Search Publications
Stellar Winds in the Small Magellanic Cloud
Fitzpatrick, Edward L.; Garmany, Catharine D.
According to the predictions of line-driven stellar wind theory, the mass loss from luminous stars should be proportional to some power of the metallicity, yet previous studies have not shown this effect clearly. We have observed 22 main-sequence and giant O-type stars in the SMC with the low-resolution mode of the IUE in order to study the stella…
Singly ionized iron as a diagnostic of stellar envelopes. II The structure of the envelopes of six luminous blue stars.
Friedjung, M.; Muratorio, G.
The methods described in Friedjung and Muratorio (1987), involving the self-absorption curve for the Fe II optical emission lines and spectral synthesis for the UV, are applied to study the surroundings of the galactic P Cygni star AG Car and of five luminous Magellanic Cloud stars. Their Fe II emission and absorption spectra are interpreted by li…
Fast Variations in the Ultraviolet Resonance Lines of alpha Camelopardalis (O9.5 Ia): Evidence for Blobs in the Wind
Snow, Theodore P.; Lamers, Henry J. G. L. M.; de Jager, Cornelis +1 more
The 72 IUE spectra of Alpha Cam and 19 IUE spectra of Kappa Cas, obtained during 72 hours of continuous IUE time in September 1978 were searched for variations in the profiles of the resonance lines of Si IV, C IV, and N V, and the results are discussed. The UV resonance lines in the spectra of Alpha Cam showed variations at the 2 percent level ne…
Time-dependent heating phenomena in coronal loops.
Barstow, M. A.; van den Oord, G. H. J.
The authors have investigated the behaviour of coronal loops subject to flare-like heating. They pay attention to the conflicting results obtained by Kuin and Martens (1982) and Craig and Schulkes (1985). They show that the description of Kuin and Martens is correct and extend it for a larger range of loop temperatures. Further, they show that the…
On the High-Energy Gamma-Ray Signature of Cosmic-Ray Sources
Ormes, J. F.; Ozel, M. E.; Morris, D. J.
If cosmic rays are accelerated by strong shocks, then cosmic-ray sources should be characterized by spectra, dN/dE is proportional to p^-(2.0-2.2)^, reflecting the strength of those shocks. This is expected from the "standard leaky box" model of cosmic-ray propagation in which the source spectra are harder than the observed spectra because higher …
EXOSAT and IUE Observations of SW UMa during Superoutburst
Szkody, Paula; Hassall, B. J. M.; Osborne, Julian
IUE and Exosat observations obtained during the March 1986 superoutburst of the SU UMa type dwarf nova SW UMa are presented. The observations show the presence of a hot, extensive, optically thick disk. The UV fluxes show an increase of 1000 over the quiescent values, implying a large increase in mass accretion rate. The Exosat obserations show an…
A Spectrophotometric Study of IR GEM at Outburst and Quiescence
Garnavich, Peter; Szkody, Paula; Feinswog, Laurie
The authors present optical spectra with 2.5 Å resolution obtained throughout the orbit of the SU UMa cataclysmic variable IR Gem during a five day sequence beginning at an outburst state and ending at quiescence. In addition, B magnitude light curves and IUE spectra throughout other quiescent-state orbits are discussed. The broad absorption and n…
A spectrophotometric study of the planetary nebula N66 in the Large Magellanic Cloud.
Ruiz, M. T.; Peña, M.
The authors present spectrophotometric data of the LMC planetary nebula N66. Combining these observations with IUE data and ionization structure models, they derive the chemical composition of the nebula and parameters of the central star.
Hot Components and Circumstellar Grains in M Supergiant Syncretic Binaries
Buss, Richard H., Jr.; Snow, Theodore P., Jr.
The authors have aqcquired ultraviolet spectra and infrared data to study grains in cool star plus hot star syncretic (VV Cep) type binaries. Though M supergiants almost always have circumstellar grains, the authors found grains, from IRAS infrared photometry, in only about half of the syncretic systems. Infrared spectra revealed that the circumst…
The Abundance of Zinc in Hg-Mn Stars
Sadakane, Kozo; Takada-Hidai, Masahide; Jugaku, Jun
The resonance line of singly ionized zinc (Zn II) at 2062.00 A is quantitatively analyzed, and the abundances of Zn in atmospheres of early-type stars have been determined for the first time. The line is analyzed in IUE spectra of six reference (normal) stars between spectral types B5 and A0 and of 23 Hg-Mn stars. The abundances of Zn in the refer…