Author name code: byrne
ADS astronomy entries on 2022-09-14
author:"Byrne, Patrick B." year:1970-1998
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Title: Erratum: Metallicity and photospheric abundances in field K
and M dwarfs
Authors: Zboril, M.; Byrne, P. B.; Rolleston, W. R. J.
Bibcode: 1998MNRAS.301.1104Z
Altcode:
No abstract at ADS
Title: The chromosphere of II Pegasi: multi-line modelling of an RS
Canum Venaticorum star
Authors: Short, C. I.; Byrne, P. B.; Panagi, P. M.
Bibcode: 1998A&A...338..191S
Altcode:
We present the first simultaneous multi-line fitting of a semi-empirical
atmospheric model with a chromosphere and transition region to the H
I and Ca II spectra of an RS CVn star (II Peg). The static component
of the Hα emission core, the line profile of Hβ , the apparent
absence of Hγ and Hdelta , and the emission core profiles of Ca II
K and two of the Ca II IR(3) lines are all approximately fitted by
a static 1D model with the following properties: log m at the onset
of the transition region is ~ -2.85, and a 6000 K plateau in the
upper chromosphere that spans about a decade in log m. In particular,
the model is able to reproduce the unusually steep Balmer decrement
(compared to the dMe stars), in which Hα is strongly in emission
and Hβ is in absorption, without recourse to extra-atmospheric
material. The Ca II IR(3) lines are best fit by a model in which
T_min is cooler by 300 K and shallower by over half a decade in log
m than that which best fits the optical lines. The emergent flux in
the IR(3) line cores arises from the T_min region, whereas the other
diagnostics arise from layers well above T_min, and it is postulated
that this may be the cause of the discrepancy. There has very recently
been evidence from other investigators that the metallicity of II Peg
may be sub-solar, and we find that models with [{A/ H}]=-0.4 provide
a somewhat better fit to all the lines considered.
Title: Metallicity and photospheric abundances in field K and M dwarfs
Authors: Zboril, M.; Byrne, P. B.
Bibcode: 1998MNRAS.299..753Z
Altcode:
Elemental abundances in late-type stars are of interest in several ways:
they determine the location of the stars in the HR diagram and therefore
their ages, as well as the atmospheric structure in their middle
and upper photospheres. Especially in the case of chromospherically
active late-type stars the question arises to what degree the upper
photosphere is influenced by the nearby chromosphere. Analysing S/N~200
and Deltalambda/lambda~20000 data, we found a mean metallicity index
[M/H]=-0.2 for programme K and M field stars based on an analysis
of spectra in the region 5500-9000 Angstroms. We also found that
the CaI 6162-Angstroms transition is a potential surface gravity
indicator for K-type stars. For the chromospheric activity interval
4.4<logF_MgII<6.6 we did not find any chromospheric activity
impact on photospheric and upper photospheric transitions. With the
derived metallicity, we confirmed the Li abundance from our previous
paper and thus its dependence on the MgII chromospheric activity
index. The nature of the spectrum for the active M-type star Gl 896A is
explained by pure rotation of 14 km s^-1. As far as the lithium-rotation
relation is concerned, the spectrum of Gl 517 is rotationally broadened
as well, by 12 km s^-1, and the Li abundance is the second highest in
our sample of stars. However, there is no link between very high Li
abundance, 2.2 dex, in the K dwarf star Gl 5 and stellar rotation.
Title: The photosphere and chromosphere of the RS Canum Venaticorum
star, II Pegasi. II. A multi-wavelength campaign in August/September
1992
Authors: Byrne, P. B.; Abdul Aziz, H.; Amado, P. J.; Arevalo, M. J.;
Avgoloupis, S.; Doyle, J. G.; Eibe, M. T.; Elliott, K. H.; Jeffries,
R. D.; Lanzafame, A. C.; Lazaro, C.; Murphy, H. M.; Neff, J. E.;
Panov, K. P.; Sarro, L. M.; Seiradakis, J. H.; Spencer, R. E.
Bibcode: 1998A&AS..127..505B
Altcode:
We describe multi-wavelength, simultaneous observations of the RS
CVn star, II Pegasi, most of which were obtained during the first
three weeks of September 1992. These observations were made using
optical and infra-red broad-band photometry, ultraviolet and optical
spectroscopy and microwave monitoring. We have detected photospheric
spots and chromospheric flares, as well as deriving a description
of mean conditions in the quiet chromosphere. One of the flares,
observed in optical photometry and ultraviolet spectroscopy is one of
the most energetic ever observed on this star. We demonstrate that in
its ``quiescent'' state II Peg is continually variable in most of its
chromospheric emissions, as well as in its coronal output.
Title: Evidence of Prominences on Cool Late-Type Stars (Review)
Authors: Byrne, P. B.; Eibe, M. T.; van den Oord, G. H. J.
Bibcode: 1998ASPC..150..227B
Altcode: 1998IAUCo.167..227B; 1998npsp.conf..227B
No abstract at ADS
Title: The Search for Low Mass Members of the Young Open Cluster
Stock 2
Authors: Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.
Bibcode: 1998ASPC..154.2101F
Altcode: 1998csss...10.2101F
We present a combined photometric and proper motion survey of the
100Myr open cluster Stock 2. BVRI CCD photometry was obtained for 21
5 x 5 arcmin fields. Fifty-nine candidate members were selected from
(B, B-V) and (R, R-I) colour magnitude diagrams using the theoretical
isochrones of D'Antona & Mazzitelli (1994). We also obtained
SuperCOSMOS scans of three POSS plates. From their position in a
proper motion vector-point diagram we estimate that 12 of the 59
candidate members selected above are likely to be cluster members. We
also present the results of analysis based only on the POSS data,
and identify 311 candidate cluster members.
Title: He I 10830 AA in Late-Type Dwarfs
Authors: Byrne, P. B.; Sarro, L. M.; Lanzafame, A. C.
Bibcode: 1998ASPC..154.1392B
Altcode: 1998csss...10.1392B
We present high-resolution, high-signal-to-noise observations of the
He 1 10830 AA line in K and M dwarf stars over a range of activity
levels. The line is detected in all our target stars in absorption and
shows no obvious correlation with X-ray flux. A flare is detected in
one star, which drives the line into net emission.
Title: Chromospheric and coronal activity levels in the nearby faint
M dwarf GL 105B
Authors: Doyle, J. G.; Short, C. I.; Byrne, P. B.; Amado, P. J.
Bibcode: 1998A&A...329..229D
Altcode:
Monitoring with the HRI onboard ROSAT failed to detect the nearby
faint M dwarf star Gl 105B (a star of anomalously low chromospheric and
coronal activity), implying log L_x < 26.1. High resolution optical
data for Caii HK indicate a surface flux of ~ 6.5 \ 10(3) \ erg \
cm(-2) \ s(-1) , in good agreement with the previously measured Mg ii
hk flux. Based on chromospheric modelling, both the Hα and Caii K line
profiles indicate an atmospheric structure which is intermediate between
that of an intermediate dM chromosphere and a basal chromosphere. Also,
the modelling indicates that a better fit is obtained using a model
atmosphere which has Tmin less than 2650 K, and a thin,
steep chromosphere. Furthermore, the Caii HK radiative losses may only
be ~ 5% of the radiative losses in the UV continuum, implying total
chromospheric losses in excess of 10(5) erg cm(-2) s(-1) .
Title: Four Color Photometry of the Young Open Cluster Collinder 140
Authors: Theissen, A.; Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.
Bibcode: 1998ASPC..154.2143T
Altcode: 1998csss...10.2143T
Cluster member candidates of the young open cluster Collinder 140 are
selected by means of four-colour BV(RI)_C CCD photometry. We show
that a reasonably small number of candidates can be separated from
the background field contamination even with non-photometric data by
matching the red clump of background stars in the colour-magnitude
diagrams to the one expected towards this sky region.
Title: Indicators of Intense Activity in the Recently Discovered
Late-Type Rapid Rotator, RE 1816+541
Authors: Eibe, M. T.; Byrne, P. B.; Robb, R. M.
Bibcode: 1998ASPC..154.1410E
Altcode: 1998csss...10.1410E
As part of a project to analyse prominence-like clouds in rapid
rotators, we have obtained time-series of high resolution spectra of the
rapidly rotating (v sin i ~61 km s^{-1}, P_rot ~0.459 d) dM1-2e star, Re
1816+541. These observations display a wide range of magnetic activity
phenomena. A strong emission transient is seen to cross the profile in
about half a rotation period and recurs on three consecutive nights,
providing evidence for plage-like features. Prominence corotating
clouds have been optically identified in the stellar atmosphere and
their analysis has led to important conclusions. A very large flare was
detected during one of the nights, showing strong effects in several
chromospheric emission lines. Finally, results from simultaneous
differential photometry suggest the existence of large spotted regions
on the stellar surface.
Title: A New Non-Solar Paradigm for Active Stars
Authors: Walter, Frederick M.; Byrne, P. Brendan Byrne
Bibcode: 1998ASPC..154.1458W
Altcode: 1998csss...10.1458W
The solar analogy is generally accepted for interpretation of stellar
activity, yet coronal and chromospheric data of active stars often show
very non-solar-like characteristics. Rather than beginning with the Sun
and extrapolating backwards, we begin with the pre-main sequence stars
and extrapolate forward in time. Among the youngest active stars, above
the main sequence, there is strong evidence for quasi-dipolar magnetic
fields. Time-series spectroscopy of chromospheres of diverse active
stars shows characteristics consistent with matter trapped in a magnetic
canopy. Radio observations suggest highly extended radio coronae. We
present new and published data in support of a new paradigm for stellar
activity based on the decay of large-scale organized magnetic fields.
Title: Mapping Stellar Surface Structures on the RS CVn Star II Peg
Authors: Zboril, M.; Byrne, P. B.; Amado, P. J.
Bibcode: 1998ASPC..154.2082Z
Altcode: 1998csss...10.2082Z
Chromospherically active late type stars exhibit most of the
characteristics of the active Sun on a globally much enhanced scale. We
analyse high signal-to-noise spectroscopic data obtained in September
and October 1993 of single-line RS CVn binary star II Peg. The results
are used to construct a Doppler image of the spot distribution at that
epoch. A multicomponent spot model is suggested with ~30% of total
spot coverage.
Title: AG Dor: SPOT Parameters From Simultaneous Optical and Infrared
Photometry and TiO Spectroscopy
Authors: Amado, P. J.; Byrne, P. B.; Zboril, M.
Bibcode: 1998ASPC..154.1923A
Altcode: 1998csss...10.1923A
As a continuation of our project to derive the distribution and
temperature of the modulating component of spots on active late-type
stars, the authors have observed a number of RS CVn, BY Dra and
dMe stars photometrically (optical UBV(RI)_c and infrared HJK)
and spectroscopically (TiO band) simultaneously in Dec. 1996 and
Jan. 1997. The simultaneity of these observations allows us to apply
two of the currently available techniques with which spot temperatures,
sizes and locations can be obtained, viz., the light-curve modelling
technique and the TiO band technique. We present here the photometric
and spectroscopic data for one of our targets, AG Dor, and the spot
model that best fits the observed light and colour curves and the
depth of the lambda 7055 AA titanium oxide band for this active star.
Title: Photometrically determined membership of the young, open
cluster IC 2391
Authors: Rolleston, W. R. J.; Byrne, P. B.
Bibcode: 1997A&AS..126..357R
Altcode:
New 4-colour BV(RI)KC CCD photometry to a limiting
magnitude of V ~19 is presented for 1428 objects observed towards
the direction of the young, open cluster IC 2391. We observed 36
(2' X 3') fields within 17 arcmin of the nominal cluster core. By
fitting the theoretical isochrones of \cite[D'Antona & Mazzitelli
(1994]{Dan94}) to a combination of colour-magnitude and colour-colour
diagrams, we have identified 17 stars as probable cluster members with
a further 85 stars as possible members. The brightness distribution of
low-mass members is compared with the luminosity function observed for
the Pleiades and we estimate that the contamination due to background
giants should be small. Figure 4 is only available in electronic form
via http://www.ed-phys.fr
Title: CCD photometry of late-type stars in the young open cluster
IC 2602
Authors: Foster, D. C.; Byrne, P. B.; Hawley, S. L.; Rolleston,
W. R. J.
Bibcode: 1997A&AS..126...81F
Altcode:
We present the results of VRI photometry of the young open cluster IC
2602. Two 15 arcmin times 15 arcmin fields were observed in February
and May 1991 using the 1-m Swope telescope at Las Campanas. Using
theoretical isochrones obtained from \cite[D'Antona & Mazzitelli
(1994)]{dam94}, and allowing for observational and other uncertainties,
we identify 78 primary candidate members with 12<V<18.5 from
their positions on colour-magnitude diagrams. We compare the cluster
field with an offset field of similar galactic latitude and estimate
the contamination due to background stars to be large, >= 50%, as
might be expected given its low galactic latitude. We also compare our
photometry with that given for the X-ray detected stars of \cite[Randich
et al. (1995)]{ran95}. We present complimentary narrow band H alpha
photometry for a subset of the stars.
Title: The CaI 4227 line as a chromospheric diagnostic for M dwarfs.
Authors: Short, C. I.; Doyle, J. G.; Byrne, P. B.
Bibcode: 1997A&A...324..196S
Altcode:
In M dwarfs the CaI 4227 line is saturated, therefore, the line
core forms at a relatively small column mass density. As a result,
the line is a potential diagnostic of chromospheric structure in
these stars. We have calculated line profiles out of LTE for a grid
of early M dwarf atmospheric models that spans the range from low to
high chromospheric pressure and covers a range of observed activity
levels. We have found that this line is sensitive to the detailed
structure of the chromosphere in the same way as well studied strong
lines such as Hα and CaII HK: as the chromospheric pressure increases,
the line changes from absorption to strong emission with a central
double reversal. Therefore, observations of the CaI 4227 line in M
dwarfs would provide a useful additional constraint on the structure
of the outer atmosphere. We also calculate consistently the line
blanketing in the upper atmosphere of models with a chromosphere and
transition region and investigate the effect of its inclusion on CaI
4227. Finally, we demonstrate that the effects of Partial Frequency
Redistribution must be taken into account if the CaI 4227 is to be
used as an accurate diagnostic of the T_min_ region in dMe stars.
Title: VizieR Online Data Catalog: Members of IC 2391 (Rolleston+
1997)
Authors: Rolleston, W. R. J.; Byrne, P. B.
Bibcode: 1997yCat..41260357R
Altcode:
The photometric measurements were performed using the 1.0-m
telescope at the South African Astronomical Observatory (SAAO)
at Sutherland (Cape Province), during the period 15-22 January
and 1-8 Februray 1994. The internal photometric errors are:
------------------------------------------ Magnitude range V B-V V-R V-I
------------------------------------------ V<=13.0 0.001 0.003 0.003
0.003 13.0-15.0 0.003 0.005 0.005 0.005 15.0-17.0 0.012 0.024 0.017
0.017 17.0-19.0 0.056 0.112 0.077 0.080 V>=19.0 0.104 0.197 0.140
0.145 ------------------------------------------ (2 data files).
