multiwavelenght analysis of Gl 355 (LQ Hya)
Authors: Covino, S.; Tagliaferri, G.; Bertone, E.; Cutispoto, G.;
   Messina, S.; Panzera, M. R.; Pasquini, L.; Pallavicini, R.; Randich,
   S.; Rodono', M.; Setiawan, J.
2001astro.ph..9410C    Altcode:
  We discuss ROSAT, ASCA, {\it Beppo}SAX and optical observations of
  the young active star Gl 355. During the ROSAT observation a strong
  flare was detected with a peak flux more than an order of magnitude
  larger than the quiescent level. Spectral analysis of the data allows
  us to study the temperature and emission measure distribution, and
  the coronal metal abundance, for the quiescent phase and, in the case
  of ROSAT, also during the evolution of the flare. We have modeled
  the flare and derived a loop semi--length of the order of $\sim 1.5$
  stellar radii. ROSAT, ASCA and {\it Beppo}SAX data suggest that the
  coronal abundance of Gl 355 is subsolar, in the range $0.1 ÷0.3
  Z/Z_\odot$. A preliminary analysis of optical spectra allows us to
  compare the photospheric and coronal metal abundances.

---------------------------------------------------------
Title: BeppoSAX observation of a large long-duration X-ray flare
    from UX Arietis
Authors: Franciosini, E.; Pallavicini, R.; Tagliaferri, G.
2001A&A...375..196F    Altcode:
  We present two X-ray observations of the RS CVn binary system UX Arietis
  performed with BeppoSAX in August 1997 and August 1998. A large flare
  lasting for about 1 day was detected during the first observation, while
  the star was quiescent during the second one. Hard X-ray emission up
  to ~ 50 keV was detected in the PDS instrument during the rise and
  at the peak of the flare. Time-resolved spectroscopy of the flare
  with the LECS and MECS detectors shows that temperatures as high as
  ~ 100 MK were reached at the flare peak; such high temperatures are
  responsible for the high-energy tail seen in the PDS. We confirm that
  the coronal abundance of UX Ari is strongly subsolar (Z/Z<SUB>sun</SUB>
  =~ 0.2-0.3); no significant variation of the metallicity is observed
  during the flare. We show that the new LECS response matrices released
  in January 2000 seem to solve the problem of the high hydrogen column
  densities systematically found in previous BeppoSAX observations of
  stellar coronae. We find in fact for the quiescent spectrum N_H =
  2.6 x 10<SUP>19</SUP> cm<SUP>-2</SUP>, compatible with the expected
  value; during the flare N_H is higher by a factor 5, probably due
  to the ejection of material. The flare evolution has been analysed
  using the two-ribbon flare model by Poletto et al. (\cite{poletto88}),
  finding a very good agreement between the model and the observations.

---------------------------------------------------------
Title: Lithium in the intermediate age cluster <ASTROBJ>NGC
3680</ASTROBJ>: Following Li evolution along the C-M diagram
Authors: Pasquini, L.; Randich, S.; Pallavicini, R.
2001A&A...374.1017P    Altcode:
  We present an analysis of high resolution spectroscopic observations
  (R ~ 30 000, S/N=60-150) of 24 members of the intermediate age ( ~
  1.5 Gyr) open cluster NGC 3680, covering all regions of the cluster
  colour-magnitude (C-M) diagram where cluster members are known to
  exist. These observations represent in many aspects challenges to our
  understanding of stellar interior and mixing. Four main sequence G
  stars have, within the errors, the same Li abundance, 0.3 dex lower
  than similar stars in the ~ 1 Gyr younger Hyades but comparable with
  those observed in the coeval cluster <ASTROBJ>IC 4651</ASTROBJ>. The
  cluster shows a clear Li-dip located around the turn-off; two stars on
  the upper part of the turn-off are out of the dip and reach solar system
  meteoritic Li abundances. Just above the turn-off, in a very small range
  of magnitudes ( ~ 0.2 in V), a factor of ~ 5 Li depletion occurs. This
  sudden decrease explains puzzling results recently obtained on field
  subgiants but it is not at all reproduced by standard (e.g. no rotation,
  no diffusion) models, whereas it is in somewhat better agreement with
  the predictions of recent models which include rotational mixing and
  atomic diffusion. Out of the six cluster giants, one is probably a
  binary; of the remaining five single cluster members, three have a Li
  abundance log n(Li) ~ 1.1 while two have Li abundances from a factor 6
  to more than a factor 30 lower than the other three. The star with no
  detected Li is the coolest and most luminous object in the sample and
  is most likely an AGB star; the other has instead a similar magnitude
  and effective temperature as the three more Li rich giants. The reasons
  for this difference in Li abundance among otherwise similar stars can
  be ascribed either to differential depletion during main-sequence
  or post-main sequence evolution, possibly induced by rotation, or
  to differences in the evolutionary status of these evolved stars. By
  comparing our results with those found for clusters of similar age and
  for field stars, we find that none of the possible scenarios gives
  a fully satisfactory explanation if the present population of NGC
  3680 giants reflect the expected ratio of clump vs. first-ascent RGB
  stars. If the more abundant Li-rich giants in NGC 3680 are indeed clump
  giants, their relatively high Li content requires that Li is produced,
  or brought to the surface, between the tip of the RGB and the clump,
  which is not consistent with observations of the similar age cluster
  NGC 752, where the more abundant, presumably clump giants have low
  Li abundances. Finally, we have used our spectra to determine the
  metallicity of the cluster giants, finding [Fe/H]=-0.17+/-0.12. This
  value is in very good agreement with that derived from spectral
  indexes analysis, but substantially lower than the value inferred
  from Strömgren photometry. Based on observations collected at ESO,
  la Silla, and at the VLT.

---------------------------------------------------------
Title: Membership, lithium, and metallicity in the young open clusters
<ASTROBJ>IC 2602</ASTROBJ> and <ASTROBJ>IC 2391</ASTROBJ>: Enlarging
    the sample
Authors: Randich, S.; Pallavicini, R.; Meola, G.; Stauffer, J. R.;
   Balachandran, S. C.
2001A&A...372..862R    Altcode: 2001astro.ph..3260R
  We present lithium abundances for ~ 50 X-ray selected candidate
  members of the 30-50 Myr old open clusters IC 2602 and IC 2391. These
  data enlarge and extend to cooler temperatures previous Li surveys
  of these clusters by Stauffer et al. (\cite{sta89}) and Randich et
  al. (\cite{R97}). We also give for the first time an estimate of
  the metallicity of the two clusters which turns out to be close to
  solar. Radial velocity measurements together with Hα chromospheric
  emission and the presence/absence of other spectroscopic features
  are used to ascertain the membership status for the sample stars not
  yet confirmed as cluster members; rotational velocities have also
  been determined for all sample stars. Stars more massive than ~
  1 M<SUB>sun</SUB> in both clusters show no sign of significant Li
  depletion, while lower mass stars are all lithium depleted, with the
  amount of Li depletion increasing to cooler temperatures. We confirm
  that the late-G and early-K stars in IC 2602 present a star-to-star
  scatter in Li abundances similar to, but not as large as the one
  in the <ASTROBJ>Pleiades</ASTROBJ>. A scatter is also seen among
  late-K and M dwarfs. Unlike in the Pleiades and <ASTROBJ>Alpha
  Per</ASTROBJ> clusters, the scatter among early-K stars in IC 2602
  shows only marginal correlation with rotation. Our data suggest
  that the drop-off of lithium towards lower masses may start at
  an earlier color in IC 2391 than in IC 2602, but larger cluster
  samples are needed to confirm this result. In addition, whereas G
  and early K stars in the two clusters are, on average, more Li rich
  than their counterparts in the Pleiades, a fraction of the coolest
  stars, in particular in IC 2391, are as depleted as the lowest-Li
  Pleiades stars of the same mass. If they continue depleting Li on
  their way to the main sequence, they are expected to be more Li
  depleted than the Pleiades at the age of the latter cluster. Based
  on observations carried out at the European Southern Observatory,
  La Silla, Chile. Tables 2-5 are also available in electronic form
  at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5})
  or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/372/862

---------------------------------------------------------
Title: High Resolution Spectroscopy with the LBT
Authors: Pallavicini, R.
2001slbt.work...95P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Quiescent and flare analysis for the chromospherically active
    star <ASTROBJ>Gl 355</ASTROBJ> (<ASTROBJ>LQ Hya</ASTROBJ>)
Authors: Covino, S.; Panzera, M. R.; Tagliaferri, G.; Pallavicini, R.
2001A&A...371..973C    Altcode: 2001astro.ph..3473C
  We discuss ROSAT and ASCA observations of the young active star
  <ASTROBJ>Gl 355</ASTROBJ>. During the ROSAT observation a strong
  flare was detected with a peak flux more than an order of magnitude
  larger than the quiescent level. Spectral analysis of the data allows
  us to study the temperature and emission measure distribution, and
  the coronal metal abundance, for the quiescent phase and, in the
  case of ROSAT, also during the evolution of the flare. The global
  coronal metallicity Z/Z<SUB>sun</SUB> ~ 0.1 derived from both ROSAT
  and ASCA data is much lower than solar and presumably also much lower
  than the photospheric abundance expected for this very young star. The
  temperature structure of the quiescent corona was about the same during
  the various observations, with a cooler component at T<SUB>1</SUB>
  ~ 7 MK and a hotter component (to which only ASCA was sensitive) at
  T<SUB>2</SUB> ~ 20 MK. During the flare, the low temperature component
  remained approximately constant and equal to the quiescent value, while
  the high-temperature component was the only one that varied. We have
  modeled the flare with the hydrodynamic-decay sustained-heating approach
  of Reale at al. (1997) and we have derived a loop semi-length of the
  order of ~ 1.5 stellar radii, i.e. much larger than the dimensions of
  flares on the Sun, but comparable with the typical dimensions inferred
  for other stellar flares. We have compared the derived loop size with
  that estimated with a simpler (but physically inconsistent) approach,
  finding that for this, as well for several other stellar flares, the
  two methods give comparable loop sizes. Possible causes and consequences
  of this result are discussed.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Lithium abundances in IC 2602
    and IC 2391 (Randich+, 2001)
Authors: Randich, S.; Pallavicini, R.; Meola, G.; Stauffer, J. R.;
   Balachandran, S. C.
2001yCat..33720862R    Altcode:
  Lithium abundances and [Fe/H] for a sample of late-type stars in the
  young open clusters IC 2602 and IC 2391. Abundances are based on high
  resolution spectra obtained at ESO (3.6m + CASPEC) and CTIO (4m +
  echelle spectrograph) (4 data files).

---------------------------------------------------------
Title: A Long BeppoSAX Observation of YY Gem (CD-ROM Directory:
    contribs/tagliaf)
Authors: Tagliaferri, G.; Covino, S.; Panzera, M. R.; Pallavicini,
   R.; Schmitt, J. H. M. M.
2001ASPC..223.1177T    Altcode: 2001csss...11.1177T
  No abstract at ADS

---------------------------------------------------------
Title: Coronal X-ray Emission of HD 9770: The ASCA Observation
(CD-ROM Directory: contribs/panzera)
Authors: Panzera, M. R.; Covino, S.; Pallavicini, R.; Tagliaferri, G.
2001ASPC..223.1108P    Altcode: 2001csss...11.1108P
  No abstract at ADS

---------------------------------------------------------
Title: Coordinated BeppoSAX and VLA observations of UX Arietis
(CD-ROM Directory: contribs/francio1)
Authors: Franciosini, E.; Pallavicini, R.; Bastian, T.; Chiuderi-Drago,
   F.; Randich, S.; Tagliaferri, G.; Massi, M.; Neidhöfer, J.
2001ASPC..223..930F    Altcode: 2001csss...11..930F
  No abstract at ADS

---------------------------------------------------------
Title: The XMM-Newton view of stellar coronae: X-ray spectroscopy
    of the corona of <ASTROBJ>AB Doradus</ASTROBJ>
Authors: Güdel, M.; Audard, M.; Briggs, K.; Haberl, F.; Magee, H.;
   Maggio, A.; Mewe, R.; Pallavicini, R.; Pye, J.
2001A&A...365L.336G    Altcode:
  We report results of deep X-ray observations of <ASTROBJ>AB
  Doradus</ASTROBJ> obtained with the XMM-Newton observatory during its
  Performance Verification phase. The main objective of the analysis
  is a study of the spectral variability of coronal plasma in a
  very active star, including investigations of the variable thermal
  structure, abundance variations, and possible density changes during
  flares. <ASTROBJ>AB Dor</ASTROBJ> revealed both quiescent and flaring
  emission. The RGS spectra show flux changes in lines of highly ionized
  Fe during the flares, and an increase of the continuum. Elemental
  abundances increase in the early flare phases, by a factor of three. The
  quiescent abundances are lower than corresponding solar photospheric
  values, and tend to increase with increasing first ionization potential,
  contrary to the behavior in the solar corona. High-resolution spectra
  show an average density of the cool plasma of ~3 10<SUP>10</SUP>
  cm<SUP>-3</SUP>; this value does not change during the flares. We
  analyse and model the temporal behavior of heating and cooling, and
  present model results for one of the flares. We find that magnetic
  loops with a semilength of the order of 2.5 10<SUP>10</SUP> cm ~ 0.3
  R_star are involved. Based on observations obtained with XMM-Newton,
  an ESA science mission with instruments and contributions directly
  funded by ESA Member States and the USA (NASA).

---------------------------------------------------------
Title: Stellar coronal activity
Authors: Pallavicini, R.
2001AdSpR..26.1713P    Altcode:
  I review recent results on coronal activity in late-type stars
  stressing the similarities and differences with respect to solar
  coronal activity. The emphasis is on recent stellar observations by
  ROSAT, ASCA and SAX and on prospects for future observations by AXAF
  and XMM. Reviewed topics include X-ray emission in different parts of
  the HR diagram, cool stars in open clusters and star forming regions,
  and X-ray spectroscopy of coronal sources.

---------------------------------------------------------
Title: Searching for New, Unknown, Late-Type Stars, in the Coma
Berenices Open Cluster (CD-ROM Directory: contribs/garcia)
Authors: García López, R. J.; Randich, S.; Zapatero Osorio, M. R.;
   Pallavicini, R.
2001ASPC..223.1414G    Altcode: 2001csss...11.1414G
  No abstract at ADS

---------------------------------------------------------
Title: X-ray emission from the active star Gl 355 (LQ Hya)
Authors: Covino, S.; Panzera, M. R.; Tagliaferri, G.; Pallavicini, R.
2001ASPC..234..101C    Altcode: 2001xras.conf..101C
  No abstract at ADS

---------------------------------------------------------
Title: The XMM-Newton view of stellar coronae: Coronal structure in
    the <ASTROBJ>Castor</ASTROBJ> X-ray triplet
Authors: Güdel, M.; Audard, M.; Magee, H.; Franciosini, E.; Grosso,
   N.; Cordova, F. A.; Pallavicini, R.; Mewe, R.
2001A&A...365L.344G    Altcode:
  We present results of a comprehensive X-ray investigation of the
  multiple stellar system <ASTROBJ>Castor</ASTROBJ> AB + <ASTROBJ>YY
  Gem</ASTROBJ>. The observations were obtained with the XMM-Newton
  observatory. We report the first spatially separated detection
  and identification of both <ASTROBJ>Castor</ASTROBJ> A and B as
  frequently flaring X-ray sources. Spectral modeling of the <ASTROBJ>YY
  Gem</ASTROBJ> and <ASTROBJ>Castor</ASTROBJ> coronal sources indicates
  a broad plasma distribution between 2-15 MK. Elemental abundances are
  found to be below solar photospheric values, with the abundance of Ne
  being highest ( ~ 0.7 times solar photospheric). The abundances increase
  during a large flare, most notably for Fe. The O Vii He-like line
  triplet indicates average coronal densities of the cooler plasma of a
  few times 10<SUP>10</SUP> cm<SUP>-3</SUP> for <ASTROBJ>YY Gem</ASTROBJ>
  and <ASTROBJ>Castor</ASTROBJ>. The <ASTROBJ>YY Gem</ASTROBJ> light curve
  shows three deep eclipses, indicating that the coronae of both binary
  components are similarly active and are relatively compact. A 3-D light
  curve inversion shows that coronal active regions follow density scale
  heights compatible with spectroscopically measured temperatures. The
  dominant densities also agree with spectroscopic values. Most active
  regions are located between +/- 50 degrees latitude, in agreement
  with findings from previous Doppler imaging. We also report the
  tentative detection of line broadening due to orbital motion. Based
  on observations obtained with {\it XMM-Newton}, an ESA science mission
  with instruments and contributions directly funded by ESA Member States
  and the USA (NASA).

---------------------------------------------------------
Title: A ROSAT HRI study of the open cluster NGC 3532 (CD-ROM
Directory: contribs/francio2)
Authors: Franciosini, E.; Randich, S.; Pallavicini, R.
2001ASPC..223.1408F    Altcode: 2001csss...11.1408F
  No abstract at ADS

---------------------------------------------------------
Title: Optical follow-up of ROSAT discovered candidate members of
    the open cluster Coma Berenices
Authors: García López, R. J.; Randich, S.; Zapatero Osorio, M. R.;
   Pallavicini, R.
2000A&A...363..958G    Altcode:
  We have carried out an optical follow-up of twelve ROSAT discovered
  candidate members of the Coma Berenices open cluster. VRI photometry
  and low resolution ( ~ 3 Å) spectroscopy in the range 3800-7000
  Åwere performed to obtain colour-magnitude diagrams, proper motions,
  spectral types, chromospheric activity levels and radial velocities
  that allow us to establish whether or not these candidates are reliable
  cluster members. Only four of these objects show optical photometry
  marginally compatible with the main sequence delineated by known
  cluster stars. They also exhibit spectral types corresponding to late-K
  and early-M, and radial velocities which are not inconsistent with
  membership in Coma Berenices. The proper motions of these candidates
  are, however, very high and incompatible with the small value associated
  with the cluster. Thus, none of the ROSAT candidates can be considered
  members of Coma Berenices. This result tends to favour the hypothesis
  that the mass of the cluster and its average mass density are lower than
  what is required for stability, allowing the cluster dissolution by
  the escape of the less massive stars. We discuss the probable nature
  of these objects on the basis of the available information. From
  our radial velocity observations we infer that five of them could be
  formed by multiple stars. In particular, we have discovered one W-type
  W UMa contact binary system (K6 spectral type) which is, in addition,
  a visual companion to a cooler star. Based on observations made with
  the Isaac Newton telescope, operated on the island of La Palma by
  the Isaac Newton Group in the Spanish Observatorio del Roque de los
  Muchachos, with the IAC80 telescope and with the European Space Agency
  OGS telescope operated on the island of Tenerife by the Instituto de
  Astrofísica de Canarias in the Spanish Observatorio del Teide of the
  Instituto de Astrofísica de Canarias.

---------------------------------------------------------
Title: High-Resolution X-Ray Spectroscopy of Zeta Puppis and Eta
    Carinae with the RGS on XMM
Authors: Leutenegger, M. A.; Audard, M.; Behar, E.; den Boggende,
   A. J.; Brinkman, A. C.; Branduardi-Raymont, G.; Cottam, J.; Erd,
   C.; Ferringo, C.; Guedel, M.; den Herder, J. W.; Kaastra, J. S.;
   Kahn, S. M.; McGee, J.; Mewe, R.; Paerels, F. B. S.; Pallavicini,
   R.; Peterson, J. R.; Rasmussen, A. P.; Raux, G.; Sako, M.; Tamura,
   T.; Sakelliou, I.; Thomsen, K.; de Vries, C.
2000HEAD....5.4201L    Altcode: 2000BAAS...32.1254L
  We present high-resolution X-ray spectra of massive stars Zeta Puppis
  and Eta Carinae obtained with the Reflection Grating Spectrometer (RGS)
  onboard the XMM/Newton observatory. The spectrum of Zeta Puppis has many
  emission lines, including bright, broad hydrogenic and helium-like lines
  from oxygen and nitrogen. Analysis of these lines indicates a plasma
  density of at least 10<SUP>10</SUP> {cm}<SUP>-3</SUP>. The spectrum
  of Eta Carinae is dominated by the bright hydrogenic nitrogen line. We
  will present the analysis of the spectra and discuss implications.

---------------------------------------------------------
Title: Design study of an adaptive optics visual echelle spectrograph
    and imager for the VLT
Authors: Pallavicini, Roberto; Pasquini, Luca; Delabre, Bernard; Hubin,
   Norbert N.; Conconi, Paolo; Mantegazza, L.; Mazzoleni, R.; Molinari,
   Emilio; Zerbi, Filippo M.; Molaro, Paolo P.; Bonifacio, P.; Santin,
   Paolo; Dimarcantonio, P.; Franchini, Mariagrazia; Bonanno, Giovanni;
   Bruno, Pietro; Cosentino, Rosario; Scuderi, Salvatore; Catalano,
   Santo; Rodono, M.; Caldara, Pasquale; Damiani, F.; Comari, Maurizio;
   Monai, S.; Passaretta, F.
2000SPIE.4008..167P    Altcode:
  We present a preliminary design study for an adaptive optics visual
  echelle spectrograph and imager/coronograph for use as parallel
  instrument of the Nasmyth Adaptive Optics System (NAOS) on unit UT3
  of the VLT. The spectrograph is intended for intermediate resolution
  spectroscopy of faint sources. It could be used for observations of
  late-type dwarfs in distant Galactic clusters and in galaxies of the
  local group as well as for spectroscopy of extra galactic objects
  like quasars and Lyman break galaxies down to a limiting magnitude
  of V equals 22.5. The implementation of an imaging gand coronograph
  mode increases the versatility of the instrument and its scientific
  objectives. The instrument takes advantage of Adaptive Optics at visible
  wavelengths both for imaging and spectroscopy. With NAOS at the VLT,
  the light concentration in these bands will be above approximately
  60 percent of the flux in a 0.3 arcsec aperture for typical Paranal
  conditions. Simulations show that a gain of more than one magnitude
  with respect to compatible non-adaptive optical spectrography will be
  possible for sky- and/or detector limited observations. In addition,
  the smaller diffraction limit in the optical than in the IR will
  allow a significant gain in imaging and coronography as well. Finally,
  the instrument will allow gathering unprecedented experience on the
  performances of AO at visible wavelengths, which will be fundamental
  for further development of AO systems, in particular for very large
  telescopes.

---------------------------------------------------------
Title: A ROSAT HRI study of the open cluster NGC 3532
Authors: Franciosini, E.; Randich, S.; Pallavicini, R.
2000A&A...357..139F    Altcode: 2000astro.ph..3091F
  NGC 3532 is a very rich southern open cluster of age ~ 200-350
  Myr; it is therefore a good candidate to investigate the X-ray
  activity-age-rotation relationship at ages intermediate between
  the Pleiades and the Hyades, where, to our knowledge, X-ray studies
  exist for only one cluster (NGC 6475). We have performed an X-ray
  study of NGC 3532 using HRI observations retrieved from the ROSAT
  archive. The observations have a limiting sensitivity L<SUB>x</SUB> ~
  4 x 10<SUP>28</SUP> erg sec<SUP>-1</SUP> in the center of the field. We
  detected ~ 50 X-ray sources above a 4 sigma threshold, half of which
  have a known optical counterpart within 10 arcsec; 15 of the X-ray
  sources have at least one cluster member as optical counterpart. A
  comparison of NGC 3532 with the nearly coeval cluster NGC 6475 indicates
  that the former cluster is considerably X-ray underluminous with respect
  to NGC 6475. However, because of the existence of possible selection
  effects, additional X-ray and optical observations are needed before
  definitively concluding that the X-ray properties of NGC 3532 and NGC
  6475 are significantly different.

