explanation blue bibcodes open ADS page with paths to full text
Author name code: pavlenko
ADS astronomy entries on 2022-09-14
author:"Pavlenko, Yakov V."
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Title: Bands of NaH lines in spectra of late type stars
Authors: Lyubchyk, Y. P.; Pavlenko, Y. V.; Lyubchyk, O. K.; Jones,
H. R. A.
2022KFNT...38c..65L Altcode:
No abstract at ADS
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Title: Analysis of actinium abundances in the atmosphere of Cepheid
HIP13962
Authors: Gopka, V. F.; Shavrina, A. V.; Yushchenko, V. A.; Pavlenko,
Y. V.; Yushchenko, A. V.; Glazunova, L. V.
2022KFNT...38...63G Altcode:
No abstract at ADS
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Title: Exocomet activity around the stars at different evolution
stages: current issues
Authors: Pavlenko, Y. V.; Shubina, O. C.; Kulyk, I. V.; Kuznyetsova,
Y. G.; Zakhozhay, O. V.; Korsun, P. P.; Borysenko, S. A.; Krushevska,
V. M.; Andreev, M. V.
2021KFNT...37b..19P Altcode: 2021KFNT...37...19P
No abstract at ADS
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Title: VizieR Online Data Catalog: HARPS and X-shooter spectra of
Southern M dwarfs (Kuznetsov+ 2019)
Authors: Kuznetsov, M. K.; Del Burgo, C.; Pavlenko, Y. V.; Frith, J.
2020yCat..18780134K Altcode:
The High-accuracy Radial-velocity Planet Searcher (HARPS) is a
high-resolution spectrograph installed on the 3.6m telescope in La
Silla. It has a resolving power of R~115000 over a spectral range of
3830-6930Å. Using the ESO Science Archive Facility, we downloaded
5567 spectra, obtained during a period between 2003 October and 2017
February, which corresponded to 420 M dwarfs from our sample. <P />The
X-shooter (Intermediate Resolution, High-Efficiency Spectrograph)
spectrograph is mounted on the VLT at the European Southern Observatory
(ESO) in Paranal, Chile. In this paper, we focused on data obtained from
the VIS spectroscopic arm of the X-shooter (5340-10200Å). The available
VIS spectra associated with the stars from our sample were retrieved
from the European Southern Observatory (ESO) science archive. The
spectra were observed between 2009 June and 2017 November. In total,
we collected spectroscopic data for 153 stars. <P />(2 data files).
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Title: Isotopic ratios in the red giant component of the recurrent
nova T Coronae Borealis
Authors: Pavlenko, Y. V.; Evans, A.; Banerjee, D. P. K.; Geballe,
T. R.; Munari, U.; Gehrz, R. D.; Woodward, C. E.; Starrfield, S.
2020MNRAS.498.4853P Altcode: 2020arXiv200812150P; 2020MNRAS.tmp.2568P
We report the determination of abundances and isotopic ratios for C,
O, and Si in the photosphere of the red giant (RG) component of the
recurrent nova (RN) T Coronae Borealis from new 2.284-2.402 μm
and 3.985-4.155 μm spectroscopy. Abundances and isotopic ratios
in the photosphere may be affected by (i) processes in the RG
interior which are brought to the surface during dredge-up and (ii)
contamination of the RG, either during the common envelope phase of
the binary evolution or by material synthesized in RN eruptions,
or a combination of the two. We find that the abundances of C, O,
and Si are reasonably consistent with the expected composition of
an RG after first dredge-up, as is the <SUP>16</SUP>O/<SUP>17</SUP>O
ratio. The <SUP>28</SUP>Si/<SUP>29</SUP>Si ratio is found to be 8.6 ±
3.0, and that for <SUP>28</SUP>Si/<SUP>30</SUP>Si is 21.5 ± 3.0. The
<SUP>12</SUP>C/<SUP>13</SUP>C ratio (10 ± 2) is somewhat lower than
expected for first dredge-up. The <SUP>16</SUP>O/<SUP>18</SUP>O ratio
(41 ± 3) is highly inconsistent with that expected either from RG
evolution (~550) or from contamination of the RG by the products of
a nova thermonuclear runaway. In particular, the C and O isotopic
ratios taken in combination are a puzzle. We urge confirmation of
our results using spectroscopy at high resolution. We also encourage
a thorough theoretical study of the effects on the secondary star in
an RN system of contamination by ejecta having anomalous abundances
and isotopic ratios.
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Title: Erratum: The first planet detected in the WTS: an inflated
hot-Jupiter in a 3.35 day orbit around a late F-star
Authors: Cappetta, M.; Saglia, R. P.; Birkby, J. L.; Koppenhoefer, J.;
Pinfield, D. J.; Hodgkin, S. T.; Cruz, P.; Kovács, G.; Sipőcz, B.;
Barrado, D.; Nefs, B.; Pavlenko, Y. V.; Fossati, L.; del Burgo, C.;
Martín, E. L.; Snellen, I.; Barnes, J.; Campbell, D.; Catalan, S.;
Gálvez-Ortiz, M. C.; Goulding, N.; Haswell, C.; Ivanyuk, O.; Jones,
H.; Kuznetsov, M.; Lodieu, N.; Marocco, F.; Mislis, D.; Murgas, F.;
Napiwotzki, R.; Palle, E.; Pollacco, D.; Sarro Baro, L.; Solano, E.;
Steele, P.; Stoev, H.; Tata, R.; Zendejas, J.
2020MNRAS.497..916C Altcode:
No abstract at ADS
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Title: VizieR Online Data Catalog: Post-AGB candidates in LMC and
SMC SALT spectra (Szczerba+, 2020)
Authors: Szczerba, R.; Hajduk, M.; Pavlenko; Ya. V.; Hrivnak, B. J.;
Kaminsky; B. M.; Volk, K.; Siodmiak, N. Gezer I.; Zacs, L.; Pych,
W.; Sarna, M.
2020yCat..36410142S Altcode:
Spectroscopic data from the South African Large Telescope shown on
Figs. 2, 3 and 4 are available in fig2.dat, fig3.dat and fig4.dat,
respectively. Each spectrum has 2 gaps: in the red setting (Figs.2
and 3) 7130-7200Å and 8170-8220Å, in the blue setting (Fig.4)
3550-3580Å and 3840-3850Å. In the notes to the tables description we
use "the left part" of the spectrum for spectrum before the first gap,
"the middle part" of the spectrum for spectrum between the two gaps,
and "the right part" of the spectrum for spectrum above the second
gap. <P />(4 data files).
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Title: HD 54361: evidence for the status of a low mass TP-AGB star
Authors: Začs, L.; Pukïtis, K.; Sperauskas, J.; Pavlenko, Y.;
Schmidt, M.; Alksnis, O.
2020Ap&SS.365...27Z Altcode:
The mass of the cool carbon star HD 54361 was suspected to be high,
assuming the membership in the stellar association CMa OB1, in
conflict with the theory of stellar evolution. The Gaia parallax and
a high-resolution spectrum in the wavelength region from about 4800
to 6900 Å was employed in order to update the distance, atmospheric
parameters and abundances using the method of spectral synthesis and
new model atmospheres. Absorption lines are broad in the spectrum
presumably because of a large macroturbulence, ξ<SUB>RT</SUB>=10
±1 kms-<SUP>1</SUP>. Radial-velocity monitoring revealed a scatter
of about 4 km s<SUP>-1</SUP>, which reflects probably a large scale
convection in the atmosphere. The effective temperature was found to
be about 3200 K by modelling the wings of Na I D doublet, a somewhat
higher than that estimated from the angular diameter. The difference
in the temperature could be due to the light/colour variation. The
abundances of iron peak elements calculated from less blended
lines blueward of 5000 Å are near solar, [M/H]=0.0 ±0.2 dex. The
neutron-capture elements are enhanced up to 1 dex. The parallax leads
to the distance of 554<SUB>-41</SUB><SUP>+49</SUP>pc, the absolute
magnitude, M<SUB>K</SUB>=-7.7 ±0.2 mag, and the bolometric magnitude,
M<SUB>bol</SUB>(K )=-4.6 ±0.2 mag. The observed stellar parameters and
abundances are typical values for the low mass ∼1.8 M<SUB>⊙</SUB>
star on the TP-AGB branch according to the isochrone calculated for
logAge (yr )=9.20 with solar initial metallicity. HD 54361 possibly
belongs to the spike in the TP-AGB star numbers associated with the
AGB-boosting effect.
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Title: Metallicity, temperature, and gravity scales of M subdwarfs
Authors: Lodieu, N.; Allard, F.; Rodrigo, C.; Pavlenko, Y.; Burgasser,
A.; Lyubchik, Y.; Kaminsky, B.; Homeier, D.
2019A&A...628A..61L Altcode: 2019arXiv190703674L
<BR /> Aims: The aim of the project is to define
metallicity/gravity/temperature scales for different spectral types of
metal-poor M dwarfs. <BR /> Methods: We obtained intermediate-resolution
ultraviolet (R ∼ 3300), optical (R ∼ 5400), and near-infrared (R
∼ 3900) spectra of 43 M subdwarfs (sdM), extreme subdwarfs (esdM),
and ultra-subdwarfs (usdM) with the X-shooter spectrograph on the
European Southern Observatory Very Large Telescope. We compared
our atlas of spectra to the latest BT-Settl synthetic spectral
energy distribution over a wide range of metallicities, gravities,
and effective temperatures to infer the physical properties for
the whole M dwarf sequence (M0-M9.5) at sub-solar metallicities
and constrain the latest atmospheric models. <BR /> Results: The
BT-Settl models accurately reproduce the observed spectra across the
450-2500 nm wavelength range except for a few regions. We find that
the best fits are obtained for gravities of log (g) = 5.0-5.5 for
the three metal classes. We infer metallicities of [Fe/H] = -0.5,
-1.5, and -2.0 ± 0.5 dex and effective temperatures of 3700-2600
K, 3800-2900 K, and 3700-2900 K for subdwarfs, extreme subdwarfs,
and ultra-subdwarfs, respectively. Metal-poor M dwarfs tend to be
warmer by about 200 ± 100 K and exhibit higher gravity than their
solar-metallicity counterparts. We derive abundances of several
elements (Fe, Na, K, Ca, Ti) for our sample but cannot describe their
atmospheres with a single metallicity parameter. Our metallicity
scale expands the current scales available for mildly metal-poor
planet-host low-mass stars. Our compendium of moderate-resolution
spectra covering the 0.45-2.5 micron range represents an important
resource for large-scale surveys and space missions to come. <P />All
observed spectra are available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A61">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A61</A>Based
on observations collected at the European Southern Observatory,
Chile, under programmes 089.C-0140(A), 091.C-0264(A), 092.D-0600(A),
and 093.C-0610(A).
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Title: VizieR Online Data Catalog: X-shooter spectra of 43 metal-poor
M dwarfs (Lodieu+, 2019)
Authors: Lodieu, N.; Allard, F.; Rodrigo, C.; Pavlenko, Y.; Burgasser,
A.; Lyubchik, Y.; Kaminsky, B.; Homeier, D.
2019yCat..36280061L Altcode:
We make public the ESO VLT X-shooter spectra of 43 subdwarfs spanning
the 560-2500nm wavelength range. Each file contains wavelength (in
nm) and the flux (in ergs/cm<SUP>2</SUP>/s/Angstroem) in the first
and second column, respectively. Spectra are corrected for telluric
absorption. Names of files are composed of spectral types of the source
followed by the date of observations. <P />(2 data files).
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Title: SiO bands in infrared spectra of late spectral stars
Authors: Pavlenko, Y. V.
2019KFNT...35d..21P Altcode:
No abstract at ADS
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Title: Masses, oxygen, and carbon abundances in CHEPS dwarf stars
Authors: Pavlenko, Y. V.; Kaminsky, B. M.; Jenkins, J. S.; Ivanyuk,
O. M.; Jones, H. R. A.; Lyubchik, Y. P.
2019A&A...621A.112P Altcode: 2018arXiv181105011P
Context. We report the results from the determination of stellar
masses, carbon, and oxygen abundances in the atmospheres of 107
stars from the Calan-Hertfordshire Extrasolar Planet Search (CHEPS)
programme. Our stars are drawn from a population with a significantly
super-solar metallicity. At least 10 of these stars are known to host
orbiting planets. <BR /> Aims: In this work, we set out to understand
the behaviour of carbon and oxygen abundance in stars with different
spectral classes, metallicities, and V sin i within the metal-rich
stellar population. <BR /> Methods: Masses of these stars were
determined using data from Gaia DR2. Oxygen and carbon abundances
were determined by fitting the absorption lines. We determined oxygen
abundances with fits to the 6300.304 Å O I line, and we used 3 lines
of the C I atom and 12 lines of the C<SUB>2</SUB> molecule for the
determination of carbon abundances. <BR /> Results: We determine masses
and abundances of 107 CHEPS stars. There is no evidence that the [C/O]
ratio depends on V sin i or the mass of the star within our constrained
range of masses, i.e. 0.82 < M<SUB>*</SUB>/M<SUB>⊙</SUB> <
1.5 and metallicities - 0.27 < [Fe/H] < +0.39. We also confirm
that metal-rich dwarf stars with planets are more carbon rich in
comparison with non-planet host stars with a statistical significance
of 96%. <BR /> Conclusions: We find tentative evidence that there
is a slight offset to lower abundance and a greater dispersion in
oxygen abundances relative to carbon. We interpret this as potentially
arising because the production of oxygen is more effective at more
metal-poor epochs. We also find evidence that for lower mass stars the
angular momentum loss in stars with planets as measured by V sin i is
steeper than stars without planets. In general, we find that the fast
rotators (V sin i > 5 km s<SUP>-1</SUP>) are massive stars. <P
/>Table A.3 is also available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/621/A112">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/621/A112</A>
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Title: Accuracies of abundance determinations in large spectroscopic
surveys
Authors: Ivanyuk, Oleksiy; Pavlenko, Y. V.; Jenkins, J. S.; Jones,
H. R. A.
2018gbx..confE..18I Altcode:
Along with our own results from the high resolution spectral analysis
of the 107 metal rich F, G, K stars from the Calan-Hertfordshire
Extrasolar Planet Search program (CHEPS) we discuss differences in
the abundances of Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn
between a number of large spectroscopic surveys. Most authors tend to
use stellar spectra to determine virtually all fundamental parameters
including effective temperature and surface gravity. We attempted to
recreate results for a dozen of common stars using available input
parameters to highlight the real scale of errors this approach might
induce. We confirm overabundance and light decline of α-elements versus
metallicity in the metal-deficient domain from -0.4 to -0.2 dex. This
trend changes for the metal-rich stars between 0.0 and 0.4 dex, but
among α-elements only Na follows positive trend - along with Mn, Ni,
Cu and Zn. Slight increase is also visible for Al. Ca continued to
show a negative trend.