Title: The NaI λλ5890,5896 resonance doublet as chromospheric
diagnostics in M dwarfs.
Authors: Andretta, V.; Doyle, J. G.; Byrne, P. B.
Bibcode: 1997A&A...322..266A
Altcode:
The Nai D lines at 5890/5896Å are very prominent features in the
spectrum of late-type stars. Nevertheless, little attention has
been devoted to the potential use of those lines as chromospheric
diagnostics. As a case study, we explore the dependence on chromospheric
activity of the D lines in a star with T_eff_=3700K, logg=4.7 and solar
metallicity. The results are compared with the better studied hydrogen
spectrum. We find that the D lines seem to be a promising diagnostic
of the lower-middle chromosphere, that can complement the information
given by lines like Hα. We also find that, for detailed quantitative
studies, it is necessary to include a proper treatment of the background
opacities. Less important, instead, is the need of careful treatment
of transitions induced by collisions with hydrogen atoms. Finally,
our calculations make it clear that, for the most active stars, the
level of coronal emission should also be taken into account.
Title: Effect of chromospheric activity on the mean colours of
late-type stars.
Authors: Amado, P. J.; Byrne, P. B.
Bibcode: 1997A&A...319..967A
Altcode:
In this paper we show, for the first time, the effect of activity on
the (U-B)_0_ vs. (B-V)_0_ colour-colour diagram for a large sample of
late type stars. We clearly see that for single-lined spectroscopic
RSCVn systems there exists an ultraviolet excess over that recorded
for quiescent stars of the same spectral type. The same effect is
seen in main-sequence stars but to a lesser extent. From simple
arguments we demonstrate that the cause is unlikely to be unresolved
flaring, the combined effect of strong chromospheric emission lines,
or X-ray/UV back-heating of the photosphere. White-light faculae are
a reasonable candidate for the effect however. In our investigation
we have not taken into account the effect that metallicity might have
on the colour indices.
Title: VizieR Online Data Catalog: IC 2602 VRI photometry (Foster+
1997)
Authors: Foster, D. C.; Byrne, P. B.; Hawley, S. L.; Rolleston,
W. R. J.
Bibcode: 1997yCat..41260081F
Altcode:
We present the results of VRI photometry of the young open cluster IC
2602. Two 15x15arcmin2 fields were observed in February
and May 1991 using the 1-m Swope telescope at Las Campanas. Using
theoretical isochrones obtained from D'Antona & Mazzitelli
(1994ApJS...90..467D), and allowing for observational and other
uncertainties, we identify 78 primary candidate members with
12<V<18.5 from their positions on colour-magnitude diagrams. We
compare the cluster field with an offset field of similar galactic
latitude and estimate the contamination due to background stars to
be large, >=50%, as might be expected given its low galactic
latitude. We also compare our photometry with that given for the
X-ray detected stars of Randich et al. (1995A&A...300..134R)
present complimentary narrow band Hα photometry for a subset of the
stars. (1 data file).
Title: CCD photometry of late-type stars in the young open cluster
Stock 2
Authors: Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.
Bibcode: 1997MmSAI..68..875F
Altcode:
No abstract at ADS
Title: Lithium abundance in field K and M dwarfs
Authors: Zboril, M.; Byrne, P. B.; Rolleston, W. R. J. R.
Bibcode: 1997MNRAS.284..685Z
Altcode:
It is widely accepted that lithium abundance in late-type
stars correlates with other stellar characteristics, such
as age, chromospheric activity and rotation. For example, the
post-main-sequence active components of RSCVn binaries have been
compared with inactive field stars of the same spectral type and found
to have excess lithium. In stars with deep convective zones lithium
is expected to be destroyed in a relatively short time. This is most
dramatically true in the main-sequence stars of the latest type. In
this paper we have examined the lithium abundances in a sample of
late-K and M-type dwarfs. High signal-to-noise ratio, high spectral
resolution spectra have been obtained of the Li i resonance doublet
(lambda6707.8A). Evidence for an appreciable lithium abundance has
been found in stars as late as early to mid-M. Furthermore, there is
evidence for a correlation between this Li abundance and chromospheric
activity in the case of K dwarfs while M dwarfs do not appear to follow
such a relation.
Title: Evidence for Prominence-Like Material in Stellar Coronae
Authors: Byrne, P. B.
Bibcode: 1997eaun.book...59B
Altcode:
No abstract at ADS
Title: Effective Temperature-Colour and Surface Brightness-Colour
Relationships for the Latest-Type Stars
Authors: Amado, P. J.; Byrne, P. B.
Bibcode: 1996IrAJ...23..177A
Altcode:
New calibrations of six broad-band optical and near infrared colours
(U-B, B-V, V-R, V-I, R-I and V-K) against accurate effective
temperatures (T_eff) derived from empirical and semi-empirical
(infrared flux) methods for G, K and M giants are presented. Polynomial
coefficients for these relationships are given. We also present
independent relationships between the visual surface brightness
parameter F_V and the colours (V-R), (V-I), (R-I) and (V-K). We find
that (U-B) and (B-V) are unsuitable as T_eff indicators. The tightest
relationship in each case is found for the (V-K) index. Our mean
relationships agree reasonably well with similar relationships derived
by other authors, where such are available. These relationships are
suitable for use in the determination of spot areas and temperatures
in active late-type stars.
Title: Cool prominences in the corona of the rapidly rotating dMe
star, HK Aquarii.
Authors: Byrne, P. B.; Eibe, M. T.; Rolleston, W. R. J.
Bibcode: 1996A&A...311..651B
Altcode:
We report the discovery of cool, prominence-like material embedded
in the hot corona of the rapidly rotating dMe flare/spot variable,
HKAqr. Using these observations we demonstrate that, unlike the case
of the rapidly rotating K dwarf, ABDor, these features form well below
the co-rotation radius. Rather they have dimensions between 3-20 times
those of the very largest solar prominences. At least seven clouds
were detected during each stellar rotation and they have a lifetime
of greater than the three nights spanned by our data.
Title: Flare energetics: analysis of a large flare on YZ Canis
Minoris observed simultaneously in the ultraviolet, optical and radio.
Authors: van den Oord, G. H. J.; Doyle, J. G.; Rodono, M.; Gary,
D. E.; Henry, G. W.; Byrne, P. B.; Linsky, J. L.; Haisch, B. M.;
Pagano, I.; Leto, G.
Bibcode: 1996A&A...310..908V
Altcode:
The results of coordinated observations of the dMe star YZ CMi
at optical, UV and radio wavelengths during 3-7 February 1983 are
presented. YZ CMi showed repeated optical flaring with the largest
flare having a magnitude of 3.8 in the U-band. This flare coincided
with an IUE exposure which permits a comparison of the emission measure
curves of YZ CMi in its flaring and quiescent state. During the flare a
downward shift of the transition zone is observed while the radiative
losses in the range 10^4^-10^7^K strongly increase. The optical flare
is accompanied with a radio flare at 6cm, while at 20cm no emission
is detected. The flare is interpreted in terms of optically thick
synchrotron emission. We present a combined interpretation of the
optical/radio flare and show that the flare can be interpreted within
the context of solar two-ribbon/white-light flares. Special attention
is paid to the bombardment of dMe atmospheres by particle beams. We
show that the characteristic temperature of the heated atmosphere is
almost independent of the beam flux and lies within the range of solar
white-light flare temperatures. We also show that it is unlikely that
stellar flares emit black-body spectra. The fraction of accelerated
particles, as follows from our combined optical/radio interpretation
is in good agreement with the fraction determined by two-ribbon flare
reconnection models.
Title: On the diagnostic contents of NA I lines in M dwarfs
Authors: Andretta, V.; Byrne, P. B.; Doyle, J. G.
Bibcode: 1996ASPC..109..559A
Altcode: 1996csss....9..559A
No abstract at ADS
Title: Lithium abundance in K and M dwarfs
Authors: Zboril, M.; Byrne, P. B.; Rolleston, W. R. J.; Douglas,
J. J. L.
Bibcode: 1996ASPC..109..707Z
Altcode: 1996csss....9..707Z
No abstract at ADS
Title: On the believability of polar spots
Authors: Byrne, P. B.
Bibcode: 1996IAUS..176..299B
Altcode:
No abstract at ADS
Title: Prominences on Late Type Active Stars
Authors: Byrne, P. B.
Bibcode: 1996mpsa.conf..139B
Altcode: 1996IAUCo.153..139B
No abstract at ADS
Title: VRI photometry of the young open cluster IC 2602
Authors: Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.; Hawley,
S. L.
Bibcode: 1996ASPC..109..357F
Altcode: 1996csss....9..357F
No abstract at ADS
Title: Helium lines in late-type dwarfs.
Authors: Lanzafame, A. C.; Byrne, P. B.
Bibcode: 1995A&A...303..155L
Altcode:
We analyse the formation of HeI lines in late-type dwarfs by statistical
equilibrium (or NLTE radiative transfer) computations. Atmospheric
models for a dK (ɛ Eri) and a dMe (V 1005Ori=Gl182) stars are
considered. The validity of the weakly non-uniform approximation for dMe
stars established in Lanzafame (???) for the lower transition region of
dMe stars implies that streaming particles have virtually no role in the
formation of the lines. Comparison with observations of the HeI(10830A)
and HeI(5876A) lines in the dMe star, V 1005Ori, indicate that it is
possible to reproduce the observed helium lines with a simple model
compatible with other observational constraints. Over-ionisation by
coronal EUV radiation is found to play a minor role in the formation
of the triplet lines.
Title: The OV 1371.29A/1218.35A emission-line ratio in solar and
stellar spectra
Authors: Keenan, F. P.; Brekke, P.; Byrne, P. B.; Greer, C. J.
Bibcode: 1995MNRAS.276..915K
Altcode:
New calculations of the theoretical electron-density-sensitive
emission-line ratio R=I(2s2p ^1P-2p^2 ^1D)/I(2s^2 ^1S-2s2p
^3P_1)=I(1371.29A)/I(1218.35A) in OV are presented, which are
significantly different from those deduced previously, principally
due to the adoption of improved atomic data in the present
analysis. Electron densities estimated from the current diagnostics,
in conjunction with observed values of R measured from solar spectra
obtained by the S082B spectrograph on board Skylab and by the High
Resolution Telescope and Spectrograph (HRTS) on board a sounding rocket
flight, are found to be in good agreement with densities determined from
line ratios in species formed at similar electron temperatures to OV,
such as OIV and NIV. These results provide experimental support for
the accuracy of the diagnostic calculations presented in this paper,
and hence the atomic data used in their derivation. The observed value
of R for the M0Ve flare star AU Mic, determined from observations made
by the Goddard High Resolution Spectrometer on board the Hubble Space
Telescope, is within 4 per cent of the expected low-density limit,
implying that logN_e<=10.4 for the OV emitting region of the AU
Mic atmosphere. This is similar to density estimates made for AU Mic
using other methods.
Title: VizieR Online Data Catalog: BVRI CCD photometry of NGC 5460
(Barrado+, 1995)
Authors: Barrado, D.; Byrne, P. B.
Bibcode: 1995yCat..41110275B
Altcode:
We present CCD photometry on the BV(RI)KC (Cape) photometric
system core of the young open cluster, NGC 5460, to a magnitude limit
V=~19, R=~19.5. We give photometry for 353 stars and identify 25 as
cluster members along with a further 27 as possible members based on
their positions in individual colour-magnitude diagrams. We estimate the
reddening to the cluster and redefine its distance and age. Four stars
are identified as possible variables and their nature discussed. (1
data file).
Title: The photosphere and chromosphere of the RS Canum Venaticorum
star, II Pegasi I. Spots and chromospheric emission in 1991.
Authors: Byrne, P. B.; Panagi, P. M.; Lanzafame, A. C.; Avgoloupis,
S.; Huenemoerder, D. P.; Kilkenny, D.; Marang, F.; Panov, K. P.;
Roberts, G.; Seiradakis, J. H.; van Wyk, F.
Bibcode: 1995A&A...299..115B
Altcode:
We report on high-resolution spectroscopy of the RSCVn binary IIPeg,
along with contemporaneous UBV(RI)_KC_ photometry, including partly
simultaneous U-band flare monitoring, during the third quarter of
1991. The spectroscopy was taken at two epochs separated by more
than 6(1)/(2) weeks or seven rotations of IIPeg. At the first epoch
we have observed the three chromospheric lines, Hα, Hβ and HeID_3_,
over a single rotation and at the second epoch we observed almost the
entire visible region, for a substantial fraction of one rotation,
including Hα-Hɛ and CaIIH. Our photometric results show that
there was an unusually complicated spot distribution at this epoch,
with at least three centres of activity discernable. We demonstrate,
for the first time on a spotted late-type star, that these centres
of spot activity have significantly different mean temperatures from
one another. Furthermore, our derived spot temperatures are markedly
lower than those previously derived from such multicolour photometry
and more similar to those derived spectroscopically. Using multiple
repeat exposures on each spectral line within each night, we are
confident that we have derived a mean, non-flaring spectrum at each
observational phase. Furthermore, the line flux variations at the two
epochs repeat very well, suggesting that the mean global chromospheric
structures are stable on a 1(1)/(2) months time scale. We discuss the
implications of the mean spectra for the non-flaring atmosphere of
IIPeg and conclude that, in the region of formation of the Hα line,
velocity fields are required to account for the line profile. These
results suggest upward motions of the deep chromosphere with a less
dramatic downflow in the high chromosphere. We examine the variation
of the chromospheric line fluxes as a function of spot visibility
and conclude that there is only a very loose spatial correlation of
chromsopheric heating with spots. The motions suggested from the Hα
profile variations appear to be spot-associated.
Title: Discovery of a white dwarf companion (EUVE J0254-053) to the
K0 IV star HD18131
Authors: Vennes, S.; Mathioudakis, M.; Doyle, J. G.; Thorstensen,
J. R.; Byrne, P. B.
Bibcode: 1995A&A...299L..29V
Altcode:
New ultraviolet (UV) observations of late-type stars detected in
the Extreme Ultraviolet Explorer (EUVE) all-sky survey revealed
an unsuspected white dwarf companion to the K0 star HD18131. The
International Ultraviolet Explorer (IUE) spectrum show a composite of a
white dwarf and a late-type star. The white dwarf dominates the emission
below 2000A while the K0 star prevails at longer wavelengths. A model
atmosphere analysis of the new ultraviolet spectrophotometry and of
the extreme ultraviolet (EUV) photometry reveals a hot, hydrogen-rich
(DA) white dwarf (Teff~30000K) that is the most likely source of the
EUV emission (EUVE J0254-053). We estimate a distance to the white
dwarf of 70-90pc. The K0 star shows a modest level of chromospheric
activity with the detection of Mg II h and k emission in the IUE
spectrum. Optical spectroscopy revealed that the K0 star is a subgiant
(K0 IV). The star is located at a distance of ~70pc, consistent with
the estimated distance of the white dwarf. Therefore, it most likely
constitutes a physical pair with the white dwarf. Until results of a
radial velocity study are made available we cannot establish whether
the pair is wide or close. In earlier works the strong EUV emission was
attributed to the K0 star; however, our multiwavelength observations
show the white dwarf as the most likely source. This discovery has
important implications for the EUV white dwarf population survey and,
in particular, for the binary frequency.