---------------------------------------------------------
Title: Evolution of lithium in solar-type stars: clues from
    intermediate age clusters
Authors: Randich, S.; Pasquini, L.; Pallavicini, R.
2000A&A...356L..25R    Altcode: 2000astro.ph..3022R
  We present Li abundances for 14 solar-type stars in the intermediate age
  ( ~ 2 Gyr) clusters IC 4651 and NGC 3680. The log n(Li) vs. effective
  temperature distributions are compared with those of the similar age
  cluster NGC 752, of the younger Hyades (600 Myr) and of the older M
  67 (4.5 Gyr) and NGC 188 (6-7 Gyr) clusters. Neither IC 4651 nor NGC
  3680 show the dispersion in Li which is observed in M 67. The 2 Gyr
  clusters have very similar Li vs. T_eff distributions; in addition,
  stars in the upper envelope of the M 67 distribution have the same Li
  content as stars in the 2 Gyr clusters, suggesting that either they
  have not suffered any significant depletion between ~ 2 and 4.5 Gyr
  or they had a much slower Li depletion. Mechanisms that lead to Li
  depletion on the main sequence are discussed in the light of these
  observations. None of the existing models seem to reproduce well the
  observed features. Based on observations carried out at the European
  Southern Observatory, La Silla, Chile

---------------------------------------------------------
Title: Twin X-ray flares and the active corona of AB Dor observed
    with BeppoSAX
Authors: Maggio, A.; Pallavicini, R.; Reale, F.; Tagliaferri, G.
2000A&A...356..627M    Altcode:
  We present two X-ray observations of the young, active star AB Dor,
  performed with BeppoSAX on Nov 9 and Nov 29 1997, and lasting 50 ksec
  and 140 ksec, respectively. Two, quite similar, large flares occurred
  during these observations, characterized by a 100-fold increase of
  the X-ray flux, peak temperatures of about 10<SUP>8</SUP> K, and peak
  emission measures of ~ 5 x 10<SUP>54</SUP> cm<SUP>-3</SUP>. We have
  performed a detailed, time-resolved analysis of the LECS and MECS
  X-ray spectra during the flares, and also in the subsequent quiescent
  phases. We have derived a metal abundance of the coronal plasma about
  half the photospheric one, with no significant increase during the
  flaring events. However, abundance variations of less than a factor
  ~ 3 cannot be excluded, within our statistical uncertainties. The
  exponential decay of the X-ray light curves, and the time evolution
  of plasma temperature and emission measure are similar to those
  observed in compact solar flares. The analysis of the flare decay,
  following the method of Reale et al. (1997), indicates the presence
  of sustained heating, and yields coronal loop maximum heights smaller
  than (but comparable with) the stellar radius, in both cases. The
  flares occurred at different rotation phases, and in one case, the
  decay was observed for one entire rotation period with no evidence of
  self-eclipse by the star. We conclude that the flaring loops may be
  located in the circumpolar region of AB Dor, but they do not appear
  to be related in any way with the large magnetic structures which
  sustain the well-known prominences of AB Dor, at several stellar radii
  above the surface. During the quiescent phase, lasting two rotation
  periods after the second flare, we have found evidence of significant
  low-level variability but no indication of rotational modulation. This
  variability, together with the high plasma temperature ( ~ 25 MK)
  and large emission measure (&lt;~ 10<SUP>53</SUP> cm<SUP>-3</SUP>),
  are interpreted in the framework of a saturated corona.

---------------------------------------------------------
Title: The active binary star II Pegasi with it BeppoSAX
Authors: Covino, S.; Tagliaferri, G.; Pallavicini, R.; Mewe, R.;
   Poretti, E.
2000A&A...355..681C    Altcode: 1999astro.ph.11352C
  <ASTROBJ>II Peg</ASTROBJ> is an ideal target to study stellar activity
  and flares, since intense and long lasting flares have been frequently
  detected from this system at all wavelengths. We report here about
  a BeppoSAX observation of <ASTROBJ>II Peg</ASTROBJ>. We followed the
  system for ~ 19 hours on December 5 and 6 1997 with BeppoSAX and the
  X-ray light curve resembles the typical behavior of a decay phase of a
  long-lasting flare. The spectral analysis shows that the <ASTROBJ>II
  Peg</ASTROBJ> X-ray spectrum is described by a two-temperature
  components, with the two dominant temperatures centered in the range of
  9-11 and 24-26 MK. The derived coronal metal abundance is low ( Z ~ 0.2
  Z_sun) compared to recent determinations of the photospheric abundance
  (Z ~ 0.6 Z_sun). Some possible explanations for this phenomenology
  are reviewed. As for most other stellar coronal sources observed
  with BeppoSAX, we find that in order to fit the BeppoSAX spectra an
  interstellar column density about a factor ten higher than previously
  determined is required.

---------------------------------------------------------
Title: Lithium in Young Open Clusters
Authors: Pallavicini, R.; Randich, S.; Stauffer, J. R.; Balachandran,
   S. C.
2000IAUS..198..350P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: EVN observations of the quiescent radio emission of HR1099
Authors: Trigilio, C.; Umana, G.; Catalano, S.; Pallavicini, R.;
   Tagliaferri, G.
2000evn..conf..173T    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: High-resolution spectroscopy of X-ray serendipitous sources
Authors: Tagliaferri, G.; Cutispoto, G.; Pallavicini, R.; Pastori,
   L.; Pasquini, L.; Randich, M. S.; Rodonò, M.
2000satp.work..115T    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A ROSAT HRI study of the open cluster NGC 6633
Authors: Franciosini, E.; Randich, S.; Pallavicini, R.
2000ASPC..198..447F    Altcode: 2000scac.conf..447F
  No abstract at ADS

---------------------------------------------------------
Title: Stellar Clusters and Associations: Convection, Rotation,
    and Dynamos
Authors: Pallavicini, R.; Micela, G.; Sciortino, S.
2000ASPC..198.....P    Altcode: 2000scac.conf.....P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium abundances and metallicity in the young open clusters
    IC 2602 and IC 2391
Authors: Meola, G.; Randich, S.; Pallavicini, R.; Stauffer, J. R.;
   Balachandran, S.
2000ASPC..198..285M    Altcode: 2000scac.conf..285M
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in the Open Cluster NGC 6475
Authors: Randich, S.; Pallavicini, R.; Mermilliod, J. -C.
2000IAUS..198..287R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in Cool Stars Detected in EUV Surveys
Authors: Tagliaferri, G.; Pastori, L.; Cutispoto, G.; Pallavicini, R.
2000IAUS..198..366T    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-ray Spectroscopy of Stellar Coronae with BeppoSAX
Authors: Pallavicini, R.; Tagliaferri, G.; Maggio, A.
2000AdSpR..25..517P    Altcode:
  We report on preliminary results of stellar coronae observations by
  BeppoSAX with emphasis on our own observations of the RS CVn binary
  UX Arietis and of the young rapidly rotating star AB Doradus. We
  discuss the temperature, emission measure distribution and elemental
  abundances derived from these observations and compare the results with
  those obtained previously by ASCA. We also report on the detection by
  BeppoSAX of hard (&gt;20 keV) X-ray emission from large stellar flares,
  and discuss briefly possible interpretations of this detection

---------------------------------------------------------
Title: High resolution optical spectrographs for large telescopes
Authors: Pallavicini, R.
2000MmSAI..71..869P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in open clusters
Authors: Pallavicini, R.; Pasquini, L.; Randich, S.
2000satp.work..107P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Commission 36: Theory of Stellar Atmospheres: (Theorie des
    Atmospheres Stellaires)
Authors: Pallavicini, R.; Dravins, D.; Barbuy, B.; Cram, L.; Hubeny,
   I.; Owocki, S.; Saio, H.; Sasselov, D.; Spite, M.; Stepien, K.;
   Wehrse, R.
2000IAUTA..24..219P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Coronal X-ray Emission of II PEG: The BeppoSAX View
Authors: Tagliaferri, G.; Covino, S.; Pallavicini, R.; Poretti, E.
2000AdSpR..25..523T    Altcode:
  The BeppoSAX observation of II Peg confirms that this is a very active
  coronal source, with a possible detection of the decay of a strong
  X-ray flare. The N<SUB>H</SUB> value as determined by BeppoSAX is a
  factor of ten higher than expected. This is now a common result for
  various coronal sources observed by BeppoSAX, that still remains to be
  explained. The coronal metal abundance determined for II Peg by BeppoSAX
  is subsolar (~ 0.3), in line with the results found for many other
  active stars. It is still an open question if this low metal abundance
  is in contradiction or not with the photospheric metallicity of II Peg

---------------------------------------------------------
Title: Division IV: Stars: (Etoiles)
Authors: Cram, Lawrence; Barbuy, Beatriz; Gerbaldi, Michele; Lambert,
   David; Pallavicini, Roberto; Zahn, Jean-Paul; Zinnecker, Hans
2000IAUTA..24..173C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Prospects of Future X-ray Missions for Low Mass Stars and
    Cluster Stars
Authors: Pallavicini, R.
2000vlms.conf..256P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in population I subgiants
Authors: Randich, S.; Gratton, R.; Pallavicini, R.; Pasquini, L.;
   Carretta, E.
1999A&A...348..487R    Altcode:
  We present a lithium survey for a sample of 91 Pop. I stars. JHKL
  photometry was also obtained for 61 stars in the sample. Besides Li
  abundances, [Fe/H] values were derived. Thanks to Hipparcos parallaxes,
  we could infer absolute V magnitudes for our sample stars and were
  able to place them on the color-magnitude diagram, which allowed us
  to constrain their evolutionary status. Masses and ages were derived
  for most of the stars by comparison with evolutionary tracks. The
  sample was originally selected so to include class IV stars later than
  spectral-type F0, but, based on the location on the color-magnitude
  diagram, we found a posteriori that a fraction of the stars (about
  20%) are either main sequence stars or evolved giants. As it is the
  case for dwarfs and giants, a large spread in lithium abundance is
  present among the subgiants in our sample. As expected, the average
  lithium decreases as the stars evolve along the subgiant branch;
  however, there is not a one-to-one relationship between the position
  on the color-magnitude diagram and lithium abundance, and the observed
  dispersion is only partially explainable as due to a dispersion in mass,
  metallicity, and age. In particular, a dispersion in lithium is seen
  among slightly evolved subgiants with masses close to solar but in the
  same evolutionary stage as the G2 IV star beta Hyi. The comparison
  of the beta Hyi-like sample with a sample of non evolved solar-like
  stars indeed suggests that beta Hyi has most likely evolved from a
  main sequence Li-rich star, rather than from a Li-poor star (like
  the Sun) that has dredged-up previously stored lithium. Our sample
  includes several stars that have completed the first-dredge up lithium
  dilution, but that have not yet evolved to the evolutionary point
  where extra-mixing in the giant phase is thought to occur. A large
  number of them have Li abundances considerably below the theoretical
  predictions of first dredge-up dilution. We confirm that this is due
  to the fact that the progenitors of these stars are most likely stars
  that have depleted lithium while on the main sequence; the fraction
  of post-dredge up Li rich/poor stars, in fact, is consistent with the
  observed distribution of Li abundances among stars that have just
  left the main sequence. The signature of the second mixing (or RGB
  extra-mixing) episode is evident in the log n(Li) vs. B-V and log n(Li)
  vs. M_bol distributions of the stars in the sample; it seems however
  that the extra-mixing occurs at luminosities lower than predicted by
  the models of Charbonnel (1994). Finally, a few evolved giants are found
  that should have passed the second mixing episode, but that do not show
  signs of it. At least half of them are spectroscopic binaries. Based
  on observations carried out at the European Southern Observatory,
  La Silla, Chile

---------------------------------------------------------
Title: VizieR Online Data Catalog: UBVRI photometry of EUV stellar
    sources (Cutispoto+ 1999)
Authors: Cutispoto, G.; Pastori, L.; Tagliaferri, G.; Messina, S.;
   Pallavicini, R.; Rodono, M.
1999yCat..41380087C    Altcode:
  We present the results of high-precision UBV(RI)<SUB>c</SUB> photo
  observations and of spectroscopic radial velocity measurements obtained
  at the European Southern Observatory for a sample of 51 cool stars
  detected in the EUV by the ROSAT Wide Field Camera (WFC). Using also
  recent results from HIPPARCOS, we infer spectral types and investigate
  the single or binary nature of the sample stars. Optical variability,
  with periods in the 0.4-13 day range, has been detected for the first
  time in 15 of these stars. (8 data files).

---------------------------------------------------------
Title: Classification of EUV stellar sources detected by the ROSAT
    WFC. I. Photometric and radial velocity studies
Authors: Cutispoto, G.; Pastori, L.; Tagliaferri, G.; Messina, S.;
   Pallavicini, R.
1999A&AS..138...87C    Altcode:
  We present the results of high-precision UBV(RI)_c photometric
  observations and of spectroscopic radial velocity measurements obtained
  at the European Southern Observatory for a sample of 51 cool stars
  detected in the EUV by the ROSAT Wide Field Camera (WFC). Using also
  recent results from HIPPARCOS, we infer spectral types and investigate
  the single or binary nature of the sample stars. Optical variability,
  with periods in the 0.4-13 day range, has been detected for the
  first time in 15 of these stars. based on data collected at the
  European Southern Observatory, La Silla, Chile. <P />Tables 1--5,
  Figs. 2-27 and the complete data set are available in electronic
  form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr or via
  http://cdsweb.u-strasbg.fr/Abstract.html

---------------------------------------------------------
Title: A it BeppoSAX observation of HD 9770: a visual triple system
    containing a recently discovered short-period eclipsing binary
Authors: Tagliaferri, G.; Covino, S.; Cutispoto, G.; Pallavicini, R.
1999A&A...345..514T    Altcode: 1999astro.ph..2329T
  We have studied the coronal X-ray emission of the recently discovered
  short-period eclipsing binary HD 9770 with the BeppoSAX satellite. The
  data from the Low Energy and Medium Energy Concentrator Spectrometers
  (LECS &amp; MECS) onboard BeppoSAX allow studying the spectrum of this
  star from 0.1 to 8 keV, confirming that this is a very active coronal
  source, with strong flaring activity. The X-ray emission most likely
  originates from the eclipsing binary itself, rather than from the
  other visual component of the system. The X-ray light curves could
  be modulated with the orbital period of the eclipsing binary, with
  a hint for a different orbital modulation of the cooler and hotter
  plasma. The X-ray spectrum is characterized by hot plasma, with the
  Fe K complex at 6.7 keV clearly detected in the MECS spectrum, and it
  is well fitted by a 2-temperature optically thin plasma model with low
  metal abundances ( ~ 0.3 Z_sun). These results are in line with those
  found for many other active stars. As expected, during the flare the
  X-ray emission is dominated by hotter plasma with a temperature &gt;
  4 keV. There is an indication that the metal abundance may be somewhat
  higher during the flare.

---------------------------------------------------------
Title: X-ray observations of the young open cluster Blanco 1
Authors: Micela, G.; Sciortino, S.; Favata, F.; Pallavicini, R.;
   Pye, J.
1999A&A...344...83M    Altcode:
  We present results from two deep ROSAT HRI exposures on the Blanco 1
  open cluster. Blanco 1 is one of the few open clusters at large distance
  from the Galactic Plane. This circumstance has suggested that it may
  have formed through a mechanism different from that responsible for the
  other nearby clusters. The age of Blanco 1 is rather uncertain since,
  depending on the adopted age indicator, it ranges between 30 and 90
  Myr. Many cluster members show chromospheric emission typical of young
  stars. The X-ray observations presented here reveal a high number of
  X-ray sources, consistent with the young age of the cluster. The typical
  X-ray luminosity of the cluster members is consistent with that of the
  Pleiades and significantly lower than the alpha Per members. These
  results suggest than the age of Blanco 1 is more similar to the age
  of the Pleiades than to that of alpha Per. The time sampling of the
  X-ray observations allows us to study the variability of the sources
  on time scales from hours to 6 months - 1 year.

---------------------------------------------------------
Title: Status of the BeppoSAX program in the field of optically
    thin plasmas
Authors: Pallavicini, R.
1999NuPhS..69...56P    Altcode:
  I present an overview of the BeppoSAX program in the field of optically
  thin plasmas, which comprises stellar coronae, supernova remnants and
  clusters of galaxies. Albeit only ~70% of the observations approved in
  AO1 have been carried out, and only part of the acquired data have as
  yet been analysed, there are already significant, and in some case
  unique results coming out from the ongoing program. The analysis
  carried out so far, although preliminary, is very important for
  assessing the capabilities of the BeppoSAX mission and for optimizing
  future observations.

---------------------------------------------------------
Title: X-ray Coronae of Stars: Some Theoretical Questions
Authors: Pallavicini, R.
1999ASPC..158..334P    Altcode: 1999ssa..conf..334P
  No abstract at ADS

---------------------------------------------------------
Title: BeppoSAX detection of hard (&gt;20keV) X-ray emission from
    the active star UX Arietis
Authors: Pallavicini, R.; Tagliaferri, G.
1999NuPhS..69...29P    Altcode:
  We present preliminary results of a BeppoSAX observation of the active
  binary star UX Arietis. We report the first detection in a star other
  the Sun of hard (&gt;20keV) X-ray emission during a large flare. Similar
  results were obtained a few days later for a flare observed by BeppoSAX
  on Algol. We analyse time-resolved spectra of the UX Ari flare obtained
  with the LECS and MECS detectors over the spectral range 0.1 to 10keV
  and we discuss possible interpretations for the high energy tail seen
  with the PDS detector.

---------------------------------------------------------
Title: Stellar coronae with BeppoSAX
Authors: Pallavicini, R.; Tagliaferri, G.
1999hxra.conf..378P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The eclipsing binary HD 9770: flaring activity and rotational
    modulation detected by the BeppoSAX satellite
Authors: Tagliaferri, G.; Covino, S.; Cutispoto, G.; Pallavicini, R.
1999NuPhS..69...48T    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in ROSAT-discovered candidate members in the Alpha
    Persei cluster
Authors: Randich, S.; Martin, E. L.; Garcia Lopez, R. J.; Pallavicini,
   R.
1998A&A...333..591R    Altcode:
  We present lithium observations of 23 X-ray selected candidate members
  of alpha Per, which are part of a larger sample of stars identified
  through two ROSAT surveys of the cluster. Our observations on one
  hand allowed us to confirm membership for 18 of the candidates,
  thus suggesting that a high percentage of the whole X-ray selected
  candidates are probably cluster members. On the other hand, we had
  the possibility to significantly enlarge the Li database for this
  cluster. The distribution of Li abundances for stars in our sample (or
  `new' members) is in good agreement with that for previously known
  (or `old') members, although `new' members in the 5000 - 4700 T_eff
  interval stay on the upper envelope of the Li vs. T_eff diagram. The
  comparison of the merged `new' + `old' sample with the younger IC
  2602 and IC 4665 clusters and with the older Pleiades confirms that
  stars more massive than the Sun do not undergo any PMS Li destruction,
  whereas some depletion occurs during the early phases on the ZAMS. We
  re-addressed the issue of the star-to-star scatter and Li-rotation
  connection for both alpha Per and the Pleiades; as several previous
  studies have pointed out, fast rotators, as a group, show higher
  lithium than slow rotators. At the same time, however, fast rotators
  exhibit a much narrower dispersion than slow rotators. We demonstrate
  that this dicothomy is unlikely due to projection effects and suggest
  that the reason for it could reside in the PMS rotational history and,
  in particular, in the presence (absence) of a circumstellar disk. As
  to very cool stars (T_eff &lt; 4500 K), we find that alpha Per members
  do not seem to have higher lithium than the Pleiades. This result,
  however, must be confirmed with a larger sample of alpha Per stars
  before any conclusion can be drawn. Based on observations made with
  the Isaac Newton telescope, operated on the island of La Palma by
  the Isaac Newton Group in the Spanish Observatorio del Roque de los
  Muchachos of the Instituto de Astrof\'\i sica de Canarias.

---------------------------------------------------------
Title: X-ray Spectroscopy of Active Stars with ASCA and BeppoSAX
Authors: Pallavicini, R.; Maggio, A.; Ortolani, A.; Tagliaferri, G.;
   Covino, S.
1998Ap&SS.261..101P    Altcode: 1999Ap&SS.261..101P
  We discuss representative cases of X-ray spectra of active stars
  obtained with ASCA and BeppoSAX. We focus in particular on our own
  observations of the RS CVn binaries γ And and UX Ari, of the BY Dra
  eclipsing binary HD9770, and of the young stars AB Dor and HD35850.

---------------------------------------------------------
Title: Lithium Abundance in NGC 3680
Authors: Pasquini, L.; Randich, S.; Pallavicini, R.
1998ASPC..154..947P    Altcode: 1998csss...10..947P
  In the framework of a long-term program aimed at studying lithium
  abundance in solar stars belonging to intermediate and old clusters,
  we present the preliminary analysis of high resolution observations
  of 21 stars belonging to the intermediate age cluster NGC 3680. % The
  targets span over the whole cluster colour-magnitude % diagram. The
  targets range from the main sequence turnoff through the sub-giant
  branch. The cluster shows a clear Li-dip, and no evidence for a spread
  is present among the observed main sequence stars. Particularly relevant
  is the finding that out of the 6 giants (which have similar magnitudes
  and temperatures) three show a strong lithium line, while the other
  three are Li depleted.

---------------------------------------------------------
Title: Spectroscopic Capabilities of XMM for Stellar Coronal Studies
Authors: Pallavicini, R.
1998ASPC..154.1138P    Altcode: 1998csss...10.1138P
  The turn of the millennium will be a marvelous time for X-ray
  astronomy with the launch of powerful missions such as AXAF, XMM, and
  ASTRO-E. Stellar coronae, with their spectra rich in emission lines,
  will be primary targets to exploit the spectroscopic capabilities of
  these missions. In particular, the CCD cameras and reflection gratings
  on XMM will allow us to address a number of key questions in stellar
  coronal physics. The capabilities of XMM for the study of stellar
  coronae are illustrated by means of simulations of EPIC and RGS spectra
  for a variety of typical stellar coronal sources. The mission time-line
  and the policy for accessing the data are also briefly illustrated.

---------------------------------------------------------
Title: Lithium in “New” alpha Per Candidates Discovered by ROSAT
Authors: Randich, S.; Martin, E.; Garcia Lopez, R.; Pallavicini, R.
1998ASPC..154.2136R    Altcode: 1998csss...10.2136R
  We present the results from a lithium survey of 23 new alpha Persei
  candidates discovered by ROSAT. The log N(Li) vs. T_eff distribution
  of these stars is compared with that of previously known members: the
  distributions for the two samples are in good agreement, although in
  the 5000-4700 K T_eff range our sample stars are located on the upper
  envelope of previously known members. We think that this is most likely
  due to the X-ray selection bias in our sample. This temperature range
  is indeed where the rotation-Li connection is most clear. The merged
  “old” + “new” sample is then compared both with the Pleiades
  and the IC 2602 and IC 4665 clusters. alpha Per stars shows a
  spread in lithium, but such a spread starts to be seen at a lower
  effective temperature than in the Pleiades. A speculative explanation,
  connecting the dispersion in lithium to a spread in the timescale for
  disk dissipation, is given.

---------------------------------------------------------
Title: A Beppo-SAX Observation of HD 9770: a Newly Discovered
    Short-Period Eclipsing Binary System
Authors: Tagliaferri, G.; Covino, S.; Cutispoto, G.; Pallavicini, R.
1998ASPC..154.1175T    Altcode: 1998csss...10.1175T
  We present the results of a Beppo-AX} observation of the short-period
  eclipsing binary star HD 9770. The Beppo-SAX data confirm that this
  is a very active coronal source, with strong flare activity. The
  0.1-10 keV light curve is modulated by the star rotation with the
  eclipse detected at all energies. However, there seem to be an hint
  of a different behaviour with energy in the eclipse. The coronal metal
  abundances determined with Beppo-SAX are subsolar (~0.2), in line with
  the results found for many other active stars.