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Title: VizieR Online Data Catalog: Carbon and oxygen in 107 dwarf
stars (Pavlenko+, 2019)
Authors: Pavlenko, Y. V.; Kaminsky, B. M.; Jenkins, J. S.; Ivanyuk,
O. M.; Jones, H. R. A.; Lyubchik, Y. P.
2018yCat..36210112P Altcode:
We used the observed spectra obtained in the framework of the
Calan-Hertfordshire Extrasolar Planet Search (CHEPS) programme (Jenkins
et al., 2009ApJ...704..975J, Cat. J/ApJ/704/975). <P />All stars in
our work were observed with the HARPS spectrograph (Mayor et al.,
2003Msngr.114...20M) at a resolving power of 115,000, and since the
spectra were taken as part of the CHEPS programme, whose primary goal
is the detection of small planets orbiting these stars, the S/N of the
spectra are all over 100 at a wavelength of 6000Å. The 107 stars in
this work are primary targets for CHEPS. <P />Carbon and Oxygen in the
CHEPS stars. Cases of the problematic determination of oxygen abundance
due to the strong blending 6300.304Å OI line by telluric lines are
marked by (*). The oxygen abundances determined by visual comparison
of computed and observed spectra are marked by (+). <P />(1 data file).
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Title: The analysis of actinium abundance in the atmospheres of
three Magellanic Clouds red supergiants stars
Authors: Gopka, V. F.; Shavrina, A. V.; Yushchenko, V. A.; Yushchenko,
A. V.; Pavlenko, Y. V.; Andrievsky, S. M.; Vasileva, S. V.; Kim, C.;
Jeong, Y.; Lyubchik, Y. P.
2018KFNT...34c..25G Altcode:
No abstract at ADS
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Title: Flare activity and photospheric analysis of Proxima Centauri
Authors: Pavlenko, Y.; Suárez Mascareño, A.; Rebolo, R.; Lodieu,
N.; Béjar, V. J. S.; González Hernández, J. I.
2017A&A...606A..49P Altcode: 2017arXiv170604678P
Context. We present the analysis of emission lines in high-resolution
optical spectra of the planet-host star Proxima Centauri (Proxima)
classified as a M5.5V. <BR /> Aims: We carry out a detailed analysis
of the observed spectra to get a better understanding of the physical
conditions of the atmosphere of this star. <BR /> Methods: We identify
the emission lines in a series of 147 high-resolution optical spectra
of the star at different levels of activity and compare them with the
synthetic spectra computed over a wide spectral range. <BR /> Results:
Our synthetic spectra computed with the PHOENIX 2900/5.0/0.0 model
atmosphere fits the observed spectral energy distribution from optical
to near-infrared quite well. However, modelling strong atomic lines
in the blue spectrum (3900-4200 Å) requires implementing additional
opacity. We show that high-temperature layers in Proxima Centauri
consist of at least three emitting parts: a) a stellar chromosphere
where numerous emission lines form; we suggest that some emission cores
of strong absorption lines of metals form there; b) flare regions above
the chromosphere, where hydrogen Balmer lines up to high transition
levels (10-2) form; and c) a stellar wind component with V<SUB>r</SUB> =
-30 km s<SUP>-1</SUP> seen in some Balmer lines as blueshifted emission
lines. We believe that the observed He line at 4026 Å in emission can
be formed in that very hot region. <BR /> Conclusions: We show that the
real structure of the atmosphere of Proxima is rather complicated. The
photosphere of the star is best fit by a normal M5 dwarf spectrum. On
the other hand, emission lines form in the chromosphere, flare regions,
and extended hot envelope. <P />The movies are available at <A
href="http://www.aanda.org/10.1051/0004-6361/201730733/olm">http://www.aanda.org</A>
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Title: VizieR Online Data Catalog: Spectroscopic properties for 107
stars (Ivanyuk+, 2017)
Authors: Ivanyuk, O. M.; Jenkins, J. S.; Pavlenko, Y. V.; Jones,
H. R. A.; Pinfield, D. J.
2017yCat..74684151I Altcode:
The tables contain derived stellar parameters and abundances along with
the spectral ranges that we used for the line profile fitting. <P />(2
data files).
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Title: New planetary systems from the Calan-Hertfordshire Extrasolar
Planet Search
Authors: Jenkins, J. S.; Jones, H. R. A.; Tuomi, M.; Díaz, M.;
Cordero, J. P.; Aguayo, A.; Pantoja, B.; Arriagada, P.; Mahu, R.;
Brahm, R.; Rojo, P.; Soto, M. G.; Ivanyuk, O.; Becerra Yoma, N.;
Day-Jones, A. C.; Ruiz, M. T.; Pavlenko, Y. V.; Barnes, J. R.; Murgas,
F.; Pinfield, D. J.; Jones, M. I.; López-Morales, M.; Shectman, S.;
Butler, R. P.; Minniti, D.
2017MNRAS.466..443J Altcode: 2016arXiv160309391J
We report the discovery of eight new giant planets, and updated orbits
for four known planets, orbiting dwarf and subgiant stars using the
CORALIE, HARPS, and MIKE instruments as part of the Calan-Hertfordshire
Extrasolar Planet Search. The planets have masses in the range 1.1-5.4
M<SUB>J</SUB>'s, orbital periods from 40 to 2900 d, and eccentricities
from 0.0 to 0.6. They include a double-planet system orbiting the
most massive star in our sample (HD147873), two eccentric giant
planets (HD128356b and HD154672b), and a rare 14 Herculis analogue
(HD224538b). We highlight some population correlations from the sample
of radial velocity detected planets orbiting nearby stars, including
the mass function exponential distribution, confirmation of the growing
body of evidence that low-mass planets tend to be found orbiting more
metal-poor stars than giant planets, and a possible period-metallicity
correlation for planets with masses >0.1 M<SUB>J</SUB>, based on a
metallicity difference of 0.16 dex between the population of planets
with orbital periods less than 100 d and those with orbital periods
greater than 100 d.
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Title: Determination of abundances in atmospheres of F-, G-, K-dwarfs
Authors: Pavlenko, Y. V.
2017KFNT...33v..24P Altcode:
No abstract at ADS
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Title: Acne at The Bottom Of The Main Sequence
Authors: Barnes, John; Haswell, C.; Jenkins, J.; Jeffers, S.; Jones,
H. R. A.; Lohr, M.; Pavlenko, Y.
2016csss.confE..10B Altcode:
Starspots are an important manifestation of stellar activity and
yet their distribution patterns on the lowest mass stars is not well
known. Time series spectra of fully convective M dwarfs taken in the
red-optical with UVES reveal numerous line profile distortions which are
interpreted as starspots. We derive Doppler images for four M4.5V - M9V
stars and find that contrast ratios corresponding to photosphere-spot
temperature differences of only 200-300 K are sufficient to model
the timeseries spectra. Although more starspot structure is found
at high latitudes, spots are reconstructed at a range of phases and
latitudes with mean spot filling factors of only a few per cent. The
occurrence of low-contrast spots at predominantly high latitudes is
in general likely to be responsible for the low amplitude photometric
variability seen in late-M dwarfs. The recovered starspot patterns
are used to assess their effect on precision radial velocity surveys
aimed at detecting planets around this population of stars.
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Title: VLT X-Shooter spectroscopy of the nearest brown dwarf binary
Authors: Lodieu, N.; Zapatero Osorio, M. R.; Rebolo, R.; Béjar,
V. J. S.; Pavlenko, Y.; Pérez-Garrido, A.
2015A&A...581A..73L Altcode: 2015arXiv150608848L
<BR /> Aims: The aim of the project is to characterise the
two components of the brown dwarf system nearest to the Sun,
WISE J104915.57-531906.1 (also called Luhman 16AB) at optical
and near-infrared wavelengths. <BR /> Methods: We obtained high
signal-to-noise intermediate-resolution (R ~ 6000-11 000) optical
(600-1000 nm) and near-infrared (1000-2480 nm) spectra of each
component of Luhman 16AB with the X-Shooter instrument on the
Very Large Telescope. <BR /> Results: We classify the primary and
secondary of the Luhman 16 system as L6-L7.5 and T0±1, respectively,
in agreement with previous measurements published in the literature. We
present measurements of the lithium pseudo-equivalent widths, which
appear of similar strength in both components (8.2 ± 1.0 Å for the
L and 8.4 ± 1.5 Å for the T component). The presence of lithium
(<SUP>7</SUP>Li) in both components implies masses lower than 0.06
M<SUB>⊙</SUB>, while the comparison with models suggests lower
limits of 0.04 M<SUB>⊙</SUB>. The detection of lithium in the T
component is the first of its kind. Similarly, we assess the strength
of other alkali lines (e.g. pseudo-equivalent widths of 6-7 Å for
RbI and 4-7 Å for CsI) present in the optical and near-infrared
regions and compare with estimates for L and T dwarfs. We also
derive effective temperatures and luminosities of each component of
the binary: -4.66 ± 0.08 dex and 1305 K for the L dwarf and -4.68
± 0.13 dex and 1320 K for the T dwarf. According to our radial
velocity determinations, the binary does not appear to belong to any
of the well-known moving group. Our preliminary theoretical analysis
of the optical and J-band spectra indicates that the L- and T-type
spectra can be reproduced with a single temperature and gravity but
different relative chemical abundances, which strongly affects the
spectral energy distribution of L/T transition objects. <P />Based on
observations collected at the European Southern Observatory, Chile,
under DDT programme 290.C-5200(B) (PI Lodieu).FITS files of the
reduced spectra are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A73">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A73</A>
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Title: VizieR Online Data Catalog: Luhman 16AB X-shooter spectra
(Lodieu+, 2015)
Authors: Lodieu, N.; Zapatero Osorio, M. R.; Rebolo, R.; Bejar,
V. J. S.; Pavlenko, Y.; Perez-Garrido, A.
2015yCat..35810073L Altcode:
VLT X-shooter optical and near-infrared spectra of each component of
the nearest brown dwarf binary system Luhman 16AB are made public. The
spectra cover the ~670nm to ~2480nm with a resolution of 11000 in the
optical (670-1000nm) and 6200 in the near-infrared (1000-2480nm). Note:
We observe a peak and a dip around 2080-2090nm in the spectra of the
components of the system not seen in other T dwarfs, as a potential
artefact in our X-shooter data. No other strong artefact is present
in our data. <P />(2 data files).
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Title: VizieR Online Data Catalog: Ji light curves of WTS-2 (Birkby+,
2014)
Authors: Birkby, J. L.; Cappetta, M.; Cruz, P.; Koppenhoefer,
J.; Ivanyuk, O.; Mustill, A. J.; Hodgkin, S. T.; Pinfield, D. J.;
Sipocz, B.; Kovacs, G.; Saglia, R.; Pavlenko, Y.; Barrado, D.; Bayo,
A.; Campbell, D.; Catalan, S.; Fossati, L.; Galvez-Ortiz, M. -C.;
Kenworthy, M.; Lillo-Box, J.; Martin, E. L.; Mislis, D.; de Mooij,
E. J. W.; Nefs, S. V.; Snellen, I. A. G.; Stoev, H.; Zendejas, J.;
Del Burgo, C.; Barnes, J.; Goulding, N.; Haswell, C. A.; Kuznetsov,
M.; Lodieu, N.; Murgas, F.; Palle, E.; Solano, E.; Steele, P.; Tata, R.
2015yCat..74401470B Altcode:
The infrared light curves of the WTS were generated from time series
photometry taken with the WFCAM imager mounted at the prime focus of
UKIRT. <P />In order to confirm the transit of WTS-2 b and to help
constrain the transit model, on 2010 July 18 we obtained further time
series photometry in the Sloan i band using the Wide Field Camera (WFC)
on the 2.5m Isaac Newton Telescope (INT) at Roque de Los Muchachos,
La Palma. <P />(2 data files).
---------------------------------------------------------
Title: A search for lithium in metal-poor L dwarfs
Authors: Lodieu, N.; Burgasser, A. J.; Pavlenko, Y.; Rebolo, R.