Title: BV(RI)_KC_ CCD photometry of the core of the young open
cluster, NGC 5460.
Authors: Barrado, D.; Byrne, P. B.
Bibcode: 1995A&AS..111..275B
Altcode:
We present CCD photometry on the BV(RI)_KC_ (Cape) photometric system
of the core of the young open cluster, NGC 5460, to a magnitude limit
V=~19, R=~19.5. We give photometry for 353 stars and identify 25 as
cluster members along with a further 27 as possible members based on
their positions in individual colour-magnitude diagrams. We estimate
the reddening to the cluster and redefine its distance and age. Four
stars are identified as possible variables and their nature discussed.
Title: Optical flaring on RS CVn stars : the case of II Peg in
1992 September.
Authors: Byrne, P. B.; Lanzafame, A. C.; Sarro, L. M.; Ryans, R.
Bibcode: 1994MNRAS.270..427B
Altcode:
Recent observational results by Mathioudakis et al. have suggested
that optical Uband flares are a frequent occurrence on the RS CVn star,
II Peg. We present U-band monitoring of II Peg in 1992 September which
failed to show any evidence of flaring to very low limits. We show that
these data are inconsistent with the flaring rates reported earlier
and suggest that either II Peg was in a state of low flare activity
in 1992, or that it was unusually active at the time of Mathioudakis
et al.'s observations. Key words: stars: activity - binaries: close -
stars: flare - stars: individual: II Peg - stars: late-type.
Title: BD +22 4409 : a rapidly rotating, low-mass member of the
Local Association.
Authors: Jeffries, R. D.; Byrne, P. B.; Doyle, J. G.; Anders, G. J.;
James, D. J.; Lanzafame, A. C.
Bibcode: 1994MNRAS.270..153J
Altcode:
We present spectroscopic and photometric observations of BD +2204409,
a nearby, low-mass star which, on the basis of its Galactic space
motions and high EUV-tobolometric luminosity ratio, has been previously
assigned membership of the young kinematic group known as the Local
Association. Our observations show that BD +2204409 is a single,
K5V-K7V, chromospherically active ultrafast rotator, with a probable
period of 10.1710.10 h and a projected equatorial velocity of 691 1 km 1
It has a comparatively high photo spheric lithium abundance of N(Li) =
1.3010.25, and this, combined with our photometry and a trigonometric
parallax, leads to the conclusion that the star is young, although
probably no younger than 20-30 Myr, and is a prime Local Association
candidate in all respects. Considerable variability is seen in the
rotationally broadened H a emission line, and can be interpreted
in terms of transient flare activity at very high latitudes or the
combination of a rotationally modulated, high-latitude active region
and a rather smaller flare at an unconstrained latitude. In either
case, the flare radiative losses in the H a line are at least 2 x 1032
erg. There is no evidence for the corotating cool prominences that
have been seen at some distance from the surfaces of other late-type
rapid rotators. This may be interpreted as a geometric effect,
whereby the low inclination deduced for BD +2204409, of 5001 100,
combined with a centrifugal flattening of any cloud system towards
the equatorial plane, renders clouds unobservable as Ha absorption
transients. Spot modelling of the photometric light curves yields
an asymmetric spot component, covering at least 4 per cent of the
total stellar surface. Variability of 1013 per cent is seen in the
strength of the Lii 6708-A line over 7 h of a rotation period, in the
sense that the peak Li I equivalent width correlates with the time of
maximum spot coverage deduced from the shapes of photospheric line
profiles. This result is consistent with calculations of the effect
of starspots on the Li I equivalent width, once projection effects
and limb-darkening are taken into account. Enhanced molecular bands
may also play a role, but very cool atmospheric models are required to
investigate this question fully. Key words: stars: abundances - stars:
activity - stars: individual: BD +2204409 - stars: late-type - stars:
rotation - open clusters and associations: general.
Title: Observing Stellar Coronae with the Goddard High Resolution
Spectrograph. I. The dMe Star AU Microscopii
Authors: Maran, S. P.; Robinson, R. D.; Shore, S. N.; Brosius, J. W.;
Carpenter, K. G.; Woodgate, B. E.; Linsky, J. L.; Brown, A.; Byrne,
P. B.; Kundu, M. R.; White, S.; Brandt, J. C.; Shine, R. A.; Walter,
F. M.
Bibcode: 1994ApJ...421..800M
Altcode:
We report on an observation of AU Mic taken with the Goddard High
Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope. The
data consist of a rapid sequence of spectra covering the wavelength
range 1345-1375 A with a spectral resolution of 10,000. The observations
were originally intended to search for spectral variations during
flares. No flares were detected during the 3.5 hr of monitoring. A
method of reducing the noise while combining the individual spectra
in the time series is described which resulted in the elimination of
half of the noise while rejecting only a small fraction of the stellar
signal. The resultant spectrum was of sufficient quality to allow the
detection of emission lines with an integrated flux of 10-15
ergs/sq cm(sec) or greater. Lines of C I, O I, O V, Cl I, and Fe XXI
were detected. This is the first indisputable detection of the 1354
A Fe XXI line, formed at T approximately = 107 K, on a
star other than the Sun. The line was well resolved and displayed
no significant bulk motions or profile asymmetry. From the upper
limit on the observed line width, we derive an upper limit of 38 km/s
for the turbulent velocity in the 107 K plasma. An upper
limit is derived for the flux of the 1349 A Fe XII line, formed at T
approximately = 1.3 x 106 K. These data are combined with
contemporaneous GHRS and International Ultraviolet Explorer (IUE) data
to derive the volume emission measure distribution of AU Mic over the
temperature range 104-107 K. Models of coronal
loops in hydrostatic equilibrium are consistent with the observed
volume emission measures of the coronal lines. The fraction of the
stellar surface covered by the footprints of the loops depends upon the
loop length and is less than 14% for lengths smaller than the stellar
radius. From the upper limit to the estimated width of the Fe XXI line
profile we find that the we cannot rule out Alfven wave dissipation
as a possible contributor to the required quiescent loop heating rate.
Title: IUE Observations of New, Bright EUVE Sources
Authors: Byrne, P. B.
Bibcode: 1994iue..prop.4948B
Altcode:
No abstract at ADS
Title: Measurement of HeI lambda 10830 angstroms in the Flare Star,
V1005 ORI (=GL 182)
Authors: Byrne, P. B.; Lanzafame, A. C.
Bibcode: 1994ASPC...64..378B
Altcode: 1994csss....8..378B
No abstract at ADS
Title: Rotational Modulation of Transition Region Emission over Two
Rotations of the RS CVn Star, II Peg
Authors: Byrne, P. B.; Lanzafame, A. C.; Murphy, H. M.; Watters, E.
Bibcode: 1994ASPC...64..381B
Altcode: 1994csss....8..381B
No abstract at ADS
Title: H alpha Variability on HK Aqr: Coronal Condensations or Plages?
Authors: Byrne, P. B.; Mathioudakis, M.; Young, A.; Skumanich, A.
Bibcode: 1994ASPC...64..375B
Altcode: 1994csss....8..375B
No abstract at ADS
Title: Where Does H alpha ARISE in the RS CVn Star, II Peg?
Authors: Byrne, P. B.; Lanzafame, A. C.; Panagi, P. M.; Avgoloupis,
S.; Seiradakis, J. H.; Kilkenny, D. M.; Marang, F.; Roberts, G.;
van Wyk, F.; Panov, K. P.
Bibcode: 1994ASPC...64..384B
Altcode: 1994csss....8..384B
No abstract at ADS
Title: Activity in late-type stars. IX. The weakest chromosphere M
dwarf yet discovered : GL 105B.
Authors: Byrne, P. B.
Bibcode: 1993A&A...278..520B
Altcode:
We present an estimate of chromospheric radiative losses from the dM(e)
star, Gl 105B, based on a measurement of the MgII h&k emission
line flux, which indicates that this star has the weakest chromospheric
heating rate yet found in any M dwarf and that it lies well below the
'basal' heating rate of derived by Schrijver (1987).
Title: Collision Strengths and Rate Coefficients for Electron Impact
Excitation in Hei - an Extrapolation of R-Matrix Calculations to
Higher Electron Impact Energies
Authors: Lanzafame, A. C.; Tully, J. A.; Berrington, K. A.; Dufton,
P. L.; Byrne, P. B.; Burgess, A.
Bibcode: 1993MNRAS.264..402L
Altcode:
Extrapolations to higher electron impact energies of collision strengths
calculated using the R-matrix method are presented for electric
dipole allowed transitions of neutral helium. The extrapolations
are based on a spline fit constrained by the high-energy limiting
behaviour deduced from the Bethe approximation. This fit allows the
calculation of the rate coefficients over a wide temperature range. The
possibility of calculating collision rates in a non-equilibrium plasma
is also discussed.
Title: Activity in late-type stars. VIII. The nature of the dM(e)
or "zero" H-alpha stars.
Authors: Byrne, P. B.
Bibcode: 1993A&A...272..495B
Altcode:
We present the results of ultraviolet spectroscopy of three M dwarf
stars which, according to Stauffer & Hartmann (1986), have no Hα,
either in absorption or emission, in their visible spectra. Using
chromospheric and transition region emission line fluxes derived
from these spectra, we demonstrate that these stars undergo lower
rates of chromospheric non-radiative heating than dM (Hα absorption)
stars. Therefore, the hypothesis that the dM(e) stars, as we have called
the zero-Hα objects, have a predominantly Hα absorption atmosphere,
filled in by the emission from a small number of active regions,
is not tenable in these cases. We also discuss the applicability
of the Schrijver (1987) basal flux relationship to the dM(e) stars,
particularly to G1 105B, which has the weakest chromospheric Mg II
emission yet observed and point out that the convective zone energy
flux of Bohn (1984) may not be sufficient to acoustically heat basal
chromospheres in the latest spectral type M stars.
Title: Rotational modulation and flares on RS Canum Venaticorum and
BY Draconis stars. XVII. UV spectroscopy and optical photometry of
AU Microscopii in 1986.
Authors: Quin, D. A.; Doyle, J. G.; Butler, C. J.; Byrne, P. B.;
Swank, J. H.
Bibcode: 1993A&A...272..477Q
Altcode:
We present IUE spectroscopy and optical photometry of the active
late type star AU Mic. The UV spectroscopy allow us to measure
the chromospheric and transition region line fluxes. No detectable
variations attributable to rotational modulation were evident in
either the chromospheric lines or optical bands. We have produced
an emission measure curve for the quiescent state of AU Mic, which
spans a temperature range 4.0 ≤ log Te ≤ 7.6 when
coupled with previous X-ray flux measurements. The quiescent radiative
losses per unit surface area over the above temperature range is ≍8
1O7 erg cm-2 s-1
Title: Spectroscopic and photometric observations of supernova
1987A. VII. Days 793 to 1770.
Authors: Caldwell, J. A. R.; Menzies, J. W.; Banfield, R. M.;
Catchpole, R. M.; Whitelock, P. A.; Feast, M. W.; Lloyd Evans,
T. H. H.; Sekiguchi, K.; Zijlstra, A.; Allen, D. A.; Bell, S. A.;
Blades, J. C.; Buckley, D. A. H.; Byrne, P. B.; Callanan, P.; Collins,
C.; Cumming, R. J.; O'Donoghue, D.; Fairall, A. P.; Freeman, F. F.;
Holmgren, D.; Jones, K.; Latham, D. W.; Maddox, S.; Meadows, V. S.;
Meikle, W. P. S.; Mittaz, J. P. D.; Monk, A.; Penny, A. J.; Pollacco,
D.; Slawson, R. D.; Soltynski, M. G.; Spyromilio, J.; Stirpe, G. M.;
Stobie, R. S.; Willmer, C.
Bibcode: 1993MNRAS.262..313C
Altcode:
We present spectroscopic and UBV(RI)_C_JHKLM photometric observations of
SN 1987A in the Large Magellanic Cloud made between days 793 and 1770
after the Kamiokande-II neutrino event, as well as some CCD UBV(RI)_C_
photometry from day 640 to day 792, which overlaps the interval covered
in the preceding paper of this series. During the period from about day
670 to day 1260, the U to M- bolometric magnitude (hereafter M_UM_)
of the supernova and its adjoining circumstellar ring (hereafter
'the enclosed supernova') dimmed at an increasingly slower rate than
during the preceding interval from day 500 to day 670. The rate of
dimming steadily increased again between days 1270 and 1770. From day
1000 onwards, the light of the circumstellar ring made an increasingly
significant contribution to the light of the enclosed supernova, and
by day 1250 had become so dominant that it is probable that useful
Earth based photometry of the bare supernova itself was not feasible
thereafter.
Title: Imaging the Photosphere &Chromosphere of the Rapidly
Rotating dMe Star, HK Aqr
Authors: Byrne, P. B.; Mathioudakis, M.
Bibcode: 1993ASSL..183..435B
Altcode: 1993pssc.symp..435B
No abstract at ADS
Title: A Bright, Blue Spot on the dMe Star, AU Mic
Authors: Byrne, P. B.
Bibcode: 1993ASSL..183..431B
Altcode: 1993pssc.symp..431B
No abstract at ADS
Title: Stellar Flares
Authors: Byrne, P. B.
Bibcode: 1993ASSL..183..489B
Altcode: 1993pssc.symp..489B
No abstract at ADS
Title: Imaging the Photosphere and Chromosphere of the RS CVn Star,
II Peg
Authors: Byrne, P. B.; Lanzafame, A. C.; Panagi, P. M.; Kilkenny,
D. W.; Marang, F.; Roberts, G.; van Wyk, F.; Avgoloupis, S.; Mavridis,
L. N.; Seiradakis, J. H.
Bibcode: 1993ASSL..183..439B
Altcode: 1993pssc.symp..439B
No abstract at ADS
Title: Dynamic phenomena on the RS Canum Venaticorum binary II Pegasi
in August 1989. I. Observational data.
Authors: Doyle, J. G.; Kellett, B. J.; Butler, C. J.; Byrne, P. B.;
Neff, J. E.; Brown, A.; Fox, D.; Linsky, J. L.; Bromage, G. E.;
Avgoloupis, S.; Mavridis, L. N.; Seiradakis, J. H.; Mathioudakis,
M.; Murphy, H. M.; Krzesinski, J.; Pajdosz, G.; Dadonas, V.;
Sperauskas, J.; van Wyk, F.; Marang, F.; Olah, K.; Collier Cameron,
A.; Antonomoulos, E.; Rovithis, P.; Rovithis-Livaniou, H.
