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Ultraviolet Observations of SN 1987A
Kirshner, Robert P.; Sonneborn, George; Crenshaw, D. Michael +1 more
UV observations of the supernova in the LMC, SN 1987A, were carried out with the IUE satellite. The earliest data show that the UV flux from the supernova was already declining while the optical flux was still rising. The UV spectrum at these epochs consists of broad features associated with the supernova atmosphere punctuated by sharp interstella…
The Dependence of Ultraviolet Chromospheric Emission upon Rotation among Late-Type Stars
Simon, Theodore; Fekel, Francis C., Jr.
The authors have obtained low-resolution IUE spectra of a large number of chromospherically active stars. Integrated fluxes of chromospheric and transition region emission lines have been measured. These fluxes, supplemented by published observations and measurements of IUE archival spectra, have been used to search for correlations between activi…
Physical Parameters for 12 Planetary Nebulae and Their Central Stars in the Magellanic Clouds
Gull, Theodore R.; Aller, Lawrence H.; Maran, Stephen P. +3 more
Nebular and central star parameters and elemental abundances of C, N, O, Ne, S, and Ar are presented for the planetary nebulae N2, N5, N43, N54, and N67 in the SMC and P2, P7, P9, P25, P33, and P40 in the LMC. The nebular chemical compositions are affected by nuclear processes in the precursor stars, which may not have been sufficiently massive to…
Highly Ionized Stellar Winds in Be Stars: The Evidence for Aspect Dependence
Grady, C. A.; Snow, T. P.; Bjorkman, K. S.
The authors present the results of an ultraviolet survey of stellar winds in 62 Be and 43 normal B stars covering spectral types B0.5 - B5 and luminosity classes V - III. They find that the wind absorption seen in the resonance lines of C IV, Si IV, and Si III in Be stars is often the result of blended absorption from multiple shortward-shifted di…
The Progenitor of SN 1987A: Spatially Resolved Ultraviolet Spectroscopy of the Supernova Field
Kirshner, Robert P.; Sonneborn, George; Altner, Bruce
Careful deconvolution of spatially resolved IUE ultraviolet spectra shows that only two of the three stars detected in plate material before 1987 are now present near the site of SN 1987A. The separation, magnitudes, and spectra of these two are consistent with their identification as star 2 and star 3 of the Sanduleak -69°202 trio. The clear impl…
EXOSAT Observations of Double-peaked Bursts with Radius Expansion from 4U/MXB 1820-30
Haberl, F.; Stella, L.; White, N. E. +2 more
A detailed analysis is presented of seven X-ray bursts from the X-ray source 4U/MXB 1820-30 in the globular cluster NGC 6624. The bursts were double-peaked, and recurred at almost equal time intervals of 3.2 hr. The persistent flux varied by only 10 percent on time scales of 60 minutes. The ratio of the total persistent energy emitted before a bur…
The Exotic Helium Variable PG 1346+082
Winget, D. E.; Wesemael, F.; Liebert, James +5 more
The results of an extensive study of the blue object PG 1346 + 082, which is both a photometric and a spectroscopic variable, are presented. The system spans the B magnitude range 13.6-17.2, is brighter than m(pg) of about 14.0 roughly 74 percent of the time, and has a photometric quasi-period of four to five days. The rapid photometric flickering…
CAL 83: A Puzzling X-Ray Source in the Large Magellanic Cloud
Thompson, I. B.; Crampton, David; Hutchings, J. B. +3 more
Spectroscopic observations of the X-ray point source no. 83 in the Columbia Astrophysics Laboratory Einstein survey of the Large Magellanic Cloud have been accumulated over 4 yr. The optical spectrum shows no stellar absorption features, but only emission lines typical of an accretion disk. Radial velocity measurements reveal a small (K = 30 km/s)…
Periodic Photospheric and Chromospheric Modulation in Alpha Orionis (Betelgeuse)
Sonneborn, G.; Dupree, A. K.; Guinan, E. F. +3 more
The bright cool supergiant Alpha Orionis has been monitored spectroscopically and photometrically over the past three years (1984-1986) in the optical and the ultraviolet wavelength regions. A 420-day periodic modulation of the flux is observed in the optical and ultaviolet continua, and in the Mg II line emission cores. Periodic photospheric puls…
X-Ray Sources in Regions of Star Formation. II. The Pre--Main-Sequence G Star HDE 283572
Roth, M.; Linsky, J. L.; Walter, F. M. +7 more
This paper reports the detection of HDE 283572, a ninth-magnitude G star 8 arcmin south of RY Tau, as a bright X-ray source. The observations reveal this object to be a fairly massive (about 2 solar masses) pre-main-sequence star associated with the Taurus-Auriga star formation complex. It exhibits few of the characteristics of the classical T Tau…