2015A&A...579A..58L Altcode: 2015arXiv150506858L
<BR /> Aims: The aim of the project is to search for lithium in
absorption at 6707.8 Å to constrain the nature and mass of the
brightest low-metallicity L-type dwarfs (referred to as L subdwarfs)
identified in large-scale surveys. <BR /> Methods: We obtained low- to
intermediate-resolution (R ~ 2500-9000) optical (~560-770 nm) spectra
of two mid-L subdwarfs, SDSS J125637.13-022452.4 (SDSS1256; sdL3.5)
and 2MASS J162620.14+392519.5 (2MASS1626; sdL4) with spectrographs on
the European Southern Observatory Very Large Telescope and the Gran
Telescopio de Canarias. <BR /> Results: We report the presence of a
feature at the nominal position of the lithium absorption doublet at
6707.8 Å in the spectrum of SDSS1256, with an equivalent width of 66
± 27 Å at 2.4σ, which we identify as arising from a CaH molecular
transition based on atmosphere models. We do not see any feature at
the position of the lithium feature in the spectrum of 2MASS1626. The
existence of overlapping molecular absorption sets a confusion detection
limit of [Li/H] = -3 for equivalently typed L subdwarfs. We provided
improved radial velocity measurements of -126±10 km s<SUP>-1</SUP> and
-239±12 km s<SUP>-1</SUP> for SDSS1256 and 2MASS1626, respectively,
as well as revised Galactic orbits. We implemented adjusting factors
for the CaH molecule in combination with the NextGen atmosphere
models to fit the optical spectrum of SDSS1256 in the 6200-7300 Å
range. We also estimate the expected Li abundance from interstellar
accretion ([Li/H] = -5), place limits on circumstellar accretion
(10<SUP>9</SUP> g/yr), and discuss the prospects of Li searches
in cooler L and T subdwarfs. <P />Optical spectra of SDSS1256 and
2MASS 1626 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/579/A58">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/579/A58</A>Based
on observations collected at the European Southern Observatory, Chile,
under programmes 089.C-0883 and 091.C-0594A.Based on observations
made with the Gran Telescopio Canarias (GTC), installed in the
Spanish Observatorio del Roque de los Muchachos of the Instituto
de Astrofísica de Canarias, in the island of La Palma (programmes
GTC64_10B and GTC38_11A).
---------------------------------------------------------
Title: VizieR Online Data Catalog: Spectra of two mid-L subdwarfs
(Lodieu+, 2015)
Authors: Lodieu, N.; Burgasser, A. J.; Pavlenko, Y.; Rebolo, R.
2015yCat..35790058L Altcode:
Intermediate-resolution optical spectra of SDSS J125637.13-022452.4 and
2MASS J162620.14+392519.5 are provided. They have been obtained with
FORS2 on the ESO Very Large Telescope (grism GRIS1200R+93) and OSIRIS
on the Gran Telescopio de Canarias (grating R2500R), respectively. <P
/>(2 data files).
---------------------------------------------------------
Title: Silicate Dust in RS Ophiuchi
Authors: Rushton, M. T.; Woodward, C. E.; Helton, L. A.; Gehrz, R. D.;
Evans, A.; Kaminsky, B.; Pavlenko, Y. V.; Eyres, S. P. S.; Maxwell, M.
2014ASPC..490..249R Altcode:
We present Spitzer IRS spectra of the recurrent nova RS Ophiuchi
obtained between 2006 and 2009. The data show emission lines due to HI,
[Ne II], [Ne V], [Ne VI] and [O IV] and the well known silicate features
at 10 μm and 18 μm, whose behaviour are reported here. The silicate
features are variable in the period covered by the observations,
appearing strongest in our 2007 data. Interestingly, the central
wavelength of the 18 μm band is shorter than observed in other
symbiotic systems and other circumstellar environments, suggesting
unusual grain properties in RS Oph. We report changes that have taken
place in the dusty environment in RS Oph and investigate the properties
of the dust grains.
---------------------------------------------------------
Title: Erratum: The first planet detected in the WTS: an inflated
hot-Jupiter in a 3.35 d orbit around a late F star
Authors: Cappetta, M.; Saglia, R. P.; Birkby, J. L.; Koppenhoefer, J.;
Pinfield, D. J.; Hodgkin, S. T.; Cruz, P.; Kovács, G.; Sipőcz, B.;
Barrado, D.; Nefs, B.; Pavlenko, Y. V.; Fossati, L.; del Burgo, C.;
Martín, E. L.; Snellen, I.; Barnes, J.; Campbell, D.; Catalan, S.;
Gálvez-Ortiz, M. C.; Goulding, N.; Haswell, C.; Ivanyuk, O.; Jones,
H.; Kuznetsov, M.; Lodieu, N.; Marocco, F.; Mislis, D.; Murgas, F.;
Napiwotzki, R.; Palle, E.; Pollacco, D.; Sarro Baro, L.; Solano, E.;
Steele, P.; Stoev, H.; Tata, R.; Zendejas, J.
2014MNRAS.444.3150C Altcode: 2014arXiv1410.3235C
We report the discovery of WTS-1b, the first extrasolar planet found
by the WFCAM Transit Survey, which began observations at the 3.8-m
United Kingdom Infrared Telescope (UKIRT) in August 2007. Light
curves comprising almost 1200 epochs with a photometric precision of
better than 1 per cent to J ~ 16 were constructed for ~60000 stars and
searched for periodic transit signals. For one of the most promising
transiting candidates, high-resolution spectra taken at the Hobby-Eberly
Telescope (HET) allowed us to estimate the spectroscopic parameters of
the host star, a late-F main sequence dwarf (V=16.13) with possibly
slightly subsolar metallicity, and to measure its radial velocity
variations. The combined analysis of the light curves and spectroscopic
data resulted in an orbital period of the substellar companion of 3.35
days, a planetary mass of 4.01 +- 0.35 Mj and a planetary radius of
1.49+0.16-0.18 Rj. WTS-1b has one of the largest radius anomalies among
the known hot Jupiters in the mass range 3-5 Mj. The high irradiation
from the host star ranks the planet in the pM class.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Catalogue of bright (K<9)
M dwarfs (Frith+, 2013)
Authors: Frith, J.; Pinfield, D. J.; Jones, H. R. A.; Barnes, J. R.;
Pavlenko, Y.; Martin, E. L.; Brown, C.; Kuznetsov, M. K.; Marocco,
F.; Tata, R.; Cappetta, M.
2014yCat..74352161F Altcode:
Using the Position and Proper Motion Extended-L (PPMXL) catalogue,
we have used optical and near-infrared colour cuts together with
a reduced proper motion cut to find bright M dwarfs for future
exoplanet transit studies. PPMXL's low proper motion uncertainties
allow us to probe down to smaller proper motions than previous similar
studies. We have combined unique objects found with this method to
that of previous work to produce 8479 K<9 M dwarfs. Low-resolution
spectroscopy was obtained of a sample of the objects found using this
selection method to gain statistics on their spectral type and physical
properties. Results show a spectral-type range of K7-M4V. This catalogue
is the most complete collection of K<9 M dwarfs currently available
and is made available here. <P />(1 data file).
---------------------------------------------------------
Title: WTS-2 b: a hot Jupiter orbiting near its tidal destruction
radius around a K dwarf
Authors: Birkby, J. L.; Cappetta, M.; Cruz, P.; Koppenhoefer,
J.; Ivanyuk, O.; Mustill, A. J.; Hodgkin, S. T.; Pinfield, D. J.;
Sipőcz, B.; Kovács, G.; Saglia, R.; Pavlenko, Y.; Barrado, D.; Bayo,
A.; Campbell, D.; Catalan, S.; Fossati, L.; Gálvez-Ortiz, M. -C.;
Kenworthy, M.; Lillo-Box, J.; Martín, E. L.; Mislis, D.; de Mooij,
E. J. W.; Nefs, S. V.; Snellen, I. A. G.; Stoev, H.; Zendejas, J.;
del Burgo, C.; Barnes, J.; Goulding, N.; Haswell, C. A.; Kuznetsov,
M.; Lodieu, N.; Murgas, F.; Palle, E.; Solano, E.; Steele, P.; Tata, R.
2014MNRAS.440.1470B Altcode: 2014MNRAS.tmp..557B; 2014arXiv1402.5416B
We report the discovery of WTS-2 b, an unusually close-in 1.02-d
hot Jupiter (M<SUB>P</SUB> = 1.12M<SUB>J</SUB>, R<SUB>P</SUB>
= 1.30R<SUB>J</SUB>) orbiting a K2V star, which has a possible
gravitationally bound M-dwarf companion at 0.6 arcsec separation
contributing ∼20 per cent of the total flux in the observed J-band
light curve. The planet is only 1.5 times the separation from its
host star at which it would be destroyed by Roche lobe overflow,
and has a predicted remaining lifetime of just ∼40 Myr, assuming a
tidal dissipation quality factor of Q_{*}^'}=10<SUP>6</SUP>. Q_{*}^'}
is a key factor in determining how frictional processes within a host
star affect the orbital evolution of its companion giant planets,
but it is currently poorly constrained by observations. We calculate
that the orbital decay of WTS-2 b would correspond to a shift in
its transit arrival time of T<SUB>shift</SUB> ∼ 17 s after 15 yr
assuming Q_{*}^'}=10<SUP>6</SUP>. A shift less than this would place a
direct observational constraint on the lower limit of Q_{*}^'} in this
system. We also report a correction to the previously published expected
T<SUB>shift</SUB> for WASP-18 b, finding that T<SUB>shift</SUB> = 356
s after 10 yr for Q_{*}^'}=10<SUP>6</SUP>, which is much larger than
the estimated 28 s quoted in WASP-18 b discovery paper. We attempted
to constrain Q_{*}^'} via a study of the entire population of known
transiting hot Jupiters, but our results were inconclusive, requiring
a more detailed treatment of transit survey sensitivities at long
periods. We conclude that the most informative and straightforward
constraints on Q_{*}^'} will be obtained by direct observational
measurements of the shift in transit arrival times in individual
hot Jupiter systems. We show that this is achievable across the mass
spectrum of exoplanet host stars within a decade, and will directly
probe the effects of stellar interior structure on tidal dissipation.
---------------------------------------------------------
Title: Abundances in the atmosphere, effective temperature and
surface gravity of the subdwarf metal-poor star G 224-58 A
Authors: Kushniruk, I.; Pavlenko, Y. V.
2014ysc..conf...18K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A catalogue of bright (K < 9) M dwarfs
Authors: Frith, J.; Pinfield, D. J.; Jones, H. R. A.; Barnes, J. R.;
Pavlenko, Y.; Martin, E. L.; Brown, C.; Kuznetsov, M. K.; Marocco,
F.; Tata, R.; Cappetta, M.
2013MNRAS.435.2161F Altcode: 2013MNRAS.tmp.2106F; 2013arXiv1308.0501F
Using the Position and Proper Motion Extended-L (PPMXL) catalogue,
we have used optical and near-infrared colour cuts together with a
reduced proper motion cut to find bright M dwarfs for future exoplanet
transit studies. PPMXL's low proper motion uncertainties allow us to
probe down to smaller proper motions than previous similar studies. We
have combined unique objects found with this method to that of previous
work to produce 8479 K < 9 M dwarfs. Low-resolution spectroscopy was
obtained of a sample of the objects found using this selection method to
gain statistics on their spectral type and physical properties. Results
show a spectral-type range of K7-M4V. This catalogue is the most
complete collection of K < 9 M dwarfs currently available and is
made available here.
---------------------------------------------------------
Title: A hot Jupiter transiting a mid-K dwarf found in the
pre-OmegaCam Transit Survey
Authors: Koppenhoefer, J.; Saglia, R. P.; Fossati, L.; Lyubchik,
Y.; Mugrauer, M.; Bender, R.; Lee, C. -H.; Riffeser, A.; Afonso,
P.; Greiner, J.; Henning, Th.; Neuhäuser, R.; Snellen, I. A. G.;
Pavlenko, Y.; Verdugo, M.; Vogt, N.
2013MNRAS.435.3133K Altcode: 2013MNRAS.tmp.2185K; 2013arXiv1308.6574K
We describe the pre-OmegaTranS project, a deep survey for transiting
extra-solar planets in the Carina region of the Galactic disc. In
2006-2008, we observed a single dense stellar field with a very high
cadence of ∼2 min using the European Southern Observatory Wide
Field Imager at the La Silla Observatory. <P />Using the Astronomical
Wide-field Imaging System for Europe environment and the Munich
Difference Imaging Analysis pipeline, a module that has been developed
for this project, we created the light curves of 16 000 stars with more
than 4000 data points which we searched for periodic transit signals
using a box-fitting least-squares detection algorithm. All light curves
are publicly available. In the course of the pre-OmegaTranS project,
we identified two planet candidates - POTS-1b and POTS-C2b - which we
present in this work. <P />With extensive follow-up observations we
were able to confirm one of them, POTS-1b, a hot Jupiter transiting a
mid-K dwarf. The planet has a mass of 2.31 ± 0.77 M<SUB>Jup</SUB>,
a radius of 0.94 ± 0.04 R<SUB>Jup</SUB> and a period of P = 3.16
d. The host star POTS-1 has a radius of 0.59 ± 0.02 R<SUB>⊙</SUB>
and a mass of 0.70 ± 0.05 M<SUB>⊙</SUB>. Due to its low apparent
brightness of I = 16.1 mag, the follow-up and confirmation of POTS-1b
was particularly challenging and costly.
---------------------------------------------------------
Title: A Hot Uranus Orbiting the Super Metal-rich Star HD 77338 and
the Metallicity-Mass Connection
Authors: Jenkins, J. S.; Jones, H. R. A.; Tuomi, M.; Murgas, F.; Hoyer,
S.; Jones, M. I.; Barnes, J. R.; Pavlenko, Y. V.; Ivanyuk, O.; Rojo,
P.; Jordán, A.; Day-Jones, A. C.; Ruiz, M. T.; Pinfield, D. J.