Bibcode: 1992A&AS...96..351D
Altcode:
Observational results are given for two flares in Pi Pegasi that were
detected by the GINGA and IUE satellites, as well as by ground-based
Johnson U-band photometry and optical spectroscopy. The best-fitting
results were obtained for a combination of a single-temperature
plasma together with a power law; for a two-temperature model, the
temperature of the second component was very high due to the tail in
the photon distribution.
Title: The Quiescent X-ray Spectrum of the RS CVn Binary II Peg in
August 1989
Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.; Kellett,
B. J.; Bromage, G. E.
Bibcode: 1992ASPC...26..356D
Altcode: 1992csss....7..356D
No abstract at ADS
Title: GL 890 - The Magnetic Brake?
Authors: Byrne, P. B.; Doyle, J. G.; Mathioudakis, M.
Bibcode: 1992ASPC...26..438B
Altcode: 1992csss....7..438B
No abstract at ADS
Title: Starspots
Authors: Byrne, P. B.
Bibcode: 1992ASIC..375...63B
Altcode: 1992sto..work...63B
The basic properties of starspots and recent progress in the study
of spots on late-type stars are reviewed. In particular, attention
is given to the basic observation phenomenon, starspot areas, spot
temperatures, Doppler imaging, polar spots, magnetic fields, and spot
lifetimes. Prospects for further research in this field are briefly
discussed.
Title: Modelling of the Large X-ray Flare on II Peg Observed with
GINGA
Authors: Kellett, B. E.; Doyle, J. G.; Bromage, G. E.; Byrne, P. B.
Bibcode: 1992LNP...397..289K
Altcode: 1992sils.conf..289K
No abstract at ADS
Title: Stellar flares
Authors: Byrne, P. B.
Bibcode: 1992sccw.conf..121B
Altcode:
No abstract at ADS
Title: Surface Inhomogeneities on Late-Type Stars
Authors: Byrne, Patrick B.; Mullan, Dermott J.
Bibcode: 1992LNP...397.....B
Altcode: 1992QB843.C6S87....; 1992sils.conf.....B
No abstract at ADS
Title: Transition Regions of dM(e) Stars
Authors: Byrne, P.
Bibcode: 1992iue..prop.4447B
Altcode:
No abstract at ADS
Title: Flaring vs Rotational Modulation on the RS CVn Star, IIPeg
Authors: Byrne, P.
Bibcode: 1992iue..prop.4453B
Altcode:
No abstract at ADS
Title: Surface Inhomogeneities on Late-type Stars (Invited)
Authors: Byrne, P. B.
Bibcode: 1992LNP...397....3B
Altcode: 1992sils.conf....3B
No abstract at ADS
Title: Optical Photometry and UV Spectroscopy of CC Eri in Nov 1989
Authors: Byrne, P. B.; Agnew, D. J.; Cutispoto, G.; Kilkenny, D. W.;
Neff, J. E.; Panagi, P. M.
Bibcode: 1992LNP...397..255B
Altcode: 1992sils.conf..255B
No abstract at ADS
Title: The SI II intercombination multiplet in late-type stars.
Authors: Dufton, P. L.; Keenan, F. P.; Hibbert, A.; Stafford, R. P.;
Byrne, P. B.; Agnew, D.
Bibcode: 1991MNRAS.253..474D
Altcode:
New atomic data are used to calculate the relative intensities of
transitions within the Si II 3s(2)3p(2)P-3s3p(2) 4P intercombination
multiplet for plasma parameters appropriate to late-type stellar
atmospheres. These ratios are found to be significantly different from
those of Dufton and Kingston, (1991), principally due to changes in
the radiative rates. A comparison with line ratios for the sun (from
Skylab S082B spectra) and late-type stars (from IUE data) indicates
that although the new theoretical line ratios are in better agreement
with observation, significant discrepancies still exist. Possible
explanations for these discrepancies are briefly discussed.
Title: High resolution observations of chromospheric lines in
late-type dwarfs.
Authors: Panagi, P. M.; Byrne, P. B.; Houdebine, E. R.
Bibcode: 1991A&AS...90..437P
Altcode:
High resolution H-alpha absorption- and emission-line profiles are
reported for 11 stars of spectral types ranging from K5V to M3V, and the
profiles of NaI(D), HeI(5876A), and CaII(IR) are given for portions of
the sample. The observations were taken with the Qubes spectrograph, and
the data are reduced by comparing the spectral data with observations
of bright K giants of known radial velocity. Emission characterized
by a strong blue H-alpha wing is reported for the active dMe stars,
and the dMe G1616.2 demonstrates evidence of binarity in three separate
lines. Chromospheric lines in absorption are identified in the remaining
sources, and differences between the present and previously observed
values are elaborated. The differences, particularly in H-alpha,
are concluded to indicate intrinsic variability in the stars by
either filling-in of absorption lines or by significant changes in
the photosphere and chromosphere.
Title: An Investigation of the Flare Star AU Mic with the Goddard
High Resolution Spectrograph on the Hubble Space Telescope
Authors: Maran, S. P.; Woodgate, B. E.; Carpenter, K. G.; Robinson,
R. D.; Shore, S. N.; Linsky, J. L.; Brown, A.; Byrne, P. B.; Kundu,
M. R.; White, S.; Brandt, J. C.; Shine, R. A.; Walter, F. M.
Bibcode: 1991BAAS...23.1382M
Altcode:
No abstract at ADS
Title: Coordinated IUE/HST Observations of the Flare Star AU mic:
Results from IUE
Authors: Carpenter, K. G.; Maran, S. P.; Brown, A.; Linsky, J. L.;
Robinson, R. D.; Byrne, P. B.; Judge, P. G.
Bibcode: 1991BAAS...23.1383C
Altcode:
No abstract at ADS
Title: Time Resolved Observations of the Lyman-Alpha Region in AU
Mic with the Goddard High Resolution Spectrograph
Authors: Woodgate, B. E.; Maran, S. P.; Carpenter, K. G.; Robinson,
R. D.; Shore, S. N.; Linsky, J. L.; Byrne, P. B.; Kundu, M. R.
Bibcode: 1991BAAS...23.1383W
Altcode:
No abstract at ADS
Title: Book-Review - Flare Stars in Star Clusters Associations and
the Solar Vicinity
Authors: Byrne, P. B.
Bibcode: 1991Obs...111..191B
Altcode:
No abstract at ADS
Title: Rotationalmodulation and flares on RS Canum Venaticorum and BY
Draconis stars. XVI. IUE spectroscopy and VLA observations of GL 182
(=V 1005 Orionis) in October 1983.
Authors: Mathioudakis, M.; Doyle, J. G.; Rodono, M.; Gibson, D. M.;
Byrne, P. B.; Avgoloupis, S.; Linsky, J. L.; Gary, D.; Mavridis,
L. N.; Varvoglis, P.
Bibcode: 1991A&A...244..155M
Altcode:
A large flare was detected simultaneously with IUE and VLA on Gl 182 on
October 5, 1983, this event showing the largest C IV flare enhancement
yet observed by IUE. A smaller flare was also detected on October 4,
although only with the IUE satellite. Line ratio and emission measure
techniques are used to derive various physical parameters of the
flares. The radiative losses in the temperature region log T(e) =
4.3-5.4 in the two flares are 2.9 x 10 to the 33rd and 8.4 x 10 to
the 32nd ergs, respectively. Total radiative losses over the whole
temperature range log T(e) = 4.0-8.0 are estimated to be of the order
of 6.4 x 10 to the 34th and 1.1 x 10 to the 34th ergs, respectively. In
the October 5, flare, a very strong ultraviolet continuum is present
with a total energy of 1.9 x 10 to the 33rd ergs over the wavelength
range 1250-1950 A.
Title: Simultaneous detection of a large flare in the X-ray and
optical regions on the RS CVn-type star II Peg.
Authors: Doyle, J. G.; Kellett, B. J.; Byrne, P. B.; Avgoloupis,
S.; Mavridis, L. N.; Seiradakis, J. H.; Bromage, G. E.; Tsuru, T.;
Makishima, K.; Makishima, K.; McHardy, I. M.
Bibcode: 1991MNRAS.248..503D
Altcode:
Results are presented for a large flare detected simultaneously on the
RS CVn star II Peg by the X-ray satellite GINGA and from ground-based
Johnson U-band measurements. The total U-band flare energy is estimated
to be at least 6.6 x 10 to the 34th erg. This compares with at least
4.6 x 10 to 34th erg in the 1-10 keV energy range. These values
are lower limits to the true radiative output, since the U-band data
relates only to the rise phase of the flare, while the X-ray data were
obtained during part of the decay phase. Using a 'smooth-burst model',
the combined U-band plus X-ray radiative output is estimated to be
about 3 x 10 to the 34th erg.
Title: Transition Region Densities in Active Late_Type Stars
Authors: Byrne, P.
Bibcode: 1991iue..prop.4061B
Altcode:
No abstract at ADS
Title: The Nature of the DM(E) Stars
Authors: Byrne, P.
Bibcode: 1991iue..prop.4094B
Altcode:
No abstract at ADS
Title: Simultaneous IUE/HST GHRS Observations of AU MIC
Authors: Byrne, P.
Bibcode: 1991iue..prop.4130B
Altcode:
No abstract at ADS
Title: Activity in late-type stars. VII. Chromospheric and transition
region line fluxes in 2 dM and dM(e) stars.
Authors: Byrne, P. B.; Doyle, J. G.
Bibcode: 1990A&A...238..221B
Altcode:
Ultraviolet spectra of the two dM stars Gl380 and Gl411 and the dM(e)
Gl900 are presented. The dM stars show mean surface fluxes in a variety
of emission lines arising throughout the chromosphere and the lower
transition region which are very similar to those of the quiet sun. In
the one star in which it could be determined the electron density at
log T(e) was roughly 4.75, also within a factor of roughly 2.5 that of
the solar value. Results for a single dM(e) star indicate higher mean
surface fluxes in these same lines, consistent with the view that they
are intermediate between the dM and the dMe stars.
Title: A Giant X-ray/optical Flare on II Peg
Authors: Byrne, P. B.; Doyle, J. G.; Tsuru, T.; Avgoloupis, S.;
Mavridis, L. N.; Seiridakis, J. H.; Kilkenny, D. W.; Laing, J. D.;
Marang, F.
Bibcode: 1990IrAJ...19..150B
Altcode:
The paper presents a preliminary account of a large X-ray flare
recorded by an X-ray satellite (it was also recorded in broadband
optical light and in hydrogen Balmer emission) as a part of a campaign
to monitor the RS CVn system II Peg with ground-based optical photometry
and spectroscopy and satellite ultraviolet and X-ray spectroscopy. Two
X-ray flares observed are described: the first one is relatively weak in
X-rays, while the second flare which is the subject of the discussion,
was present when the source was reacquired after earth occultation on
August 17, 1989. Flare energy, temperature, and emission measure and
volume are analyzed, and emphasis is placed on the observation of a
line feature at approximately 6.8 keV, coinciding in energy to the
position of the H-like FeXXVI line at 1.79 A.
Title: Activity in late-type stars. VI. Optical photometry and UV
spectroscopy of the active dMe star, FK Aquarii in late 1983.
Authors: Byrne, P. B.; Butler, C. J.; Lyons, M. A.
Bibcode: 1990A&A...236..455B
Altcode:
Optical photometry and UV spectroscopy are reported for the flare/BY
Dra star FK Aqr from 1983. These data are used to derive the rate of
optical energy release in U-band flaring and compare it to four previous
epochs. No conclusive evidence of any variation in this rate over an
8-yr interval has been found. No measurable BY Dra variations were
present, but a comparison with the mean magnitude in 1979 suggests
that spots were present in 1983, but were uniformly distributed
in longitude. A comparison of transition-region line fluxes with
those recorded in 1979 does not indicate any large changes, but the
chromospheric Mg II line flux is smaller by about 25 percent.
Title: Lyman-alpha and MG II H and K fluxes in a sample of dwarf
M stars.
Authors: Doyle, J. G.; Panagi, P.; Byrne, P. B.
Bibcode: 1990A&A...228..443D
Altcode:
Ly-alpha and Mg II fluxes are given for a group of M dwarfs. The
Ly-alpha and Mg II lines were extracted from low resolution spectra
taken with the IUE satellite. The Ly-alpha line is shown to be an
important source of radiative losses in dMe chromospheres, being at
least a factor of two more important than Mg II. Overall it contributes
approximately 25 percent of the total chromospheric losses, about
the same as the more commonly observed H-alpha line. In order to have
approximately equal contributions from these lines, one requires either
a plateau region in the lower transition region or different filling
factors for the two lines. In dM stars, Ly-alpha is approximately the
same magnitude as Mg II.
Title: Activity in late-type stars. V. Rotational modulation and
flaring in UV lines on the most rapidly rotating dMe star, GL 890
(BD -16 6218).
Authors: Byrne, P. B.; McKay, D.
Bibcode: 1990A&A...227..490B
Altcode:
A series of UV spectra of GI 890 taken at two epochs separated by
more than two years (on October 11-13, 1984 and on December 26, 1986)
where obtained by the IUE satellite and using both the spectrograph's
short-wavelength and long-wavelength cameras. Based on these data,
the energy balance in the star's magnetically heated chromosphere and
the transition region is investigated. Evidence for the rotational
modulation of the Mg II line flux, with the maximum emission occurring
close to the maximum spottedness derived from the optical light curve,
is examined. A sharp dip in the Mg II flux, seen on two separate
rotations is considered to be an eclipse by an unseen companion of
the GI 890 star.
Title: Do Chromospheres Exist in Fully Convective DM Stars ?
Authors: Byrne, P.
Bibcode: 1990iue..prop.3883B
Altcode:
No abstract at ADS
Title: Chromospheres/Transition Regions of DM(e) Stars
Authors: Byrne, P.
Bibcode: 1990iue..prop.3881B
Altcode:
No abstract at ADS
Title: Ultraviolet flares on II Pegasi.
Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.
Bibcode: 1989A&A...224..153D
Altcode:
UV spectroscopic observations of the RS CVn star, II Peg, were obtained
in February 1983. The observations show evidence for flare activity
in greatly enhanced chromospheric and transition region emission
lines. The flare radiation is isolated and the electron pressures of
the mean quiescent atmosphere and the two flares are derived from the
intersystem line flux ratios. Estimates are given of the total flare
power output over the whole atmosphere and the surface filling factor
for the flares. The implications of the observations for studies of
flares on RS CVn stars are considered.
Title: Rotational modulation and flares on RS CVn and BY Draconis
stars. XIII. IUE spectroscopy and photometry of II Pegasi during
September 1986.
Authors: Doyle, J. G.; Butler, C. J.; Byrne, P. B.; Rodono, M.; Swank,
J.; Fowles, W.