---------------------------------------------------------
Title: Lithium in Cool Stars Detected in EUV Surveys: ZAMS, PTTS,
    or PMS?
Authors: Pastori, L.; Tagliaferri, G.; Cutispoto, G.; Pallavicini, R.
1998ASPC..154..954P    Altcode: 1998csss...10..954P
  High-resolution spectra in the region of the Li 1 6707.8 AA doublet
  were obtained for more than 50 stars, of spectral type from F5 to
  K5, EUV-selected with the ROSAT WFC. We find that one third of these
  stars are as young as the Pleiades or younger. In particular there
  are 11 stars that are between the Pleiades and IC 2602 lithium upper
  envelopes, which means that they are just arrived or are arriving
  on the ZAMS. Four stars of our sample are in a region where only PMS
  stars should lie. These results, though preliminary, would imply that
  the PMS stars detected by Neuhauser et al. (1997) are in fact due to
  a high concentration of young objects in the Gould Belt.

---------------------------------------------------------
Title: The XMM GT Programme on Stellar Coronae: an Overview
Authors: Pallavicini, R.
1998sxmm.confE..11P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-Ray Coronae from Stars
Authors: Pallavicini, R.
1998IAUS..188...13P    Altcode:
  Hot optically thin coronal envelopes are common to stars of virtually
  all spectral types and luminosity classes. The study of stellar coronae
  provides a powerful tool to investigate the interaction of hot plasmas
  with the magnetic field and the mechanisms of generation, transport
  and dissipation of non-radiative energy in stellar atmospheres. Recent
  results on X-ray emission from stellar coronae obtained with ROSAT,
  EUVE and ASCA will be reviewed with emphasis on observations of cool
  stars in clusters and associations, and on spectroscopic determinations
  of elemental abundances and emission measure distribution. These
  observations have substantially increased our knowledge of stellar
  coronae with respect to that obtained previously with missions like
  Einstein, EXOSAT and GINGA. They also provide the basis for planning
  future observations with the coming missions AXAF, XMM and ASTRO-E.

---------------------------------------------------------
Title: Flares on AB Doradus Observed with ASCA
Authors: Ortolani, A.; Pallavicini, R.; Maggio, A.; Reale, F.; White,
   S. M.
1998ASPC..154.1532O    Altcode: 1998csss...10.1532O
  ASCA observations of the young rapidly rotating star AB
  Doradus are analysed with special emphasis on its flaring
  behaviour. Multitemperature model fits with either fixed or variable
  abundances are used. The results for the quiescent emission are compared
  with those obtained previously by Mewe et al. (1996) confirming the
  very low coronal metallicity (nearly one tenth solar) of this star in
  spite of its measured solar photospheric metallicity. The results for
  the flares are compared with recent models based on full hydrodynamic
  calculations (Reale et al. 1997) and realistic values for the loop
  length and the heating duration are derived. It is shown that the
  flare is essentially a high temperature phenomenon with little effect
  on the low-temperature component of the quiescent star.

---------------------------------------------------------
Title: Chromospheric models of dwarf M stars.
Authors: Mauas, P. J. D.; Falchi, A.; Pasquini, L.; Pallavicini, R.
1997A&A...326..249M    Altcode:
  We present chromospheric models for two dM stars considered as “basal”
  stars due to the low level of chromospheric activity, and compare them
  with the model for a very active, flare star obtained in a previous
  paper. These models are not based on a single spectral feature, but
  on the continuum in a broad wavelength range (3500-9000Å), on many
  line profiles corresponding to three different atoms (H, Ca, Na),
  and on the Mg II h and k flux. We show that a marked chromosphere
  is present even for stars with the lowest levels of activity, and
  that the active stars have both a chromospheric temperature rise
  at larger column mass and a higher chromospheric temperature. These
  characteristics are responsible for the presence of the Balmer lines
  in emission in the dMe stars. We also show that the additional energy
  required to transform a dM star into an active star must be deposited
  in the high chromosphere, just below the transition region.

---------------------------------------------------------
Title: The X-ray coronal emission of λ Andromedae observed with
    ASCA and ROSAT.
Authors: Ortolani, A.; Maggio, A.; Pallavicini, R.; Sciortino, S.;
   Drake, J. J.; Drake, S. A.
1997A&A...325..664O    Altcode:
  We present an observation of the long-period RS CVn binary λ And
  obtained with ASCA. We also discuss a previous observation by ROSAT of
  the same star, that we have retrieved from the public archive. There
  was little variation in the quiescent X-ray flux of λ And between these
  two observations almost 5 years apart, but they offer different, and in
  part complementary, views of its corona. The ASCA spectra of λ And are
  well described by a 2-T model with a main component at T_1_=~0.9keV and
  a smaller component at T_2_=~3keV, with EM_2_/EM_1_=~0.15. The fitted
  coronal metallicity is Z=~0.1, much lower than solar but consistent
  within a factor of 2 with the reported photospheric metallicity
  Z_phot_=~0.2. On the contrary, a successful 2-T fit of the ROSAT
  spectrum yields a cool component at =~0.5keV and a hotter component
  at =~1.4keV, with EM_2_/EM_1_=~2 and Z=~0.25. Because of these
  differences, we were unable to find an acceptable fit to the joint
  ASCA and ROSAT data. We discuss possible causes for the discrepancy,
  including spectral time variability, uncertainties in the plasma
  emission codes and in the instrumental calibration, and limitations
  in the adopted fitting model. The hydrogen column density toward λ
  And, well constrained by ROSAT, is N_H_=~1x10^19^cm^-2^, a factor ~2
  larger than estimated from UV observations from Copernicus and the
  Hubble Space Telescope. Albeit small, this difference may indicate
  the presence of substantial ionization of the interstellar medium.

---------------------------------------------------------
Title: Lithium in M 67: evidence for spread in a solar age cluster.
Authors: Pasquini, L.; Randich, S.; Pallavicini, R.
1997A&A...325..535P    Altcode:
  We present high resolution observations of main sequence stars in the
  solar age, solar metallicity open cluster M 67. For the first time
  we show conclusively that a spread in lithium abundances exists among
  solar-type stars belonging to this cluster. This implies that standard
  models with only convection as a mixing mechanism can hardly account for
  the spread at each colour, and that the Li abundance is not a good age
  indicator for solar-type stars. The comparison of Li abundances in M 67
  (age ~4.7x10^9^ yrs) with those in the younger Hyades cluster (~7x10^8^
  yrs) shows that the less depleted stars in M 67 have a Li content
  only ~ 0.25 dex below similar stars in the Hyades. Considering the ~
  4 Gyrs difference between the two clusters, this indicates that standard
  lithium destruction mechanisms are very inefficient (if present at all)
  in many solar-type stars during most of their main sequence lifetime. On
  the other hand, almost 40% of our sample stars show a significant Li
  depletion, with values comparable to the Sun. Our sample also includes
  one SB2 binary, for which a very high Li abundance was previously
  reported. We found an abundance significantly higher than in single
  stars, but our spectra are inconsistent with those previously published.

---------------------------------------------------------
Title: A SAX/LECS X-ray observation of the active binary Capella.
Authors: Favata, F.; Mewe, R.; Brickhouse, N. S.; Pallavicini, R.;
   Micela, G.; Dupree, A. K.
1997A&A...324L..37F    Altcode: 1997astro.ph..7061F
  We present a SAX/LECS X-ray observation of the active binary Capella,
  the first coronal source observed in the SAX Guest Investigator
  program. The analysis of this observation, performed using the mekal
  plasma emission code, shows that the LECS spectrum is well fit by a
  two-component optically-thin plasma model. A differential emission
  measure (DEM) obtained by direct inversion of the X-ray spectrum
  shows no additional features in addition to the double-peaked
  structure implied by the direct two-temperature analysis. Such a
  simple temperature stratification is however not compatible with the
  EUVE emission from the same object, which is well represented by a more
  complex DEM, with a power-law-like tail toward the low temperatures. At
  the same time, the EUVE-derived DEM predicts well the softer part
  of the Capella LECS spectrum, but it fails to correctly reproduce
  the higher energy part of the Capella LECS spectrum. Possible causes
  for this discrepancy are discussed. The coronal metallicity derived
  from the SAX observation is compatible both with the EUVE-derived
  metallicity as well as with the photospheric metallicity of Capella,
  thus showing no evidence for coronal under-abundances.

---------------------------------------------------------
Title: Lithium abundances in the young open cluster IC 2602.
Authors: Randich, S.; Aharpour, N.; Pallavicini, R.; Prosser, C. F.;
   Stauffer, J. R.
1997A&A...323...86R    Altcode:
  We have obtained high-resolution spectra for 28 candidate late-type
  stars in the 30 Myr old cluster IC 2602. NLTE Li abundances have been
  derived from measured equivalent widths. The log n(Li)-T_eff_ and log
  n(Li)-mass distributions for our sample stars have been compared with
  those of the Pleiades and α Persei. Our data show that F stars in
  the three clusters have the same lithium content, which corresponds
  to the initial content for Pop. I stars. G and early-K IC 2602 stars
  are, on average, somewhat more Li-rich than their counterparts in
  the two slightly older clusters. Finally, the latest-type IC 2602
  stars are heavily Li depleted, with their Li content being as low
  as the lowest measured among the Pleiades. As in the Pleiades and α
  Per, a star-to-star scatter in lithium is observed among 30 Myr old
  late-K/early-K dwarfs in IC 2602, indicating that this spread develops
  in the pre-main sequence phases.

---------------------------------------------------------
Title: Coronal X-ray emission of HD 35850: the ASCA view.
Authors: Tagliaferri, G.; Covino, S.; Fleming, T. A.; Gagne, M.;
   Pallavicini, R.; Haardt, F.; Uchida, Y.
1997A&A...321..850T    Altcode: 1996astro.ph.11160T
  We present the analysis of the X-ray data of the young active star
  HD 35850 obtained with ASCA and ROSAT. Our main goal was to see if
  there is a difference in the elemental abundances of active stars
  between young and more evolved objects. A two temperature plasma
  with subsolar abundances, of the order of Z=0.15-0.3 , is required to
  fit the SIS spectra. Similar results are obtained from a ROSAT PSPC
  observation. Metal abundances of 0.2-0.4 the solar value are required
  to fit both the ASCA and ROSAT data together. From a simultaneous
  SIS0+SIS1 spectral fit, with 2T plasma models and abundances free to
  vary in non-solar proportions, we find that, besides N, O and Ne for
  which we find very low values, all other elements have values relative
  to solar abundances around 0.2-0.3. These subsolar abundances are in
  line with those typically observed in more evolved, active stars like RS
  CVn and Algol-type binaries. The two temperature values required to fit
  the ASCA SIS spectra are about 0.5 and 1.0 keV. These temperatures,
  especially the higher one, are lower with respect to the values
  found for the RS CVn and Algol binaries or for the young star AB Dor,
  but higher than other single G/K stars. All our data show that this
  single, late F-type star is actually a very active source, indirectly
  confirming that this fast rotating star is probably a young object. In
  the simultaneous fit of the ASCA+ROSAT data, a third temperature is
  required. However this is not just an addition of a softer component,
  but is more a redistribution of the dominant temperatures. Indeed, the
  range spanned by the three temperatures, from 5 to 15 million degrees,
  is not very large.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Chromospheric models of dwarf M
    stars (Mauas+ 1997)
Authors: Mauas, P.; Falchi, A.; Pasquini, L.; Pallavicini, R.
1997yCat..33260249M    Altcode:
  Tables 4 and 5 give the atmospheric parameters for our models of
  dM stars Gl 588 and Gl 628. The columns give the column mass in
  g/cm<SUP>-2</SUP>, the electron temperature in K, the microturbulent
  velocity in km/s; the continuum optical depth at 5000Å; the hydrogen,
  proton, and electron density in particles per cm<SUP>-3</SUP>; and
  the height h (in km) above the level where tau<SUB>5000</SUB>=1. (2
  data files).

---------------------------------------------------------
Title: Lithium in solar-type stars of the old open cluster M 67.
Authors: Pallavicini, R.; Pasquini, L.; Randich, S.
1997MmSAI..68..933P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: ASCA Observation of Coronal X-Ray Emission from the Dwarf
    Star HD 35850
Authors: Tagliaferri, G.; Covino, S.; Pallavicini, R.; Uchida, Y.
1997xisc.conf..575T    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Cool stars in clusters and associations: magnetic activity
    and age indicators. Proceedings. Workshop, Palermo (Italy), 20 -
    23 May 1997.
Authors: Micela, G.; Pallavicini, R.; Sciortino, S.
1997MmSAI..68..783M    Altcode:
  The following topics were dealt with: evolutionary models and age
  determinations; membership determination; proper motion surveys and CCD
  photometry; rotation and angular momentum evolution; lithium abundance
  in clusters and associations; chromospheric activity in cluster stars;
  X-ray observations of open clusters; star formation and young stellar
  objects; X-ray surveys of star forming regions; solar-type coronal
  loop modelling of X-ray flares.

---------------------------------------------------------
Title: Prospects for Stellar Coronae Observations
Authors: Pallavicini, Roberto
1997ngxo.conf...27P    Altcode:
  A brief summary is given of the current status and future prospects for
  X ray observations of stellar coronae. The need for high-throughput
  high-resolution spectroscopy on fainter and more distant objects
  (e.g. late-type stars in open clusters of different ages, and in
  star forming regions) is emphasized. A combination of large effective
  area (A(eff) approximately 10,000 cm<SUP>2</SUP> at 1 keV) and high
  spectral resolution (Delta(E) approximately 2 eV at energies &gt;
  1 keV and Delta(lambda) approximately 0.03 A at energies &lt; 1 keV)
  on a telescope with HEW approximately 5 arcsec is required to advance
  significantly beyond the capabilities of future missions like AXAF,
  XMM and ASTRO-E.

---------------------------------------------------------
Title: X-ray observations of the young open cluster dzeta Sculptoris.
Authors: Micela, G.; Sciortino, S.; Favata, F.; Pallavicini, R.;
   Pye, J.
1997MmSAI..68..989M    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Abundances and Flares in the ASCA Observation of the Young
    k0 Star AB Doradus
Authors: White, S. M.; Pallavicini, R.; Mewe, R.; Kaastra, J. S.;
   Lim, J.
1997xisc.conf..573W    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The Sun as a variable star
Authors: Pallavicini, R.
1997MmSAI..68..369P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Simultaneous EUVE &amp; ASCA observations of AB Doradus:
    temperature structure and abundances of the quiescent corona.
Authors: Mewe, R.; Kaastra, J. S.; White, S. M.; Pallavicini, R.
1996A&A...315..170M    Altcode:
  We have analyzed EUV and X-ray spectra of the non-flaring state of AB
  Dor, obtained from simultaneous observations with EUVE and ASCA. The
  coronal temperature structure and the coronal elemental abundances
  have been derived by jointly fitting the spectra, including lines
  and continuum. We have applied a multi-temperature fitting method
  and we have found that an optically thin plasma model with solar
  abundances (relative to hydrogen) does not yield a good fit. A 4-T
  fit allowing the abundances of the more important elements (Fe, S,
  Si, Mg, Ne, and O) plus four other less important abundances (N, Ar,
  Ca, and Ni) to vary improves the fit markedly. This results in values
  of the first 6 abundances relative to solar photospheric values that
  are significantly (a factor 2-3) below solar except for Ne, which is
  solar, while most of the remaining four abundances are consistent both
  with solar and reduced abundances. In the course of the 4-T fitting
  we have determined a best-fit value for the interstellar hydrogen
  column density of N_H_=(2.0+/-0.5)10^18^cm^-2^. We have applied four
  differential emission measure (DEM) distribution analysis techniques,
  viz.: (i) regularization method, (ii) polynomial method, (iii) clean
  algorithm, and (iv) genetic algorithm. The four different methods
  all yield a qualitatively similar DEM, showing two maxima in the
  temperature intervals 5-8MK and 20-30MK. Our analysis demonstrates the
  great value of simultaneous ASCA and EUVE observations in determining
  the fundamental parameters of stellar coronae.

---------------------------------------------------------
Title: Lithium abundance in the open cluster IC 2602
Authors: Randich, S.; Aharpour, N.; Pallavicini, R.; Prosser, C. F.;
   Stauffer, J. R.; Schmitt, J. H. M. M.
1996ASPC..109..379R    Altcode: 1996csss....9..379R
  No abstract at ADS

---------------------------------------------------------
Title: A study of a sample of cool stars X-ray selected with EXO
    SAT using ROSAT data
Authors: Panarella, A.; Tagliaferri, G.; Pallavicini, R.
1996ASPC..109..623P    Altcode: 1996csss....9..623P
  No abstract at ADS

---------------------------------------------------------
Title: Atmospheric models of dM stars
Authors: Falchi, A.; Pallavicini, R.; Mauas, P. J. D.; Pasquini, L.
1996ASPC..109..603F    Altcode: 1996csss....9..603F
  No abstract at ADS

---------------------------------------------------------
Title: Spectroscopic Diagnostics of Astrophysical Plasmas
Authors: Pallavicini, R.
1996LNP...468..241P    Altcode: 1996plas.conf..241P
  This paper summarises a series of lectures on spectroscopic diagnostics
  of astrophysical plasmas given to graduate students. It focusses on
  optically thin thermal plasmas and on X-ray spectroscopy. The basic
  diagnostic techniques are first discussed in a general way and then
  applied to specific astrophysical cases, including the solar corona,
  stellar coronae, supernova remnants and clusters of galaxies. The
  limitations of current spectroscopic data in terms of both resolution
  and sensitivity are emphasised, and future prospects are briefly
  mentioned. These lectures are intended as an introduction to the field
  rather than as a survey of the most recent literature. The emphasis
  therefore is on basic concepts and the cited bibliography is limited
  mainly to review papers where further details and references to the
  original works can easily be found.

---------------------------------------------------------
Title: The X-ray spectra of flares from AB Doradus
Authors: White, S. M.; Pallavicini, R.; Lim, J.
1996ASPC..109..299W    Altcode: 1996csss....9..299W
  No abstract at ADS

---------------------------------------------------------
Title: An ASCA observation of HD 35850
Authors: Tagliaferri, G.; Covino, S.; Haardt, F.; Fleming, T. A.;
   Pallavicini, R.
1996ASPC..109..295T    Altcode: 1996csss....9..295T
  No abstract at ADS

---------------------------------------------------------
Title: Millimeter Continuum Observations of Stars
Authors: Pallavicini, Roberto; White, S. M.
1996slma.conf..268P    Altcode:
  We review the scientific advances to be expected from millimeter
  continuum observations of stars by a Large Southern Array (LSA). We
  discuss briefly several topics including millimeter observations of the
  Sun, winds of hot stars, circumstellar disks of pre-main sequence stars,
  circumstellar shells and mass loss in cool giants, symbiotic stars,
  and non-thermal emission in active binaries, flare stars and accretion
  powered X-ray sources. We show that even in the more limited area of
  continuum observations, the proposed LSA will allow major advances in
  virtually all fields of stellar astronomy.

---------------------------------------------------------
Title: Stellar Magnetic Activity; Activity Cycles, and Dynamos
Authors: Pallavicini, R.
1996mpsa.conf..359P    Altcode: 1996IAUCo.153..359P
  No abstract at ADS

---------------------------------------------------------
Title: Photometric and spectroscopic studies of cool stars discovered
    in EXOSAT X-ray images. III. Photometric properties.
Authors: Cutispoto, G.; Tagliaferri, G.; Pallavicini, R.; Pasquini,
   L.; Rodono, M.
1996A&AS..115...41C    Altcode:
  We present high-precision UBV(RI)_c_ photometry for a sample of active
  stars detected serendipitously by the EXOSAT satellite. Fourteen
  objects, out of 47 likely optical counterparts, turned out to be
  clearly variable, with periods in the range 1-8 days, including a newly
  discovered eclipsing binary. For most of them the optical variability
  is consistent with the presence of photospheric cool spots. We have
  used our multicolour photometry to estimate spectral classifications
  and distances. The derived distances indicate that some of the observed
  stars are previously unidentified nearby (d&lt;=25pc) M dwarfs. When
  combined with the results of high resolution spectroscopy, our
  photometric observations allow us to investigate the stellar content
  of the selected X-ray sample. Young stars and RS CVn-type binaries
  appear to constitute a large fraction of the selected sample.

---------------------------------------------------------
Title: The corona of AB Dor: temperatures and abundances determined
    with ASCA and EUVE
Authors: Mewe, R.; Kaastra, J. S.; White, S. M.; Pallavicini, R.
1996ASPC..109..273M    Altcode: 1996csss....9..273M
  No abstract at ADS

---------------------------------------------------------
Title: In memoriam of C.-C. Cheng
Authors: Pallavicini, R.
1996ASPC..109...43P    Altcode: 1996csss....9...43P
  No abstract at ADS

---------------------------------------------------------
Title: Cool stars, stellar systems, and the sun : 9 : 1995
Authors: Pallavicini, Roberto; Dupree, Andrea K.
1996ASPC..109.....P    Altcode: 1996csss....9.....P
  No abstract at ADS

---------------------------------------------------------
Title: X-ray spectroscopy of RS CVn binaries: the EXOSAT and SSS
    spectra revisited
Authors: Ortolani, A.; Pallavicini, R.; Tagliaferri, G.
1996ASPC..109..279O    Altcode: 1996csss....9..279O
  No abstract at ADS

---------------------------------------------------------
Title: VizieR Online Data Catalog: UBV(RI) photometry of cool stars
    (Cutispoto+, 1996)
Authors: Cutispoto, G.; Tagliaferri, G.; Pallavicini, R.; Pasquini,
   L.; Rodono, M.
1995yCat..41150041C    Altcode:
  We present high-precision UBV(RI)<SUB>c</SUB> photometry for a sample
  of stars detected serendipitously by the EXOSAT satellite. Fourteen
  objects, out of 47 likely optical counterparts, turned out to be
  clearly variable, with periods in the range 1-8 days, including
  a newly discovered eclipsing binary. For most of them the optical
  variability is consistent with the presence of photospheric cool
  spots. We have used our multicolour photometry to estimate spectral
  classifications and distances. The derived distances indicate that
  some of the observed stars are previously unidentified nearby
  (d&lt;=25pc) M dwarfs. When combined with the results of high
  resolution spectroscopy, our photometric observations allow us to
  investigate the stellar content of the selected X-ray sample. Young
  stars and RS CVn-type binaries appear to constitute a large fraction
  of the selected sample. For a description of the UBV and (RI)c
  photometric systems, see e.g. http://obswww.unige.ch/gcpd/ph01.html
  and http://obswww.unige.ch/gcpd/ph54.html. (2 data files).

---------------------------------------------------------
Title: Photometry of cool stars detected in extreme-ultraviolet
    (EUV) all-sky surveys.
Authors: Cutispoto, G.; Pallavicini, R.; Kuerster, M.; Rodono, M.
1995A&A...297..764C    Altcode:
  We present high-precision UBV(RI)_c_ photometry for a small sample of
  cool stars detected at EUV wavelengths by the ROSAT WFC and/or the EUVE
  all-sky survey. Four out of the five stars observed are variable and
  one of them is an eclipsing binary. Amplitudes up to 0.38 magnitudes
  in the V band have been observed and clear colour variations have been
  found. We have computed the photometric periods and deduced approximate
  spectral classifications and distances.

---------------------------------------------------------
Title: Lithium in Tidally Locked Binaries
Authors: Pallavicini, R.; Randich, S.
1995lea..conf..311P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Flares in Late-type Stars: X-ray
Authors: Pallavicini, Roberto
1995LNP...454..148P    Altcode: 1995flfl.conf..148P; 1995IAUCo.151..148P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium abundances in Pop I subgiants.
Authors: Randich, S.; Pallavicini, R.; Pasquini, L.; Gratton, R.
1995MmSAI..66..383R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in Late-Type Subgiants
Authors: Randich, S.; Pallavicini, R.; Pasquini, L.; Gratton, R.
1995lea..conf..284R    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: ASCA X-ray Spectra of Quiescent and Flaring Emission from
    AB Doradus
Authors: White, S. M.; Pallavicini, R.; Lim, J.
1995LNP...454..168W    Altcode: 1995IAUCo.151..168W; 1995flfl.conf..168W
  No abstract at ADS

---------------------------------------------------------
Title: Stellar and interstellar lithium and primordial
    nucleosynthesis. Proceedings. IAU Joint Discussion 11 of the 22. IAU
General Assembly: Stellar and interstellar lithium and primordial
    nucleosynthesis, The Hague (Netherlands), 22 Aug 1994.
Authors: Spite, F.; Pallavicini, R.
1995MmSAI..66..307S    Altcode:
  A collection of papers on the latest observations and theories on
  lithium. A few invited talks are not published in this volume.

