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Ultraviolet P-Cygni profile variations in HD 50896.
Howarth, I. D.; Willis, A. J.; Smith, L. J. +2 more
An analysis of 68 high-resolution IUE UV spectra of HD 50896 obtained at 9 separate epochs during the 1978-1983 period is presented. No evidence is found for the presence of a neutron star companion, and it is suggested that the observed UV profile variations are due to changes which are intrinsic to the WN5 stellar wind. The 46 spectra obtained d…
IUE observations of the M dwarfs CM Draconis and Rossiter 137B : magnetic activity at saturated levels.
Linsky, J. L.; Vilhu, O.; Neff, J. E. +4 more
IUE observations of two active M dwarfs with known rotation rate or age and presumed to be almost totally convective are presented. The first of these stars, CM Draconis (Gl 630.1), is an old Population II binary with its components in tidally induced rapid rotation (P = 1.27 d, dM 4 + dM 4). The other one, Rossiter 137 B, forms with HD 36705 (AB …
On the Size Distribution of Newly Formed Grains in Red Supergiant Atmospheres
Snow, Theodore P.; Seab, C. Gregory
Theoretical ultraviolet extinction curves have been calculated for comparison with observed curves for circumstellar dust in M supergiants. The theoretical curves assume a silicate grain composition, because silicate grains are expected in the oxygen-rich environments that are observed. Calculations were performed with and without the inclusion of…
The distance of the helium-variable B star HD 37479.
Heber, U.; Groote, D.; Hunger, K.
The gravity of HD 37479 (Sigma Ori E) is redetermined using eight high resolution and high S/N ratio spectrograms. The analysis is carried out differentially with respect to the main sequence stars Gamma Peg and Sigma Ori D. It is confirmed that the gravity of HD 37479 is log g = 3.95 + or - 0.15. Evidence is presented for a peculiar interstellar …
The Peculiar Planetary Nebula in M22
Cohen, J. G.; Gillett, F. C.
The source discovered by the IRAS satellite near the center of the globular cluster M22, IRAS 18333-2357, has been studied using the IUE satellite and a ground-based optical telescope. The northern component of the close pair of stars is not a member of the cluster. The southern component is a hot star with T(eff) of about 50,000 K illuminating a …
A 4.1 keV spectral feature in a type 1 X-ray burst from EXO 1747-214.
van Paradijs, J.; Lewin, W. H. G.; Magnier, E. +3 more
We present the results of a spectral analysis of two type 1 bursts from EXO 1747-214 detected during 9.4 h of observing with EXOSAT. The spectrum, during the rise of the strongest burst, shows a spectral feature, which can be well represented by an absorption line at 4.05 +/- 0.1 keV; the line has an equivalent width of 570 +/- 87 eV; the upper li…
Constraints from the UV delay in dwarf nova outbursts.
Meyer, F.; Meyer-Hofmeister, E.
Observations of outbursts of the dwarf nova system VW Hydri show a delay of the rise of the UV flux with respect to that of the optical flux. The difficulties in modeling this feature in the context of the accretion disk instability are discussed and a modified limit cycle based on the same value of the frictional parameter alpha for the cool disk…
X-Ray Timing and Spectral Measurements of X Persei
Robba, N. R.; Warwick, R. S.
The results of an X-ray timing and spectral study of the Be star X-ray binary system X Per are reported, based on two series of Exosat observations. The timing measurements indicate that the neutron star in the X Per system was in a net spin-down mode during the 1984-1986 period and that this trend may have been in progress since 1978. The phase-a…
IUE observations of variability in the WN6 star HD 192163.
Willis, A. J.; Smith, L. J.; Conti, P. S. +3 more
Results are presented of a study of 77 high-resolution IUE spectra of the WN6 star HD 192163, for which new IUE observations obtained over 48 hrs in 1987 were combined with data drawn from the IUE archive, covering various epochs over the 1978-1987 period. The 1987 series of 48 spectra were found to exhibit significant variability over a period of…
The X-ray spectrum of QSO 1821+643.
Barstow, M. A.; Warwick, R. S.; Yaqoob, T.
Pravdo & Marshall have reported an unusually soft X-ray spectrum for the high-luminosity QSO 1821 + 643, based on measurements from the A2 experiment on HEAO-1. However, in a series of EXOSAT observations of this object we have found the medium-energy X-ray spectrum to be consistent with the canonical form observed in low-luminosity active gal…