Bibcode: 1989A&A...223..219D
Altcode:
UV spectroscopy obtained for the RS CVn star II Pegasi in September,
1986, indicates the presence of a rotational modulation effect for the
Mg II h and k and O I 1305 A lines; the largest flux is observed when
the primary spot concentration is nearly on the opposite hemisphere,
and the rotational modulation is noted to be of opposite sense to that
observed in 1981. Optical photometry shows the largest concentration
of spots on one hemisphere ever observed on II Peg, implying a spot
group covering over 50 percent of the projected area of one hemisphere.
Title: Activity in late-type stars. IV. The 1980 August 20 flare on
proxima Centauri revisited.
Authors: Byrne, P. B.; McKay, D.
Bibcode: 1989A&A...223..241B
Altcode:
This paper presents a reanalysis of simultaneous ultraviolet and soft
X-ray observations of a flare on the dMe star, Proxima Centauri. Using
an emission measure analysis, as well as density sensitive line ratios,
the electron density and the total emitting volume of the flare plasma
which is at midtransition region temperatures are derived. These, and
the corresponding parameters derived from the previously published
X-ray light curve, are compared in the framework of a simple loop
model of the flare. This analysis suggests that the coronal X-rays and
the transition-region UV line emission arose in volumes of comparable
extent. The combined L-alpha and total transition region line losses
are found to be comparable to the estimated total coronal losses
during the flare. This latter conclusion disagrees with the original
deduction of Haisch et al. (1983) that the transition region losses
are unimportant compared with the coronal losses.
Title: Has Gl890 a Planetary Companion?
Authors: Byrne, P. B.
Bibcode: 1989IrAJ...19...54B
Altcode:
No abstract at ADS
Title: Campaign of Simultaneous, Multiwavelength Observations of
the Flare/spotted Variable, CC Eri
Authors: Byrne, P. B.
Bibcode: 1989IBVS.3376....1B
Altcode:
No abstract at ADS
Title: Rotational modulation and flares on RS Canum Venaticorum and
BY Draconis stars. XII. Near-to-simultaneous high resolution UV and
optical observations of II Pegasi during July 1984.
Authors: Byrne, P. B.; Panagi, P.; Doyle, J. G.; Englebrecht, C. A.;
McMahan, R.; Marang, F.; Wegner, G.
Bibcode: 1989A&A...214..227B
Altcode:
Nearly simultaneous high resolution ground-based optical and IUE
satellite UV spectroscopy and an optical light curve of the RS CVn
star II Peg are presented. It is shown that the chromospheric and
transition region radiative losses of the star in July 1984 are lower
than previously recorded means. The flux in the Lyman-alpha line is
estimated and evidence is given for variability in all of the emission
lines. This variability appears to be correlated with the optical
spots. Line profiles at two rotational phases for the principal UV
emission lines show an excess broadening over and above the combined
instrumental plus Doppler broadening.
Title: Qubes - a High-Resolution Echelle Spectrograph
Authors: Byrne, P. B.
Bibcode: 1989IrAJ...19R...4B
Altcode:
No abstract at ADS
Title: Multi-Wavelength Observations of Stellar Flares
Authors: Byrne, P. B.
Bibcode: 1989SoPh..121...61B
Altcode: 1989IAUCo.104...61B
We present observational data on stellar flares from a range of
wavelength regimes, many of which were obtained simultaneously. Physical
parameters of these flares are derived and discussed in the frame-work
of the general solar flare model. It is found that flares on dMe stars
are solar-like, except in mean energy. The parameters of flares on RS
CVn stars are more extreme, however, and may require new models for
their interpretation.
Title: Activity in late-type dwarfs. III. Chromospheric and transition
region line fluxes for two dM stars.
Authors: Byrne, P. B.; Doyle, J. G.
Bibcode: 1989A&A...208..159B
Altcode:
Weak upper-chromospheric and transition-region emission from
two dM stars (Gl 784 and Gl 825) has been observed using deep UV
spectroscopy. Ly-alpha fluxes for the two stars were also determined
for the first time. Using these results it is shown that the transition
from weakly active dM to active dMe star is probably due to increasing
surface coverage by solarlike active regions. Also discussed are the
relative importance of Ly-alpha and Mg II as chromospheric coolants
in the M dwarfs and how this changes between dM and dMe stars. The
interrelationship between X-ray, He II (1640-A) and C IV (1550-A)
fluxes is discussed in the light of these results, and it is shown
that all three are tightly related over three orders of magnitude
in each. Several flux-period relationships are used to predict the
rotation periods of the two stars.
Title: LYMAN: A new Prospect for Ultraviolet Astronomy
Authors: Byrne, P. B.
Bibcode: 1989IrAJ...19S...4B
Altcode:
No abstract at ADS
Title: Deep SWP Exposures of DM Stars
Authors: Byrne, P.
Bibcode: 1989iue..prop.3615B
Altcode:
No abstract at ADS
Title: A Coordinated Study of Flares and Active Regions on CC Eri
Authors: Byrne, P.
Bibcode: 1989iue..prop.3590B
Altcode:
No abstract at ADS
Title: Energetic flares on RS CVn stars.
Authors: Doyle, J. G.; Byrne, P. B.; van den Oord, G. H. J.
Bibcode: 1989sasf.confP.115D
Altcode: 1988sasf.conf..115D; 1989IAUCo.104P.115D
Ultraviolet spectroscopic observations of the RS CVn star II Peg in
February 1983 show evidence for flare activity in greatly enhanced
chromospheric and transition region emission lines. The total
radiative losses from the chromosphere and transition region during
the flare is 3.1×1035erg. Over the whole atmosphere the
authors estimate total radiative losses of 2.4×1036erg,
(excluding hydrogen line radiation). At flare peak, the flare radiated
1.5×1032erg s-1. Adopting a two-ribbon flare
model, where the filament is located between the two stars of the
system, one can have 1039(l/Rsun) erg of magnetic
energy available, where l is the filament length. Therefore, only a
small fraction of this magnetic energy need be converted into heating
of the flare plasma.
Title: A flare on AD Leo observed in optical, UV and microwaves.
Authors: Byrne, P. B.; Gary, D. E.
Bibcode: 1989sasf.confP..63B
Altcode: 1988sasf.conf...63B; 1989IAUCo.104P..63B
The authors report a simultaneous IUE, VLA and ground-based photometric
observation of a flare on the dMe star, AD Leo, on 2nd February
1983. The optical flare was extremely impulsive, lasting in total only
about 3 mins. A relatively longlived 6 cm flare was observed with the
VLA which was initially 100% polarized. An IUE spectrum, taken ≍8
min after the onset of the optical U band flare, shows more than a
factor of 2 increase in the He II λ1640 Å emission line. The other
mid-transition region lines such as C IV λλ1548/52 Å show almost
no response.
Title: Transition regions of dM stars
Authors: Byrne, P. B.; Doyle, J. G.
Bibcode: 1988ESASP.281a.319B
Altcode: 1988uvai....1..319B; 1988IUE88...1..319B
Weak upper-chromospheric and transition region (TR) emission from two dM
stars (Gl784 and Gl825) were observed using deep IUE SWP exposures. In
addition to the usual TR lines, Lyman alpha fluxes for the two stars
were also determined. The relative importance of Lyman alpha and Mg II
as chromospheric coolants in the M dwarfs and the status of the X-ray/He
II (1640A) relationship in the light of these results are discussed.
Title: UV flares on II Peg
Authors: Doyle, J. G.; Byrne, P. B.
Bibcode: 1988ESASP.281a.307D
Altcode: 1988uvai....1..307D; 1988IUE88...1..307D
Observations by IUE of the RS CVn star II Peg in the upper chromospheric
and transition regions lines Mg II k, C IV, and He II in Feb. 1983 show
evidence for flare activity. The electron pressure derived from the mean
of two different line ratios produces good agreement between the allowed
and intersystem lines in the differential emission measure curves. The
total radiative losses from the chromosphere and transition region for
the first flare on Feb. 2 is 2.46 times 10 to the 35th power erg, and
at least 1.91 times 10 to the 34th power erg, for the flare on Feb. 4.
Title: Electron densities in late-type stars.
Authors: Byrne, P. B.; Dufton, P. L.; Kingston, A. E.; Lennon, D. J.;
Murphy, H. M.
Bibcode: 1988A&A...197..205B
Altcode:
Recently published atomic calculations for the C II UV 0.01 intersystem
multiplet at 2325 Å are combined with dearchived IUE data on a number
of late-type giants and supergiants to derive the electron densities in
these stars' upper chromospheres/lower transition regions. The results
represent a substantial change from previously derived values. The
implications of this change are briefly discussed.
Title: Problems with Spots
Authors: Byrne, P. B.
Bibcode: 1988IrAJ...18..203B
Altcode:
No abstract at ADS
Title: Giant Starspots and Stellar Flares: The View from Space
Authors: Byrne, Patrick B.
Bibcode: 1988IrAJ...18..172B
Altcode:
Satellite observations of starspots and stellar flares are examined. The
properties of sunspots and solar flares are reviewed and the method
used to infer the existence of starspots is described. IUE observations
of the atmospheres of spotted stars and Exosat X-ray observations
of solar flares are discussed. Also, an IUE spectrum of II Peg and a
U-band light curve of a flare on YZ CMi are presented.
Title: Prospects for studies of activity in cool stars with LYMAN.
Authors: Byrne, P. B.; Rodono, M.
Bibcode: 1988Gemin..21....4B
Altcode:
The plans to consider LYMAN as a future ESA scientific satellite
offer exciting possibilities for the study of solar-like activity in
late-type stars. In this article the authors attempt to illustrate
some of these possibilities.
Title: Chromospheres/Transition Regions of DM(E) Stars
Authors: Byrne, P.
Bibcode: 1988iue..prop.3280B
Altcode:
No abstract at ADS
Title: Activity in late-type dwarfs. II. Flares and SPOT variations
on GL 867A (=FK Aqr) in 1981.
Authors: Byrne, P. B.; Doyle, J. G.
Bibcode: 1987A&A...186..268B
Altcode:
We present optical photometry of flares and spot variations on the
flare/BY Draconis star G1 867A (= FK Aqr). Time-integrated rates
of energy lost by optical flaring are derived and compared with
previously published results. No evidence of season-to-season changes
are evident. No spot variations were detected but there is an unusually
large scatter in the mean light curve.
Title: Activity in late-type dwarfs. I. Walvaren and Johnson
photometry of flares and SPOT variations on GL 867A (= FK Aqr)
in 1979.
Authors: Byrne, P. B.; Black, E.; The, P. S.
Bibcode: 1987A&A...186..261B
Altcode:
We present optical photometry of flares and spot variations on the
flare/BY Draconis star Gl 867A (= FK Aqr). These observations are
made in the Walraven intermediate passband system. Based on this and
other material already published a new period determination has been
made. The result suggests that the system may not be corotating as
suggested earlier. In this regard it is similar to the prototype spotted
star. BY Dra itself. Time-integrated rates of energy lost by optical
flaring are derived and compared with previously published results. No
evidence of season-to-season changes are evident. The advantages of
the Walraven photometric system for the study of stellar flares are
discussed and the nature of the optical flare light is examined in
the light of measurements made in this system.
Title: Giant Spots on II Peg in late 1986
Authors: Byrne, P. B.; Marang, F.
Bibcode: 1987IrAJ...18...84B
Altcode:
During September 1986 a light curve was recorded for II Peg which was of
an unprecedentedly large amplitude. To establish the duration of this
unusual phenomenon a second set of photometric observations was made
which established that the curve was essentially the same a full two
months later. The purpose of this paper is to report the preliminary
results of the analysis of these observations and to outline briefly
their implications for the starspot hypothesis.
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. VI. Physical parameters of the chromospheres/transition
regions of V711 Tau (HR 1099), II Peg and AR Lac during october 1981.
Authors: Byrne, P. B.; Doyle, J. G.; Brown, A.; Linsky, J. L.;
Rodono, M.
Bibcode: 1987A&A...180..172B
Altcode:
Ground-based optical and IUE satellite-ultraviolet observations of
three RS CVn stars are combined with density sensitive line ratios
and differential emission measure curves to describe the physical
conditions in their outer atmospheres. Solar-like densities are found
to be representative of average conditions on two of the stars, V 711
Tau and AR Lac. The total radiative losses from these two stars are
estimated and found to be larger than the sun by at least two orders of
magnitude. Consideration of the volume emitting in two of the principal
transition region lines suggests a possible relation between the disk
'filling factor' for these two lines and the dynamo-related Rossby
number. Only one hemisphere of the star II Peg, the one showing least
evidence of starspots, is similar. On the opposite hemisphere the
presence of a discrete emitting region is deduced which is almost
coincident in phase with the passage of the dominant optical spot
group across the visible disk. The dimensions of this region, and an
illustrative interpretation in terms of a large emitting magnetic loop,
are discussed. It is compared to large active region loops on the sun.
Title: Rotational modulation and flares on RS CVn and BY DRA
stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac.
Authors: Rodono, M.; Byrne, P. B.; Neff, J. E.; Linsky, J. L.; Simon,
T.; Butler, C. J.; Catalano, S.; Cutispoto, G.; Doyle, J. G.; Andrews,
A. D.; Gibson, D. M.
Bibcode: 1987A&A...176..267R
Altcode:
The authors present observations of three RS CVn stars, which
were obtained over the stellar rotation cycles with the IUE
satellite. Emission lines from high-temperature transition regions
and chromospheres analogous to those observed in the solar spectrum
were observed. However, the stellar line surface fluxes are hundreds
of times the solar values. The only visible component of II Peg and
both components of V711 Tau and AR Lac appear to be chromospherically
active. The emission line fluxes for II Peg and, marginally, for the
other two systems were observed to vary in anti-phase with the optical
varations at the time of the authors' IUE observations. By comparing
the results of two-spot models from Paper I with the variation of UV
line flux, the authors find evidence of a close spatial correlation
between spot and plage-like features. They interpret these correlations
in terms of large spot areas in the stellar photospheres with overlying
magnetic loops, which form plages in the outer atmosphere.
Title: Rotational modulation and flares on RS CVn and BY DRA
systems. II. IUE observations of BY Draconis and AU Microscopii.
Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.;
Linsky, J. L.; Bornmann, P. L.; Rodono, M.; Pazzani, V.; Simon, T.
Bibcode: 1987A&A...174..139B
Altcode:
The modulation of the strong chromospheric and transition region lines
over one cycle of the optical light curves of BY Dra and AU Mic is
studied using IUE observations. The IUE observations were made from
October 2-5, 1981 and include 7 short wavelength (SW) spectra and 13
long wavelength (LW) spectra. The integrated line flux data reveal that
for BY Dra in the SW spectra there is modulation in the C IV, C II, O
I, and He II lines and nonflare surface fluxes; and in the LW spectra,
flares are detected in the Mg II and Fe II bands. It is observed that
there is no modulation in AU Mic, and the optical photometry data reveal
a poor correlation between optical flare strength and UV emission line
enhancements. The differential emission measure curves for BY Dra and
AU Mic are compared with solar curves. It is noted that both stars
show the presence of hot material throughout their rotation period.