---------------------------------------------------------
Title: Stellar and interstellar lithium and primordial nucleosynthesis
Authors: Spite, Francois; Pallavicini, Roberto
1995silp.conf.....S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium abundances of nearby solar-like stars.
Authors: Pasquini, L.; Liu, Q.; Pallavicini, R.
1994A&A...287..191P    Altcode:
  We discuss Li abundances in a well defined sample of nearby (G0-G5)
  solar-like stars. High resolution (R=100,000), high S/N (&gt;=
  150) data have been analysed using state-of-the-art techniques and
  up-to-date atmospheric models. We have investigated whether the
  abundance of Li in solar-type stars can be described in terms of
  stellar physical parameters like T_eff_, age and metallicity. We
  confirm the presence of a group of stars with high Li content, but
  apparently old age, finding that this group is rather conspicuous and
  not restricted to a few exceptional cases. The analysis of our data,
  together with published observations of G dwarfs in open clusters,
  strongly suggests that for stars older than ~1Gyr another parameter
  in addition to the overmentioned ones plays a relevant role in Li
  depletion. When this additional mechanism is effective, it depletes Li
  by a factor 10-100, but in some stars it may not act at all during a
  large part of their main sequence lifetimes. We make some suggestions
  as to the nature of this additional parameter but none of them can be
  definitely proven. When compared to the other stars in our sample, the
  Sun appears to be representative of the low-Li stars, which comprise
  about one half of the G dwarfs having stellar parameters and ages
  similar to the Sun. We confirm that Li is not a good tracer of age for
  solar-type stars, but we show that a high Li content coupled to high
  chromospheric activity can be used to identify stars significantly
  younger than the Hyades.

---------------------------------------------------------
Title: Photometric and spectroscopic studies of cool stars discovered
    in EXOSAT X-ray images II. Lithium abundances
Authors: Tagliaferri, G.; Cutispoto, G.; Pallavicini, R.; Randich,
   S.; Pasquini, L.
1994A&A...285..272T    Altcode:
  We present high-resolution spectra in the Li I 6708 A region,
  and multicolor photometry, for a sample of active stars detected
  serendipitously by the EXOSAT satellite. We analyse the spectral
  data with a spectral synthesis code and derive Li abundances,
  rotation rates and metallicities. We use our multicolor photometry
  to infer the spectral classification and distance of the stars in the
  sample. The derived Li abundances are compared with those of various
  samples including randomly selected field stars, RS CVn binaries, and
  clusters and associations of different ages. We show that Li per se is
  not sufficient to determine unambiguously the nature and evolutionary
  state of the sample stars, but can provide useful constraints if used
  in conjunction with other diagnostics like binarity, spectral class,
  rotation rate and X-ray luminosity. We show in particular that at least
  one third of the EXOSAT sample is constituted by young stars, with ages
  comparable to or younger than the Pleiades (~7x10^7^ yr). Another third
  consists of RS CVn binaries, while the classification of the remaining
  objects is uncertain. They could be either young stars or evolved
  active binaries. We argue that a similar composition also applies to
  the sample of X-ray stellar sources detected serendipitously by the
  Einstein Observatory.

---------------------------------------------------------
Title: Emission lines in the EUVE spectra of EQ Pegasi.
Authors: Fossi, B. C. Monsignori; Landini, M.; Pallavicini, R.
1994AAS...184.0518F    Altcode: 1994BAAS...26..866M
  The EUV spectra of dMe flare star EQ Pegasi were obtained during a guest
  observation using the Extreme Ultraviolet Explorer satellite (EUVE)
  on August 31, 1993. The EQ Peg was detected in all three spectrometer
  channels, although the LW detection, apart the He II line, was mainly
  the result of the second order throughput. The main features of the
  spectra in SW and MW channels are identified: a number of lines are
  due to highest ionization stages of iron.

---------------------------------------------------------
Title: Lithium in RS Canum Venaticorum binaries and related
    chromospherically active stars. III. Northern RS CVn systems.
Authors: Randich, S.; Giampapa, M. S.; Pallavicini, R.
1994A&A...283..893R    Altcode:
  High-resolution spectra of Northern RS CVn binaries obtained at the
  NSO-Kitt Peak are analyzed with a spectrum synthesis code to derive Li
  abundances, metallicities and rotation rates. The data are then combined
  with previous observations of Southern RS CVn binaries obtained at ESO,
  yielding a total sample of 67 individual components in 54 catalogued
  RS CVn binaries. We confirm the presence of substantial amounts of
  Li in many chromospherically active stars in the sample, with no
  significant difference between the Northern and Southern samples. We
  specifically address the question of whether these relatively high
  Li abundances are due to enhanced chromospheric activity or rather
  are a consequence of evolutionary history in stars of sufficiently
  high mass. We investigate the dependence of Li abundance on mass by
  using mass determinations in binary systems as well as comparison
  with theoretical evolutionary tracks. We show that while Li abundances
  in subgiants and in the warmer stars of the sample may be consistent
  with a dependence on mass, there is no clear indication in the data
  that the cooler giants with larger Li abundances are also the more
  massive ones. Uncertainties in the comparison with evolutionary tracks
  may partially be responsible for this negative result. Alternatively,
  Li depletion and dilution in evolved stars may be more complex than
  predicted by standard evolutionary models.

---------------------------------------------------------
Title: A search for cold dust around post-T Tauri candidates.
Authors: Gahm, G. F.; Zinnecker, H.; Pallavicini, R.; Pasquini, L.
1994A&A...282..123G    Altcode:
  We have made 1.3 mm continuum observations of 15 age-dated post-T
  Tauri candidates that occur as secondaries in binary systems with a
  primary of early spectral type (so-called Lindroos systems). Most of the
  objects have estimated ages of 10-100 Myr. None of the companions were
  detected at 3 sigma upper limits ranging from 13-134 mJy. This implies
  upper limits on the mass of cold circumstellar dust of approximately
  8 x 10<SUP>-6</SUP> - 3 x 10<SUP>-4</SUP> solar mass. The absence
  of dust emission suggests that the dust grains may have grown
  into planetsimals or planets, or they may have been dispersed or
  accreted. Our observations put a limit on the lifetime of optically
  thin dusty disks of order 10<SUP>7</SUP> yr in these systems. Two
  primaries were also included in this survey, again with no detections.

---------------------------------------------------------
Title: 15-30 arcsec resolution replica x-ray optics for AXAF-S
Authors: Stella, Luigi; Chincarini, G.; Citterio, Oberto; Conconi,
   Paolo; Maccacaro, T.; Tagliaferri, G.; Trinchieri, G.; Wolter, A.;
   Bignami, Giovanni F.; Bocchino, F.; Maggio, A.; Micela, G.; Sciortino,
   Salvatore; Serio, Salvatore; Collura, Alfonso; Giommi, P.; Maraschi,
   L.; Pallavicini, R.; Pellegrini, S.; Peres, G.
1994SPIE.2011..149S    Altcode:
  This document describes a proposal for a replica X-ray optics to be
  developed in Italy for NASA's X-ray spectroscopy mission AXAF-S. The
  program is based on state of the art technology for the production of
  replica X-ray optics. On the basis of the experience with the Jet-X
  mirror shells (to be flown on the Spectrum X-(gamma) satellite),
  a spatial resolution of 15 - 30 arcsec half power diameter (HPD)
  can be achieved for the AXAF-S optics. The characteristics of the
  proposed optical system are described and its performances evaluated
  by using the current baseline configuration for the array of X-ray
  calorimeters in the focal plane. The impact of the proposed replica
  X-ray optics is briefly outlined and a comparison with foil optics
  (1 - 3 arcmin HPD resolution) is carried out.

---------------------------------------------------------
Title: Optical Studies of Cool Stars Discovered by EXOSAT: Li
    Abundances and H alpha Spectroscopy
Authors: Tagliaferri, G.; Cutispoto, G.; Pallavicini, R.; Pasquini,
   L.; Randich, S.
1994ASPC...64..303T    Altcode: 1994csss....8..303T
  No abstract at ADS

---------------------------------------------------------
Title: The Radio Spectra of Weak-Lined T Tauri Stars
Authors: White, S. M.; Pallavicini, R.; Lim, J.
1994ASPC...64..501W    Altcode: 1994csss....8..501W
  No abstract at ADS

---------------------------------------------------------
Title: Photometry of Serendipitous X-Ray Sources Detected by
    EXOSAT. II. an Update
Authors: Cutispoto, G.; Rodono, M.; Pallavicini, R.; Tagliaferri, G.
1994ASPC...64..687C    Altcode: 1994csss....8..687C
  No abstract at ADS

---------------------------------------------------------
Title: Lithium Abundances in Nearby Solar-Like Stars
Authors: Pasquini, L.; Edvardsson, B.; Liu, Q.; Pallavicini, R.
1994ASPC...64..294P    Altcode: 1994csss....8..294P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium, Activity and Post-Main-Sequence Evolution (Invited
    Review)
Authors: Pallavicini, R.
1994ASPC...64..244P    Altcode: 1994csss....8..244P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in RS CVn binaries and related chromospherically
    active stars . II. Spectrum synthesis analysis.
Authors: Randich, S.; Gratton, R.; Pallavicini, R.
1993A&A...273..194R    Altcode:
  The results of the extensive survey of the Li I 6708 Å line in RS
  CVn binaries and other chromospherically active stars carried out by
  Pallavicini et al. (1992) are reanalyzed using synthetic spectra. This
  allows us to obtain more accurate values of Li abundances and to
  separate the contributions of individual components of 5B2 binaries. As
  a byproduct, metallicities and rotational velocities are also obtained
  for all stars in the sample. An effort is made to identify physically
  homogeneous subgroups of stars within the original sample, including:
  a) pre-main sequence objects; b) young and/or warm stars on the main-
  sequence; c) cool evolved stars at T<SUB>eff</SUB> ≤ 5000 K (both
  members of spectroscopic binaries and single K-type giants). We confirm
  that the latter group (which includes many catalogued RS CVn binaries)
  presents an excess Li abundance with respect to what typically observed
  in evolved stars of the same spectral type. However, the Li abundance is
  moderate (log n(Li) ≤ 1.5) and with no obvious dependence on activity
  parameters such as rotation and chromospheric emission. A significant
  amount of Lithium is observed only in a fraction of these active cool
  stars and the presence of Li does not appear to be a characteristic
  property of RS CVn stars as a class. We argue, in agreement with
  Fekel et al. (1987), that the cool giants with excess Lithium -
  might have evolved from main-sequence progenitors with shallow outer
  convective zones (M ≥ 1.5 M<SUB>sun</SUB>). Other possibilities
  discussed by Pallavicini et al. (1992), such as enhancement of the Li
  line in spotted stars, production of Li by spallation reactions in
  flares, and reduced rotationally-induced mixing in rapidly-rotating
  tidally-coupled binaries, cannot be excluded, but appear less likely. We
  find a significant metal deficiency for many stars in the sample, with
  no apparent correlation with Li abundance. However, the spectral lines
  could be significantly affected by surface activity (spots and plages)
  and may not represent a true metal deficiency. Finally, we briefly
  comment on the possible role of active binaries in the Li enrichment
  of the Galaxy on the galactic evolutionary timescale.

---------------------------------------------------------
Title: The effects of stellar surface activity on the strength of
    the lithium 6708 A line.
Authors: Pallavicini, R.; Cutispoto, G.; Randich, S.; Gratton, R.
1993A&A...267..145P    Altcode:
  We have investigated the effects of stellar surface activity on the
  strength of the Li I 6708 A line both observationally, by searching
  for rotational modulation of the Li line in spotted stars, and
  theoretically, by means of spectrum synthesis simulations. We have
  monitored nearly simultaneously four spotted stars in the Li I line
  and in broad-band multi-color photometry, finding no significant
  variations of the Li equivalent width (at levels as low as a few
  percent) in spite of the photometric variations, indicative of spots,
  observed at the same time. We show by means of computer simulations
  that the effects of surface activity on the Li line, though present,
  may be less pronounced than what had previously been suggested on
  the basis of the solar analogy and of the strong enhancement of the
  Li line in sunspots. We show that the lack of significant rotational
  modulation of the Li line in our stars is not inconsistent with the
  spot coverage factors inferred from the photometric variations. We
  also argue that large cool spots cannot be a viable explanation for
  the anomalously strong Li line sometimes observed in evolved RS CVn
  binaries and other spotted stars.

---------------------------------------------------------
Title: X-Ray Spectroscopic Diagnostics of the Hydrodynamics of Flares
    on M Dwarf Stars
Authors: Cheng, C.; Pallavicini, R.
1993uxrs.conf..525C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in Stars X-ray Selected by EXOSAT
Authors: Tagliaferri, G.; Randich, S.; Pallavicini, R.; Cutispoto, G.
1993ASSL..183..307T    Altcode: 1993pssc.symp..307T
  No abstract at ADS

---------------------------------------------------------
Title: A high resolution spectrograph for the Galileo National
    Telescope
Authors: Gratton, R.; Bhatia, R.; Bonanno, G.; Bruno, P.; Cali, A.;
   Catalano, S.; Cavazza, A.; Claudi, R.; Cosentino, R.; Douglas, N.;
   Merighi, R.; Molaro, P.; Pallavicini, R.; Viotti, R.
1993MmSAI..64..672G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Time Variability of Stellar X-ray Emission
Authors: Pallavicini, R.
1993ASSL..183..237P    Altcode: 1993pssc.symp..237P
  No abstract at ADS

---------------------------------------------------------
Title: Optical spectroscopy of post-T Tauri star candidates.
Authors: Pallavicini, R.; Pasquini, L.; Randich, S.
1992A&A...261..245P    Altcode:
  We report on spectroscopic observations of Post-T Tauri star candidates
  carried out using various instruments at ESO. The program stars were
  taken from the list of Lindroos (1986) and are late-type secondaries of
  visual binaries with early-type primaries. If the binaries are physical
  and not just optical pairs, their late type secondaries should still
  be contracting toward the ZAMS, or should have recently arrived upon
  it. Lindroos proposed all these stars as likely members of physical
  systems. We have observed spectroscopically 37 of the 41 secondaries
  in Lindroos' list classified of spectral type later than F2. We have
  also observed two additional systems that were discarded by Lindroos
  as likely optical pairs. For all 39 objects, we obtained moderate
  resolution (about 2 A) spectra in a region comprising the Li I 6708-A
  line and H-alpha. For 32 of these, we also obtained moderate resolution
  (about 1 A) spectra in the Ca II H and K lines. A few bright objects
  were also observed at high resolution (about 0.1 A) in the red. From
  our spectroscopic results we conclude that only a small fraction (less
  than 40 percent) of the surveyed stars show clear evidence of youth,
  the others being more likely optical pairs. All stars that appear to
  be young are located in the HR diagram very close to the ZAMS.

---------------------------------------------------------
Title: High Resolution Spectroscopy of Stellar X-Ray Sources
Authors: Tagliaferri, G.; Randich, S.; Pallavicini, R.; Cutispoto, G.
1992ESOC...40..171T    Altcode: 1992hrsw.conf..171T
  No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Spectrum Synthesis Analysis of Late-Type
    Spectroscopic Binaries
Authors: Randich, S.; Gratton, R.; Pallavicini, R.
1992ESOC...40..155R    Altcode: 1992hrsw.conf..155R
  No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Optical Spectroscopy of Cool Stars
Authors: Pallavicini, R.; Pasquini, L.; Randich, S.
1992ESOC...40..151P    Altcode: 1992hrsw.conf..151P
  No abstract at ADS

---------------------------------------------------------
Title: Radio flares and magnetic fields on weak-line T Tauri stars.
Authors: White, S. M.; Pallavicini, R.; Kundu, M. R.
1992A&A...259..149W    Altcode:
  We report the first detection of circular polarization in the radio
  emission of two weak-line T Tauri stars. This is direct confirmation
  of the presence of magnetic fields in the coronae of these stars. The
  degree of polarization at 5 GHz is small, consistent with previous
  observations which did not find measurable polarization. We have also
  observed a radio flare on one of the two stars. The rising spectrum
  of the radio emission together with the low degree of polarization
  are strong evidence that radio outbursts on this class of stars are
  due to nonthermal gyrosynchrotron emission which is optically thick
  in the microwave range. One of the two stars shows no evidence for
  circumstellar material, and thus can be classified as 'naked'. However
  the other apparently has a dust disk, and the evidence of flaring on
  this star indicates that the mechanism involved does not require an
  empty circumstellar environment.

---------------------------------------------------------
Title: X-Ray Spectroscopic Diagnostics of the Hydrodynamics of Flares
    on M Dwarf Stars
Authors: Cheng, C. -C.; Pallavicini, R.
1992AAS...180.6007C    Altcode: 1992BAAS...24..826C
  No abstract at ADS

---------------------------------------------------------
Title: A 5GHz radio survey of selected POST T Tauri and naked T
    Tauri stars.
Authors: White, S. M.; Pallavicini, R.; Kundu, M. R.
1992A&A...257..557W    Altcode:
  Results of a radio survey of weak-lined T Tauri (variably
  classified as either post T Tauri or naked T Tauri) stars at 5
  GHz are reported. Thirty-two targets, chosen on the basis of known
  high-activity levels or youth indications, were observed, and 15,
  including eight previously unknown radio sources, were detected. It
  is suggested that most weak-lined T Tauris with high activity levels,
  e.g., as indicated by a high X-ray flux, are likely to be detectable
  radio sources at some time, but the radio emission goes through high
  and low phases. For the subsample of 14 stars observed in Taurus-Auriga
  which were thoroughly studied at IR, optical, and X-ray wavelengths,
  a clear association is found between radio activity and youth.

---------------------------------------------------------
Title: Mg II absolute line profiles for late-type stars and for
    spatially-resolved solar regions.
Authors: Cerruti-Sola, M.; Cheng, C. -C.; Pallavicini, R.
1992A&A...256..185C    Altcode:
  The authors present the results of a comparison of Mg II h and k line
  profiles and fluxes for late-type stars observed with IUE and for
  spatially resolved solar regions observed at comparable resolution by
  the NRL Spectrograph on Skylab. They show that the spatially resolved
  solar observations are in good agreement with the disk integrated
  stellar observations, thus suggesting that different Mg II emission
  levels observed in stars of similar spectral type are due to different
  fractions of their surface covered by magnetic regions. The authors
  confirm that the Mg II stellar fluxes are well correlated with other
  chromospheric and transition-region fluxes, and show that the spatially
  resolved solar data obey the same flux-flux relationships as the stellar
  data with virtually the same slope. They compare some important line
  diagnostic parameters (k/h, Δk<SUB>1</SUB>, Δk<SUB>2</SUB>, and FWHM
  of the k line) in disk integrated stellar data and in spatially resolved
  solar regions, finding no significant discrepancies between the two
  cases. Finally, the authors discuss the possibility and limitations
  of using the comparison of solar and stellar Mg II fluxes to infer
  the fraction of a star's surface covered by magnetic regions.

---------------------------------------------------------
Title: A Low-Resolution Spectroscopic Survey of Post-T Tauri
    Candidates
Authors: Pallavicini, R.; Pasquini, L.; Randich, S.
1992ASPC...26..337P    Altcode: 1992csss....7..337P
  No abstract at ADS

---------------------------------------------------------
Title: Solar and stellar coronae. Proceedings. IAU Joint Commission
    Meeting on Solar and Stellar Coronae, Buenos Aires (Argentina),
    30 Jul 1991.
Authors: Pallavicini, R.
1992MmSAI..63..537P    Altcode:
  Dedicated to the memory of Giuseppe Vaiana. The material presented
  in this volume gives an up-to-date picture of the field of solar and
  stellar coronae just before the launch of the satellite Yohkoh and in
  the early stages of analysis of stellar data from ROSAT and HST.

---------------------------------------------------------
Title: Photometry of Serendipitous X-ray Sources Detected by EXOSAT
Authors: Cutispoto, G.; Pallavicini, R.; Pasquini, L.; Rodono, M.;
   Tagliaferri, G.
1992ASPC...26..119C    Altcode: 1992csss....7..119C
  No abstract at ADS

---------------------------------------------------------
Title: A Comparison of MG II h; K Lines in the Sun; Cool Stars
Authors: Cerruti-Sola, M.; Cheng, C. -C.; Pallavicini, R.
1992ASPC...26..268C    Altcode: 1992csss....7..268C
  No abstract at ADS

---------------------------------------------------------
Title: A 5 GHz Survey of Weak-Lined T Tauri Stars
Authors: White, S. M.; Pallavicini, R.; Kundu, M. R.
1992ASPC...26..334W    Altcode: 1992csss....7..334W
  No abstract at ADS

---------------------------------------------------------
Title: Optical Spectroscopy of Cool Stars Detected by EXOSAT
Authors: Tagliaferri, G.; Cutispoto, G.; Giommi, P.; Pallavicini,
   R.; Pasquini, L.; Rodono, M.
1992ASPC...26..122T    Altcode: 1992csss....7..122T
  No abstract at ADS

---------------------------------------------------------
Title: A Search for Rotational Modulation of the Lithium Line in
    Spotted Stars
Authors: Pallavicini, R.; Cutispoto, G.; Randich, S.
1992LNP...397..319P    Altcode: 1992sils.conf..319P
  No significant rotational modulation of the equivalent width of the
  LiI blend was detected for any of the programme stars. The derived
  upper limits (ΔW/W &lt; 5-10%) are substantially smaller than what
  had been suggested previously on the basis of the solar analogy. If
  we assume that the enhancement of the equivalent width of the LiI line
  in starspots is about the same as for the Sun, the above upper limits
  imply a spot coverage factor of only a few percent, much smaller than
  that derived from the photometric variations (15-25%). It is clear
  therefore that the enhancement of the Lithium line in the spots of
  these stars, if present, is certainly lower than for the Sun.

---------------------------------------------------------
Title: Phase Dependent Variations of the Hα Line in Chromospherically
    Active Stars
Authors: Cutispoto, G.; Pallavicini, R.
1992LNP...397..264C    Altcode: 1992sils.conf..264C
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in RS CVn binaries and related chromospherically
    active stars. I.Observational results.
Authors: Pallavicini, R.; Randich, S.; Giampapa, M. S.
1992A&A...253..185P    Altcode:
  The present survey of the Li I 6708 A line in a sample of spectral type
  G and K stars with luminosity classes III, IV, and V shows that many
  K-type stars in the sample, including a large number of RS CVn binaries,
  show an anomalously high Li abundance relative to typical inactive stars
  of the same spectral type. Only a few stars in the sample are likely to
  be premain sequence objects of stars which have recently arrived on the
  main sequence. Mechanisms that could lead to the enhanced Li absorption
  in chromospherically active stars are discussed; these encompass large
  cool spots on the stellar surface, the production of Li in stellar
  flares by spallation reactions, and the evolution from main-sequence
  progenitors without, or with very shallow, outer convective zones.

---------------------------------------------------------
Title: Variability of solar and stellar coronae.
Authors: Cheng, C. -C.; Pallavicini, Roberto
1992MmSAI..63..697C    Altcode:
  The time variability of the coronal emission from the sun and other
  late-type stars is analyzed using solar data as a guideline to
  interpreting the spatially unresolved stellar observations. Results
  of numerical simulation of solar and stellar flares are compared
  with observations by Exosat. It is noted that solar observations at a
  variety of different wavelengths have revealed, in addition to flares,
  the presence of less energetic shorter-lived events, 'microflares',
  that occur randomly in space and time. The origin of these microflares
  is discussed.