2013ApJ...766...67J Altcode: 2012arXiv1207.1012J
We announce the discovery of a low-mass planet orbiting the
super metal-rich K0V star HD 77338 as part of our ongoing
Calan-Hertfordshire Extrasolar Planet Search. The best-fit planet
solution has an orbital period of 5.7361 ± 0.0015 days and with a
radial velocity semi-amplitude of only 5.96 ± 1.74 ms<SUP>-1</SUP>,
we find a minimum mass of 15.9^{+4.7}_{-5.3} M <SUB>⊕</SUB>. The
best-fit eccentricity from this solution is 0.09^{+0.25}_{-0.09},
and we find agreement for this data set using a Bayesian analysis
and a periodogram analysis. We measure a metallicity for the star
of +0.35 ± 0.06 dex, whereas another recent work finds +0.47 ±
0.05 dex. Thus HD 77338b is one of the most metal-rich planet-host
stars known and the most metal-rich star hosting a sub-Neptune-mass
planet. We searched for a transit signature of HD 77338b but none was
detected. We also highlight an emerging trend where metallicity and
mass seem to correlate at very low masses, a discovery that would be
in agreement with the core accretion model of planet formation. The
trend appears to show that for Neptune-mass planets and below, higher
masses are preferred when the host star is more metal-rich. Also a lower
boundary is apparent in the super metal-rich regime where there are no
very low mass planets yet discovered in comparison to the sub-solar
metallicity regime. A Monte Carlo analysis shows that this low-mass
planet desert is statistically significant with the current sample
of 36 planets at the ~4.5σ level. In addition, results from Kepler
strengthen the claim for this paucity of the lowest-mass planets in
super metal-rich systems. Finally, this discovery adds to the growing
population of low-mass planets around low-mass and metal-rich stars and
shows that very low mass planets can now be discovered with a relatively
small number of data points using stable instrumentation. <P />Based
on observations collected at the La Silla Paranal Observatory, ESO
(Chile) with the HARPS spectrograph on the ESO 3.6 m telescope, under
the program IDs 079.C-0927, 081.C-0148, 087.C-0368, and 088.C-0662.
---------------------------------------------------------
Title: WTS-2 b: Too close for comfort?
Authors: Birkby, J. L.; Cappetta, M.; Cruz, P.; Koppenhoefer, J.;
Ivanyuk, O.; Mustill, A.; Hodgkin, S. T.; Pinfield, D. J.; Sipőcz,
B.; Kovács, G.; Saglia, R.; Pavlenko, Y.; RoPACS Collaboration;
del Burgo, Carlos
2013EPJWC..4701004B Altcode:
We report the discovery of WTS-2 b, a typical hot Jupiter in an
unusually close 1.02-day orbit to a K-dwarf star. This is the second
planet to be discovered in the infrared light curves of the WFCAM
Transit Survey (WTS) and is only one-and-a-half times the separation
from its host star at which is would be destroyed by Roche lobe
overflow. The predicted remaining lifetime of the planet is just 38
Myrs, assuming a tidal dissipation quality factor of Q'<SUB>*</SUB> =
10<SUP>6</SUP>. The magnitude of Q'<SUB>*</SUB> is largely unconstrained
by observations, thus WTS-2 b provides a useful calibration point for
theories describing how frictional processes within a host star affect
the tidal orbital evolution of its companion giant planets. It is
expected that stars with large convective envelopes are more efficient
at dissipating the orbital energy of the planet, and WTS-2 b provides an
observational constraint in the sparsely populated K-dwarf regime. In
addition, despite its relatively faint magnitude, the favourable size
ratio of the WTS-2 star-planet system and the predicted hot equilibrium
temperature of the planet will make it possible to characterise the
planet's atmosphere via secondary eclipse measurements using existing
ground-based instrumentation.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Detached M dwarf eclipsing binaries
in WTS (Birkby+, 2012)
Authors: Birkby, J.; Nefs, B.; Hodgkin, S.; Kovacs, G.; Sipocz, B.;
Pinfield, D.; Snellen, I.; Mislis, D.; Murgas, F.; Lodieu, N.; de
Mooij, E.; Goulding, N.; Cruz, P.; Stoev, H.; Cappetta, M.; Palle,
E.; Barrado, D.; Saglia, R.; Martin, E.; Pavlenko, Y.
2013yCat..74261507B Altcode:
We identified our new MEBs using observations from the WTS (WFCAM
Transit Survey). The WTS is an ongoing photometric monitoring campaign
that operates on the 3.8-m United Kingdom Infrared Telescope (UKIRT)
at Mauna Kea, Hawaii. <P />The survey began on 2007 August 5, and the
eclipsing systems presented in this paper are all found in just one of
the four WTS fields. <P />Photometric follow-up observations to help
test and refine our light-curve models were obtained in the Sloan i
band using the Wide-Field Camera (WFC) on the 2.5-m INT at Roque de
Los Muchachos, La Palma. <P />(6 data files).
---------------------------------------------------------
Title: The spectroscopic study of M8.5-M9.5 stars and brown dwarfs
Authors: Kuznetsov, M. K.; Pavlenko, Y. V.; Galvez-Ortiz, M. C.
2013EPJWC..4704002K Altcode:
We present high-resolution spectra analysis of the three late-M dwarfs
LP944-20, SIPS J2045-6332 and DENIS-P J0021.0-4244. The stellar spectra
were observed with Very Large Telescope/Ultraviolet-Visual Echelle
Spectrograph (VLT/UVES) in optical and near-infrared regions. The
effective temperatures T<SUB>eff</SUB> and log g was defined by
comparing observed and theoretical energy distributions for the
investigated objects. Synthetic spectra were calculated for PHOENIX
atmosphere models - COND and DUSTY, as well as for Semi-empirical
atmosphere model. We discuss the influence of the effects associated
with dust in stellar atmosphere on the energy distribution in the
stellar spectra.
---------------------------------------------------------
Title: The Abundances of Heavy Elements in Red Supergiants of
Magellanic Clouds
Authors: Gopka, V.; Yushchenko, A.; Kovtyukh, V.; Shavrina, A.;
Yushchenko, V.; Vasilyeva, S.; Pavlenko, Y.; Andrievsky, S.
2013OAP....26...54G Altcode:
The spectra of Magellanic Clouds (MC) supergiants PMMR23, PMMR144
and RM 1-667 with resolving power R=30,000 and signal to noise ratio
near 100 obtained at 3.6 meter telescope in Chile were analysed. We
present are port on the detailed investigation of MC supergiants,
with special attention to the thorium abundance in these stars. The
abundance patterns of three supergiants show that r-process elements
are clearly detected in the atmospheres of investigated stars, but
the bundances of s-processes elements can vary from star to star.
---------------------------------------------------------
Title: The first planet detected in the WTS: an inflated hot Jupiter
in a 3.35 d orbit around a late F star
Authors: Cappetta, M.; Saglia, R. P.; Birkby, J. L.; Koppenhoefer, J.;
Pinfield, D. J.; Hodgkin, S. T.; Cruz, P.; Kovács, G.; Sipőcz, B.;
Barrado, D.; Nefs, B.; Pavlenko, Y. V.; Fossati, L.; del Burgo, C.;
Martín, E. L.; Snellen, I.; Barnes, J.; Bayo, A.; Campbell, D. A.;
Catalan, S.; Gálvez-Ortiz, M. C.; Goulding, N.; Haswell, C.; Ivanyuk,
O.; Jones, H. R.; Kuznetsov, M.; Lodieu, N.; Marocco, F.; Mislis, D.;
Murgas, F.; Napiwotzki, R.; Palle, E.; Pollacco, D.; Sarro Baro, L.;
Solano, E.; Steele, P.; Stoev, H.; Tata, R.; Zendejas, J.
2012MNRAS.427.1877C Altcode: 2012arXiv1210.1217C
We report the discovery of WTS-1b, the first extrasolar planet found
by the WFCAM Transit Survey, which began observations at the 3.8-m
United Kingdom Infrared Telescope (UKIRT) in 2007 August. Light
curves comprising almost 1200 epochs with a photometric precision
of better than 1 per cent to J ∼ 16 were constructed for ∼60 000
stars and searched for periodic transit signals. For one of the most
promising transiting candidates, high-resolution spectra taken at the
Hobby-Eberly Telescope (HET) allowed us to estimate the spectroscopic
parameters of the host star, a late-F main-sequence dwarf (V = 16.13)
with possibly slightly subsolar metallicity, and to measure its radial
velocity variations. The combined analysis of the light curves and
spectroscopic data resulted in an orbital period of the substellar
companion of 3.35 d, a planetary mass of 4.01 ± 0.35 M<SUB>J</SUB>
and a planetary radius of 1.49-0.18+0.16 R<SUB>J</SUB>. WTS-1b has
one of the largest radius anomalies among the known hot Jupiters in
the mass range 3-5 M<SUB>J</SUB>. The high irradiation from the host
star ranks the planet in the pM class. Based on observations collected
at the 3.8-m United Kingdom Infrared Telescope (Hawaii, USA), the
Hobby-Eberly Telescope (Texas, USA), the 2.5-m Isaac Newton Telescope
(La Palma, Spain), the William Herschel Telescope (La Palma, Spain),
the German-Spanish Astronomical Centre (Calar Alto, Spain), the Kitt
Peak National Observatory (Arizona, USA) and the Hertfordshire's
Bayfordbury Observatory.
---------------------------------------------------------
Title: Lithium abundance in atmospheres of F- and G-type supergiants
and bright giants
Authors: Lyubimkov, Leonid S.; Lambert, David L.; Kaminsky, Bogdan M.;
Pavlenko, Yakov V.; Poklad, Dmitry B.; Rachkovskaya, Tamara M.
2012MNRAS.427...11L Altcode: 2012arXiv1212.6057L
Lithium in the atmosphere of a F or G supergiant reflects the initial
Li abundance and the internal history of the star. During evolution of a
star from the main sequence (MS) to the supergiant phase, lithium may be
destroyed by, for example, rotationally induced mixing in the MS stars
and strongly diluted by development of the supergiant's convective
envelope. In order to probe the connection between atmospheric
Li abundance and evolutionary predictions, we present a non-local
thermodynamic equilibrium abundance analysis of the resonance doublet
Li I at 6707.8 Å for 55 Galactic F and G supergiants and bright
giants (we observed 43 of them, the remaining 12 are added from Luck
and Wepfer's list). The derived lithium abundances log ɛ(Li) may be
considered in three groups, namely: (i) 10 Li-rich giants with log
ɛ(Li) = 2.0-3.2 (all 10 are F-type or A9 stars); (ii) 13 G- to K0-type
stars with Li abundances in the narrow range log ɛ(Li) = 1.1-1.8;
(iii) all other stars provide just upper limits to the Li abundance. <P
/>The derived Li abundances are compared with theoretical predictions
of 2-15 M<SUB>⊙</SUB> stars (both rotating and non-rotating). Our
results are generally in good agreement with theory. In particular,
the absence of detectable lithium for the majority of programme stars
is explainable. The comparison suggests that the stars may be separated
by mass M into two groups, namely M ≲ 6 M<SUB>⊙</SUB> and M >
6 M<SUB>⊙</SUB>. All Li-rich giants and supergiants with log ɛ(Li)
≥ 2.0 have masses M < 6 M<SUB>⊙</SUB>; this conclusion follows
not only from our work but also from a scrutiny of published data. 11 of
13 stars with log ɛ(Li) = 1.1-1.8, specifically the stars with M <
6 M<SUB>⊙</SUB>, show good agreement with the post-first dredge-up
surface abundance log ɛ(Li) ≈ 1.4 predicted for the non-rotating 2-6
M<SUB>⊙</SUB> stellar models. An absence of Li-rich stars in the range
M > 6 M<SUB>⊙</SUB> agrees with the theoretical prediction that F
and G supergiants and giants with M > 6 M<SUB>⊙</SUB> cannot show
detectable lithium. <P />We note that present theory appears unable to
account for the derived Li abundances for some stars, namely for (i) a
few relatively low-mass Li-rich giants (M < 6 M<SUB>⊙</SUB>), whose
high Li abundances accompanied by rather high rotational velocities
or substantial nitrogen excess contradict theoretical predictions;
(ii) the relatively high-mass supergiants HR 461 and HR 8313 (M >
6 M<SUB>⊙</SUB>) with the detected abundances log ɛ = 1.3-1.5. It
is possible that the lithium in such stars was synthesized recently.
---------------------------------------------------------
Title: Intermediate Resolution Near-infrared Spectroscopy of 36 Late
M Dwarfs
Authors: Deshpande, R.; Martín, E. L.; Montgomery, M. M.; Zapatero
Osorio, M. R.; Rodler, F.; del Burgo, C.; Phan Bao, N.; Lyubchik,
Y.; Tata, R.; Bouy, H.; Pavlenko, Y.
2012AJ....144...99D Altcode: 2012arXiv1207.2781D
We present observations of 36 late M dwarfs obtained with the Keck
II/NIRSPEC in the J band at a resolution of ~20,000. We have measured
projected rotational velocities, absolute radial velocities, and
pseudo-equivalent widths of atomic lines. Twelve of our targets did not
have previous measurements in the literature. For the other 24 targets,
we confirm previously reported measurements. We find that 13 stars
from our sample have v sin i below our measurement threshold (12 km
s<SUP>-1</SUP>) whereas four of our targets are fast rotators (v sin i
> 30 km s<SUP>-1</SUP>). As fast rotation causes spectral features to
be washed out, stars with low projected rotational velocities are sought
for radial velocity surveys. At our intermediate spectral resolution,
we have confirmed the identification of neutral atomic lines reported
in McLean et al. We also calculated pseudo-equivalent widths of 12
atomic lines. Our results confirm that the pseudo-equivalent width of
K I lines is strongly dependent on spectral types. We observe that the
pseudo-equivalent width of Fe I and Mn I lines remains fairly constant
with later spectral type. We suggest that these lines are particularly
suitable for deriving metallicities for late M dwarfs.