Title: IUE/Optical/VLA Flares on AD Leo
Authors: Gary, Dale E.; Byrne, P. B.; Butler, C. J.
Bibcode: 1987LNP...291..106G
Altcode: 1987LNP87.291..106G; 1987csss....5..106G
We discuss joint observations of flares on the dMe star AD Leo made
with IUE, the VLA, and the Tinsley photometer at the University of
Hawaii's 24-inch reflector on Mauna Kea. We find that optical emission
is correlated with C IV while radio emission is better correlated with
He II. We reach some tentative conclusions concerning timescales and
source characteristics.
Title: The Giant Spot on II Peg in Late 1986
Authors: Byrne, P. B.
Bibcode: 1987LNP...291..491B
Altcode: 1987LNP87.291..491B; 1987csss....5..491B
During September and November 1986 a light curve was recorded for
the RS CVn star II Peg which was of an unprecedentedly large amplitude
(Byrne, 1986). During December two moderately high resolution (∼25000)
Hα spectra were obtained, one at light maximum, the other near light
minimum. Analysis of the light and colour curves indicates that at least
16% of the star's surface was spotted. The Hα spectra indicate the
presence of an appreciable column density of hydrogen gas, associated
with the dominant spot and undergoing a systematic downward motion at
∼50 km s-1.
Title: Evidence for an Additional Source of Opacity During the
Impulsive Phase of Stellar Flares
Authors: Murphy, M.; Doyle, J. G.; Byrne, P. B.
Bibcode: 1987LNP...291..170M
Altcode: 1987LNP87.291..170M; 1987csss....5..170M
Broad-band photometric observations of YZ CMi show a 1.2 magnitude
U-band flare at 19:55 UT on 4 March 1985. During the flare the Ca I
feature at 4227A changed dramatically. In the spectrum taken during
the rise phase, Ca I was both narrower and weaker than that of either
the preflare spectrum or spectra taken later in the flare. We interpret
this as evidence that the photospheric flare continuum observed here is
a combination of a normal dM4.5e continuum plus an overlying continuum
with a temperature of less than 4000 - 5000 K and a pressure of at
least an order of magnitude less than the photosphere of a dM4.5e star.
Title: Broadening of Hydrogen Balmer Lines During a Flare on the
dMe Star YZ CMi
Authors: Doyle, J. G.; Byrne, P. B.
Bibcode: 1987LNP...291..173D
Altcode: 1987csss....5..173D; 1987LNP87.291..173D
Broad-band photometric observations of YZ CMi show a 1.2 magnitude
U-band flare at 19:55 UT on 4 March 1985. During the flare, optical
spectra show excess emission in the wings of all the hydrogen Balmer
lines. Interpreted in terms of mass flows would imply material
moving at ∼300 km s-1 simultaneously to the blue and
red or alternatively random mass motions with a velocity of a similar
magnitude. At flare maximum, all the Balmer lines show excess emission
in the wings with H α and 11 δ showing symmetrically broadened
lines while higher members of the series such as H ζ and H η show
predominately red shifted material.
Title: Large Amplitude Spot Variations on II Peg
Authors: Byrne, P. B.
Bibcode: 1986IBVS.2951....1B
Altcode:
No abstract at ADS
Title: Model for a Stellar Active Region
Authors: Byrne, P. B.
Bibcode: 1986IrAJ...17..470B
Altcode:
No abstract at ADS
Title: Rotational modulation and flares on RS CVn and BY Dra-type
stars. I. Photometry and SPOT models for BY Dra, AU Mic, AR Lac,
II Peg and V711 Tau (=HR 1099).
Authors: Rodono, M.; Cutispoto, G.; Pazzani, V.; Catalano, S.;
Byrne, P. B.; Doyle, J. G.; Butler, C. J.; Andrews, A. D.; Blanco,
C.; Marilli, E.; Linsky, J. L.; Scaltriti, F.; Busso, M.; Cellino,
A.; Hopkins, J. L.; Okazaki, A.; Hayashi, S. S.; Zeilik, M.; Helston,
R.; Henson, G.; Smith, P.; Simon, T.
Bibcode: 1986A&A...165..135R
Altcode:
Multicolor wide-band photometry of five active stars is presented. The
observations were carried out at several places before, during and
after the period of IUE observations for the purpose of determining
the location, sizes, and evolution of photospheric spots at the time
when chromospheric, transition region, and coronal activity data were
obtained from UV and radio observations. II Peg, BY Dra, and AU Mic
show fairly stable quasi-sinusoidal light curves, while AR Lac and V
711 Tau show double-peaked light curves. For V 711 Tau, a remarkable
evolution of the spotted area extent and/or longitude distribution
is found. Small, but definite color variations that are consistent
with the cool spot hypothesis have also been detected for BY Dra,
II Peg and V 711 Tau.
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Byrne, P. B.; Rodono, M.; Kurtz, D.
Bibcode: 1986MNSSA..45...67B
Altcode:
No abstract at ADS
Title: Optical photometry and spectroscopy for five dwarf M stars.
Authors: Doyle, J. G.; Byrne, P. B.; Menzies, J. W.
Bibcode: 1986MNRAS.220..223D
Altcode:
The authors report on a search for flaring and BY Dra (spotted)
variations on five M-dwarf stars, Gliese 1, 461, 825, 899 and 908. The
results for Gl 461 and 825 are compared with predictions of activity
levels based on the measured quiescent X-ray flux. The chromospheric
radiative loss rate in the Ca H and K lines are determined for Gl 461.
Title: Flares and Coronal Heating
Authors: Byrne, P. B.
Bibcode: 1986IrAJ...17..216B
Altcode:
Attention is given to a growing body of evidence obtained through
both solar and stellar X-ray observations which indicates that flares
play a direct role in coronal heating. An evaluation is made of
X-ray light curves of impulsive events, the correlation between mean
X-ray luminosity and time-averaged luminosity in U-band flare light,
and Einstein Observatory X-ray observations of Prox Cen. The optical
flares of the latest type M dwarfs, such as Prox Cen, are noted to
bear a striking resemblance to solar impulsive X-ray events.
Title: Spots on II Peg
Authors: Byrne, P. B.; Panagi, P.
Bibcode: 1986IrAJ...17..401B
Altcode:
The authors make a preliminary report on a photometric and spectroscopic
study of the star during mid-1984.
Title: HDE 319139
Authors: Byrne, P. B.
Bibcode: 1986IrAJ...17..294B
Altcode:
An evaluation is made of observations of HDE 319139 conducted since
1984. The photometry obtained gives only marginal evidence of spot
modulation during the period in which spectroscopy was taken. Several
of the spectra show distinct evidence of doubling of the absorption
lines. The unusual intensity of the emission line spectrum makes
this star unique among late-type dwarfs; emission line strengths bear
comparison with those of T Tauri stars. HDE 319139 appears to be an
intermediate object between premain sequence T Tauri stars and the
main sequence flare and spotted stars.
Title: Coordinated IUE and ground-based observations of stellar
flares: YZ CMi, Proxima Cen and AD Leo.
Authors: Foing, B. H.; Rodono, M.; Cutispoto, G.; Catalano, S.; Linsky,
J. L.; Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne,
P. B.; Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo,
G.; Vittone, A.; Scaltriti, F.
Bibcode: 1986RMxAA..12..213F
Altcode:
Coordinated observations of stellar flares were obtained with lUE
and several ground-based facilities in March 1984.The simultaneous
observations allowed it to cover a wide range of wavelengths from ii5nm
to 6cm.We intend to study the effect ofthe observed flares at different
atmospheric heights in order to estimate the energy budget,the time
scales and the cooling processes.Our observations includetime-resolved
IUE spectroscopy at SWP(115-195nm) and LWP(190-320nm),optical
spectroscopy at the ESO 3.6m+IDS (355-440nm),high resolution
spectroscopy at the ESO 1.4m CAT+CES(653-659nm),narrow band H alpha
and wide band optical photometry, infrared photometry at 2.2microns
and microwave observations at 2,6 and 20 cm We present for some
flare events,among the results,the first detection of infrared flux
decrease -or "negative flare"-in coincidence with the flux increase
at the other wavelengths:the broadening and changes of the Balmer H
lines,He and high excitation lines;the appearance of higher members
of the Balmer serie;the enhancements of Mg II doublet and Fe II blend
(260nm);and the flare detection at 2cm and 6cm
Title: Trajectory Determinations and Collection of Micrometeoroids
on the Space Station
Authors: Doyle, J. G.; Byrne, P. B.; Butler, C. J.
Bibcode: 1986A&A...156..283D
Altcode:
We report on a search for flaring and BY Draconis type variability on
the M-dwarf Balmer emission line star, Gliese 867 B. The time-averaged
flare energy in the Johnson U-band is similar to that measured in 1977
and 1978. A typical wave4ike variation of 0.15 magnitudes, seemingly
due to rotational modulation of large spotted areas, was observed in
the V-band with a period 1.95 days.
Title: The Extraordinary Flare/BY Dra Star HDE319139
Authors: Byrne, Patrick B.
Bibcode: 1986LNP...254..320B
Altcode: 1986csss....4..320B
No abstract at ADS
Title: Spots and Plages on II Peg During 1984
Authors: Byrne, Patrick B.; Panagi, Peter
Bibcode: 1986LNP...254..317B
Altcode: 1986csss....4..317B
No abstract at ADS
Title: Faint optical flares from the dwarf M star Gliese 812
(Ross 193).
Authors: Doyle, J. G.; Byrne, P. B.
Bibcode: 1986A&A...154..370D
Altcode:
The authors report on a search for flaring on the Balmer emission line
star, Gliese 812. Three flares were detected in a total monitoring
time of 11.66 h. The time-averaged flare energy in the Johnson U-band
is substantially smaller than in other stars of similar absolute U
magnitude, such as AD Leo, EQ Peg and EV Lac.
Title: Flare activity and by-Draconis type variability on the
late-type dMe star gliese 867B
Authors: Doyle, J. G.; Byrne, P. B.; Butler, C. J.
Bibcode: 1986LNP...254..231D
Altcode: 1986csss....4..231D
We report on an analysis of flaring and BY-Draconis type variability
on the Balmer emission line star, Gliese 867B. The time-averaged flare
energy in the Johnson 1-band is similar to that measured in 1977 and
1978. A variation of 0.15 magnitudes was observed in the V-band with
a period l.95 days.
Title: Deep Lores Study of the Chromospheres/Transition Regions of
Two DM Stars
Authors: Byrne, P.
Bibcode: 1986iue..prop.2684B
Altcode:
No abstract at ADS
Title: Study of the Chromosphere/Corona
Authors: Byrne, P.
Bibcode: 1986iue..prop.2719B
Altcode:
No abstract at ADS
Title: Deep Hires Study of UV Line Profiles in the RS CVN Star II Peg
Authors: Byrne, P.
Bibcode: 1986iue..prop.2685B
Altcode:
No abstract at ADS
Title: CII Line Electron Density Diagnostics in Late-Type Stars
Authors: Byrne, P.
Bibcode: 1986iue..prop.2702B
Altcode:
No abstract at ADS
Title: A Supermassive Star in 30-DORADUS
Authors: Byrne, P. B.
Bibcode: 1985IrAJ...17..154B
Altcode:
No abstract at ADS
Title: Energetics of a double flare on November 8, 1980
Authors: Doyle, J. G.; Byrne, P. B.; Dennis, B. R.; Emslie, A. G.;
Poland, A. I.; Simnett, G. M.
Bibcode: 1985SoPh...98..141D
Altcode:
Here we complete an energy balance analysis of a double impulsive
hard X-ray flare. From spatial observations, we deduce both
flares probably occur in the same loop within the resolution of the
data. For the first flare, the energy in the fast electrons (assuming
a thick-target model) is comparable to the convective up-flow energy,
suggesting that these are related successive modes of energy storage and
transfer. The total energy lost through radiation and conduction, 2.0 ×
1028 erg, is comparable to the energy in fast electrons 2.5
× 1028 erg. For the second flare, the energy in the fast
electrons is more than one order of magnitude greater than the energy
of the convective up-flow. Total energy losses are within a factor
of two lower than the calculated fast electron energy. We interpret
the observations as showing that the first flare occurred in a small
loop with fast electrons heating the chromosphere and resulting in
chromospheric evaporation increasing the density in the loop. For the
second flare most of the heating occurred at the electron acceleration
site. The two symmetrical components of the Ca XIX resonance line and a
high velocity down-flow of 115 km s −1 observed at the end
of the second hard X-ray burst are consistent with the flare eruption
(reconnection) region being high in the flare loop. The estimated
altitude of the acceleration site is 5500 km above the photosphere.
Title: Optical photometry and spectroscopy of the flare star Gliese
229 (=HD42581).
Authors: Byrne, P. B.; Doyle, J. G.; Menzies, J. W.
Bibcode: 1985MNRAS.214..119B
Altcode:
The authors present optical flare photometry and a search for spotted
variations on the star Gl 229. These results rule out the presence of
a large-scale asymmetric spot distribution and indicate a low level of
flare activity. This is in agreement with other indicators of stellar
activity including coronal X-ray emission and radiative losses from
the lower chromosphere as gauged from the strength of Ca H and K and
the Balmer lines.
Title: Magnetic Fields in Late-type Stars
Authors: Byrne, P. B.
Bibcode: 1985IrAJ...17...69B
Altcode:
No abstract at ADS
Title: Optical photometry and UV spectroscopy of the flare star GL
735 (=V1285 Aql).
Authors: Byrne, P. B.; Doyle, J. G.; Butler, C. J.; Andrews, A. D.
Bibcode: 1984MNRAS.211..607B
Altcode:
The authors present optical photometry of flares and possible spot
variations on the star Gl 735. Consideration of the energetics of the
optical flares suggests that the star may be underactive when compared
to other flare stars of the same spectral type. This conclusion is
not supported however by an estimate of the radiative loss rate from
the lower chromosphere due to Mg II h and k. Radiative losses from the
upper chromosphere, transition zone and corona are also normal for a
flare star of its spectral type.
Title: Book-Review - Activity in Red Dwarf Stars - I.A.U. Colloquium
NO.71
Authors: Byrne, P. B.; Rodono, M.; Whitehouse, D.
Bibcode: 1984JBAA...94..286B
Altcode:
No abstract at ADS
Title: Erratum - Solar Maximum Mission Observations of a Compact
Flare - Interpretation and Theoretical Implications for Flare Theory
Authors: Doyle, J. G.; Byrne, P. B.
Bibcode: 1984IrAJ...16..286D
Altcode:
No abstract at ADS
Title: Rotational modulation of spots and plages on RS CVn stars.