---------------------------------------------------------
Title: A Comparison of Star SPOT Distributions for Various Active
    Stars Based on Doppler Images
Authors: Kürster, M.; Hatzes, A. P.; Pallavicini, R.; Randich, S.
1992ASPC...26..249K    Altcode: 1992csss....7..249K
  No abstract at ADS

---------------------------------------------------------
Title: X-ray Spectroscopic Diagnostics of the Hydrodynamics of Flares
    on M Dwarf Stars
Authors: Cheng, C. -C.; Pallavicini, R.
1992AAS...179.9306C    Altcode: 1992BAAS...24R.684C
  No abstract at ADS

---------------------------------------------------------
Title: Radio observations of weak-lined T Tauri stars.
Authors: White, S. M.; Pallavicini, R.; Kundu, M. R.
1992MmSAI..63..751W    Altcode:
  We report the results of a search for radio-continuum emission from
  weak-lined T Tauri stars selected on the basis of a range of criteria. A
  correlation is found with strong X-ray emission and with youth. All the
  stars in the survey older than about 20 million years were not detected
  as radio sources. A flare was seen on one of the survey targets, with
  a rise time of several hours. Circular polarization was also seen in
  two of the targets, providing the first direct confirmation of the
  presence of magnetic fields on these stars.

---------------------------------------------------------
Title: Stellar Flares: Observations and Modelling
Authors: Pallavicini, R.
1992ASIC..373..509P    Altcode: 1992sla..conf..509P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium Abundances in Northern RS CVn Binaries
Authors: Randich, S.; Giampapa, M. S.; Pallavicini, R.
1992ASPC...26..576R    Altcode: 1992csss....7..576R
  No abstract at ADS

---------------------------------------------------------
Title: Stellar Flares - Confined or Eruptive Events
Authors: Pallavicini, R.
1992LNP...399..289P    Altcode: 1992IAUCo.133..289P; 1992esf..coll..289P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in RS CVn Binaries and Related Chromospherically
    Active Stars
Authors: Pallavicini, R.; Randich, S.; Giampapa, M. S.
1992LNP...397..108P    Altcode: 1992sils.conf..108P
  No abstract at ADS

---------------------------------------------------------
Title: IAU, Joint Commission Meeting on Solar and Stellar Coronae,
    Buenos Aires, Argentina, July 30, 1991, Proceedings
Authors: Pallavicini, Roberto
1992MmSAI..63.....P    Altcode:
  Papers are presented on coronal emission and stellar evolution,
  high-resolution observations of the solar corona, modeling solar
  coronal loops, heating and momentum deposition in hot stars,
  and heating of solar and stellar chromospheres and coronae by MHD
  waves, and magnetized and collimated meridional outflows. Other
  papers are on X-ray activity and magnetic fields of T Tauri stars,
  X-ray spectroscopy of solar and stellar coronae, radio observations
  of solar and stellar coronae, stellar coronae and their relation
  to convection zones and rotation rates, results from an extensive
  Einstein Observatory survey of B-type stars, and transient optical
  periodicities in coronal red dwarfs. Particular attention is given to
  radio observations of weak-lined T Tauri, spectra of MHD turbulence in
  the solar corona, the thermodynamic decay scaling laws in solar loop
  flares, the differential emission measure and the composition of the
  solar corona, the structural instability of nonlinear Alfven waves,
  and heating of solar coronal holes by reflected Alfven waves. (For
  individual items see A93-26152 to A93-26175)

---------------------------------------------------------
Title: X-rays from Both Components of the Flare Star Binary Gliese 867
Authors: Pollock, A. M. T.; Tagliaferri, G.; Pallavicini, R.
1992LNP...397..331P    Altcode: 1992sils.conf..331P
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulations of Flares on Late-type Stars:
    Hydrodynamics and X-ray Spectra
Authors: Cheng, Chung-Chieh; Pallavicini, Roberto
1992LNP...397..258C    Altcode: 1992sils.conf..258C
  No abstract at ADS

---------------------------------------------------------
Title: Optical Properties of Cool Stars Discovered by EXOSAT
Authors: Tagliaferri, G.; Cutispoto, G.; Giommi, P.; Pallavicini,
   R.; Pasquini, L.; Rodonó, M.
1992LNP...397..340T    Altcode: 1992sils.conf..340T
  No abstract at ADS

---------------------------------------------------------
Title: Stellar flares: Confined or eruptive events?
Authors: Pallavicini, R.
1992LNP...399..287P    Altcode:
  Observations in different spectral bands have shown the existence of
  many similarities between solar and stellar flares, in spite of the
  far larger energies that are typically involved in the latter. The
  analogy may go as far as to include the occurrence on stars of both
  confined and eruptive flares similar to those observed on the Sun. The
  observational evidence for the existence of stellar eruptive flares
  is reviewed and it is shown that the data are still inconclusive in
  this respect. Models of stellar flares as either confined or eruptive
  magnetic structures are also discussed and it is concluded that models
  are unable at present to discriminate between the two cases.

---------------------------------------------------------
Title: Stellar Chromospheres, Coronae, and Winds
Authors: Pallavicini, R.
1992ASIC..373..313P    Altcode: 1992sla..conf..313P
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulations of Flares on M Dwarf
    Stars. I. Hydrodynamics and Coronal X-Ray Emission
Authors: Cheng, Chung-Chieh; Pallavicini, Roberto
1991ApJ...381..234C    Altcode:
  Flare-loop models are utilized to simulate the time evolution and
  physical characteristics of stellar X-ray flares by varying the values
  of flare-energy input and loop parameters. The hydrodynamic evolution
  is studied in terms of changes in the parameters of the mass, energy,
  and momentum equations within an area bounded by the chromosphere
  and the corona. The zone supports a magnetically confined loop for
  which processes are described including the expansion of heated
  coronal gas, chromospheric evaporation, and plasma compression at
  loop footpoints. The intensities, time profiles, and average coronal
  temperatures of X-ray flares are derived from the simulations and
  compared to observational evidence. Because the amount of evaporated
  material does not vary linearly with flare-energy input, large loops
  are required to produce the energy measured from stellar flares.

---------------------------------------------------------
Title: H-alpha absolute chromospheric fluxes in G and K dwarfs
    and subgiants.
Authors: Pasquini, L.; Pallavicini, R.
1991A&A...251..199P    Altcode:
  High resolution, high S/N H-alpha observations for a sample of 85 dwarfs
  and subgiants of spectral type F8 to K5 are presented. A calibration
  procedure to convert the observed equivalent widths to absolute fluxes
  at the stellar surface is developed and these fluxes are compared with
  those obtained in the Ca II K line are compared. Within the observed
  range of spectral types there is some evidence that the ratio of H-alpha
  to Ca II K line fluxes increases toward cooler stars, suggesting that
  this effect, which is prominent in M dwarfs, is already significant
  for K stars. For G and early K stars the H-alpha flux is found to
  increase with increasing activity more slowly than the Ca II K flux,
  giving flux-flux relationships that are similar to those observed
  for solar plages. It is also found that all subgiants in the sample
  have very low H-alpha fluxes, typically lower than for dwarfs of the
  same spectral type. The survey clearly shows that the H-alpha line,
  although being a useful diagnostic of stellar chromospheres, and easily
  accessible to modern solid-state detectors, is not particularly suitable
  for an accurate determination of absolute chromospheric fluxes.

---------------------------------------------------------
Title: The Role of Magnetic Loops in Solar Flares
Authors: Pallavicini, R.
1991RSPTA.336..389P    Altcode:
  X-ray and ultraviolet observations of flares have provided much
  important information on their spatial structure and magnetic
  topology. The early observations from Skylab emphasized the role
  of simple loops and loop arcades, but later observations from the
  Solar Maximum Mission have greatly complicated this picture. Flares
  appear in a multitude of loops with complex spatial and temporal
  interrelations. In many cases, interactions between different loops
  appear to play a crucial role. The inferred magnetic topology of solar
  flares will be reviewed with emphasis on the implications for processes
  of energy release and transfer. It will be shown that the spatial
  resolution of the observations obtained so far is still inadequate
  for solving many basic questions of solar flare research.

---------------------------------------------------------
Title: Book-Review - Hot Thin Plasma in Astrophysics
Authors: Pallavicini, R.; Boller, T.
1991AN....312..277P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulations of Flares on M Dwarf Stars
Authors: Cheng, C. -C.; Pallavicini, R.
1991BAAS...23..902C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Photometric and spectroscopic studies of cool stars
    discovered in EXOSAT X-ray images. I. Time variability and spectral
    classification of eight southern stars.
Authors: Cutispoto, G.; Tagliaferri, G.; Giommi, P.; Gouiffes, C.;
   Pallavicini, R.; Pasquini, L.; Rodono, M.
1991A&AS...87..233C    Altcode:
  As part of a larger program to study the optical properties of
  serendipitous Exosat sources, optical photometry and low-resolution
  spectroscopy are presented for eight southern stars which have been
  identified as optical counterparts of Exosat sources. X-ray flux
  variability has been detected for three of them. In all three cases the
  optical counterparts show RS CVn-type variability. Of the remaining
  five stars, two are found to be variable in the optical. The high
  X-ray luminosities inferred from the derived spectroscopic parallaxes
  indicates that these variable sources are all very active systems,
  possibly RS CVn binaries. The three nonvariable sources are more likely
  normal main-sequences stars, two of them with a rather high level of
  coronal emission.

---------------------------------------------------------
Title: Quiscent and flaring X-rays from both Gliese 867A and Gliese
    867B.
Authors: Pollock, A. M. T.; Tagliaferri, G.; Pallavicini, R.
1991A&A...241..451P    Altcode:
  X-ray observations of the flare-star binary system Gliese 867AB
  obtained with the Low Energy instrument on the Exosat Observatory
  were analyzed. By applying a likelihood method, it is shown that
  both components of the system were contributing to the observed X-ray
  emission with an intensity ratio A:B of about 3:1. It is also shown
  that X-ray flares with energies of the order of 10 to the 32nd erg
  originated from both stars. In the light of these results, previous
  X-ray observations, made with the IPC instrument aboard the Einstein
  Observatory were reanalyzed, and it was found, somewhat unexpectedly,
  that during those observations G867B was roughly as bright as G867A. It
  was also found that the variations observed in the Einstein data
  were due to changes in both components, much like the flares observed
  with Exosat, rather than to the earlier suggestion by Agrawal (1988)
  of rotational modulation of G867A.

---------------------------------------------------------
Title: Low-Resolution Spectra of Stellar Coronae and Flares with
EXOSAT: The Iron K-line
Authors: Pallavicini, R.; Tagliaferri, G.
1991LNP...385...26P    Altcode: 1991ildx.conf...26P
  No abstract at ADS

---------------------------------------------------------
Title: Lithium abundance and chromospheric activity.
Authors: Randich, S.; Pallavicini, R.
1991MmSAI..62...75R    Altcode:
  The relationship between chromospheric activity and lithium abundance
  in late-type stars is not well understood. For solar-type stars, it is
  generally believed that chromospheric emission and Li abundance should
  both decrease with age. However, there are a number of stars with
  low Ca-II emission and high Li content. The Li line is also strong in
  many K-type chromospherically active stars including members of RS CVn
  binaries. Some of these stars may be young or even pre-main-sequence
  objects; many other, however, are apparently evolved post-main-sequence
  stars. Recent observational data are presented that show the presence
  of lithium in the cool components of many RS CVn binaries and in
  other K-type stars with active chromospheres. Several possibilities
  to explain the observed Li excess in these stars are discussed.

---------------------------------------------------------
Title: The role of magnetic loops in solar flares.
Authors: Pallavicini, R.
1991psf..conf..389P    Altcode:
  The inferred magnetic topology of solar flares is reviewed with emphasis
  on the implications for processes of energy release and transfer. It
  is shown that the spatial resolution of the observations obtained
  so far is still inadequate for solving many basic questions of solar
  flare research.

---------------------------------------------------------
Title: Lithium Abundance and Rotation in Southern Chromospherically
    Active Stars
Authors: Randich, S.; Pallavicini, R.
1991ASIC..340..251R    Altcode: 1991amey.conf..251R
  No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Activity in Late-Type Giants and Supergiants:
    Constraints on Heating Theories (With 1 Figure)
Authors: Pasquini, L.; Brocato, E.; Pallavicini, R.
1991mcch.conf..222P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Lithium in chromospherically active stars.
Authors: Pallavicini, R.; Randich, S.; Giampapa, M.; Cutispoto, G.
1990Msngr..62...51P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Chromospheric activity of evolved late-type stars -
    Chromospheric activity in evolved stars
Authors: Pasquini, L.; Brocato, E.; Pallavicini, R.
1990A&A...234..277P    Altcode:
  Ca II K emission in a homogeneous sample of late-type giants
  and supergiants is analyzed. The Wilson-Bappu relationship and
  color-temperature scales are used to construct an H-R diagram which
  is compared with theoretical evolutionary tracks. It is shown that in
  spite of the errors involved in the determination of the fundamental
  stellar parameters, a clear relationship between chromospheric surface
  activity and stellar mass is present. 5-10 solar mass stars in He
  burning phase show the highest levels of activity; on the other hand,
  less massive stars ascending along the Red Giant Branch are extremely
  quiet. A correlation between surface activity and rotation is found,
  and it is shown that a knowledge of the stellar evolutionary history is
  essential for understanding chromospheric emission from evolved stars.

---------------------------------------------------------
Title: X-ray emission from solar neighbourhood flare stars : a
    comprehensivesurvey of EXOSAT results.
Authors: Pallavicini, R.; Tagliaferri, G.; Stella, L.
1990A&A...228..403P    Altcode:
  Exosat Observatory observations of flare stars pertaining to 25
  separate sources are examined. The Exosat instrumentation is described,
  and a data sample is presented. Quiescent and flaring emissions from
  UV Ceti-type flare stars as observed with a low-energy experiment on
  Exosat are discussed, and the results of the timing analysis of the
  low-energy data are analyzed, along with the results of the spectral
  analysis of the Exosat medium-energy flare data. It is observed
  that while all sources are detected by the low-energy experiment, the
  medium-energy data is limited only to large flares. It is concluded that
  the quiescent X-ray luminosity of different flare stars is related to
  the bolometric luminosity, with the quiescent X-ray emission changing
  little from one observation to another, and that there is a substantial
  variability over a different time scales, appearing in the form of
  either individual flares or of more gradual variations.

---------------------------------------------------------
Title: Flaring and quiescent X-rays from Castor.
Authors: Pallavicini, R.; Tagliaferri, G.; Pollock, A. M. T.; Schmitt,
   J. H. M. M.; Rosso, C.
1990A&A...227..483P    Altcode:
  Using data obtained with the Low Energy (LE) and Medium Energy
  instruments aboard Exosat, the first detection of both flaring and
  quiescent X-ray emission from the A-type visual binary Castor (alpha
  Gem) is reported. In the LE, Castor was clearly resolved from the
  nearby star YY Gem, which was also observed to flare some hours after
  Castor. After verifying that the Castor flare was indeed an X-ray as
  opposed to a UV event, physical parameters of the flaring source are
  derived. The detection of the quiescent emission led to reevaluation
  of the previous X-ray observations by the Einstein Observatory showing
  that, contrary to earlier reports, Castor was strongly detected in the
  IPC. Possible interpretations of the results are discussed by devoting
  some attention to the multiplicity of the Castor system, suggesting
  that the X-rays originate from an unseen late-type companion rather
  than from the A-type primaries.

---------------------------------------------------------
Title: Spectroscopy of stellar coronal sources with the medium energy
    experiment on EXOSAT
Authors: Pallavicini, R.; Pasquini, L.; Schmitt, J. H. M. M.;
   Tagliaferri, G.
1990hrxr.conf..122P    Altcode: 1990IAUCo.115..122P
  Results obtained on the spectral analysis of the Exosat medium-energy
  observations of stellar coronal sources are summarized. Special
  attention is given to the time-resolved spectroscopy of stellar flares
  and determination of the temperature structure of quiescent RS CVn
  binaries. Substantial differences were found between the coronae of
  RS CVn stars and the coronae of the sun and other single late-type
  stars. The results suggest that either the coronae of most RS CVn
  stars involve more than one family of loops (also indicated by eclipse
  observations of White et al., 1988) or the coronal structures in these
  stars have a more complex emission measure distribution than the simple
  power-law assumed in this study.

---------------------------------------------------------
Title: X-Ray Emission from Solar Neighbourhood Flare Stars
Authors: Pallavicini, R.; Stella, L.; Tagliaferri, G.
1990IAUS..137..147P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: High-resolution spectroscopy of cool stars at ESO.
Authors: Pasquini, L.; Pallavicini, R.
1990MmSAI..61..737P    Altcode:
  An overview of the instrumentation presently available at La Silla
  for high-resolution spectroscopy is presented, and several programs
  that have been carried out recently using these instruments are
  discussed. Discussed topics include the determination of chromospheric
  radiative losses in the Ca II H and K lines and in H-alpha, the search
  for rotational modulation in H-alpha and in the Li I 6708 A line, the
  measurement of stellar rotation rates, and the investigation of lithium
  abundance in RS CVn binaries and other chromospherically active stars.

---------------------------------------------------------
Title: Time variability of stellar coronal sources observed by EXOSAT
Authors: Pallavicini, R.; Schmitt, J. H. M. M.
1990AdSpR..10b.125P    Altcode: 1990AdSpR..10..125P
  We present an overview of time variability in stellar coronal sources
  as observed with the EXOSAT satellite. We focus on M dwarf flare stars
  and we discuss both quiescent and flaring emission. We also outline
  recent developments in the modelling of stellar flares.

---------------------------------------------------------
Title: Energy Release in Stellar Flares
Authors: Pallavicini, R.
1990IAUS..142...77P    Altcode:
  Flarelike events similar to those observed on the sun occur on many
  different types of stars, particularly on late K and M dwarfs. Although
  the physical mechanisms responsible for these events remain largely
  unknown, it is likely that the flare energy derives from dissipation of
  magnetic fields as is the case for solar flares. The basic observational
  facts that suggest an analogy between solar and stellar flares are
  reviewed, and the ways in which the different physical conditions
  occurring on stars may affect the application of current solar-type
  models to the stellar case are discussed. It is shown that, in
  spite of a qualitative agreement found between model predictions and
  observations, there is still no convincing evidence that stellar flares
  are simply scaled-up versions of solar flares. Major advances in the
  observations of stellar flares are required before this fundamental
  question can be safely addressed.

---------------------------------------------------------
Title: The differential emission measure of Lambda And
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1990hrxr.conf...36L    Altcode: 1990IAUCo.115...36L
  Results are presented from an analysis of X-ray and UV observations
  of Lambda And binary, carried out simultaneously on November 11,
  1985 from the Exosat and the IUE. The results were used to derive the
  differential emission measure (DEM) as a function of temperature up
  to a maximum of 35 x 10 exp 6 K. The DEM exhibited a minimum around
  2 x 10 exp 5 K and increased at higher temperature. The derived DEM
  is compatible with a loop model having a half length of 10 exp 12 cm,
  a cross section of 3 x 10 exp 22 sq cm, and a pressure of 15 dyn/sq cm.

---------------------------------------------------------
Title: X-ray spectroscopy of RS CVn stars with EXOSAT.
Authors: Pasquini, L.; Schmitt, J. H. M. M.; Pallavicini, R.
1989A&A...226..225P    Altcode:
  Results are presented of a spectral analysis of a sample of RS CVn
  stars which comprises all (except two) cataloged RS CVn binaries
  observed by Exosat. Data from both the Medium Energy and Low Energy
  Exosat experiments are analyzed assuming simple spectral models and
  the dependence of the fitted coronal parameters on the signal-to-noise
  ratio. Evidence is found for multitemperature coronal structures in
  RS CVn stars, together with indications of intrinsic differences in
  the temperature stratification of different stars.

---------------------------------------------------------
Title: Erratum - Calibration Stars for Cross-Correlation Studies of
    Stellar Rotation and an Examination of the Archival Data
Authors: Soderblom, D. R.; Pendleton, J.; Pallavicini, R.
1989AJ.....98..737S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Rotation Rates of Giant Stars
Authors: Gray, David F.; Pallavicini, R.
1989PASP..101..695G    Altcode:
  The rotation rates and macroturbulence dispersion of 14 G and K giants
  were measured using Fourier reduction of spectral-line profiles. The
  high-spectral-resolution, high-signal-to-noise observations were
  taken with the Coude Echelle Spectrometer of the European Southern
  Observatory. Good agreement was found between the present results and
  previous investigations, showing that no large systematic differences
  are introduced by using different spectrographs and detectors. The
  results generally confirm the low rotation seen for cool giants.

---------------------------------------------------------
Title: X-ray emission from stellar coronae
Authors: Pallavicini, R.
1989A&ARv...1..177P    Altcode:
  Stars of nearly all spectral types and luminosity classes are surrounded
  by tenuous high-temperature ( T≈10<SUP>6</SUP>-10<SUP>7</SUP>K)
  coronae, which emit most of their radiation in the soft X-ray part of
  the spectrum. This paper reviews our present observational knowledge
  and theoretical understanding of stellar coronae, as has emerged from
  the extensive observations carried out with the Einstein and EXOSAT
  Observatories. We argue that different physical mechanisms are likely
  to be responsible for coronal emission in different parts of the HR
  diagram and we discuss the principal scenarios that have been proposed
  to account for the data. We show that in spite of the enormous progress
  made during the past decade, our understanding of stellar coronal
  emission remains incomplete and largely phenomenological. We outline
  major unsolved problems to be addressed by future space missions.

---------------------------------------------------------
Title: Book-Review - Hot Thin Plasmas in Astrophysics
Authors: Pallavicini, R.
1989Sci...244..996P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Absolute flux calibration of the H and K lines of CA II :
    chromospheric radiative losses in F and G-type stars.
Authors: Pasquini, L.; Pallavicini, R.; Dravins, D.
1989A&A...213..261P    Altcode:
  Ca II H and K spectra of 81 (mainly Southern) F and G stars are
  analyzed using two different calibration methods. It is shown that, for
  spectra of sufficiently high resolution, and for stars of relatively
  low rotation rates, the calibrations of Linsky et al. (1979) and
  of Pasquini et al. (1988) give essentially the same results. These
  calibrations are used to derive absolute surface fluxes in the H and
  K lines of Ca II for 64 stars. It is shown that several late-F and
  early-G giants and supergiants have Ca II H and K fluxes in excess
  of about 10 to the 6th erg/sq cm s, much larger than those typically
  observed for normal giants of later spectral types.

---------------------------------------------------------
Title: A comparison of solar and stellar ultraviolet spectra obtained
    with SKYLAB and IUE.
Authors: Cappelli, A.; Cerruti-Sola, M.; Cheng, C. C.; Pallavicini, R.
1989A&A...213..226C    Altcode:
  A comparison is presented of 78 Short-Wavelength Primary (SWP)
  low-resolution IUE spectra of 45 late-type stars and 10 high-resolution
  Skylab spectra of spatially-resolved solar regions of various degrees
  of magnetic activity, including quiet areas, plage regions, and one
  flare. The results show that the different levels of chromospheric and
  transition region emission observed in stars of similar spectral types
  are paralleled by a similar behavior displayed by solar regions of
  different magnetic activity and that the spatially-resolved solar data
  obey the same flux-flux relationships as the stellar data over more
  than three order of magnitude. It is argued that the similar behavior
  of the solar and stellar UV line fluxes, together with the dependence
  of the stellar fluxes on rotation, presents an evidence that stellar
  activity is of magnetic origin and likely results from a dynamo process.

---------------------------------------------------------
Title: Calibration Stars for Cross-Correlation Studies of Stellar
    Rotation, and an Examination of the Archival Data
Authors: Soderblom, David R.; Pendleton, James; Pallavicini, Roberto
1989AJ.....97..539S    Altcode:
  Precise v sin i values have been measured for more than 60 F and G
  dwarfs. Spanning the range of 5-80 km/s, they are primarily useful
  for calibrating cross correlations up to about 50 km/s. The present
  values are compared to older ones from photographic spectra and it is
  found that most of the older data are adequate but have fairly large
  errors. However, the rotational-velocity catalog of Uesugi and Fukuda
  (1982) is contaminated with erroneous data and is, therefore, suspect
  as a source of stellar rotational information.