---------------------------------------------------------
Title: Four ultra-short-period eclipsing M-dwarf binaries in the
WFCAM Transit Survey
Authors: Nefs, S. V.; Birkby, J. L.; Snellen, I. A. G.; Hodgkin, S. T.;
Pinfield, D. J.; Sipőcz, B.; Kovacs, G.; Mislis, D.; Saglia, R. P.;
Koppenhoefer, J.; Cruz, P.; Barrado, D.; Martin, E. L.; Goulding, N.;
Stoev, H.; Zendejas, J.; del Burgo, C.; Cappetta, M.; Pavlenko, Y. V.
2012MNRAS.425..950N Altcode: 2012MNRAS.tmp.3514N; 2012arXiv1206.1200N
We report on the discovery of four ultra-short-period (P ≤ 0.18 d)
eclipsing M-dwarf binaries in the Wide-Field Camera (WFCAM) Transit
Survey. Their orbital periods are significantly shorter than that of
any other known main-sequence binary system, and are all significantly
below the sharp period cut-off at P ∼ 0.22 d as seen in binaries of
earlier-type stars. The shortest-period binary consists of two M4-type
stars in a P = 0.112 d orbit. The binaries are discovered as part of
an extensive search for short-period eclipsing systems in over 260
000 stellar light curves, including over 10 000 M-dwarfs down to J =
18 mag, yielding 25 binaries with P ≤ 0.23 d. In a popular paradigm,
the evolution of short-period binaries of cool main-sequence stars is
driven by the loss of angular momentum through magnetized winds. In
this scheme, the observed P ∼ 0.22 d period cut-off is explained as
being due to time-scales that are too long for lower-mass binaries to
decay into tighter orbits. Our discovery of low-mass binaries with
significantly shorter orbits implies that either these time-scales
have been overestimated for M-dwarfs, e.g. due to a higher effective
magnetic activity, or the mechanism for forming these tight M-dwarf
binaries is different from that of earlier-type main-sequence stars.
---------------------------------------------------------
Title: Coupled azimuthal modes propagating in current-carrying
plasma waveguides
Authors: Girka, V.; Girka, I.; Pavlenko, I.; Girka, O.; Girka, A.
2012JPlPh..78..105G Altcode:
The paper is devoted to the theory of electromagnetic surface
waves propagating along the azimuthal direction in cylindrical metal
waveguides, which are filled with current-carrying plasmas. The problem
is solved by the method of successive approximation. Adequacy of this
method application is proved here. To study the coupling of ordinary
(O-) and extraordinary (X-) azimuthal modes, the linear theory of the
eigenazimuthal X- and O-modes is applied as zero approximation. Plasma
particles are described in the framework of magneto-hydrodynamics,
electromagnetic fields of the coupled azimuthal modes are determined
from Maxwell equations. Spatial distribution of electromagnetic field
of these coupled modes and their damping caused for different reasons
are studied. Possibility to observe experimentally the phenomena,
which accompany propagation of these coupled modes, is estimated
numerically. Branches of their possible utilization are discussed
as well.
---------------------------------------------------------
Title: Benchmark cool companions: ages and abundances for the PZ
Telescopii system
Authors: Jenkins, J. S.; Pavlenko, Y. V.; Ivanyuk, O.; Gallardo,
J.; Jones, M. I.; Day-Jones, A. C.; Jones, H. R. A.; Ruiz, M. T.;
Pinfield, D. J.; Yakovina, L.
2012MNRAS.420.3587J Altcode: 2011arXiv1111.7001J
We present new ages and abundance measurements for the pre-main-sequence
star PZ Telescopii (more commonly known as PZ Tel). PZ Tel was
recently found to host a young and low-mass companion. Such
companions, whether they are brown dwarfs or planetary systems,
can attain benchmark status by detailed study of the properties of
the primary, and then evolutionary and bulk characteristics can be
inferred for the companion. Using Fibre-fed Extended Range Optical
Spectrograph spectra, we have measured atomic abundances (e.g. Fe
and Li) and chromospheric activity for PZ Tel and used these to
obtain the metallicity and age estimates for the companion. We have
also determined the age independently using the latest evolutionary
models. We find PZ Tel A to be a rapidly rotating (v sin i= 73 ± 5
km s<SUP>-1</SUP>), approximately solar metallicity star [log N(Fe)
=-4.37 ± 0.06 dex or [Fe/H] = 0.05 ± 0.20 dex]. We measure a
non-local thermodynamic equilibrium lithium abundance of log N(Li)
= 3.1 ± 0.1 dex, which from depletion models gives rise to an age
of 7? Myr for the system. Our measured chromospheric activity (? of
-4.12) returns an age of 26 ± 2 Myr, as does fitting pre-main-sequence
evolutionary tracks (τ<SUB>evol</SUB>= 22 ± 3 Myr), both of these
are in disagreement with the lithium age. We speculate on reasons
for this difference and introduce new models for lithium depletion
that incorporate both rotation and magnetic field effects. We also
synthesize solar, metal-poor and metal-rich substellar evolutionary
models to better determine the bulk properties of PZ Tel B, showing
that PZ Tel B is probably more massive than previous estimates, meaning
the companion is not a giant exoplanet, even though a planetary-like
formation origin can go some way to describing the distribution of
benchmark binaries currently known. We show how PZ Tel B compares
to other currently known age and metallicity benchmark systems and
try to empirically test the effects of dust opacity as a function of
metallicity on the near-infrared colours of brown dwarfs. Current models
suggest that in the near-infrared observations are more sensitive to
low-mass companions orbiting more metal rich stars. We also look for
trends between infrared photometry and metallicity amongst a growing
population of substellar benchmark objects, and identify the need for
more data in mass-age-metallicity parameter space.
---------------------------------------------------------
Title: High-Resolution Spectroscopy of the Cool R CrB Star Candidates
V1983 Cyg and V2074 Cyg
Authors: Smirnova, O.; Začs, L.; Pavlenko, Y. V.
2011ASPC..445..177S Altcode:
Preliminary results of high-resolution optical spectral analysis
of two carbon-rich long-term variables, V1983 Cyg and V2047 Cyg,
are presented. The stars were suspected to be cool R CrB variables
according to their photometric light curves, although our spectroscopic
study suggests that both stars are more similar to ordinary N-type
carbon stars. For V1983 Cyg, possible absorption in the Balmer lines
is detected.
---------------------------------------------------------
Title: Theory of azimuthal surface waves propagating in non-uniform
waveguides
Authors: Girka, V. O.; Girka, I. O.; Girka, A. V.; Pavlenko, I. V.
2011JPlPh..77..493G Altcode:
This paper is devoted to the theory of surface waves propagating
across axis of symmetry in non-uniform cylindrical metal waveguides
with plasma filling. The presented results are devoted to: first,
studying an influence of plasma density non-uniformity on the features
of these waves; second, studying an influence of an external magnetic
fields' non-uniformity on their dispersion properties; third, studying
possibility to sustain gas discharge by propagation of these waves
under different operating regimes. The problems have been solved both
analytically and numerically. Plasma particles are described in the
framework of hydrodynamics; fields of the studied waves are determined
by a set of Maxwell equations. Analytical research of the obtained
equations is carried out by the method of successive approximation;
adequacy of such approach is proved here as well. Numerical evaluations
of the possibilities to observe experimentally the phenomena, which
accompany propagation of these waves, are carried out.
---------------------------------------------------------
Title: Spectroscopic Analysis of Cool Galactic R CrB Star Candidates
Authors: Smirnova, O.; Zavcs, L.; Pavlenko, Y. V.; Kaminsky, B.
2011IAUS..280P.340S Altcode:
The results of optical spectra analysis of two carbon-rich long-period
variables V1983 Cyg and V2047 Cyg are presented. The stars were
suspected to be cool R CrB variables candidates according to the
photometric light curves. We compared the spectroscopic properties
of the selected stars with those of DY Per and ordinary carbon
stars to check their possible connection to cool RCBs. Also the
spectral synthesis technique was used for analysis of the obtained
high-resolution spectra, dominated by strong absorption features
of carbon-bearing molecules. Our spectroscopic study suggests that
both stars are more similar to ordinary N-type carbon stars than to
DY Per star. For V1983 Cyg star possible absorption in Balmer lines
is detected.
---------------------------------------------------------
Title: Infrared Mn I laboratory oscillator strengths for the study
of late type stars and ultracool dwarfs
Authors: Blackwell-Whitehead, R.; Pavlenko, Y. V.; Nave, G.; Pickering,
J. C.; Jones, H. R. A.; Lyubchik, Y.; Nilsson, H.
2011A&A...525A..44B Altcode:
<BR /> Aims: The aim of our new laboratory measurements is to measure
accurate absolute oscillator strengths for neutral manganese transitions
in the infrared needed for the study of late-type stars and ultracool
dwarfs. <BR /> Methods: Branching fractions have been measured by high
resolution Fourier transform spectroscopy and combined with radiative
level lifetimes in the literature to yield oscillator strengths. <BR
/> Results: We present experimental oscillator strengths for 20 Mn
I transitions in the wavelength range 3216 to 13 997 Å, 15 of which
are in the infrared. The transitions at 12 899 Å and 12 975 Å are
observed as strong features in the spectra of late-type stars and
ultracool dwarfs. We have fitted our calculated spectra to the observed
Mn I lines in spectra of late-type stars. Using the new experimentally
measured Mn I log(gf) values together with existing data for Mn I
hyperfine structure splitting factors we determined the manganese
abundance to be log N(Mn) = -6.65 ± 0.05 in the atmosphere of the Sun,
log N(Mn) = 6.95 ± 0.20 in the atmosphere of Arcturus, and log N(Mn)
= -6.70 ± 0.20 in the atmosphere of M 9.5 dwarf 2MASSW 0140026+270150.
---------------------------------------------------------
Title: Spectral Investigations of CM Dra
Authors: Kuznetsov, M. K.; Pavlenko, Y. V.; Pinfield, D.; Jones, H.
2010OAP....23...74K Altcode:
We present an analysis of a high resolution (R=47000) echelle spectra
of the low-mass eclipsing binary CM Draconis, which were obtained on
the 4.2-m William Herschel Telescope. Spectra were obtained for various
phases of the orbit. There are some difficulties in echelle spectra
processing of cool stars, since it is hard to get energy distribution
in a large scale in such spectra. We proposed an efficient method
for making the continuum of spectrum of cool stars. We refined the
parameters (effective temperature, rotational velocity and metallicity)
of the components of the system CM Dra using the method of stellar
atmospheres. The data that we obtained are in good agreement with the
results obtained by other authors. It is indicate on efficiency of our
technique. The errors of temperature and metallicity determinations
is about 100 K and 0.3 dex respectively.
---------------------------------------------------------
Title: Line Identification And Equivalent Width Measurements Of
Atomic Lines In Spectra Of 40 Late M Dwarfs
Authors: Deshpande, Rohit; Martin, E. L.; Montgomery, M. M.; Lyubchik,
Y.; Zapatero Osorio, M. R.; Rodler, F.; del Burgo, C.; Pavlenko, Y.
2010AAS...21560604D Altcode: 2010BAAS...36R1130D
We present preliminary results of line identification and equivalent
width measurements in spectra of late M Dwarfs. We obtained 3.5
nights on Keck NASA time to collect high resolution (R 20,000)
near-infrared (J-band) spectra using the NIRSPEC instrument on the
Keck II telescope. Our sample consists of 40 nearby (distance <
20 pc) late M dwarfs (spectral type M5 - M9.5). Using VALD database
we identified new atomic lines and verified them by comparing our
results to those obtained through models of synthetic spectra. We
obtained equivalent width of new and previously observed atomic
lines. Our results of existing atomic lines compare well with those
from Cushing et al. 2005. We observe a linearly increasing trend in
equivalent widths of strong lines such as K I l while a decreasing
trend is found in weakening lines like Na I.
---------------------------------------------------------
Title: Rotational Velocities for M Dwarfs
Authors: Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko,
Y.; Gallardo, J.; Barnes, J. R.; Pinfield, D. J.
2009ApJ...704..975J Altcode: 2009arXiv0908.4092J
We present spectroscopic rotation velocities (v sin i) for 56 M dwarf
stars using high-resolution Hobby-Eberly Telescope High Resolution
Spectrograph red spectroscopy. In addition, we have also determined
photometric effective temperatures, masses, and metallicities ([Fe/H])
for some stars observed here and in the literature where we could
acquire accurate parallax measurements and relevant photometry. We
have increased the number of known v sin i values for mid M stars
by around 80% and can confirm a weakly increasing rotation velocity
with decreasing effective temperature. Our sample of v sin is peak
at low velocities (~3 km s<SUP>-1</SUP>). We find a change in the
rotational velocity distribution between early M and late M stars,
which is likely due to the changing field topology between partially
and fully convective stars. There is also a possible further change
in the rotational distribution toward the late M dwarfs where dust
begins to play a role in the stellar atmospheres. We also link v
sin i to age and show how it can be used to provide mid-M star age
limits. When all literature velocities for M dwarfs are added to our
sample, there are 198 with v sin i <= 10 km s<SUP>-1</SUP> and 124
in the mid-to-late M star regime (M3.0-M9.5) where measuring precision
optical radial velocities is difficult. In addition, we also search
the spectra for any significant Hα emission or absorption. Forty three
percent were found to exhibit such emission and could represent young,
active objects with high levels of radial-velocity noise. We acquired
two epochs of spectra for the star GJ1253 spread by almost one month
and the Hα profile changed from showing no clear signs of emission,
to exhibiting a clear emission peak. Four stars in our sample appear
to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with
both GJ3129 and Gl802 exhibiting double Hα emission features. The
tables presented here will aid any future M star planet search target
selection to extract stars with low v sin i. <P />Based on observations
obtained with the Hobby-Eberly Telescope, which is a joint project of
the University of Texas at Austin, the Pennsylvania State University,
Stanford University, Ludwig-Maximilians-Universität München, and
Georg-August-Universität Göttingen.