Authors: Byrne, P. B.; Doyle, J. G.; Andrews, A. D.; Butler, C. J.;
Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Catalano, S.;
Blanco, C.; Marilli, E.; Pazzani, V.
Bibcode: 1984ESASP.218..343B
Altcode: 1984iue..conf..343B
Observations of three RS CVn stars made with the IUE satellite are
presented. Emission line fluxes are found to vary in anti-phase with the
stars' optical variations. The authors interpret these correlations in
terms of large-scale spots in the stellar photospheres with overlying
magnetic loops, giving rise to non-thermal heating of the layers above
the spots. Evidence of nonthermal gas motions is also presented which
appear to be associated with the most active regions of the stars.
Title: Coordinated IUE and ground-based observations of active stars:
flare events on YZ CMi, V1005 Ori, AD Leo and AR Lac.
Authors: Rodonò, M.; Cutispoto, G.; Catalano, S.; Linsky, J. L.;
Gibson, D. M.; Brown, A.; Haisch, B. M.; Butler, C. J.; Byrne, P. B.;
Andrews, A. D.; Doyle, J. G.; Gary, D. E.; Henry, G. W.; Russo, G.;
Vittone, A.; Scaltriti, F.; Foing, B.
Bibcode: 1984ESASP.218..247R
Altcode: 1984iue..conf..247R
Observations of stellar flares were obtained with IUE and ground-based
facilities simultaneously over a wide range of wavelengths in order
to study the effect of the flare radiation at different atmospheric
levels. Observations include time-resolved IUE and optical spectroscopy,
narrow and wide-band optical photometry, IR photometry, and microwave
observations. Results include detection of IR flux decrease, or negative
flare, in coincidence with flux increase at all other wavelengths.
Title: Models for the active and quiescent regions on the RS CVn-type
systemII Pegasi (HD 224085).
Authors: Linsky, J. L.; Brown, A.; Marstad, N. C.; Rodono, M.; Andrews,
A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1984ESASP.218..351L
Altcode: 1984iue..conf..351L
The IUE observations of the RS CVn binary system II Pegasi obtained
during the period 1981 October 1-7 were used to derive the emission
measure distributions and to calculate transmission region models
of the quiescent and plage (active) regions of II Peg. Active region
models were calculated assuming area coverages of 10%, 6%, 3% and 1%
of the visible hemisphere. These models are used to provide lower
limits to the electron pressure in the quiescent and plage regions,
which are compared with the available density diagnostics. The amount
of mechanical energy deposition required to account for the observed
radiative losses is very large.
Title: IUE observations of BY Draconis.
Authors: Butler, C. J.; Doyle, J. G.; Andrews, A. D.; Byrne, P. B.;
Linsky, J. L.; Simon, T.; Marstad, N. C.; Rodono, M.; Pazzani, V.;
Cutispoto, C.
Bibcode: 1984ESASP.218..243B
Altcode: 1984iue..conf..243B
Phased IUE low resolution observations of BY Draconis are
discussed. They show no significant modulation of the prominent
SWP emission lines over one rotation period. However a marginally
significant anticorrelation of the MgII flux, and the flux in the LWR
continuum, with the V light curve is observed, and is interpreted as
due to plage type areas over the photospheric spots. Two SWP spectra
show sporadic enhancements of the emission lines, as seen in other
IUE spectra of flares.
Title: Book-Review - Activity in Red Dwarf Stars - I.A.U. Colloquium
NO.71
Authors: Byrne, P. B.; Rodono, M.; Stickland, D.
Bibcode: 1984Obs...104..100B
Altcode:
No abstract at ADS
Title: An Amateur Filar Micrometer (An Evaluation)
Authors: Byrne, P. B.; Beesley, D. E.; Dunsby, P.
Bibcode: 1984IrAJ...16..181B
Altcode:
No abstract at ADS
Title: Analysis of the 1981 October 3 Flare on HR 1099 Based on High
and Low Resolution IUE Spectra
Authors: Gross, B.; Linsky, J.; Marstad, N.; Byrne, P. B.; Butler,
C. J.; Andrews, A. D.; Rodono, M.; Simon, T.
Bibcode: 1984BAAS...16..473G
Altcode:
No abstract at ADS
Title: SMM Observations of a Compact Flare.Interpretation and
Theoretical Implications of Flare Theory
Authors: Doyle, J. G.; Byrne, P. B.
Bibcode: 1984IrAJ...16..226D
Altcode:
In the present completion of an energy balance analysis for a
double impulsive, hard X-ray flare, it is deduced on the basis
of spatial observations that both flares occurred in the same
loop. From observations of the Ca XIX resonance line during the
second flare's hard X-ray burst, it appears that two symmetrically
displaced components are moving apart at thermal velocities of about
60 km/sec. These are interpretable in terms of in situ heating, where
most of the fast electrons are stopped in the loop close to the site
of the acceleration (and long before they reach the chromosphere)
to produce the 'evaporated' up-flow. The two symmetrical components,
and a high velocity downflow of 115 km/sec observed at the end of
the second hard X-ray burst, are consistent with the flare eruption
region's location high in the flare loop.
Title: Optical photometry and ultraviolet spectroscopy of the flare/BY
DRA star GL 182(V 1005 Ori).
Authors: Byrne, P. B.; Doyle, J. G.; Butler, C. J.
Bibcode: 1984MNRAS.206..907B
Altcode:
G1 182 was previously reported to be a rapidly rotating BY Dra star
which flares at an anomalously high rate. The present observations
confirm its BY Dra nature but revise the rotation period, such that it
is shown to rotate much more slowly. The time-averaged energy output
in flares is shown to be normal for a flare star of its spectral type,
and its rate of flaring is normal. IUE spectra show chromospheric
features whose surface fluxes compare with those of BY Dra itself.
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Byrne, P. B.; Rodono, M.
Bibcode: 1984S&T....67S.429B
Altcode:
No abstract at ADS
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Byrne, P. B.; Rodono, M.; Zwaan, C.
Bibcode: 1984SSRv...38..180B
Altcode:
No abstract at ADS
Title: Book-Review - Activity in Red Dwarf Stars - I.A.U. COLL.71 -
Catania - 1982AUG
Authors: Byrne, P.; Rodono, M.
Bibcode: 1984Mercu..13X..92B
Altcode:
No abstract at ADS
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Byrne, P. B.; Rodono, M.
Bibcode: 1984Sci...223Q.584B
Altcode:
No abstract at ADS
Title: Book-Review - Activity in Red Dwarf Stars
Authors: Byrne, P. B.; Rodono, M.
Bibcode: 1983JBAA...94...41B
Altcode:
No abstract at ADS
Title: Element identifications in the ultraviolet spectrum of
HD 101065.
Authors: Wegner, G.; Cummins, D. J.; Byrne, P. B.; Stickland, D. J.
Bibcode: 1983ApJ...272..646W
Altcode:
Ultraviolet spectroscopic observations with the IUE satellite
of the controversial peculiar star HD 101065 are presented and
discussed. Low-resolution spectra combined with published visual and
infrared broad-band photometry show that the star's spectral energy
distribution is greatly distorted, presumably by the severe line
blanketing. However, the presence of observable ultraviolet flux below
1900 A suggests that HD 101065 is considerably hotter than 6000 K. A
detailed examination of the high-resolution spectrum of HD 101065 in the
region 1900-3200 A found that the lines of the iron-peak elements Fe II,
Cr II, Mn II, and Ti II are strongly represented in the ultraviolet
spectrum. The implications of the presence of these elements for the
temperature estimate and nature of HD 101065 are discussed.
Title: Coordinated Ultraviolet, Microwave, and Optical Observations
of Flares on YZ CMi and AD Leo
Authors: Linsky, J. L.; Bornmann, P.; Brown, A.; Gary, D. E.; Rodono,
M.; Pazzani, V.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1983BAAS...15..650L
Altcode:
No abstract at ADS
Title: HD101065- The Most Peculiar Star?
Authors: Byrne, P. B.
Bibcode: 1983IrAJ...16...58B
Altcode:
IUE 6-A and 0.1-A-resolution spectra of HD101065, an object
discovered and classified as a cool Ap star by Przybylski (1961,
1963), are analyzed, summarizing the results presented by Wegener et
al. (1983). The spectral flux distribution is calculated from the
low-resolution data and visible and near-IR photometry and plotted
from 120 to 2500 nm for comparison with the stellar-atmosphere models
of Kurucz (1979). An effective temperature between 7000 and 8000 K is
estimated. Examination of the individual lines of the high-resolution
spectra indicates the presence of Ce II, Cr II, Gd II, Ho II, Fe II, Mg
I, Mg II, Nm II, Tm II, Ti II, and Zr II, supporting the classification
of HD101065 as an Ap star with spectral peculiarities.
Title: Optical photometry of flares and flare statistics
Authors: Byrne, P. B.
Bibcode: 1983ASSL..102..157B
Altcode: 1983IAUCo..71..157B; 1983ards.proc..157B
Optical photometry observations of flares on solar-neighborhood
flare stars are discussed along with the results obtained from these
observations. The definition of a flare is presented and the colors
of flare light are addressed. The time distribution of flares and
the time-averaged energy released in flares are considered. Other
correlations with luminosity are discussed. Variations in activity
with time, preflare dips and increases, and polarization are covered.
Title: IUE spectra of the BY Dra/flarestar AU MIC
Authors: Butler, C. J.; Andrews, A. D.; Doyle, J. G.; Byrne, P. B.;
Linsky, J. L.; Simon, T.; Marstad, N.; Rodono, M.; Pazzani, V.
Bibcode: 1983ASSL..102..249B
Altcode: 1983ards.proc..249B; 1983IAUCo..71..249B
Ground-based optical and IUE observations of BY Dra variables undertaken
to follow the spectral variation of these stars over one cycle are
discussed. It is noted that in the first series, 20 LWR and 19 SWP
trailed spectra were taken of AU Mic over a three-day period, August
4-6, 1980. The mean integrated flux are shown here for the strong
emission lines in th SWP spectra of AU Mic over the observed phase
interval of 0.14 to 0.8, together with an approximate V light curve
determined by the FES and IUE. Several points emerge from comparing
the emission line intensities and FES magnitudes. The first is that
the light curve at this time had at least three and possibly four
minima. If this is to be interpreted as deriving from the rotation of
a spotted star, several spotted regions would be required, distributed
in stellar longitude. The second point is that repeated flaring of AU
Mic makes it difficult to perceive any clearly defined modulation of
the emission line intensities owing to plage regions in the vicinity
of the spots. The third point is that following flare activity during
SWP 9695 and WP 9698, it appears that the intensity of the HeII and
SiII lines has remained high for some time after the drop in intensity
of the CIV line.
Title: IUE spectra of RS CVn stars
Authors: Andrews, A. D.; Byrne, P. B.; Butler, C. J.; Linsky,
J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.; Catalano, S.;
Marilli, E.
Bibcode: 1983ASSL..102..443A
Altcode: 1983IAUCo..71..443A; 1983ards.proc..443A
Three RS CVn stars are observed during the period October 1-7,
1981. Eight spectra of II Peg, 10 of HR1099, and four of AR Lac are
obtained. The observations are well distributed with respect to the
phase of the optical light curves. The ground-based data reveal that
all three stars had well established wavelike variations. Evidence
is presented that in RS CVn stars the UV chromospheric and transition
region line fluxes vary in such a way that maximum line flux corresponds
to optical minimum or maximum spot visibility. This, it is pointed out,
is consistent with a solar-type dark spot model.
Title: Coordinated Ultraviolet, Optical and Radio Observations of
RS CVn and Flare Stars
Authors: Byrne, P. B.; Butler, C. J.; Andrews, A. D.; Rodono, M.;
Catalano, S.; Pazzani, V.; Linsky, J. L.; Bornman, P.; Haisch, B. M.
Bibcode: 1983IBVS.2258....1B
Altcode:
No abstract at ADS
Title: Activity in red-dwarf stars
Authors: Byrne, P. B.; Rodono, M.
Bibcode: 1983ASSL..102.....B
Altcode: 1983IAUCo..71.....B; 1983ards.proc.....B
Results of studies of activity in red dwarf stars are discussed. General
characteristics of active dwarfs, including chromospheres, transition
regions, and emissions from these regions are considered. Observed
activity in red dwarfs and related objects are covered, such as sunspots
and starspots, flares, line and light curve variations, radio emission,
chromospheric phenomena, and binary contact phenomena. Theoretical
problems are considered, including models of spots and flares, flare
triggering mechanisms, thermal and magnetic instabilities, and magnetic
accretion. Future research directions are discussed. For individual
items see A83-47477 to A83-47551
Title: Optical and UV Observations of Spotted Stars
Authors: Byrne, P. B.
Bibcode: 1982IrAJ...15..323B
Altcode:
No abstract at ADS
Title: Observations of the occultation of HD 197999 by the Minor
planet 105 Artenis.
Authors: Byrne, P. B.; Coulson, I. M.; Doyle, J. G.; Taylor, G. E.
Bibcode: 1982MNRAS.200P..65B
Altcode:
A minimum value of 110 km for the diameter Artemis is derived from
observations of its occultation of a star.
Title: Variability of cool stars at optical and ultraviolet
wavelengths. II - The binary (?) flare star AU Mic.
Authors: Linsky, J. L.; Bornmann, P. L.; Rodono, M.; Pazzani, V.;
Andrews, A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1982ESASP.176..165L
Altcode: 1982IUE3r.R....129L; 1982iue..conf..165L
Ground based optical, and IUE observations of AU Mic are described. One
definite flaring event, remarkable changes of the BY Dra-type optical
light curve and evidence of slow variability in the chromospheric and
transition region line fluxes (probably due to the rotational modulation
of photospheric starspots and plages, respectively), was found. The
fractional surface area covered by active regions (filling factor) shows
a definite variability with the temperature of line formation, i.e.,
with atmospheric height. This suggests significant surface and vertical
structuring of active regions in the outer atmosphere of AU Mic.
Title: Rotational modulation of chromospheric features in late-type
stars.
Authors: Byrne, P. B.; Butler, C. J.; Andrews, A. D.; Linsky,
J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.; Catalano, S.;
Marilli, E.
Bibcode: 1982ESASP.176..125B
Altcode: 1982iue..conf..125B; 1982IUE3r......125B
Three RS CVn-type binaries (HR 1099, II Peg, and AR Lac) and the
prototype BY Dra binary system were observed by IUE at regular intervals
throughout their 2.0 to 6.7 day periods. Ground based photometry and
radio observations were also made. Flux variations of emission lines
formed in the chromospheres and transition regions of two of these
stars are discussed. The phase relationship between the photometric
observations and the line variations and their relevance to the
location of dark star spots are considered. The evidence suggests
that in the spotted variables the fluxes of the chromospheric and
transition region lines vary in a manner such that maximum line flux
corresponds to optical minimum or maximum spot visibility. This is
consistent with a model of a solar-like dark spot distribution on the
surface of these stars.