---------------------------------------------------------
Title: Recent advances in stellar coronal physics.
Authors: Pallavicini, R.
1989MmSAI..60...33P    Altcode: 1989MSAIt..60...33P
  A brief summary is given of recent advances in our understanding
  of X-ray emission from stellar coronae. Results from the European
  satellite EXOSAT are presented and discussed in some detail.

---------------------------------------------------------
Title: X-ray emission from stellar flares: EXOSAT results.
Authors: Pallavicini, R.; Tagliaferri, G.
1989sasf.confP..17P    Altcode: 1989IAUCo.104P..17P; 1988sasf.conf...17P
  The authors present an overview of recent observations of stellar X-ray
  flares obtained with the EXOSAT Observatory. They discuss a few examples
  of flares from M dwarf flare stars, from RS CVn and Algol-type binaries,
  from single late-type stars (including a GO dwarf and an A-type visual
  binary), and from pre-main-sequence objects. The authors also draw
  some general conclusions from the preliminary analysis of the EXOSAT
  data samples.

---------------------------------------------------------
Title: Flare energetics.
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veck, N. J.
1989epos.conf..377W    Altcode:
  The authors have sought to establish a comprehensive and self-consistent
  picture of the sources and transport of energy within a flare. To
  achieve this goal, they chose five flares in 1980 that were well
  observed with instruments on the Solar Maximum Mission, and with other
  space-borne and ground-based instruments. The events were chosen to
  represent various types of flares. Details of the observations available
  for them and the corresponding physical parameters derived from these
  data are presented. The flares were studied from two perspectives,
  the impulsive and gradual phases, and then the results were compared
  to obtain the overall picture of the energetics of these flares. The
  authors also discuss the role that modeling can play in estimating the
  total energy of a flare when the observationally determined parameters
  are used as the input to a numerical model. Finally, a critique of
  our current understanding of flare energetics and the methods used to
  determine various energetics terms is outlined, and possible future
  directions of research in this area are suggested.

---------------------------------------------------------
Title: A giant X-ray flare from a B9 + post-T Tauri system detected
    by EXOSAT.
Authors: Tagliaferri, G.; Giommi, P.; Angelini, L.; Osborne, J. P.;
   Pallavicini, R.
1989sasf.confP.131T    Altcode: 1989IAUCo.104P.131T; 1988sasf.conf..131T
  The authors report the serendipitous discovery by EXOSAT of a flaring
  X-ray source in the field of the Seyfert type I galaxy III ZW 2. They
  identify this source with the visual binary HD 560 (B9V + G5Ve)
  and argue that virtually all of the observed X-ray flux, including
  the flare, came from its late-type component (HD 560 B). Optical
  studies have lead to the identification of HD 560 B as a post-T Tauri
  star. Since these stars are difficult to detect by optical methods,
  X-ray observations may prove to be the best way to identify them.

---------------------------------------------------------
Title: Stellar coronal physics with the High-Throughput X-Ray
    Spectroscopy Mission (XMM)
Authors: Pallavicini, R.
1989MmSAI..60..289P    Altcode:
  The High-Throughput X-Ray Spectroscopy Mission (XMM) to be flown
  by the end of this century is the second 'cornerstone' project in
  the ESA Long-Term Program for Space Science. It will consist of a
  high-throughput multi-mirror grazing incidence telescope coupled
  to dispersive and nondispersive imaging spectrometers. With
  its unprecedented sensitivity over a wide band, the capability
  of simultaneous medium- and low-resolution spectroscopy, and the
  continuous-look capability, it will make possible a major advance in all
  fields of X-ray astronomy. This paper illustrates the capabilities of
  XMM for the study of stellar coronae with emphasis on the determination
  of the physical parameters (temperature, density, fluid motions)
  of coronal plasmas, the investigation of coronal heating mechanisms,
  the determination of the geometrical and thermal structure of coronae,
  and the study of variability on all time scales from seconds to days.

---------------------------------------------------------
Title: An X-Ray Flare from a B9+ Post--T Tauri Star System in the
    Field of the Seyfert Galaxy III ZW 2
Authors: Tagliaferri, G.; Giommi, P.; Angelini, L.; Osborne, J. P.;
   Pallavicini, R.
1988ApJ...331L.113T    Altcode:
  We report the serendipitous discovery by EXOSAT of a flaring X-ray
  source in the field of the Seyfert type I galaxy III Zw 2. In contrast
  to an earlier report that attributed the variability observed by the
  medium energy experiment to III Zw 2, we show that the variability was
  entirely due to the serendipitous source. We identify this source with
  the visual binary HD 560 (B9V+G5Ve) and we argue that virtually all
  of the observed X-ray flux from the binary, including the flare, came
  from its late-type component. These X-ray observations bring support
  to the optical classification of HD 560 B as a post-T Tauri star.

---------------------------------------------------------
Title: Modeling of long-duration two-ribbon flares on M dwarf stars.
Authors: Poletto, G.; Pallavicini, R.; Kopp, R. A.
1988A&A...201...93P    Altcode:
  A time-dependent model of magnetic reconnection for the decay phase
  of solar two-ribbon flares is applied to long-duration stellar flares
  observed by the Einstein and Exosat observatories on the stars EQ Peg
  and Prox Cen. It is shown that the model reproduces correctly the
  energy release rate and temporal evolution during the decay phase
  of the observed events. It is concluded that the observed behavior
  is consistent with the interpretation of these flares as stellar
  counterparts of solar two-ribbon flares. In addition, taking into
  account recent measurements of stellar magnetic fields by Saar and
  Linsky (1985), it is shown that the agreement between the data and the
  analytical model results in a well-defined set of physical parameters
  for the emitting region.

---------------------------------------------------------
Title: Ultraviolet emission from the sun and stars: A comparison of
    IUE and SKYLAB spectra
Authors: Cappelli, A.; Cerruti-Sola, M.; Cheng, C. C.; Pallavicini, R.
1988ESASP.281a.287C    Altcode:
  Low-resolution IUE SWP spectra of late-type stars and high-resolution
  Skylab spectra of spatially-resolved solar regions of various degrees
  of magnetic activity (quiet areas, plages, flares) are compared. The
  high-resolution solar spectra are degraded to the same resolution
  of IUE and the solar and stellar data are analyzed in exactly the
  same way. It is shown that the different levels of chromospheric
  and transition region emission observed in stars of similar spectral
  types are paralleled by a similar behavior displayed by solar regions
  of different magnetic activity. Spatially-resolved solar data obey
  the same flux-flux relationships as the stellar data over more than
  three orders of magnitude, with virtually the same slope and similar
  scatter. The similar behavior of the solar and stellar UV line fluxes,
  together with the dependence of the stellar fluxes on rotation, are
  indirect evidence that stellar activity is of magnetic origin and
  likely results from a dynamo process. The contribution of blends,
  under different activity conditions, to line fluxes derived from IUE
  low-reslution spectra varies depending on the activity level, and may
  be substantial for the lines of O I at 1304 A and He II at 1640 A.

---------------------------------------------------------
Title: VLBI observations of RS CVn and Algol-type binaries.
Authors: Massi, M.; Felli, M.; Pallavicini, R.; Tofani, G.; Palagi,
   F.; Catarzi, M.
1988A&A...197..200M    Altcode:
  The authors report on intercontinental VLBI observations of four
  RS CVn binaries and of Algol made on 12 June 1986 at λ = 6 cm. All
  sources were detected at least on the shortest baselines. For one of
  them (UX Ari) the larger amount of data available allows to conclude
  that the emission came from an extended, possibly structured region,
  comparable in size with the binary separation. The authors compare their
  observations with those obtained previously by Mutel et al. (1985)
  and discuss briefly the physical implications of these observations
  for the modelling of radio emission in active late-type binaries.

---------------------------------------------------------
Title: Co-ordinated VLA and EXOSAT observations of the flrae stars
    UV Ceti, EQ Pegasi, YZ Canis Minoris and AD Leonis.
Authors: Kundu, M. R.; Pallavicini, R.; White, S. M.; Jackson, P. D.
1988A&A...195..159K    Altcode:
  The authors have observed four flare stars (UV Cet, EQ Peg, YZ CMi
  and AD Leo) simultaneously with the VLA and the EXOSAT satellite over
  continuous periods of 7 - 10 h. This is the first time that flare stars
  were observed simultaneously in X-rays and at microwave frequencies
  with high sensitivity instrumentation. All stars were detected both at
  the quiescent level and during flares. Although considerable activity
  in both X-rays and in the radio was found, there was little correlation
  between the two wavelength domains. The auhors discuss the significance
  of these observations for coronal activity in red dwarf flare stars.

---------------------------------------------------------
Title: CA II absolute line profles of southern late-type stars.
Authors: Pasquini, L.; Pallavicini, R.; Pakull, M.
1988A&A...191..253P    Altcode:
  The authors have used the Coudé Echelle Spectrometer and
  Reticon detector at the European Southern Observatory to acquire
  high-resolution, high-quality spectra in the H and K lines of Ca II for
  50 (mostly Southern) late-type dwarfs and giants. They have developed
  a calibration procedure for converting the observed line profiles
  into absolute flux units at the star surface and derived chromospheric
  radiative losses in these lines. They discuss spectral features observed
  in stars of different effective temperature and gravity and stress the
  relevance of these observations for the study of stellar chromospheres.

---------------------------------------------------------
Title: Stellar coronae with EXOSAT : broad band spectroscopy of
    nearby coronal sources.
Authors: Pallavicini, R.; Monsignori-Fossi, B. C.; Landini, M.;
   Schmitt, J. H. M. M.
1988A&A...191..109P    Altcode:
  Broad-band observations of stellar coronae obtained with the Low Energy
  experiment on board the Exosat satellite are presented, together with
  a technique for the analysis of Exosat low-energy data. The limitations
  of filter spectroscopy with Exosat are discussed. Specific relationships
  are provided for extracting physical quantities (temperature, emission
  measure, luminosities) from the observed count rates for the case of
  nearby coronal sources. A continuous temperature distribution exists
  in the coronae of late-type stars; the differential emission measure
  distribution extends to temperatures in excess of 10 million K for flare
  stars and RS CVn binaries, even during quiescent conditions. Coronal
  loop models, similar to those developed for magnetically confined
  structures on the sun, should be used for interpreting spatially
  integrated observations of stellar coronae.

---------------------------------------------------------
Title: Temporal and Spatial Relationships between O V and Fe XXI
    Emissions in Solar Flares
Authors: Cheng, Chung-Chieh; Pallavicini, Roberto
1988ApJ...324.1138C    Altcode:
  The temporal-spatial structure of simple solar flares observed with the
  Ultraviolet Spectrometer and Polarimeter of the Solar Maximum mission
  satellite has been studied in order to investigate the relationships
  between the impulsive O V and the gradual Fe XXI emissions. The
  point-like flares are characterized by the cotemporal evolution of
  the O V and Fe XXI emissions. The simple loop flares have a much
  larger spatial extent and show two distinctive phases: an initial
  impulsive phase with its emission localized in loop footpoints, and a
  gradual phase with its emission distributed in the loop. The temporal
  evolution of the Fe XXI and O V emissions in a flare is found to be
  closely related to its spatial structure.

---------------------------------------------------------
Title: Stellar coronae.
Authors: Pallavicini, R.
1988sscd.conf...19P    Altcode:
  Some of the current problems in stellar coronal physics are reviewed
  with emphasis on the contribution given to their solution by the EXOSAT
  Observatory. After a brief overview of the results obtained previously
  with the EINSTEIN satellite, the author focuses on the structure and
  variability of the coronae of late-type stars.

---------------------------------------------------------
Title: Stellar coronae - The EXOSAT picture
Authors: Pallavicini, R.
1988MmSAI..59...71P    Altcode:
  This paper gives a summary of Exosat results on stellar coronae
  focussing on the following topics: (1) the temperature stratification of
  coronae, as has been derived from low- and medium-resolution spectral
  data; (2) the coronal spatial structure, as has been inferred from
  observations of eclipsing binary systems; (3) the time variability of
  coronal emission, as has been detected with the long, uninterrupted
  observations made possible by the highly eccentric orbit of Exosat.

---------------------------------------------------------
Title: X-ray astronomy with EXOSAT
Authors: Pallavicini, R.; White, N. E.
1988xraw.book.....P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Stellar magnetic fields: measurements and diagnostics
Authors: Pallavicini, R.
1988ASSL..143...25P    Altcode: 1988acse.conf...25P
  Magnetic fields are central to our understanding of surface activity in
  cool stars. This paper reviews recent progresses in the measurements of
  photospheric magnetic fields and stresses some of the main difficulties
  in the analysis of magnetic field observations. It also discusses
  indirect diagnostics of stellar magnetic fields with emphasis on recent
  X-ray and microwave observations. At present, these observations
  provide the only means to infer the topology of magnetic fields at
  coronal heights.

---------------------------------------------------------
Title: Modeling of long-decay stellar flares on EQ Peg and Prox Cen
Authors: Pallavicini, R.; Poletto, G.; Kopp, R. A.
1988ASSL..143..171P    Altcode: 1988acse.conf..171P
  A magnetic reconnection model of solar 2-ribbon flares is applied to
  long-duration events observed by Einstein and Exosat on the stars
  EQ Peg and Prox Cen. The authors show that the model is capable of
  reproducing the energy release rate and temporal evolution of the decay
  phase of the observed events, strongly supporting their identification
  as stellar counterparts of solar 2-R flares. The model is also used
  to put constraints on the physical parameters of the emitting region.

---------------------------------------------------------
Title: Variations of VLBI Structure in UX Ari
Authors: Catarsi, M.; Felli, M.; Massi, M.; Palagi, F.; Pallavicini,
   R.; Tofani, G.
1988IAUS..129..283C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Stellar coronae - The EXOSAT picture
Authors: Pallavicini, R.
1988xraw.book...71P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Hot thin plasmas in astrophysics
Authors: Pallavicini, R.
1988ASIC..249.....P    Altcode: 1988htpa.conf.....P
  No abstract at ADS

---------------------------------------------------------
Title: EXOSAT observations of quiescent and flaring emission from
    M dwarf flare stars
Authors: Pallavicini, R.
1988ASSL..143..249P    Altcode: 1988acse.conf..249P
  The author presents preliminary results of a comprehensive survey
  of X-ray observations of M dwarf flare stars obtained with the
  EXOSAT satellite. He discusses quiescent and flaring emission, and
  provides evidence for the occurrence on stars of both short-lived and
  long-duration events, closely resembling compact and 2-ribbon flares on
  the Sun. He concludes that there is no observational evidence in EXOSAT
  data for continuous low-level microflaring activity of the type recently
  suggested as a mechanism of coronal heating in M dwarf flare stars.

---------------------------------------------------------
Title: Some EXOSAT Results on Stellar Coronae
Authors: Pallavicini, R.
1988ASIC..249..121P    Altcode: 1988htpa.conf..121P
  No abstract at ADS

---------------------------------------------------------
Title: EXOSAT observations of RSCVn stars
Authors: Pasquini, L.; Schmitt, J. H. M. M.; Pallavicini, R.
1988ASSL..143..241P    Altcode: 1988acse.conf..241P
  EXOSAT observations of RS CVn stars are analyzed using simple spectral
  models; the authors argue first, that the X-ray emission from these
  stars requires the presence of emitting plasma continuously distributed
  in temperature and second, that there are intrinsic differences in
  the coronal temperature stratification of these stars.

---------------------------------------------------------
Title: The Gradual and Impulsive Reconnection and the Preheating of
    Solar Flares
Authors: Li, Hong-Wei; Pallavicini, R.; Cheng, Chung-Chieh
1987SoPh..107..271L    Altcode:
  We discuss the preheating phase of solar flares triggered by emerging
  magnetic flux. We consider the development of microinstabilities in
  the diffusion region during the emergence process and we propose four
  different types of reconnection, by which we explain the preheating,
  as well as the impulsive phase of flares. We find that during the
  emergence of new magnetic flux the current sheet will not `jump' from
  the initial classical state to a fully turbulent one, but will remain
  in a marginally turbulent state which may develop either gradually or
  impulsively depending on the conditions of emergence. As a consequence
  of this, we find that four cases of reconnection are indeed possible:
  a week gradual heating, a weak impulsive process, a gradual preheating
  followed by an impulsive phase, and violent bursty reconnection.

---------------------------------------------------------
Title: Analysis of Ultraviolet and X-Ray Observations of Three
    Homologous Solar Flares from SMM
Authors: Cheng, Chung-Chieh; Pallavicini, Roberto
1987ApJ...318..459C    Altcode:
  Three homologous flares observed in the UV lines of Fe XXI and O
  V and in X-rays from the SMM were studied. It was found that: (1)
  the homology of the flares was most noticeable in Fe XXI and soft
  X-ray emissions; (2) the three flares shared many of the same loop
  footprints which were located in O V bright kernals associated with
  hard X-ray bursts; and (3) in spite of the strong spatial homology,
  the temporal evolution in UV and X-ray emissions varied from flare
  to flare. A comparison between the UV observations and photospheric
  magnetograms revealed that the basic flare configuration was a complex
  loop system consisting of many loops or bundles of loops.

---------------------------------------------------------
Title: A comparison of coronal X-ray emission observed with the
    Einstein andEXOSAT observatories.
Authors: Schmitt, J. H. M. M.; Pallavicini, R.; Monsignori-Fossi,
   B. C.; Harnden, F. R., Jr.
1987A&A...179..193S    Altcode:
  The present Einstein and Exosat observatories' star coronal X-ray
  emission data are subjected to a spectral analysis which employs the
  Raymond and Smith (1977) and Landini and Fossi (1984) computer codes
  to calculate X-ray emission from optically thin plasmas that are in
  collisional equilibrium. It is found that the derived coronal parameters
  depend only loosely on the details of the calculated theoretical X-ray
  spectrum, although the spectra nevertheless differ in their prediction
  of X-ray fluxes in various lines. It is demonstrated that the Einstein
  spectra and Exosat filter ratios can be naturally and simultaneously
  explained by assuming an underlying, continuous distribution of emission
  measure with temperature, as in the case of the solar corona.

---------------------------------------------------------
Title: Lithium abundances of southern F, G and K dwarfs and subgiants.
Authors: Pallavicini, R.; Cerruti-Sola, M.; Duncan, D. K.
1987A&A...174..116P    Altcode:
  The Li abundances of 27 southern dwarfs and subgiants of spectral types
  F, G, and K are derived using high-resolution spectra obtained with a
  coude echelle spectrometer. The derived Li abundances are compared with
  determinations of rotation rates and chromospheric Ca II K fluxes. The
  relation between the Li abundance and ages is examined. The Li-6/Li-7
  isotope ratio is evaluated, and an upper limit of 0.1 is obtained. The
  data reveal that old slowly rotating stars with low surface activity
  and high Li content have maintained high Li abundances by reduced
  metallicity, and the strong Li line in active binaries of the RS CVn
  type may be related to the presence of huge starspots on their surface
  and to the lower ionization degree of Li in cool spots. It is noted
  that for F8-G5 spectral stars a high Li abundance condition is required,
  but this condition is not adequate for the star to be young.

---------------------------------------------------------
Title: Solar and Stellar Coronae
Authors: Pallavicini, R.
1987LNP...292...98P    Altcode: 1987ssp..conf...98P
  Our present understanding of coronal heating, structuring and
  variability that has emerged from space observations of the Sun and
  nearby stars are reviewed. It is shown that a basic analogy exists
  between solar coronal physics and the phenomena observed in the coronae
  of other late-type stars. Recent X-ray observations of stellar coronae
  from EXOSAT are used to illustrate the main points.

---------------------------------------------------------
Title: Hydrodynamic Flare Modeling: Comparison of Numerical
Calculations with SMM Observations of the 1980 November 12 17:00
    UT Flare
Authors: Peres, G.; Reale, F.; Serio, S.; Pallavicini, R.
1987ApJ...312..895P    Altcode:
  The results of calculations of the evolution of flaring plasma
  in a simple coronal loop are compared with SMM observations of a
  well-studied compact flare. Calculations assuming different models of
  impulsive heating are performed, all starting from the same initial
  static loop configuration. A mechanism of local heat deposition and
  a mechanism of flare heating by energetic electron beams are tested
  with a variety of parameters. It is found that the evolution of the
  soft X-ray compact flare is mainly dominated by the thermodynamic and
  hydrodynamic properties of the confined plasma. In order to obtain
  a close match between calculated and observed X-ray polychromator
  light curves, a sizable fraction of impulsive energy must be deposited
  directly in the corona. Local Fe XXV brightenings in the flaring loop
  do not provide a good diagnostic of the site of energy deposition in
  solar flares. The total amount of impulsive energy necessary to match
  the calculated light curves with the observations depends strongly on
  the effective deposition depth.

---------------------------------------------------------
Title: Characterization of the Total Flare Energy
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.41W    Altcode: 1986epos.confE..41W
  No abstract at ADS

---------------------------------------------------------
Title: Energetics of the Impulsive Phase
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf..5.5W    Altcode: 1986epos.confE...5W
  No abstract at ADS

---------------------------------------------------------
Title: Energetics of the Gradual Phase
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.20W    Altcode: 1986epos.confE..20W
  No abstract at ADS

---------------------------------------------------------
Title: Review of Impulsive Phase Phenomena
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.60W    Altcode: 1986epos.confE..60W
  No abstract at ADS

---------------------------------------------------------
Title: Flares Chosen for Energetics Study
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.47W    Altcode: 1986epos.confE..47W
  No abstract at ADS

---------------------------------------------------------
Title: Relationships among the Phases
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veek, N. J.
1986epos.conf.5.39W    Altcode: 1986epos.confE..39W
  No abstract at ADS

---------------------------------------------------------
Title: X-Ray Observations of Flare Stars with EXOSAT
Authors: Pallavicini, R.
1986BAAS...18R.962P    Altcode: 1986BAAS...18Z.962P
  No abstract at ADS

---------------------------------------------------------
Title: Modeling of Long Duration Stellar Flares
Authors: Poletto, G.; Pallavicini, R.; Kopp, R. A.
1986BAAS...18Q.962P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: IUE and Skylab spectra of solar-type stars and of
    spatially-resolved solar regions
Authors: Pallavicini, R.; Cerruti-Sola, M.; Cheng, C. C.
1986ESASP.263...45P    Altcode: 1986NIA86.......45P; 1986niia.conf...45P
  Short-wavelength IUE spectra of nearby solar-type stars are compared
  with high-resolution spatially resolved ultraviolet spectra of
  individual solar features (quiet region, plage, flare) obtained with
  the slit spectrograph on board Skylab. Comparison reveals remarkable
  similarity between the range of emission fluxes observed in stars of
  various activity levels and the range of fluxes emitted by individual
  solar regions. Since the solar features considered differ mainly in
  the level of magnetic activity, it is likely that the same occurs
  for stars. The strong similarities between spectra of active stars
  and spectra of solar plages suggest that active regions cover a much
  larger fraction of the stellar surface in young rapidly rotating stars.

---------------------------------------------------------
Title: EXOSAT detection of an X-ray flare from the solar type star
    pi 1 UMa.
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.;
   Piro, L.
1986A&A...157..217L    Altcode:
  An X-ray flare has been detected on the G0 dwarf star π<SUP>1</SUP>UMa
  using the European satellite EXOSAT. With the exception of the Sun,
  this is the first time that an X-ray flare has been observed in a
  normal solar-type star, which is not a member of a binary system and
  is not a classical flare star. As a member of the Ursa Major Cluster,
  π<SUP>1</SUP>UMa is a young, rapidly rotating star with a high level
  of chromospheric and coronal activity. The energy emitted in X-rays by
  the observed flare is at least one order of magnitude higher than the
  total energy released in large solar flares. The authors interpret the
  event as occurring in one or more magnetic loops which occupy only a
  small fraction of the star surface. The flare is found to cool both by
  radiation and conduction. The authors derive physical parameters for
  the emitting region and compare them with transient events occurring
  on the Sun, on dMe flare stars and on RS CVn and Algol-type binaries.