---------------------------------------------------------
Title: Model Atmospheres and Spectra of Peculiar Stars
Authors: Pavlenko, Y. V.; Evans, A.; Duerbeck, H. W.; Geballe, T.;
Yakovina, L.; Kaminsky, B.; Kerr, T.
2008ASPC..401..124P Altcode: 2009ASPC..401..124P
The method and results of the computation of the model atmospheres
and spectral energy distributions of chemically peculiar stars
are discussed. The models and spectra are computed with special
consideration of the particular problems encountered for peculiar
and hydrogen deficient stars in the later stages of evolution. We
present some computed model atmospheres and fits to observed spectra
of Sakurai's object, V838 Mon, and RS Oph.
---------------------------------------------------------
Title: Fifteen new T dwarfs discovered in the UKIDSS Large Area Survey
Authors: Pinfield, D. J.; Burningham, B.; Tamura, M.; Leggett, S. K.;
Lodieu, N.; Lucas, P. W.; Mortlock, D. J.; Warren, S. J.; Homeier,
D.; Ishii, M.; Deacon, N. R.; McMahon, R. G.; Hewett, P. C.; Osori,
M. R. Zapatero; Martin, E. L.; Jones, H. R. A.; Venemans, B. P.;
Day-Jones, A. C.; Dobbie, P. D.; Folkes, S. L.; Dye, S.; Allard, F.;
Baraffe, I.; Barrado Y Navascués, D.; Casewell, S. L.; Chiu, K.;
Chabrier, G.; Clarke, F.; Hodgkin, S. T.; Magazzù, A.; McCaughrean,
M. J.; Nakajima, T.; Pavlenko, Y.; Tinney, C. G.
2008MNRAS.390..304P Altcode: 2008arXiv0806.0294P
We present the discovery of 15 new T2.5-T7.5 dwarfs (with estimated
distances ~24-93pc), identified in the first three main data releases
of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky
Survey. This brings the total number of T dwarfs discovered in the
Large Area Survey (LAS) (to date) to 28. These discoveries are confirmed
by near-infrared spectroscopy, from which we derive spectral types on
the unified scheme of Burgasser et al. Seven of the new T dwarfs have
spectral types of T2.5-T4.5, five have spectral types of T5-T5.5, one is
a T6.5p and two are T7-7.5. We assess spectral morphology and colours
to identify T dwarfs in our sample that may have non-typical physical
properties (by comparison to solar neighbourhood populations), and find
that three of these new T dwarfs may have unusual metallicity, two may
have low surface gravity, and one may have high surface gravity. The
colours of the full sample of LAS T dwarfs show a possible trend to
bluer Y - J with decreasing effective temperature, and some interesting
colour changes in J - H and z - J (deserving further investigation)
beyond T8. The LAS T dwarf sample from the first and second main data
releases show good evidence for a good level of completion to J =
19. By accounting for the main sources of incompleteness (selection,
follow-up and spatial) as well as the effects of unresolved binarity,
Malmquist and Eddington bias, we estimate that there are 17 +/- 4 >=
T 4 dwarfs in the J <= 19 volume of the LAS second data release. This
value is most consistent with theoretical predictions if the substellar
mass function exponent α (dN/dm ~ m<SUP>-α</SUP>) lies between -1.0
and 0. This is consistent with the latest 2-Micron All Sky Survey
(2MASS)/Sloan Digital Sky Survey (SDSS) constraint (which is based
on lower number statistics) and is significantly lower than the α ~
1.0 suggested by L dwarf field populations, which is possibly a result
of the lower mass range probed by the T dwarf class.
---------------------------------------------------------
Title: Model Atmospheres and Spectra for Cool Hydrogen-Deficient
Stars and Peculiar Giants
Authors: Pavlenko, Y. V.
2008ASPC..391...65P Altcode:
New model atmospheres, spectra and spectral energy distributions
of hydrogen-deficient chemically peculiar stars are presented. The
methods used in the computation of these models are discussed, with
special consideration given to the treatment of opacity. Some of the
model atmospheres have been computed for R CrB stars with different
H/He ratios and carbon abundances. In order to test these models the
observed spectra of Sakurai's object and some carbon-rich giants are
fit with the newly computed spectral energy distributions.
---------------------------------------------------------
Title: Metallicities and activities of southern stars
Authors: Jenkins, J. S.; Jones, H. R. A.; Pavlenko, Y.; Pinfield,
D. J.; Barnes, J. R.; Lyubchik, Y.
2008A&A...485..571J Altcode: 2008arXiv0804.1128J
Aims: We present the results from high-resolution spectroscopic
measurements to determine metallicities and activities of bright
stars in the southern hemisphere. <BR />Methods: We measured the
iron abundances ([Fe/H]'s) and chromospheric emission indices (log
h{R}'<SUB>{HK</SUB>}) of 353 solar-type stars with V = 7.5-9.5. [Fe/H]
abundances are determined using a custom χ<SUP>2</SUP> fitting
procedure within a large grid of Kurucz model atmospheres. The
chromospheric activities were determined by measuring the amount of
emission in the cores of the strong Caii HK lines. <BR />Results: Our
comparison of the metallicity sample to other [Fe/H] determinations
was found to agree at the ±0.05 dex level for spectroscopic values
and at the ±0.1 dex level for photometric values. The distribution
of chromospheric activities is described by a bimodal distribution,
agreeing with the conclusions from other works. Also an analysis of
Maunder minimum status was attempted, and it was found that 6 ± 4 stars
in the sample could be in a Maunder minimum phase of their evolution
and hence the Sun should only spend a few per cent of its main sequence
lifetime in Maunder minimum. <P />Based on observations made with the
ESO telescopes at the La Silla Paranal observatory under programme ID's
076.C-0578(B) and 077.C-0192(A). Table 4 is 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/485/571
---------------------------------------------------------
Title: VizieR Online Data Catalog: Metallicities & activities
of southern stars (Jenkins+, 2008)
Authors: Jenkins, J. S.; Jones, H. R. A.; Pavlenko, Y.; Pinfield,
D. J.; Barnes, J. R.; Lyubchik, Y.
2008yCat..34850571J Altcode:
This table comprises a list of stellar metallicities and activities
for a number of solar-type stars in the southern hemisphere using
high-resolution (R~46000) spectra acquired at the ESO-MPI 2.2m telescope
and the instrument FEROS. The stars all have B-V colours in the range
0.5-0.9, V magnitudes between 7.5-9.5 and were selected from the
Hipparcos catalogue (Perryman et al., 1997, Cat. ). The chromospheric
activities along with their photon counting errors are shown, and were
extracted by comparing the flux in triangular bandpasses centred in the
cores of the Calcium II H and K lines (wavelengths of 3933.664{AA} and
3968.470{AA}) against the flux in two square bandpass regions centred
on the continuum at either side of these lines (wavelengths of 3891{AA}
and 4001{AA}). These values have been calibrated onto the Mt. Wilson
system of measurements (Duncan et al., 1991, Cat. ) and then converted
to the commonly used logRhk system (Noyes et al. 1984ApJ...287..769N)
to remove the photospheric component of the flux. The metallicities
shown in column 6, were measured by comparing a grid of synthetic
spectra (WITA6; Pavlenko et al., 1995A&A...303..807P) to a number
of mostly weak and unblended FeI lines at this spectral resolution. The
internal errors were determined by fitting the Chi-squared parabola and
after comparison with other works these values were found to agree to
<0.1dex or 0.05dex with other high-resolution spectral abundances
(e.g. Valenti & Fischer, 2005, Cat. ). The tail of objects with
really high errors were mainly lower S/N spectra due to changing
weather patterns. <P />(1 data file).
---------------------------------------------------------
Title: Spectral analysis of high resolution near-infrared spectra
of ultra cool dwarfs
Authors: Lyubchik, Y.; Jones, H. R. A.; Pavlenko, Y. V.; Martin, E.;
McLean, I. S.; Prato, L.; Barber, R. J.; Tennyson, J.
2007A&A...473..257L Altcode: 2007arXiv0708.2676L
Aims:We present an analysis of high resolution spectra in the J band
of five ultra cool dwarfs from M6 to L0. <BR />Methods: We make use
of a new ab initio water vapour line list and existing line lists of
FeH and CrH for modelling the observations. <BR />Results: We find a
good fit for the Mn I 12 899.76 Å line. This feature is one of the
few for which we have a reliable oscillator strength. Other atomic
features are present but most of the observed features are FeH and
H2O lines. While we are uncertain about the quality of many of the
atomic line parameters, the FeH and CrH line lists predict a number
of features which are not apparent in our observed spectra. We infer
that the main limiting factor in our spectral analysis is the FeH and
CrH molecular spectra.
---------------------------------------------------------
Title: Eight new T4.5-T7.5 dwarfs discovered in the UKIDSS Large
Area Survey Data Release 1
Authors: Lodieu, N.; Pinfield, D. J.; Leggett, S. K.; Jameson, R. F.;
Mortlock, D. J.; Warren, S. J.; Burningham, B.; Lucas, P. W.; Chiu,
K.; Liu, M. C.; Venemans, B. P.; McMahon, R. G.; Allard, F.; Baraffe,
I.; Barrado y Navascués, D.; Carraro, G.; Casewell, S. L.; Chabrier,
G.; Chappelle, R. J.; Clarke, F.; Day-Jones, A. C.; Deacon, N. R.;
Dobbie, P. D.; Folkes, S. L.; Hambly, N. C.; Hewett, P. C.; Hodgkin,
S. T.; Jones, H. R. A.; Kendall, T. R.; Magazzù, A.; Martín, E. L.;
McCaughrean, M. J.; Nakajima, T.; Pavlenko, Y.; Tamura, M.; Tinney,
C. G.; Zapatero Osorio, M. R.
2007MNRAS.379.1423L Altcode: 2007MNRAS.tmp..609L; 2007arXiv0705.3727L
We present eight new T4.5-T7.5 dwarfs identified in the UKIRT
(United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS)
Large Area Survey (LAS) Data Release 1 (DR1). In addition we have
recovered the T4.5 dwarf SDSSJ020742.91+000056.2 and the T8.5 dwarf
ULASJ003402.77-005206.7. Photometric candidates were picked up in
two-colour diagrams over 190deg<SUP>2</SUP> (DR1) and selected in at
least two filters. All candidates exhibit near-infrared spectra with
strong methane and water absorption bands characteristic of T dwarfs
and the derived spectral types follow the unified scheme of Burgasser
et al.. We have found six new T4.5-T5.5 dwarfs, one T7 dwarf, one T7.5
dwarf and recovered a T4.5 dwarf and a T8.5 dwarf. We provide distance
estimates which lie in the 15-85pc range; the T7.5 and T8.5 dwarfs are
probably within 25pc of the Sun. We conclude with a discussion of the
number of T dwarfs expected after completion of the LAS, comparing these
initial results to theoretical simulations. <P />Based on observations
made with the United Kingdom Infrared Telescope, operated by the Joint
Astronomy Centre on behalf of the UK Particle Physics and Astronomy
Research Council. <P />E-mail: nlodieu@iac.es ‡ <P />Alfred P. Sloan
Research Fellow.
---------------------------------------------------------
Title: Two T dwarfs from the UKIDSS early data release
Authors: Kendall, T. R.; Tamura, M.; Tinney, C. G.; Martín, E. L.;
Ishii, M.; Pinfield, D. J.; Lucas, P. W.; Jones, H. R. A.; Leggett,
S. K.; Dye, S.; Hewett, P. C.; Allard, F.; Baraffe, I.; Barrado Y
Navascués, D.; Carraro, G.; Casewell, S. L.; Chabrier, G.; Chappelle,
R. J.; Clarke, F.; Day-Jones, A.; Deacon, N.; Dobbie, P. D.; Folkes,
S.; Hambly, N. C.; Hodgkin, S. T.; Nakajima, T.; Jameson, R. F.;
Lodieu, N.; Magazzù, A.; McCaughrean, M. J.; Pavlenko, Y. V.; Tadashi,
N.; Zapatero Osorio, M. R.
2007A&A...466.1059K Altcode: 2007astro.ph..2534K
Context: We report on the first ultracool dwarf discoveries from the
UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey Early Data
Release (LAS EDR), in particular the discovery of T dwarfs which
are fainter and more distant than those found using the 2MASS and
SDSS surveys. <BR />Aims: We aim to show that our methodologies for
searching the ~27 deg<SUP>2</SUP> of the LAS EDR are successful for
finding both L and T dwarfs via cross-correlation with the Sloan
Digital Sky Survey (SDSS) DR4 release. While the area searched so
far is small, the numbers of objects found shows great promise for
near-future releases of the LAS and great potential for finding large
numbers of such dwarfs. <BR />Methods: Ultracool dwarfs are selected
by combinations of their YJH(K) UKIDSS colours and SDSS DR4 z-J and
i-z colours, or, lower limits on these red optical/infrared colours
in the case of DR4 dropouts. After passing visual inspection tests,
candidates have been followed up by methane imaging and spectroscopy
at 4 m and 8 m-class facilities. <BR />Results: Our main result is the
discovery following CH4 imaging and spectroscopy of a T4.5 dwarf, ULAS
J 1452+0655, lying ~80 pc distant. A further T dwarf candidate, ULAS J
1301+0023, has very similar CH4 colours but has not yet been confirmed
spectroscopically. We also report on the identification of a brighter
L0 dwarf, and on the selection of a list of LAS objects designed to
probe for T-like dwarfs to the survey J-band limit. <BR />Conclusions:
Our findings indicate that the combination of the UKIDSS LAS and SDSS
surveys provide an excellent tool for identifying L and T dwarfs down
to much fainter limits than previously possible. Our discovery of
one confirmed and one probable T dwarf in the EDR is consistent with
expectations from the previously measured T dwarf density on the sky.