Title: Results of an IUE program of monitoring the ultraviolet
emission line fluxes of four binary systems: HR 1099, II Peg, AR Lac,
and BY Dra.
Authors: Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Blanco, C.;
Catalano, S.; Marilli, E.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1982NASCP2238..554M
Altcode: 1982auva.nasa..554M; 1982NASCP2338..554M; 1982IUE82......558B
A program to obtain IUE spectra and optical photometry and spectra
of three RS CVn-type binaries (HR 1099, II Peg, and AR Lac) and the
prototype BY Dra system is reported. The systems were monitored for
at least one orbital phase, and periodic variations in emission line
flux from II Peg and HR 1099, indicative of notational modulation
of an active region on these stars were detected. It is found that
for II Peg the active region is in phase with photometric minimum as
expected, but for HR 1099 ultraviolet emission maximum occurs at the
time of photometric maximum.
Title: Results of an IUE program of monitoring the ultraviolet
emission line fluxes of four binary systems : HR 1099, II Peg,
AR Lac, and BY Dra.
Authors: Marstad, N.; Linsky, J. L.; Simon, T.; Rodono, M.; Blanco, C.;
Catalano, S.; Marilli, E.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1982IUE82......554M
Altcode:
No abstract at ADS
Title: IUE Spectra of Active Stars in Binary Systems.
Authors: Butler, C. J.; Andrews, A. D.; Byrne, P. B.; Doyle, J. G.;
Linsky, J. L.; Marstad, N.; Simon, T.; Rodono, M.; Blanco, C.;
Catalano, S.; Pazzani, E.; Marilli, V.
Bibcode: 1982uxsa.coll...14B
Altcode: 1982IAUCo..73...14B
No abstract at ADS
Title: Ultraviolet spectra of dwarf solar neighbourhood stars. I.
Authors: Butler, C. J.; Byrne, P. B.; Andrews, A. D.; Doyle, J. G.
Bibcode: 1981MNRAS.197..815B
Altcode:
Short-wavelength IUE spectra of three nearby M-type dwarfs are
presented. Two of these stars, Gliese 867 A and AU Mic, are active UV
Ceti flare stars and their UV spectra exhibit strong emission lines,
characteristic of active chromospheres. The third star, Gliese 825,
is a low-activity flare star and its spectrum reveals no chromospheric
lines. A strong UV continuum exists in one of the spectra of Gliese 867
A and it is deduced that a flare took place during the exposure. A
spectrum of the flare light is extracted and compared with the
predictions of various flare models.
Title: IUE Spectroscopy of Dwarf M Stars
Authors: Byrne, P. B.
Bibcode: 1981IrAJ...15..113B
Altcode:
No abstract at ADS
Title: Gliese 825 - a new flare star.
Authors: Byrne, P. B.
Bibcode: 1981MNRAS.195..143B
Altcode:
The bright dM star Gl 825 is shown to be a flare star, and comparison
with similar stars indicates that its overall activity level may be
unusually low for a star of its spectral type. Characteristics of the
star such as the absence of chromospheric emission lines in its UV
spectrum, and its space motion, are consistent with a somewhat later
evolutionary stage than that of typical solar neighborhood UV Ceti
flare stars and with its reduced level of chromospheric activity. It
is concluded that the absence of BY Draconis variations throughout
1979 is also consistent with the interpretation.
Title: Results of an IUE Program of Monitoring the Ultraviolet
Emission Line Fluxes of Four Binary Systems
Authors: Linsky, J. L.; Simon, T.; Marstad, N.; Rodono, M.; Blanco, C.;
Catalano, S.; Marilli, E.; Andrews, A. D.; Butler, C. J.; Byrne, P. B.
Bibcode: 1981BAAS...13R.872L
Altcode:
No abstract at ADS
Title: Gliese 867 - Further observations of a multiple flare star
system.
Authors: Byrne, P. B.; McFarland, J.
Bibcode: 1980MNRAS.193..525B
Altcode:
Light curves of flares on both G867A and G867B are presented. It
is shown that activity levels determined during 1977 are
maintained. Differential magnitudes between G867A and a number of
nearby comparison stars are discussed and used to place upper limits
to BY Draconis variations during 1978 and 1979.
Title: Ultra-Violet Spectroscopy of Flare Stars
Authors: Byrne, P. B.; Butler, C. J.; Andrews, A. D.
Bibcode: 1980IrAJ...14..219B
Altcode:
Results of an IUE satellite investigation of a selection of nearby
dwarf stars of spectral type M are given. Spectra were obtained for
seven stars in IUE's long wavelength range and for three stars in
the short wavelength range, including both known flare stars and
stars as yet not known to flare. The most prominent feature of the
long wavelength spectra is the ionized magnesium h and k resonance
doublet at 2795/7A wavelength. Radii are estimated from the mean of
results obtained from mean relationships between radius and absolute
magnitude, radius and spectral type, and from empirical relationships
between radius and the star's colors. The most active flare stars
show higher emission, suggesting a greater rate of energy deposition
in their lower chromospheres. The short wavelength data included the
first-ever UV spectrum of a flaring star. Most sample stars showed
strong lines in the short wavelength region, and their surface fluxes
were calculated and compared to the quiet sun.
Title: Request for Cooperation from Optical and Radio Observers
Authors: Byrne, P. B.
Bibcode: 1980IBVS.1768....1B
Altcode:
No abstract at ADS
Title: Przybylski's Star
Authors: Byrne, P. B.
Bibcode: 1980iue..prop..585B
Altcode:
No abstract at ADS
Title: UV Spectroscopy of Flare
Authors: Byrne, P.
Bibcode: 1980iue..prop..647B
Altcode:
No abstract at ADS
Title: The angular diameter of the carbon star AQ Sagittarii.
Authors: Walker, A. R.; Wild, P. A. T.; Byrne, P. B.
Bibcode: 1979MNRAS.189..455W
Altcode:
The angular diameter of the N-type carbon star AQ Sagittarii was
measured on 1977 August 25 by the lunar occultation method. The uniform
disc diameter is 5.48 ± 0.45 ms arc, implying an effective temperature
of 2684±110K.
Title: Book-Review - Active Galactic Nuclei - NATO Summer School -
Cambridge 1977
Authors: Hazard, C.; Mitton, S.; Byrne, P. B.
Bibcode: 1979IrAJ...14..103H
Altcode:
No abstract at ADS
Title: Commission No. 27 - Working Group on Flare Stars
Authors: Byrne, P. B.; Andrews, A. D.
Bibcode: 1979IBVS.1671....1B
Altcode:
No abstract at ADS
Title: Astronomers at the Royal Observatory Cape-Of
Authors: Byrne, P. B.
Bibcode: 1979IrAJ...14..105B
Altcode:
No abstract at ADS
Title: OAO 1653-40
Authors: Byrne, P.; Levine, A.; Lang, F.; Dobson, C. A.; Doty, J. P.;
Howe, S. K.; Primini, F. A.; Wheaton, W. A.; Lewin, W. H. G.
Bibcode: 1979IAUC.3368....1B
Altcode:
P. Byrne, A. Levine, F. Lang, C. A. Dobson, J. P. Doty, S. K. Howe,
F. A. Primini, W. A. Wheaton and W. H. G. Lewin, Massachusetts Institute
of Technology, report the position of a hard x-ray source detected
in the region of OAO 1653-40. Both spectral and positional evidence
strongly indicate that this source is the 38-s pulsar (IAUC 3342). The
four corners of the error region (1.5-sigma level of confidence) are
given by R.A. = 16h54m, Decl. = -41o40'; 16h54m.3, -41o10'; 16h58m.6,
-41o16'; 16h58m.3, -41o45' (equinox 1950.0). The observations were made
with the UCSD/MIT HEAO-A4 experiment in the spinning mode. The error
box clearly excludes V861 Sco, in agreement with the HEAO-A3 result
(IAUC 3342). When the A4 detector was pointed in the above direction,
38-s pulsations were detected up to about 80 keV.
Title: Gliese 867 - a multiple flare star system.
Authors: Byrne, P. B.
Bibcode: 1979MNRAS.187..153B
Altcode:
High-speed photometric observations of flares on both components of
the visual binary G 867 are presented. The mean release of energy
due to flaring is similar to UV Ceti flare stars of similar spectral
types. Some other parameters of the flaring are discussed and compared
with previous results.
Title: Hard X-ray Observations of a 38 sec Pulsar
Authors: Byrne, P.; Dobson, C. A.; Doty, J. P.; Howe, S. K.; Lang,
F.; Levine, A. M.; Primini, F. A.; Wheaton, W. A.; Lewin, W. H. G.;
Gruber, D. E.; Matteson, J. L.; Peterson, L. E.
Bibcode: 1979BAAS...11..424B
Altcode:
No abstract at ADS
Title: Preliminary Results of the HEAO A4 Hard X-ray Sky Survey
(13-180 keV)
Authors: Levine, A.; Lang, F.; Byrne, P.; Cooke, B. A.; Dobson, C. A.;
Doty, J. P.; Hoffman, J. A.; Howe, S. K.; Primini, F. A.; Scheepmaker,
A.; Wheaton, W. A.; Lewin, W. H. G.; Matteson, J. L.; Knight, F. K.;
Nolan, P.; Peterson, L. E.
Bibcode: 1979BAAS...11..429L
Altcode:
No abstract at ADS
Title: HEAO-1 Observations of High Energy X-rays from MKN509
Authors: Dil, S.; Primini, F.; Byrne, P.; Dobson, C.; Doty, J.; Howe,
S.; Lang, F.; Levine, A.; Wheaton, W. A.; Lewin, W. H. G.; Baity,
W. A.; Matteson, J. L.; Peterson, L. E.
Bibcode: 1979BAAS...11..467D
Altcode:
No abstract at ADS
Title: Manpower in Astronomy in Europe
Authors: Byrne, P. B.
Bibcode: 1978IrAJ...13..250B
Altcode:
No abstract at ADS
Title: Book-Review - the Atlas of Mercury
Authors: Cross, C.; Moore, P.; Byrne, P. B.
Bibcode: 1978IrAJ...13..264C
Altcode:
No abstract at ADS
Title: Gliese 867 - a New Flare-Star System
Authors: Byrne, P. Brendan
Bibcode: 1978IBVS.1407....1B
Altcode:
No abstract at ADS
Title: Interstellar MG I and MG II Absorption
Authors: Byrne, P.
Bibcode: 1978iue..prop..126B
Altcode:
No abstract at ADS
Title: Gliese 867 - a new flare star system.
Authors: Byrne, P. B.
Bibcode: 1978sss..meet..C13B
Altcode:
No abstract at ADS
Title: BOOKS (with comments): "Relativity and Cosmology", by
W. J. Kaufmann
Authors: Byrne, P. B.
Bibcode: 1977IrAJ...13..146B
Altcode:
No abstract at ADS
Title: Books: "Eyes on the Universe", by Isaac Asimov
Authors: Byrne, P. B.
Bibcode: 1977IrAJ...13...70B
Altcode:
No abstract at ADS
Title: Optical flashes from burst X-ray sources?
Authors: Byrne, P. B.; Wayman, P. A.
Bibcode: 1977MNRAS.178P..45B
Altcode:
Previously observed occasional double or multiple flashes at optical
wavelengths from a source probably located close to the Galactic
Center (GC) are tentatively linked with the burst X-ray source
MXB 1743-293. Distributions of interarrival times are examined for
light flashes recorded from the GC area of the sky and from a nearby
(control) region; it is found that the flashes from the GC area tend
to group more closely in time than would be expected from randomly
distributed events. In addition, the time scale of the GC flashes
is shown to be similar to that of multiple X-ray bursts from MXB
1743-293. The total optical energy for this source is estimated to
be two orders of magnitude greater than the X-ray energy per burst,
a ratio comparable to that observed for solar flares.
Title: The Binary X-ray Sources
Authors: Byrne, P. B.
Bibcode: 1976IrAJ...12..193B
Altcode:
The UHURU satellite (launched in 1970) has provided for the first
time the opportunity to survey the entire sky at X-ray energies. The
observations have provided new information on many well-known objects,
in addition to discovering a large number of hitherto unknown
objects. For most of these objects, there were no obvious optical
counterparts. Optical identification was made difficult by the poor
positional accuracy of the UHURU detectors. Identification, however,
has been relatively successful for a class of X-ray objects known as
binary X-ray sources. In the present paper, the principal properties of
the binary X-ray sources are reviewed, and the model of the phenomenon
is discussed.
Title: A search for optical pulses from the galactic Centre
Authors: Byrne, P. B.; Wayman, P. A.
Bibcode: 1975MNRAS.173..537B
Altcode:
A search has been carried out for optical flashes in the direction of
the centre of the Galaxy. Most of the flashes recorded are adequately
accounted for by faint meteors crossing the area of the sky under
examination. There remain a few multipie optical pulses, closely
grouped in time, which are not readily explained. Possible origins
are discussed.
Title: Candidate for LMC X-5
Authors: Byrne, P. B.
Bibcode: 1975Natur.257..110B
Altcode:
A NEW X-ray source in the Large Magellanic Cloud, LMC X-5, has been
reported1. I wish to draw attention to the close proximity of
the radio sources MC32 and MC33 to the best X-ray position. According
to the positions of MC32/33 given by McGee et al.2 they lie
just outside the X-ray 90% confidence level error box for LMC X-5. In
Fig. 1 I show the 6-cm radio contours of MC32/33 from ref. 2 with the
X-ray error box superimposed on a plate of the region.
Title: A search for optical evidence of condensed matter
Authors: Byrne, Patrick Brendan
Bibcode: 1974PhDT.......229B
Altcode:
No abstract at ADS
Title: Possible Candidate for LMC X-1
Authors: Byrne, P. B.; Butler, C. J.
Bibcode: 1973NPhS..244....6B
Altcode: 1973Natur.244....6B
AN X-ray source, LMC X-1 (2U0540-69), has been reported1 in
the Large Magellanic Cloud south of 30 Doradus. Here we draw attention
to the proximity of the radio sources MC76 and MC77 to this X-ray
source. According to the position for MC77 given by Broten2
this source lies within the Uhuru 90% confidence level error box
given by Giacconi et al.3. In Fig. 1 we show the 6 cm radio
contours of MC76 and MC77 as given in ref. 2 with the X-ray error box
from ref. 3 superimposed on a B plate of the region.
Title: Photographic Photometry of the Proposed Optical Candidate
for SMC X-1
Authors: Butler, C. J.; Byrne, P. B.
Bibcode: 1973NPhS..243..136B
Altcode: 1973Natur.243..136B
Leong et al.1 have reported a variable X-ray source, SMC X-1
(2U0115-73), in the direction of the Wing of the Small Magellanic
Cloud. A regular variation with period 3.8927 d has since been
reported2. The nature of the regular variations suggests
that the X-ray source is one component of an eclipsing binary system. If
this object were in the SMC it would be intrinsically the most powerful
binary X-ray source known and would have the most accurately defined
distance of any such source.