---------------------------------------------------------
Title: Simultaneous optical and X-ray observations of a flare on
    BY Draconis.
Authors: de Jager, C.; Heise, J.; Avgoloupis, S.; Cutispoto, G.;
   Kieboom, K.; Herr, R. B.; Landini, M.; Langerwerf, A. F.; Mavridis,
   L. N.; Melkonian, A. S.; Molenaar, R.; Monsignori-Fossi, B. C.;
   Nations, H. L.; Pallavicini, R.; Piirola, V.; Rodono, M.; Seeds,
   M. A.; van den Oord, G. H. J.; Vilhu, O.; Waelkens, C.
1986A&A...156...95D    Altcode:
  The authors present a first report on a campaign for simultaneous
  observations in the visual, radio and X-ray ranges of stellar flares
  on the binary BY Dra. During two nights of observations they observed
  one significant flare, simultaneously in soft X-rays and visible
  wavelengths, and one or two smaller bursts. The main flare impulsively
  heated an area of ⪉2×10<SUP>7</SUP>km<SUP>2</SUP> of the stellar
  photosphere to a brightness temperature ⪆25000K, during about 5
  min, and generated hot plasma, emitting soft X-rays. This emission
  reached maximum after the impulsive burst and lasted for about an
  hour; it covered a much larger area on the star than the optical
  emission. There was no significant hard X-ray component. The authors
  ascribe the optical continuous emission to the flare's impulsive phase,
  and the soft X-ray emission to the gradual phase.

---------------------------------------------------------
Title: Preliminary Catalog of Chromospheric, Transition Region and
    Coronal Fluxes of Late-Type Stars
Authors: Governini, G.; Pallavicini, R.
1986LNP...254...67G    Altcode: 1986csss....4...67G
  No abstract at ADS

---------------------------------------------------------
Title: Coronal magnetic fields
Authors: Pallavicini, R.
1986HiA.....7..447P    Altcode:
  The use of coronal X-ray emission in determining the configuration of
  the magnetic field lines in the corona is discussed. Spatially-resolved
  X-ray observations provided by Skylab and subsequently by missions
  such as OSO-8 and SMM show the solar corona to be inhomogeneous, with
  open and closed structures determined by the topology of the magnetic
  field. The scenario provided by observations from the Einstein,
  Exosat, and IUE satellites includes the activity in the sun and
  late-type stars resulting from the emergence of magnetic fields at
  the star surface. Data demonstrate the dependence of chromospheric
  and coronal emission on rotation, while there is no evidence that
  convection zone depths determine the level of magnetic activity, except
  for early F stars and possibly very late M stars. Results suggest that
  most late-type dwarfs of all spectral types may have coronae similar
  to, although often much more active than, the solar corona, and are
  characterized by confined magnetic structures with typical emission
  heights significantly smaller than the stellar radius.

---------------------------------------------------------
Title: Southern Stars Observed at ESO: Absolute Surface Fluxes in
    the K Line of Ca II
Authors: Pasquini, L.; Pallavicini, R.; Pakull, M.
1986LNP...254...74P    Altcode: 1986csss....4...74P
  No abstract at ADS

---------------------------------------------------------
Title: EXOSAT observations of quiescent and flaring emission from
    active late-type stars
Authors: Pallavicini, R.; Monsignori-Fossi, B. C.; Landini, M.; Kundu,
   M. R.; Lang, K. R.
1986AdSpR...6h.125P    Altcode: 1986AdSpR...6Q.125P
  The authors present the highlights of several guest investigator
  programs carried out with the EXOSAT satellite. They discuss quiescent
  as well as flaring emission from normal F to M dwarfs, from dMe flare
  stars and from RS CVn binaries.

---------------------------------------------------------
Title: Programmi spaziali di fisica solare: il satellite europeo SOHO.
Authors: Pallavicini, R.
1986GAst...12....6P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Coronal X-ray temperatures from Einstein and EXOSAT
    observations
Authors: Schmitt, J. H. M. M.; Pallavicini, R.; Monsignori-Fossi,
   B. C.; Harnden, F. R., Jr.
1986AdSpR...6h.141S    Altcode: 1986AdSpR...6..141S
  Spectral analysis of coronal X-ray emission from stars observed with
  both the Einstein and EXOSAT Observatories is presented. Using computer
  codes developed by Raymond and Smith /1/ and Landini and Fossi /2/ to
  calculate the X-ray emission from optically thin plasma in collisional
  equilibrium we find that the derived coronal parameters depend only
  rather insensitively on the details of the calculated theoretical X-ray
  spectrum and demonstrate how both the Einstein Observatory IPC spectra
  and the EXOSAT LE filter ratios can be naturally and simultaneously
  explained by assuming an underlying continuous emission measure
  distribution as is the case in the solar corona.

---------------------------------------------------------
Title: UV spectra of late-type stars and of representative solar
    features
Authors: Sola, M. Cerruti; Cheng, C. C.; Pallavicini, R.
1986AdSpR...6h..77S    Altcode: 1986AdSpR...6...77S
  We compare low-resolution short-wavelength IUE spectra of solar-type
  stars with high-resolution spatially-resolved SKYLAB spectra of
  individual solar features (quiet region, plage, flare). The comparison
  is used to obtain insights into the magnetic activity of stars.

---------------------------------------------------------
Title: X-ray, UV, optical and radio observations of the visual binary
    53 AQR
Authors: Pallavicini, R.; Cerruti Sola, M.; Monsignori-Fossi, B. C.;
   Pasquini, L.
1986AdSpR...6h.121P    Altcode: 1986AdSpR...6..121P
  The authors present optical (ESO), ultraviolet (IUE), X-ray (EXOSAT)
  and radio (VLA) observations of the visual binary 53 Aquarii. They
  show that the two components of the system can be used to infer the
  properties of the Sun at a much earlier epoch.

---------------------------------------------------------
Title: EXOSAT Detection of a Very Large Flare on EQ Peg
Authors: Pallavicini, R.; Kundu, M. R.; Jackson, P. D.
1986LNP...254..225P    Altcode: 1986csss....4..225P
  No abstract at ADS

---------------------------------------------------------
Title: Coronae of Late-Type Stars Observed with EXOSAT
Authors: Pallavicini, R.; Monsignori-Fossi, B. C.; Landini, M.
1986LNP...254..212P    Altcode: 1986csss....4..212P
  No abstract at ADS

---------------------------------------------------------
Title: Magnetic reconnection and energy release in a long-duration
    stellar flare
Authors: Poletto, G.; Pallavicini, R.; Kopp, R. A.
1986AdSpR...6h.145P    Altcode: 1986AdSpR...6..145P
  A dynamical model of magnetic reconnection in solar two-ribbon flares
  is applied to EXOSAT observations of a long-decay flare from the star
  EQ Peg. We show that the model is able of reproducing correctly the
  energy release rate and temporal evolution of the decay phase of the
  observed flare. We conclude that the flare was the stellar counterpart
  of solar two-ribbon flares and we derive the physical parameters of
  the emitting region.

---------------------------------------------------------
Title: Coronal models of late-type stars observed with EXOSAT
Authors: Monsignori-Fossi, B. C.; Landini, M.; Pallavicini, R.;
   Tribioli, F.
1986AdSpR...6h.137M    Altcode: 1986AdSpR...6..137M
  Differential emission measure distributions for transition region and
  corona able to reproduce X-ray and UV emission are investigated. The
  EXOSAT, EINSTEIN and IUE data for the solar type star K Cet are
  analyzed. A multitemperature differential emission measure distribution
  gives a satisfactory fit of the data.

---------------------------------------------------------
Title: Flare energetics.
Authors: Wu, S. T.; de Jager, C.; Dennis, B. R.; Hudson, H. S.;
   Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner,
   M. E.; Cargill, P. J.; Crannell, C. J.; Doyle, J. G.; Hyder, C. L.;
   Kopp, R. A.; Lemen, J. R.; Martin, S. F.; Pallavicini, R.; Peres,
   G.; Serio, S.; Sylwester, J.; Veck, N. J.
1986NASCP2439....5W    Altcode:
  In this investigation of flare energetics, the authors establish a
  comprehensive and self-consistent picture of the sources and transport
  of energy within a flare. They chose five flares in 1980 that were
  well observed with instruments on the SMM, and with other space-borne
  and ground-based instruments. Details of the observations available
  for them and the corresponding physical parameters derived from these
  data are presented. The flares were studied from two perspectives,
  the impulsive and gradual phases, and then the results were compared
  to obtain the overall picture of the energetics of these flares. The
  authors also discuss the role that modeling can play in estimating the
  total energy of a flare when the observationally determined parameters
  are used as the input to a numerical model.

---------------------------------------------------------
Title: Solar-type phenomena in stars: an overview of the solar-stellar
    connection.
Authors: Pallavicini, R.
1986RALR...85....1P    Altcode:
  An overview is given of the solar-stellar connection with emphasis
  on the following topics: (1) the relationship between convection,
  rotation and magnetic fields in stars possessing subphotospheric
  convection zones; (2) the observational evidence for the presence of
  solar-type phenomena in stars at various atmospheric levels; (3) the
  modelling of magnetically confined coronal structures during quiescent
  as well as flaring conditions.

---------------------------------------------------------
Title: UV spectra of late-type stars and of representative solar
    features
Authors: Cerruti Sola, M.; Pallavicini, R.; Cheng, C. C.
1986AdSpR...6h..77C    Altcode: 1986AdSpR...6...77C
  The authors compare low-resolution short-wavelength IUE spectra
  of solar-type stars with high-resolution spatially-resolved Skylab
  spectra of individual solar features (quiet region, plage, flare). The
  comparison is used to obtain insights into the magnetic activity
  of stars.

---------------------------------------------------------
Title: Southern Stars Observed at ESO: Lithium Abundances for G and
    K Dwarfs and Subgiants
Authors: Cerruti-Sola, M.; Pallavicini, R.
1986LNP...254...46C    Altcode: 1986csss....4...46C
  No abstract at ADS

---------------------------------------------------------
Title: The preheating of solar flares and reconnection
Authors: Li, H. -W.; Pallavicini, R.; Cheng, C. -C.
1986AdSpR...6f..69L    Altcode: 1986AdSpR...6...69L
  We discuss the preheating phase of solar flares trigerred by emerging
  magnetic flux. We consider the development of microinstabilities inside
  the diffusion region during the emergence process and propose four
  different types of reconnection, by which we are able to interpret
  the preheating, as well as the impulsive phase of flares.

---------------------------------------------------------
Title: Detection of an X-Ray Flare from a Single G Dwarf Star
Authors: Monsignori-Fossi, B. C.; Pallavicini, R.; Landini, M.;
   Piro, L.
1986LNP...254..222M    Altcode: 1986csss....4..222M
  No abstract at ADS

---------------------------------------------------------
Title: Energy release topology in a multiple-loop solar flare
Authors: Cheng, C. -C.; Pallavicini, R.; Acton, L. W.;
   Tandberg-Hanssen, E.
1985ApJ...298..887C    Altcode:
  The temporal and spatial structures of the UV and X-ray emissions
  and the magnetic field configuration in the November 12, 1980 flare
  observed from SMM have been studied. The UV observations were done in
  the O V and Fe XXI lines with a spatial resolution of 10 arcsec. The
  observations show that the impulsive UV bursts, and also the hard
  X-ray bursts by their temporal correlation with the impulsive O V
  emission, occurred in small localized kernels. By comparing the O V,
  Fe XXI, and X-ray raster images of the flare with the magnetogram,
  these emission kernels were identified as footpoints of interacting
  magnetic flux loops. The temporal evolution of the O V/Fe XXI emission
  shows that there was considerable preheating in the flare plasma some
  8-9 minutes prior to the onset of the main hard X-ray bursts. The
  results are interpreted as indicating that the primary flare energy
  release occurred in a highly sheared multiloop structure, which lies
  along a magnetic neutral line. By either beam particle propagation or
  convective motion, flare energy is transported via a common footpoint to
  another loop which brightened later. The preheating of the flare plasma
  is shown to create a more favorable environment for energetic particle
  acceleration which resulted in the main impulsive hard X-ray bursts.

---------------------------------------------------------
Title: Multiwavelength Analysis of a Well Observed Flare from Solar
    Maximum Mission
Authors: MacNeice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.;
   Antonucci, E.; Shine, R. A.; Rust, D. M.; Jordan, C.; Dennis, B. R.
1985SoPh...99..167M    Altcode:
  We describe and analyse observations of an M1.4 flare which began at 17:
  00 UT on 12 November, 1980. Ground based Hα and magnetogram data have
  been combined with EUV, soft and hard X-ray observations made with
  instruments on-board the Solar Maximum Mission (SMM) satellite. The
  preflare phase was marked by a gradual brightening of the flare site
  in Ov and the disappearance of an Hα filament. Filament ejecta were
  seen in Ov moving southward at a speed of about 60 km s<SUP>−1</SUP>,
  before the impulsive phase. The flare loop footpoints brightened in Hα
  and the CaXIX resonance line broadened dramatically 2 min before the
  impulsive phase. Non-thermal hard X-ray emission was detected from the
  loop footpoints during the impulsive phase while during the same period
  blue-shifts corresponding to upflows of 200-250 km s<SUP>−1</SUP>
  were seen in Ca XIX. Evidence was found for energy deposition in both
  the chromosphere and corona at a number of stages during the flare. We
  consider two widely studied mechanisms for the production of the high
  temperature soft X-ray flare plasma in the corona, i.e. chromospheric
  evaporation, and a model in which the heating and transfer of material
  occurs between flux tubes during reconnection.

---------------------------------------------------------
Title: Microwave observations of late-type stars with the Very
    Large Array.
Authors: Pallavicini, R.; Willson, R. F.; Lang, K. R.
1985A&A...149...95P    Altcode:
  The Very Large Array was used to search for microwave emission from
  32 stars of late spectral type including RS CVn type stars, dwarf
  M stars, and stars with active chromospheres, coronae, or intense
  magnetic fields. The RS CVn stars were detected at 6 cm wavelength,
  and upper limits are established for another six. Radio emission
  was detected from three dwarf M flare stars, UV Cet, EQ Peg and YZ
  CMi. Both impulsive (no more than 20 s) and more gradual (at least
  ten minutes) bursts were observed from the flare star YZ CMi. Radio
  emission was not confirmed at 6 cm from the solar type star Chi(1)
  Ori, with an upper limit that is three times lower than the detections
  reported by other observers. Microwave emission could not be detected
  from any other solar type star of spectral class F to K. The quiescent
  radio emission from dwarf M flare stars was interpreted as nonthermal
  gyrosynchrotron emission by mildly relativistic electrons accelerated
  more or less continuously in the magnetic fields of starspots.

---------------------------------------------------------
Title: VLA Observations of Late-Type Stars
Authors: Lang, K.; Willson, R.; Pallavicini, R.
1985ASSL..116..267L    Altcode: 1985rst..conf..267L
  The authors report the results of a program of observations of late-type
  stars at λ = 6 cm using the V.L.A. The source list includes stars
  with active chromospheres and coronae, UV Ceti-type flare stars, and RS
  CVn stars. Of the 31 objects surveyed, the authors have detected 6 and
  they have established upper limits for the remaining 25. The detected
  sources are all RS CVn and UV Ceti-type flare stars. No dwarf star
  of spectral type G and K has been detected, including the previously
  reported radio source χ<SUP>1</SUP>Ori.

---------------------------------------------------------
Title: The Solar-Stellar Connection (Invited Paper)
Authors: Pallavicini, R.
1985ASSL..116..197P    Altcode: 1985rst..conf..197P
  This review summarizes the many contact points between solar and stellar
  physics stressing the similarities and differences between phenomena
  observed on the sun and on stars with outer convective mantles. Topics
  discussed include: (1) the relationship between convection, rotation and
  magnetic fields as a source of magnetic activity in late-type stars;
  (2) the observation of solar-type phenomena (spots, plages, activity
  cycles etc.) on other stars; (3) the structuring and heating of high
  temperature coronae; (4) the observation and interpretation of radio
  emission from the sun and late-type stars.

---------------------------------------------------------
Title: Observations of the Physical Conditions in Solar Flare
    Transition Zone Plasmas from SMM
Authors: Cheng, Chung-Chieh; Pallavicini, R.; Tandberg-Hanssen, E.
1985BAAS...17..629C    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: EXOSAT Observations of Late-Type Stars - the Application of
    Coronal Loop Models
Authors: Landini, M.; Monsignori-Fossi, B. C.; Pallavicini, R.
1985SSRv...40...43L    Altcode:
  We apply solar-type coronal loop models to X-ray and UV observations of
  late-type stars. We derive from EXOSAT and IUE observations constraints
  on the temperature, pressure and size of the emitting structures.

---------------------------------------------------------
Title: X-ray, ultraviolet, optical and radio observations of cool
    stars
Authors: Pallavicini, R.
1985MmSAI..56..813P    Altcode:
  An outline is presented of ongoing activity, with preliminary results,
  at the Arcetri Observatory, where an extensive program is under way to
  investigate the physical properties of late-type stars using a variety
  of observational techniques, from X-ray to radio wavelengths. The
  research is largely based on Guest Investigator programs, making
  use of both spaceborne and ground-based facilities. The UV and X-ray
  emission from stellar chromospheres, transition regions and coronae
  is being investigated using data from IUE, Einstein, and Exosat. The
  optical properties of late-type stars (rotation, lithium abundance,
  chromospheric emission, etc.) are being studied using instrumentation
  available at the European Southern Observatory (ESO) in Chile. Radio
  emission from stars is investigated using the VLA as well as VLBI
  techniques. The observational data are interpreted in the framework
  of dynamo-generated magnetic activity, using the solar analogy as a
  convenient working hypothesis and exploring the extent to which solar
  models can be extrapolated to other stars.

---------------------------------------------------------
Title: EXOSAT observations of late-type stars: preliminary results.
Authors: Landini, M.; Monsignori-Fossi, B. C.; Pallavicini, R.
1985xra..conf...31L    Altcode: 1984xra..conf...31L
  The authors present preliminary results of a program of observations
  of late-type stars using EXOSAT. They derive temperatures and emission
  measures and compare their results with previous Einstein observations
  of the same targets.

---------------------------------------------------------
Title: Analysis of the Magnetic Field Configuration of a Filament
    Associated Flare from X-Ray Ultraviolet and Optical Observations
Authors: Cheng, C. -C.; Pallavicini, R.
1984SoPh...93..337C    Altcode:
  X-ray and ultraviolet observations from SMM of a filament-associated
  event on 22 November, 1980 are examined in conjunction with ground-based
  optical observations, in order to determine the magnetic field
  configuration involved in the flaring process. We find evidence that the
  flare was produced by gradual energy release in a large sheared magnetic
  loop which interacted with another smaller loop. Non-thermal processes,
  as indicated by hard X-ray emission and impulsive UV kernels, were
  produced in the interaction of the two loops. Although this flare shared
  some of the characteristics of Long Duration (class II) Events, we found
  no indication of a helmet-type configuration, as generally envisaged
  for class II events. On the contrary, the magnetic configuration of the
  22 November, 1980 event was more similar to that of a compact (class I)
  flare, although on a much larger spatial scale and longer time scale.

---------------------------------------------------------
Title: Active Chromospheres and Coronae of Late-Type Stars
Authors: Pallavicini, R.
1984iue..prop.1928P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Chromospheric emission, rotation and X-ray coronae of
    late-type stars
Authors: Pallavicini, R.
1984Msngr..35....5P    Altcode:
  X-ray observations have shown that chromospheres, transition regions
  and coronae are common to stars throughout the HR diagram, and that
  magnetic fields play a fundamental role in the heating of outer stellar
  atmospheres. The observed emission levels are in both qualitative
  and quantitative disagreement with the predictions of the standard
  theory of coronal formation via the generation and dissipation of
  acoustic waves. As a result of recent emphasis on heating mechanisms
  which are based on the stressing and dissipation of magnetic fields
  generated by dynamo action in the subphotospheric convection zones,
  stellar rotation has assumed a central role in the heating problem as
  a controlling factor in dynamo process efficiency.

---------------------------------------------------------
Title: Coronal physics with the Solar and Heliospheric Observatory
Authors: Pallavicini, R.
1984MmSAI..55..549P    Altcode:
  Previously acquired X-ray and UV data gathered on the solar corona are
  summarized to indicate the progress which could be made in solar physics
  with the launch of an ESA Solar and Heliospheric Observatory (SOHO). The
  existing data base was collected with instrumentation on, e.g., Skylab,
  OSO-8, SMM, HRTS spacecraft. Arch-shaped coronal loops have been
  discovered, as has a transition region, which is significant in coronal
  heating, and closed and open magnetic fields. The holes are known
  to be the exit points for the solar wind. The SOHO spacecraft could
  help identify the heating source for the corona and the acceleration
  mechanism for the solar wind. Furthermore, SOHO could record data on
  the solar wind and coronal structures simultaneously, thus allowing
  fluctuation in one to be related to activities in the other.

---------------------------------------------------------
Title: The Solar Maximum Mission
Authors: Pallavicini, R.
1984MmSAI..55..633P    Altcode:
  Contents: Introduction. The spacecraft. The experiment payload: Gamma
  Ray Experiment, Hard X-ray Burst Spectrometer, Hard X-ray Imaging
  Spectrometer, Soft X-ray Polychromator, Ultraviolet Spectrometer
  and Polarimeter, Coronograph/Polarimeter, Active Cavity Radiometer
  Irradiance Monitor. Data acquisition and analysis. Highlights of
  results. The Italian participation.

---------------------------------------------------------
Title: Frontiers of astronomy and astrophysics
Authors: Pallavicini, Roberto
1984faa..conf.....P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Results from the Solar Maximum Mission.
Authors: Pallavicini, R.
1984MmSAI..55C.629P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Frontiers of astronomy and astrophysics. Invited papers
    presented at the Seventh European Regional Astronomy Meeting, held
    in Florence, Italy, 12 - 16 December 1983.
Authors: Pallavicini, R.; Pacini, F.
1984faai.book.....P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Observations of Cool Stars with the ESO
    Coud&amp;eacute Echelle Spectrometer
Authors: Pallavicini, R.; Pakull, M.
1984LNP...193..108P    Altcode: 1984csss....3..108P
  No abstract at ADS

---------------------------------------------------------
Title: Broad-Band Spectroscopy of Late-Type Stars with EXOSAT
Authors: Landini, M.; Monsignori-Fossi, B. C.; Pallavicini, R.
1984uxsa.coll...68L    Altcode: 1984uxsa.conf...68L; 1984IAUCo..86...68L
  No abstract at ADS

---------------------------------------------------------
Title: Coronal Magnetic Heating in the Sun and in Late-type Stars
Authors: Pallavicini, R.
1984faa..conf...83P    Altcode:
  In this paper the author reviews some of the problems related to the
  subject of coronal magnetic heating. He also refers to a number of
  review papers on the same, and related, topics, which appeared recently
  in the literature.

---------------------------------------------------------
Title: Thin plasmas: galactic sources.
Authors: Pallavicini, R.
1984PhST....7..181P    Altcode: 1984PhyS....7..181P
  Papers presented in the session "Thin plasmas" during the European
  workshop on "Very hot astrophysical plasmas" (Nice, November 1982)
  are critically reviewed. Emphasis is given to problems related to
  emission mechanisms, solar and stellar coronae, supernova remnants,
  and the hot phase of the interstellar medium.

---------------------------------------------------------
Title: Closed coronal structures. V - Gasdynamic models of flaring
    loops and comparison with SMM observations
Authors: Pallavicini, R.; Peres, G.; Serio, S.; Vaiana, G.; Acton,
   L.; Leibacher, J.; Rosner, R.
1983ApJ...270..270P    Altcode:
  The hydrodynamic response of confined magnetic structures to strong
  heating perturbations is investigated by means of a time-dependent
  one-dimensional colde which incorporates the energy, momentum, and
  mass conservation equations. The entire atmospheric structure from the
  chromosphere to the corona is taken into account. Models with different
  energy input, heating time dependence, preflare conditions and heating
  location have been examined in the numerical simulations. <P />The
  result of model calculations are compared with observations of flares
  obtained with the X-ray Polychromator experiment on the Solar Maximum
  Mission. These include light curves of spectral lines formed over a
  wide range of coronal flare temperatures, as well as determinations
  of Doppler shifts for the high temperature plasma. Several examples
  are used to illustrate the range of the observational variation. <P
  />It is shown that the predictions of the numerical simulations
  are in good overall agreement with the observed evolution of the
  flare coronal plasma. The model reproduces correctly the temporal
  profile of X-ray spectral lines and -- to first order at least --
  their relative intensities. The upflow velocities predicted by
  model calculations are in agreement with the observed blueshifts,
  supporting the interpretation of the blueshifts as due to evaporation
  of chromospheric material. The possibility of using the comparison
  of model predictions with observations to derive information on the
  processes of energy release and transfer in solar flares is discussed.