---------------------------------------------------------
Title: Modelling the Spectrum and SED of V838 Mon
Authors: Pavlenko, Y.; Kaminsky, B.; Lyubchik, Y.; Yakovina, L.
2007ASPC..363..225P Altcode: 2006astro.ph..9604P
We model the spectra and spectral energy distribution of V838 Mon which
were observed in February, March, and November, 2002. Theoretical
spectra are calculated using the classical model atmospheres taking
into account absorption of atomic and molecular lines. By fitting the
observed spectra we determine the physical parameters of the atmosphere
of V838 Mon. These parameters are determined to be {T<SUB>eff</SUB> }
= 5330 ± 300 K, 5540 ± 270 K, 4960 ± 190 K, and 2000 ± 200 K for
February 25, March 2, March 26, and November 6, respectively.
---------------------------------------------------------
Title: Experimental TiI oscillator strengths and their application
to cool star analysis
Authors: Blackwell-Whitehead, R. J.; Lundberg, H.; Nave, G.; Pickering,
J. C.; Jones, H. R. A.; Lyubchik, Y.; Pavlenko, Y. V.; Viti, S.
2006MNRAS.373.1603B Altcode: 2006astro.ph.12656B; 2006MNRAS.tmp.1308B
We report experimental oscillator strengths for 88 TiI transitions
covering the wavelength range 465-3892 nm, 67 of which had no previous
experimental values. Radiative lifetimes for 13 energy levels, including
the low energy levels 3d<SUP>2</SUP>(<SUP>3</SUP>F) 4s4p (<SUP>3</SUP>P)
z <SUP>5</SUP>D°<SUB>j</SUB>, have been measured using time-resolved
laser-induced fluorescence. Intensity-calibrated TiI spectra have been
measured using Fourier transform spectroscopy to determine branching
fractions for the decay channels of these levels. The branching
fractions are combined with the radiative lifetimes to yield absolute
transition probabilities and oscillator strengths. Our measurements
include 50 transitions in the previously unobserved infrared region
λ > 1.0μm, a region of particular interest to the analysis of
cool stars and brown dwarfs.
---------------------------------------------------------
Title: Theoretical modelling of optical and IR spectra of brown
dwarfs and ultracool dwarfs
Authors: Pavlenko, Y. V.
2005AN....326..934P Altcode:
The current state of theoretical modelling of the spectra of cool
dwarfs and ultracool objects are discussed. Fits of synthetical spectral
energy distributions (SEDs) in the optical and IR spectral regions to
observed spectra show problems of theoretical modelling. Problems of
interpretation of observed spectra are more obvious for the case of L
and T dwarfs. Still even for late-M dwarfs the situation is far from
being perfect. Some examples of the fine analysis of the spectra of
ultracool dwarfs are presented.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Linelist of HCN and HNC (Harris+,
2006)
Authors: Harris, G. J.; Tennyson, J.; Kaminskiy, B.; Pavlenko, Y. V.;
Jones, H. R. A.
2005yCat.6121....0H Altcode:
We present an energy level list which contains the ab initio energies
and exact quantum numbers from HPT, together with lab determined
energies and assigned approximate quantum numbers where available. A
new HCN/HNC linelist is presented. Lab determined energy levels were
used to compute accurate line frequencies, where available. Where
lab data is not available frequencies are computed from ab initio
energy levels. The linelist is truncated at a minimum frequency of
3*10-28^cm/mol at T=3000K. Resulting in a linelist of 38 million
lines, which accounts for 99.99% of the opacity of the full linelist
at 3000K. The file has been compressed using bzip2. The data is sorted
into increasing frequency order. A FORTRAN code is supplied to convert
the Einstein A coefficients of HPT and the new energy level list into
a usable linelist. <P />(3 data files).
---------------------------------------------------------
Title: Temperatures in the atmopshere of the cool component of
CH Cygni
Authors: Jurdana-Sepic, R.; Kotnik-Karuza, D.; Majlinger, Z.; Pavlenko,
Y. V.
2004ASPC..318..371J Altcode: 2004ssrc.conf..371J
We have investigated the temperatures in the atmosphere of the cool
component of CH Cygni by use of highly resolved optical and near
infrared spectra taken in a short epoch of the 1998-2000 active
phase. TiO absorption bands belonging to α, γ, γ', β, δ, φ and
ɛ band systems with partly resolved rotational structure have been
studied and vibrational temperatures belonging to γ' and φ system
were obtained from the relative intensities of vibrational band
heads. In order to determine the effective temperature we used model
atmospheres appropriate for M giants and computed synthetic spectra
by the line-to-line approach. Results are discussed in view of the
previously determined rotational temperature.
---------------------------------------------------------
Title: Atomic lines in infrared spectra for ultracool dwarfs
Authors: Lyubchik, Y.; Jones, H. R. A.; Pavlenko, Y. V.; Viti, S.;
Pickering, J. C.; Blackwell-Whitehead, R.
2004A&A...416..655L Altcode: 2003astro.ph.12578L
We provide a set of atomic lines which are suitable for the description
of ultracool dwarf spectra from 10 000 to 25 000 Å. This atomic
linelist was made using both synthetic spectra calculations and existing
atlases of infrared spectra of Arcturus and Sunspot umbra. We present
plots which show the comparison of synthetic spectra and observed
Arcturus and Sunspot umbral spectra for all atomic lines likely to
be observable in high resolution infrared spectra. <P />Figure 1
is only available in electronic form at http://www.edpsciences.org
<P />Tables 1 and 2 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/416/655
---------------------------------------------------------
Title: Draco 461, an intrinsic carbon star in a metal poor stellar
population: 3<SUP>rd</SUP> dredge up and mixing
Authors: Domínguez, I.; Abia, C.; Straniero, O. Cristallo, S.;
Pavlenko, Y. V.
2004MmSAI..75..601D Altcode:
In July 2003 we observed the first Li-rich carbon star in a dwarf
spheroidal galaxy. We compute stellar models for AGB stars and, by
comparing them to the available photometric and spectroscopic data,
conclude that D461 is an intrinsic carbon star, more massive and
younger than the dominant stellar population of Draco.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Atomic lines in IR spectra for
ultracool dwarfs (Lyubchik+, 2004)
Authors: Lyubchik, Y.; Jones, H. R. A.; Pavlenko, Y. V.; Viti, S.;
Pickering, J. C.; Blackwell-Whitehead, R.
2004yCat..34160655L Altcode:
Table 1 contains all identified lines with central intensities
deeper than 0.8 of residual flux using "ultracool dwarf model"
identifications. <P />Table 2 investigates the sensitivity of priority 1
lines identified in Table 1 to temperature, gravity and metallicity. <P
/>We compute some synthetic spectra for ultracool objects varying
parameters of Teff, log g and metallicity to show the sensitivity of
the central intensities of identified lines to these parameters. For
our computations we chose the minimal step in model atmospheres grid:
{Delta}Teff=100K, {Delta}logg=0.5, {Delta}[M/H]=-0.5. STeff shows the
dependence of residual fluxes on effective temperature. For comparison a
2100/5.0/0.0 synthetic spectrum was used. One can see that only a few
lines show strong temperature dependence for {Delta}=100K. <P />The
NextGen 2000/4.5/0.0 model was used with 2000/5.0/0.0 to test gravity
sensitivity. The dependence for {Delta}(log g)=0.5 is also relatively
weak for most lines. <P />The NextGen model atmospheres 2000/5.0/-0.5
and 2000/5.0/0.0 to test metallicity sensitivity. The metallicity
dependence is relatively high for all lines. <P />(2 data files).
---------------------------------------------------------
Title: A Comparison of Water Vapour Line Lists
Authors: Jones, H. R. A.; Pavlenko, Y.; Viti, S.; Tennyson, J.
2003csss...12..899J Altcode:
M dwarf spectra, at wavelengths beyond 1.35 μm, are dominated by water
vapour yet terrestrial water vapour makes it notoriously difficult to
make accurate measurement from ground-based observations. We have used
the short wavelength spectrometer on the Infrared Space Observatory
to obtain the 2.5--3.0 μm region. The observations show a good
match with synthetic spectra based on the Partridge & Schwenke
(1997) line list though not with the SCAN (Jorgensen et al. 2001)
line list. Nonetheless, the Partridge & Schwenke calculations for
water vapour lines still need to be extended to higher energy levels
with good convergence for reliable modelling of hot water vapour. Then
water bands can assume their natural role as the primary tool for the
spectroscopic analysis of M stars.
---------------------------------------------------------
Title: Model Atmospheres and SEDs of Chemically Peculiar Stars
Authors: Pavlenko, Y. V.
2003IAUS..210P.A16P Altcode: 2002astro.ph..9022P
Procedure and results of computations of stellar model atmospheres and
spectral energy distributions are discussed. Model atmospheres of some
chemically peculiar stars are computed taking into account detailed
information about their abundances: -- R CrB-like stars of Teff $\sim$
7000 K, -- Sakurai's object (V4334 Sgr) of 4000 $<$ \Tef $<$
7000 K -- Przybylski's star of Teff $\sim$ 6500 K. We show that our
self-consistent approach provides a unique possibility to investigate
the temporal changes of physical parameters of chemically peculiar
stars. Some problems of computation of model atmospheres of M and
C-giants are also considered.
---------------------------------------------------------
Title: Stellar Abundance Patterns. What is the Possible Level of
Completeness Today?
Authors: Gopka, V.; Yushchenko, A.; Musaev, F.; Galazutdinov, G.;
Kim, C.; Shavrina, A.; Pavlenko, Y.; Polosukhina, N.; North, P.
2003IAUS..210P..E5G Altcode: 2003astro.ph..8339G
We discuss the way of increasing of the number of chemical elements,
investigated in stellar spectra. We can reach it by using spectrum
synthesis method, new atomic data and observation of stellar spectra
with resolution comparable to solar spectral atlases. We show two
examples of this kind researches. The first is the implementation
of new atomic data to well known Przybylski's star. We show that the
number of spectral lines, which can be identificated in the spectrum
of this star can be significantly higher. The second example is the
investigation of zeta Cyg. We found the abundances of 51 elements in
the atmosphere of this mild barium star.
---------------------------------------------------------
Title: Carbon monoxide bands in M dwarfs
Authors: Pavlenko, Y. V.; Jones, H. R. A.
2002A&A...396..967P Altcode: 2002astro.ph.10017P
We compare the observational and theoretical spectra of the Delta v
= 2 CO bands in a range of M dwarfs. We investigate the dependence
of theoretical spectra on effective temperatures as well as carbon
abundance. In general we find that the synthetic CO bands fit the
observed data extremely well and are excellent diagnostics. In
particular the synthetic spectra reasonably match observations and
the best fit temperatures are similar to those found by empirical
methods. We also examine the <SUP>12</SUP>C/<SUP>13</SUP>C isotopic
ratio. We find that fundamental <SUP>13</SUP>CO bands around 2.345 and
2.375 mu m are good discriminators for the <SUP>12</SUP>C/<SUP>13</SUP>C
ratio in M dwarfs. The 2.375 mu m band is more useful because it doesn't
suffer such serious contamination by water vapour transitions. Our
current dataset does not quite have the wavelength coverage to perform
a reliable determination of the <SUP>12</SUP>C/<SUP>13</SUP>C ratio in
M dwarfs. For this we recommend observing the region 2.31-2.40 mu m
at a resolution of better than 1000. Alternatively the observational
problems of contamination by water vapour at 2.345 mu m maybe solved
by observing at resolutions of around 50 000. We also investigated the
possibility of using the Delta v = 1 CO bands around 4.5 mu m. We find
that the contamination due to water vapour is even more of a problem
at these wavelengths.
---------------------------------------------------------
Title: Models of infrared spectra of Sakurai's Object (V4334 Sgr)
in 1997
Authors: Pavlenko, Y. V.; Geballe, T. R.
2002A&A...390..621P Altcode: 2002astro.ph..5528P
Theoretical spectral energy distributions computed for a grid
of hydrogen-deficient and carbon-rich model atmospheres have been
compared with the observed infrared (1-2.5 mu m) spectra of V4334 Sgr
(Sakurai's Object) on 1997 April 21 and July 13. The comparison yields
an effective temperature of T<SUB>eff</SUB> = 5500 +/- 200 K for the
April date and T<SUB>eff</SUB> = 5250 +/- 200 K for July. The observed
spectra are well fitted by Asplund et al. (\cite{Asplund99}) abundances,
except that the carbon abundance is higher by 0.3 dex. Hot dust produces
significant excess continuum at the long wavelength ends of the 1997
spectra. Based on observations obtained at the United Kingdom Infrared
Telescope (UKIRT), which is operated by the Joint Astronomy Centre on
behalf of the U. K. Particle Physics and Astronomy Research Council.
---------------------------------------------------------
Title: Formation of the Optical Spectra of L Dwarfs
Authors: Pavlenko, Y.
2001udns.conf...33P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: About Use of Quantum Effects and Fundamental Physical
Constants for Elaboration of the Measurement Standards in the Field
of Electronic Measurements
Authors: Niemeyer, J.; Pavlenko, Y.; Anikin, V.; Kolbasin, A.;
Seredniy, V.
2001pems.conf..341N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Formation of the Optical Spectra of the Coolest M- and L-dwarfs
and Lithium Abundances in their Atmospheres
Authors: Pavlenko, Y. V.
2000IAUS..198..454P Altcode: 2000astro.ph..2144P
Theoretical aspects of modeling of spectra of late M- and L-dwarfs are
discussed. We show, that the processes of formation of spectra of M-
and L-dwarfs are basically different. Instead of the case of M-dwarfs,
atoms of Ti and V should be depleted into grains in the atmospheres
of L-dwarfs. Overall shape of the L-dwarf spectra is governed by
the K I + Na I resonance line wings of the huge strength. To fit
lithium lines observed in spectra of the coolest dwarfs we used
two additional suggestions: a) there are some EXTRA depletions of
molecular species absorbed in the optical spectra of L-dwarfs; b)
there may be (a few?) additional (“dusty”?) opacity sources in their
atmospheres. Problems of lithium line formation and the “natural”
limitation of their use for the “lithium test” for the case of
L-dwarfs are considered.