---------------------------------------------------------
Title: Hydrodynamics of Flaring Loops - SMM Observations and Numerical
    Simulations
Authors: Pallavicini, R.; Peres, G.
1983SoPh...86..147P    Altcode:
  The hydrodynamic response of confined magnetic structures to strong
  heating perturbations is investigated by means of a timedependent
  one-dimensional code which incorporates the energy, momentum and
  mass conservation equations. The entire atmospheric structure from
  the chromosphere to the corona is taken into account. The results of
  model calculations are compared with observations of flares obtained
  with the X-Ray Polychromator experiment on the Solar Maximum Mission.

---------------------------------------------------------
Title: Solar flares with SMM and implications for the physics of
    stellar flares
Authors: Pallavicini, R.
1983ASSL..102..321P    Altcode: 1983ards.proc..321P; 1983IAUCo..71..321P
  XUV flare observations from the Solar Maximum Mission are examined,
  and the results are compared with recent X-ray observations of stellar
  flares. Two problems of flare physics are considered in detail: (1)
  the role of nonthermal electrons in the overall flare energetics; and
  (2) the process of chromospheric evaporation during the thermal phase
  of a flare.

---------------------------------------------------------
Title: Meccanismi di emissione e assorbimento della radiazione in
    situazioniastrofisiche.
Authors: Landi Degl'Innocenti, E.; Pallavicini, R.
1983GAst....9...25L    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Observations of Flares in Loops
Authors: Pallavicini, R.
1982Obs...102..120P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Temporal evolution of soft X-ray emitting plasma in solar
    flares.
Authors: Pallavicini, R.; Peres, G.
1982BAAS...14..776P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Chromospheric emission, stellar rotation and X-ray coronae.
Authors: Pallavicini, R.; Golub, L.; Rosner, R.; Vaiana, G.
1982SAOSR.392B..77P    Altcode: 1982csss....2...77P
  No abstract at ADS

---------------------------------------------------------
Title: Einstein detection of X-rays from the alf CEN system.
Authors: Golub, L.; Harnden, F. R., Jr.; Pallavicini, R.; Rosner,
   R.; Vaiana, G. S.
1982ApJ...253..242G    Altcode:
  Detection of quiescent X-ray emission from the stellar components
  of the Alpha Cen system: Alpha Cen A (G2 V) and Alpha Cen B (K1 V)
  is reported. Contrary to previous theoretical expectations, both
  stars are found to be X-ray emitters and at about the same level:
  L<SUB>x</SUB> = 1.2 x 10 to the 27th and 2.8 x 10 to the 27th ergs/s
  for A and B, respectively; the sum of these values is in agreement
  with the emission level previously reported for Alpha Cen by Nugent and
  Garmire (1978). Comparison with previous chromospheric and transition
  region measurements suggests that Alpha Cen A and B may have changed
  in relative strength in recent years. The coronal temperature of the
  combined Cen AB source, which is dominated (approximately 2/3 of the
  total) by the K star is (2.1 + or - 0.4) x 10 to the 6th K, similar to
  that of the average solar corona; it is noted that this value is not
  consistent with the estimate of 5 x 10 to the 5th K quoted by Nugent
  and Garmire.

---------------------------------------------------------
Title: Solar flares from space - Implications of spatially resolved
    XUV observations
Authors: Pallavicini, R.
1982MmSAI..53..461P    Altcode:
  Recent X-ray and EUV observations of solar flares obtained with
  the Apollo Telescope Mount/Skylab and the Solar Maximum Mission are
  reviewed. Flares are subdivided into the physically distinct classes:
  compact flares and large-scale, long-decay events. The physical
  processes pertaining to these two classes are discussed with special
  attention to the space and time dependence of the energy release process
  as well as to the source of mass filling the flaring structure. It is
  suggested that flares of class II may comprise events of two different
  types: energetic two-ribbon flares and more gradual filament-associated
  events in and outside active regions.

---------------------------------------------------------
Title: Proceedings of the workshop on "Cosmic magnetic fields", in
    honour ofGiorgio Abetti, held in Florence, Italy, 21 - 23 October
    1982, on theoccasion of the 26th annual meeting of the Italian
    Astronomical Society.
Authors: Pallavicini, R.; Tagliaferri, G.; Paternò, L.; Fulchignoni,
   M.; Perinotto, M.; Salvati, M.
1982MmSAI..53C.789P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Cosmic magnetic fields
Authors: Pallavicini, R.
1982MmSAI..53.....P    Altcode:
  The magnetic fields treated are those in the sun, in planets and
  the interplanetary medium, in stars and the interstellar medium,
  and in high-energy sources. Papers are presented on the solar dynamo,
  on the equilibrium and stability of magnetized plasmas, on spectral
  analysis at maximum resolution, and on radio pulse behavior above
  50 MeV. Attention is also given to the central powerhouse of active
  galactic nuclei, to magnetic fields in galactic jets, to the theory of
  the magnetic activity of late-type stars, and to recent developments
  in flare dynamics. For individual items see A83-39227 to A83-39251

---------------------------------------------------------
Title: Magnetic heating of solar and stellar coronae
Authors: Pallavicini, R.
1982MmSAI..53..849P    Altcode:
  The current status of the question is summarized, stressing the
  fundamental similarities between the solar and stellar cases. The
  treatment concentrates on late-type stars since only these stars
  possess, like the sun, an outer convection zone and are likely to also
  have differential rotation and dynamo-generated magnetic fields. It is
  pointed out that the heating of the coronas of early-type stars may be
  fundamentally different from the heating of the solar corona. For this
  reason it is not considered. It is shown that whereas there is ample
  evidence at present that the coronas of late-type stars are heated
  magnetically, there is still considerable uncertainty regarding the
  detailed way (Alfvenic surface waves or anomalous current dissipation)
  in which the heating may actually occur.

---------------------------------------------------------
Title: X-Ray Flare Spectroscopy: SMM Observations and Loop Modeling.
Authors: Acton, L.; Pallavicini, R.; Peres, G.; Vaiana, G.
1982uxsa.coll....1A    Altcode: 1982IAUCo..73....1A
  No abstract at ADS

---------------------------------------------------------
Title: Relations among stellar X-ray emission observed from Einstein,
    stellar rotation and bolometric luminosity.
Authors: Pallavicini, R.; Golub, L.; Rosner, R.; Vaiana, G. S.; Ayres,
   T.; Linsky, J. L.
1981ApJ...248..279P    Altcode:
  The correlation between observed stellar X-ray luminosities, bolometric
  luminosities, and projected rotational velocities for stars of various
  spectral types and luminosity classes are determined. Early type
  stars (O3 to A5) have X-ray luminosities independent of rotational
  velocities, and correlating with bolometric luminosities. Late type
  stars of spectral type G to M have luminosities well correlated to
  equatorial rotational velocities, and are independent of luminosity
  class. The dependence of late type stars is found to be equivalent
  to a relation between the X-ray surface flux and the stellar angular
  velocity. F stars are intermediate with X-ray luminosities higher
  than would be predicted on the basis of the early type star relation,
  although lower than expected from the late type velocity dependence. The
  location of RS CVn stars as a class is also discussed, and it is found
  that the heating of late type stellar coronas does not result from
  direct conversion of ratational energy.

---------------------------------------------------------
Title: Closed coronal structures. III - Comparison of static models
    with X-ray, EUV, and radio observations
Authors: Pallavicini, R.; Peres, G.; Serio, S.; Vaiana, G. S.; Golub,
   L.; Rosner, R.
1981ApJ...247..692P    Altcode:
  Numerical models of static coronal loops in energy balance are compared
  with high spatial resolution observations of extreme ultraviolet lines,
  broad-band X-ray emission, and interferometric observations at 2.8 cm
  of a solar active region. Difficulties of using scaling laws to test
  static models of coronal loops are reviewed. The theoretical model
  used for the comparison is summarized; the detailed X-ray, EUV, and
  microwave observations of the selected active region are presented;
  and the comparison of the model with the observations is performed. It
  is shown that simple static models with conductive flux vanishing at the
  loop base reproduce satisfactorily the observed properties in the upper
  portion of loop structures from compact, high-pressure loops in the
  core of the region to more extended, fainter loops and to large-scale
  loops interconnecting different active regions. Effects of changing
  loop parameters are investigated, and it is argued, that in contrast
  to the present approach, scaling laws cannot be used to discriminate
  between different static energy balance models. Some discrepancy is
  found between model predictions and observations for the lower sections
  of loop structures. Possible causes of the discrepancy are discussed.

---------------------------------------------------------
Title: X-ray, EUV, and centimetric observations of solar active
    regions - an empirical model for bright radio sources
Authors: Pallavicini, R.; Sakurai, T.; Vaiana, G. S.
1981A&A....98..316P    Altcode:
  Coordinated observations of solar active regions in X-rays, EUV, and
  2.8 cm radio waves, and current-free extrapolations of the photospheric
  magnetic field to coronal levels are used to determine the emission
  mechanism of bright radio sources. High spatial resolution X-ray and
  EUV observations of the active regions show that the temperature and
  density structure of the atmosphere above the sunspots differs greatly
  from that above the plages. Extended low brightness temperature
  radio sources, associated with plage areas, are consistent with
  thermal free-free emission from the transition region and the corona
  above the active centers. High brightness temperature radio sources,
  associated with sunspots, cannot be explained by thermal free-free
  emissions either in hot, dense loops or in the cooler, lower pressure
  loops, observed emanating from sunspot umbrae. There is evidence that
  thermal gyroresonance absorption at the second and third harmonics of
  the gyrofrequency can produce sunspots associated with bright radio
  sources. The empirical models of the coronal loops, based on energy
  balance, and the effects of electric currents flowing in the corona
  above the sunspots are discussed.

---------------------------------------------------------
Title: Magnetic Field Extrapolations, XUV Observations and the Nature
    of Microwave Emission from Sunspots
Authors: Pallavicini, R.; Sakurai, T.; Vaiana, G. S.
1980BAAS...12..896P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Transition Region and Corona in Solar Active Regions:
    Observations and Numerical Modeling
Authors: Golub, L.; Pallavicini, R.; Peres, G.; Rosner, R.; Serio,
   S.; Vaiana, G. S.
1980BAAS...12..908G    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: The flare of September 7, 1973: A typical example of a newly
    recognized class of solar transients
Authors: Pallavicini, R.; Vaiana, G. S.
1980SoPh...67..127P    Altcode:
  X-ray, extreme-ultraviolet and optical observations of a solar flare are
  discussed. It is shown that the flare exemplifies a class of transient
  events characterized by long duration and long decay time and by the
  development of high systems of loops, generally brighter at the top.

---------------------------------------------------------
Title: On the origin of microwave emission from sunspots
Authors: Pallavicini, R.
1980IAUS...86..119P    Altcode:
  Coordinated high-resolution XUV and centimetric observations of active
  regions obtained from Skylab and Stanford are compared with the aim of
  determining the nature of the centimetric radiation. It is concluded
  that the thermal gyroresonance process is the most likely emission
  mechanism for the bright compact radio sources associated with sunspots.

---------------------------------------------------------
Title: The coronal atmosphere above solar active regions: comparison
    of high spatial resolution soft X-ray and centimetric observations.
Authors: Pallavicini, R.; Vaiana, G. S.; Tofani, G.; Felli, M.
1979ApJ...229..375P    Altcode:
  High spatial resolution observations of solar active regions in soft
  X-rays and centimetric wavelengths are compared using X-ray and radio
  data obtained during the 1973 Skylab mission. An overall correspondence
  in position and size between regions of enhanced X-ray emission and
  regions of enhanced microwave emission was noticed. However, a closer
  analysis of the findings suggested that substantial differences exist
  between the emission properties of the atmosphere over sunspots and
  that over plages, with the difference probably related to the average
  intensity of the magnetic field, which was found to be higher over
  sunspot umbrae than over plage areas.

---------------------------------------------------------
Title: Ricerche su fenomeni transitori della corona solare mediante
    osservazioni ottiche, ultraviolette ed X.
Authors: Pallavicini, R.; Serio, S.; Vaiana, G. S.
1979RSAI...22..163P    Altcode:
  No abstract at ADS

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Title: Risultati recenti e problemi aperti in fisica solare.
Authors: Pallavicini, R.; Poletto, G.
1979GAst....5...19P    Altcode:
  No abstract at ADS

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Title: Is there anything new on the sun?
Authors: Pallavicini, R.; Poletto, G.
1978Mercu...7...23P    Altcode:
  The current state of knowledge regarding the sun and the processes
  taking place in it is examined. It is found that in addition to the
  neutrino problem there are many other intriguing problems. Recent
  observations represent a challenge with respect to basic theoretical
  interpretations of solar phenomena. Elementary facts about the sun
  are considered, taking into account the significance of the presence
  of sunspots with their very strong magnetic fields, flares, auroras,
  faculae, and the differential rotation of the sun. A description is
  presented of a theory which explains the high temperatures of the
  chromosphere and the corona. Investigations based on observations
  of radio waves, infrared and ultraviolet radiation, and X-rays are
  considered. Attention is also given to holes in the solar corona,
  quiescent periods in solar activity, and problems related to an
  occurrence of 'Maunder minima'.

---------------------------------------------------------
Title: L'evoluzione stellare.
Authors: Pallavicini, R.
1978GAst....4..251P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Study of solar active regions by means of coordinated soft
    X-ray and 2.8-cm observations
Authors: Pallavicini, R.; Tofani, G.
1977MmSAI..48..829P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Identificazione di due classi di brillamenti X mediante
    osservazioni di eventi al bordo con l'esperimento Skylab S-054.
Authors: Pallavicini, R.; Serio, S.; Vaiana, G.
1977MmSAI..48..760P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: A survey of soft X-ray limb flare images: the relation between
    their structure in the corona and other physical parameters.
Authors: Pallavicini, R.; Serio, S.; Vaiana, G. S.
1977ApJ...216..108P    Altcode:
  The data used in the investigation were obtained by the American
  Science and Engineering S-054 experiment on board Skylab. The instrument
  employed was a grazing incidence X-ray telescope which records images
  of the sun on film. The morphology of limb flares is investigated
  and the observed spatial structure is related with the other physical
  parameters of the region (temperature, density, characteristic times,
  and energy density). It is concluded that two physically distinct
  classes of flares exist that differ both in their morphology and in
  the physical properties which characterize the emitting regions.

---------------------------------------------------------
Title: Aspects of the observation of solar-flare phenomena
Authors: Pallavicini, R.
1977MmSAI..48..161P    Altcode:
  A review is presented of electromagnetic and particle emission from
  solar flares, with particular emphasis on relationships between
  characteristic features of flares in different spectral bands. Three
  main phases in the development of a typical event are identified:
  precursor, pulsed, and gradual. The association of hard X-ray bursts
  with pulsed EUV and microwave bursts as well as with pulsed optical
  phenomena and type III bursts is discussed. Considerable attention is
  given to magnetic fields associated with flares and to the location
  of sources of different types of emission with respect to the magnetic
  field structure.

---------------------------------------------------------
Title: Spatially-Resolved Observations of Solar Active Regions in
    Soft X-Ray and Centimetric WAVELENGTHS."
Authors: Pallavicini, R.; Tofani, G.; Vaiana, G. S.
1977uxsa.coll...44P    Altcode: 1977IAUCo..43...44P
  No abstract at ADS

---------------------------------------------------------
Title: Non-stationary heating of solar flare plasma by non-thermal
    electrons.
Authors: Giachetti, R.; Pallavicini, R.
1976A&A....53..347G    Altcode:
  A general solution of the energy-transfer equation for nonthermal
  particles in an absorbing medium at constant density is obtained by
  the Green's function method. The derived particle distributions are
  used to compute the collisional heating of the high-temperature region
  of solar flares. The space and time dependence of the energy deposition
  is determined for a variety of nonthermal-particle sources. The results
  are discussed on the basis of presently available flare observations,
  and suggestions are given for the use of the computed energy-deposition
  functions in the investigation of flare models.

---------------------------------------------------------
Title: The spatial structure of a solar flare in soft X-rays and
    centimetric wavelengths.
Authors: Pallavicini, R.; Vaiana, G. S.
1976SoPh...49..297P    Altcode:
  High-resolution images of the decay phase of a soft X-ray flare observed
  by the S-054 experiment on Skylab are compared with interferometric
  scans of the radio burst obtained simultaneously at 2.8 cm (Felli
  et al., 1975). The spatial resulution of the radio instrument in
  one direction, although lower than the X-ray telescope resolution,
  is high enough for a detailed comparison. The comparison clarifies
  the relationship between the sources of soft X-ray and thermal radio
  emission in solar flares. The X-ray emission is localized in a loop-like
  structure which appears spatially coincident with the rapidly varying
  component of the radio burst. The more stable components of the radio
  source, which do not appear to contribute substantially to X-ray
  emission, are found to be spatially associated with the extremes of
  the X-ray loop. A model of plasma-filled loops is suggested which
  accounts for the emissions in both spectral ranges and for their
  spatial location and temporal development.

---------------------------------------------------------
Title: Spatial Structure and Temporal Development of a Solar X-Ray
    Flare Observed from Skylab on June 15, 1973
Authors: Pallavicini, R.; Vaiana, G. S.; Kahler, S. W.; Krieger, A. S.
1975SoPh...45..411P    Altcode:
  A solar flare on June 15, 1973 has been observed with high spatial and
  temporal resolution by the S-054 grazing-incidence X-ray telescope on
  Skylab. Both morphological and quantitative analyses are presented. Some
  of the main results are: (a) the overall configuration of the flare
  is that of a compact region with a characteristic size of the order of
  30″ at the intensity peak, (b) this region appears highly structured
  inside with complex systems of loops which change during the event, (c)
  a brightening over an extended portion of the active region precedes
  the flare onset, (d) the impulsive phase indicated by the non-thermal
  radio emission is a period during which a rapid brightening occurs in
  loop structures, (e) the X-ray emission is centered over the neutral
  line of longitudinal magnetic field, and the brightest structures at the
  flare onset bridge the neutral line, (f) loop systems at successively
  increasing heights form during the decay phase, finally leading to
  the large loops observed in the postflare phase, (g) different parts
  of the flare show distinctly different light curves, and the temporal
  development given by full disk detectors is the result of integrating
  the different intensity vs time profiles.

---------------------------------------------------------
Title: Thermal Models of Flaring Region Based on Observations by
    the SOLRAD 10 Satellite
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1975SoPh...44..101L    Altcode:
  A number of solar X-ray bursts, observed with the SOLRAD 10 satellite
  on 1971 September 14, 17, November 28 and 1972 August 1, have been
  analysed. From the differential emission measure distribution deduced
  from the observations the temporal and spatial distribution in a flaring
  region has been evaluated and compared with models of instantaneous or
  continuous energy injection and conductive redistribution. Assuming
  a power law for the differential emission measure in dependence of
  electron temperature the ratios of the counting rates observed in
  different spectral bands have been compared with theoretical predictions
  so as to test the validity of this particular class of models.

---------------------------------------------------------
Title: The Structure and Intensity Evolution of a Solar Burst at
    2.8 cm and the Relation with the Soft X-Ray Emitting Region
Authors: Felli, M.; Pallavicini, R.; Tofani, G.
1975SoPh...44..135F    Altcode:
  The decay phase of a microwave burst was observed with a one-dimensional
  angular resolution of 16″ at 2.8 cm. The structure was found to be
  composed of several bursting regions with different evolution. The
  event was also observed in soft X-rays by full-disk detectors. The
  joint analysis of these data suggests that the complete event has
  thermal origin and that the soft X-ray emission is associated with the
  rapidly varying component of the radio structure. From these results
  the average values of the electron temperatures and densities were
  computed for each component.

---------------------------------------------------------
Title: X-ray and radio emission for the June 15, 1973 solar flare.
Authors: Pallavicini, R.; Kahler, S.; Krieger, A. S.; Silk, J. K.;
   Vaiana, G. S.
1975MmArc.104..157P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-ray and radio emission for the June 15, 1973 solar flare
Authors: Pallavicini, R.; Kahler, S.; Krieger, A. S.; Silk, J. K.;
   Vaiana, G. S.
1975xtcg.work..157P    Altcode:
  Results are summarized for observations of a solar flare by the
  grazing-incidence X-ray telescope on the Apollo Telescope Mount
  which were made with high spatial and temporal resolution. The
  X-ray observations are compared with ground-based radio, optical,
  and magnetogram observations as well as with X-ray data from other
  satellite instruments. The temporal development of the flare as shown
  by X-ray pictures is outlined, and an X-ray picture taken at the
  flare peak is compared with a magnetogram obtained at the end of the
  flare and an H-alpha picture taken during its decay. Other data used
  in the analysis include satellite measurements of hard and soft X-ray
  fluxes, and radio fluxes measured at several frequencies between 245
  and 15,400 MHz. The volume, temperature, density, and emission measure
  of the flare region are determined along with the temporal evolution
  of these parameters. It is shown that the soft X-ray and microwave
  emissions originated from a thermal plasma whose temperature and
  density increased during the rising part of the event and decreased
  during the decay phase. It is suggested that plasma heating was due
  to collisional losses of nonthermal electrons accelerated during the
  rising phase and that conductive and radiative cooling contributed
  equally to the flare's decay.

---------------------------------------------------------
Title: An X-ray flare from Skylab: results and interpretations.
Authors: Vaiana, G. S.; Kahler, S.; Krieger, A.; Pallavicini, R.;
   Silk, J. K.
1974BAAS....6..265V    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: An Experimental Model of Solar Flares in the Corona
Authors: Silk, J. K.; Kahler, S.; Krieger, A.; Timothy, A.; Vaiana,
   G.; Pallavicini, R.
1974BAAS....6T.294S    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: X-ray and Radio Emission for the June 1. 1973 Solar Flare
Authors: Pallavicini, R.; Kahler, S.; Krieger, A. S.; Silk, J. K.;
   Vaiana, G. S.
1974OMOAA.104..157P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Non-Thermal Ionization and Recombination Processes during
    Solar Flares
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1973SoPh...29...93L    Altcode:
  Ionization and recombination processes are studied for a plasma of
  which the electrons follow a power-law energy distribution.

---------------------------------------------------------
Title: Radio flux measurement simultaneous with a flare observed
    from Skylab
Authors: Pallavicini, R.; Patriarchi, P.
1973MmSAI..44..431P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Ionization and Recombination Processes for Non-Thermal Plasmas
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1973sari.conf..120L    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: Thermal and Non-Thermal Soft X-Ray Bursts
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1972SoPh...27..164L    Altcode:
  X-ray bursts observed for energies lower than 25 keV are usually
  interpreted as being produced by a thermal plasma with several million
  degrees of temperature.

---------------------------------------------------------
Title: Thermal and Non-Thermal Soft X-Ray Bursts
Authors: Landini, M.; Monsignori Fossi, B. C.; Pallavicini, R.
1972SSRv...13..825L    Altcode: 1972IAUCo..14..825L
  No abstract at ADS

---------------------------------------------------------
Title: Il problema dei bursts X non termici (Rassegna)
Authors: Pallavicini, R.
1972MmSAI..43..195P    Altcode:
  No abstract at ADS

---------------------------------------------------------
Title: La scuola estiva "Physics and chemistry of upper atmospheres"
    (Congressi e Simposi)
Authors: Pallavicini, R.
1972MmSAI..43..567P    Altcode:
  No abstract at ADS