---------------------------------------------------------
Title: The formation of lithium lines in the atmospheres of super
Li-rich AGB stars
Authors: Abia, C.; Pavlenko, Y.; de Laverny, P.
1999A&A...351..273A Altcode: 1999astro.ph..4420A
The formation of lithium lines in the atmosphere of C-rich giants is
discussed. LTE and NLTE approximations are used to model lithium lines
in the spectra of super Li-rich AGB stars. The system of equations
of the statistical balance of neutral Li in plane-parallel model
atmospheres is solved for a 20-level atom model. JOLA and line-by-line
models of molecular absorption are used to compute synthetic spectra as
well as the opacity in the frequencies of bound-bound and bound-free
transitions of the lithium lines. Curves of growth and synthetic
spectra are computed in LTE and NLTE for several model atmospheres
of different {T_eff} and C/O ratios for four lithium absorptions,
namely: the lambda 4603, lambda 6104, lambda 6708 and lambda 8126 Å
Li I lines. The sensitivity of NLTE effects on {T_eff} and the C/O
ratio is discussed. We found that NLTE mainly affects the resonance
line doublet (lambda6708 ) while the impact of NLTE effects on the
lithium subordinate lines, formed in the inner regions of C-rich
giant atmospheres, is rather weak. Therefore the use of these lines is
recommended for Li determination in AGB stars. However, in no case can
we properly account for the formation of Li lines in AGB stars until
sphericity, velocity stratifications, dust, chromospheres and other
related phenomena, which are in fact present in AGB star atmospheres,
are considered. Our results are used to derive Li abundances in three
super-Li rich C-stars taking into account NLTE effects. Finally, the
net Li yield from this class of stars into the interstellar medium
is reconsidered.
---------------------------------------------------------
Title: The Lithium Lines Formation in Brown Dwarf Atmospheres:
Molecules, Chromospheres, NLTE
Authors: Pavlenko, Y. V.
1998ASPC..134..416P Altcode: 1998bdep.conf..416P
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet NH bands as indicators of nitrogen abundance in
the atmospheres of cool stars.
Authors: Yakovina, L. A.; Pavlenko, Y. V.
1998KPCB...14..195Y Altcode:
Nitrogen abundance indicators were selected for spectral resolutions
of 0.0025 nm and 0.02 nm in the NH band region at λ336 nm. For this
purpose a list of atomic lines from LOWLINES, DAT (CD-ROM No. 1 in
Kurucz's 1993 database) and lists of molecular lines from CD-ROM
No. 18 were tested and corrected using the spectrum of the Sun as
a star. The effect of line list completeness on nitrogen abundance
estimates is examined.
---------------------------------------------------------
Title: New and accurate Li abundance determinations in super Li-rich
AGB stars
Authors: Abia, C.; de Laverny, P.; Pavlenko, Y.
1998IAUS..191P.101A Altcode:
Super lithium-rich AGB stars constitute the sole observational evidence
of a stellar production of lithium. Abundance determinations report
values as high as Li/H ~10^{-7} in their atmospheres (i.e. more
than 10-100 times the cosmic abundance), therefore these stars might
represent an important source of lithium in the galaxies. However most
of these abundance analyses are based on the study of the resonance line
of LiI 6708 Angstroms which usually is very strong or near saturation
even in AGB stars with normal lithium abundances. Here we have used
high-resolution and high signal-to-noise ratio spectra of three
well known super Li-rich carbon stars (WZ Cas, WX Cyg and IY Hya)
to derive LTE/N-LTE lithium abundances using two other accessible
less-intense Li lines at 6103 and 8126 Angstroms for the first time
in AGB stars. We show that N-LTE effects are very important for the
resonance line. Furthermore, the core of the 6708 Angstroms line forms
very high in the atmosphere of AGB stars where the structure of the
atmosphere is almost unknown. That excludes the use of this line for
realistic Li abundance determinations in AGB stars. On the contrary, we
found that N-LTE effects are weak for the two other lines. Although it
is saturated, the subordinate Li line at 8126 Angstroms is recommended
to derive abundances in Li-rich AGB stars.
---------------------------------------------------------
Title: Common envelope evolution and Li in V471 Tauri.
Authors: Martin, E. L.; Pavlenko, Y.; Rebolo, R.
1997A&A...326..731M Altcode:
We have observed the spectral regions around the LiI resonance 670.8nm
and subordinate 610.4nm lines of V471 Tau. This is an eclipsing post
common-envelope (CE) binary system. A revision of several independent
measurements of the parallax and proper motion of V471 Tau allow
us to argue that this system is indeed a Hyades cluster member by
examining and rejecting earlier, flawed results. Using spectral
synthesis and taking into account NLTE effects, we have derived a
photospheric Li abundance of log N(Li)=2.35+/-0.25 for the K dwarf,
which is a factor >100 higher than single Hyades members of the
same mass. We argue that two mechanisms are responsible for this:
a) Accretion of a substantial amount of Li-rich material onto the
K dwarf during CE evolution inside the giant precursor of the white
dwarf. Recently, a number of Li-rich giants have been observed and
they appear to undergo large mass-loss. We speculate that CE evolution
could actually explain the properties of these giants as well. b)
Reduced Li depletion in the K dwarf due to sustained fast rotation
in a short-period tidally-locked orbit. This process accounts for the
preservation of Li after CE evolution has ceased.
---------------------------------------------------------
Title: Formation of lithium lines in very cool dwarfs.
Authors: Pavlenko, Y. V.; Rebolo, R.; Martin, E. L.; Garcia Lopez,
R. J.
1995A&A...303..807P Altcode:
We present LTE and NLTE results on the formation of LiI lines (λ6103,
λ6708, and λ8126) in the atmospheres of solar metallicity dwarfs with
effective temperatures in the range 5500K to 2000K. NLTE effects are
governed by overionization of Li and by the interlocking effects of
energy levels. For stars with T_eff_>=4000K, we confirm previous
findings by Magazzu et al. (1992). NLTE corrections can lower the
LTE Li abundances derived from strong LiIλ6708 lines by up to 0.5
dex. Our computations using model atmospheres with T_eff_ between 3000K
and 2000K show that prominent LiI lines are formed. We give a set of
line profiles, which support the feasability of the Li test for brown
dwarfs. The ionization-dissociation equilibrium for Li species was
carefully considered. NLTE effects on the LiI lines of very cool dwarfs
are found to be small, implying corrections to the LTE Li abundances
lower than 0.1 dex. Several numerical tests have been carried out to
estimate the effects of chromosphere-like structures on the formation
of LiI lines. Our preliminary results suggest that in the presence of
very strong chromospheres, the line strengths are reduced.
---------------------------------------------------------
Title: Li I Lines in POP II Dwarf Spectra: NLTE Effects
Authors: Pavlenko, Y. V.
1995lea..conf..324P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpretations of stellar spectra: NLTE effects
Authors: Pavlenko, Y. V.
1995MmSAI..66..441P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interpretations of stellar spectra: NLTE effects
Authors: Pavlenko, Y. V.
1995HiA....10..453P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Behaviour of the Lithium Abundance Along the Pre-Main
Sequence
Authors: Magazzú, A.; Martín, E. L.; Rebolo, R.; García Lopez,
R. J.; Pavlenko, Y. V.
1995lea..conf..260M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Statistical Equilibrium of Lithium in the Atmospheres of
Dwarfs with Various Metallicities
Authors: Pavlenko, Y. V.
1994AZh....71..600P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Beryllium abundances in unevolved metal deficient stars.
Authors: Rebolo, R.; Garcia Lopez, R. J.; Martin, E. L.; Beckman,
J. E.; McKeith, C. D.; Webb, J. K.; Pavlenko, Y. V.
1993oee..conf..149R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Beryllium and Lithium abundances in stars with a range of
metallicities
Authors: Garcia Lopez, R. J.; Martin, E. L.; Rebolo, R.; Beckman,
J. E.; McKeith, C. D.; Webb, J. K.; Pavlenko, Y. V.
1993ASPC...40..180G Altcode: 1993IAUCo.137..180G; 1993ist..proc..180G
No abstract at ADS
---------------------------------------------------------
Title: Observational patterns of lithium depletion in pre-main
sequence stars
Authors: Martín, E. L.; Rebolo, R.; Garcia Lopez, R. J.; Magazzu,
A.; Pavlenko, Y. V.
1993ASPC...40..165M Altcode: 1993ist..proc..165M; 1993IAUCo.137..165M
No abstract at ADS
---------------------------------------------------------
Title: Nonlte Effects and Strong Lii Lines in the Spectra of the K
Giants HD9746 and HD112127
Authors: Pavlenko, Y. V.
1992SvA....36..605P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Lithium Abundances in Classical and Weak T Tauri Stars
Authors: Magazzu, Antonio; Rebolo, Rafael; Pavlenko, Iakov V.
1992ApJ...392..159M Altcode:
A study on the lithium abundance in 36 T Tauri stars (mass range
0.4-2.25 solar masses), partly based on high-dispersion spectra taken
with the Isaac Newton Telescope, is presented. A study of non-LTE
effects in the formation of the lithium double in T Tauri stars and
derived corrections to the abundances in the LTE in the range 1.0-4.0
log N(Li) is presented. Tor T(eff) of 400-4500 K, a significant upward
correction to the LTE abundance (about 0.3-0.6 dex) is found. For
T(eff) close to 500 K, smaller corrections (about 0.2 dex), and for
log N(Li) greater than about 3, downward corrections (about 0.1 dex)
are found. The initial value of the lithium abundance in T Tauri
stars is estimated at 3.2 +/- 0.1, which is in close agreement with
the accepted present cosmic abundance.
---------------------------------------------------------
Title: Statistical Equilibrium and the Lii 670.766-NM and 670.791-NM
Absorption Lines in the Spectrum of Red Giants - Results
Authors: Pavlenko, Y. V.
1991SvA....35..623P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The statistical equilibrium and the 670.776- and 670.791-nm
absorption lines of Li I in red-giant spectra - Methodology
Authors: Pavlenko, Y. V.
1991AZh....68..776P Altcode:
A method for calculating the statistical equilibrium for lithium in the
atmospheres of red giants without LTE is analyzed. The cool-atmosphere
opacity circulation method (absorption mean) is investigated. The
analysis makes it possible to determine the role played by free-bound
transitions from different levels in establishing the lithium ionization
balance in the atmospheres of late stars.
---------------------------------------------------------
Title: Statistical Equilibrium and the 670.776-NM and 670.791-NM
Lii Absorption Lines in the Spectrum of Red Giants - Procedure
Authors: Pavlenko, Y. V.
1991SvA....35..384P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Atmosphere of the K2III-STAR Alpha-Arietis
Authors: Berdyugina, S. V.; Boyarchuk, M. E.; Pavlenko, Y. V.; Savanov,
I. S.; Shavrina, A. V.
1991SvA....35..387B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Determination of C N and O Abundances in the Atmospheres of
Late Type Stars - Extreme Value Problem
Authors: Pavlenko, Y. V.
1991SvA....35..212P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The determination of C, N, and O abundances in late-type star
atmospheres - Extremum problem
Authors: Pavlenko, Y. V.
1991AZh....68..431P Altcode:
The possibility of determining carbon, nitrogen, and oxygen abundances
through the extremum problem treatment is discussed. The minimized
functional consists of differences between observed and calculated
parameters of atomic and molecular absorption lines or their blends. A
brief description of the procedure and C, N, and O abundance data for
the atmosphere of a K giant are presented.
---------------------------------------------------------
Title: Li C N and O Abundances and the 12/C/13/C Isotope Ratio in
the Atmospheres of the K Giants 39-CYGNI and Alpha-Arietis
Authors: Boyarchuk, M. E.; Pavlenko, Y. V.; Shavrina, A. V.
1991SvA....35..143B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectral Features in the Circumstellar Envelope of the Close
Binary System V367-CYGNI
Authors: Menchenkova, E. V.; Pavlenko, Y. V.
1990SvA....34..489M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The determination of physical parameters of the atmosphere
of the primary star of the system V367 Cygni with the method of
atmosphere models.
Authors: Menchenkova, E. V.; Pavlenko, Y. V.
1989AZh....66..194M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solution of the NLTE Problem for MGI in Atmosphere of M Giants
with Chromosphere - Part One - Menzel Coefficients
Authors: Pavlenko, Y. V.
1988Afz....28..163P Altcode:
Results of a solution of the NLTE problem for magnesium in the
atmosphere of a red giant M2 (T<SUB>eff</SUB> = 3800K, log g = 1.5) are
discussed. An empirical model chromosphere was used. The over-ionization
of magnesium in the atmosphere of the M2 giant takes place only in
the region of the temperature minimum. In contrast, the number of
Mg<SUP>+</SUP> ions in the chromosphere decreased compared with LTE.
---------------------------------------------------------
Title: The Over Ionization of Metals in Atmospheres of M Giants
Authors: Pavlenko, Y. V.
1983ATsir1267....6P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Curve of Growth and Radiation Diffusion in the Case of
a Hydrogen Multilevel Atom in Prominences
Authors: Yakovkin, N. A.; Zeldina, M. Y.; Pavlenko, Y. V.
1980BSolD..12...89Y Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Diffusion of Hydrogen Radiation in Prominences
Authors: Yakovkin, N. A.; Zeldina, M. Y.; Pavlenko, Y. V.
1979SvA....23..585Y Altcode:
No abstract at ADS