Search Publications
Observations of a partial X-ray eclipse in the long-period low mass X-ray binary 2S 0921-630.
Branduardi-Raymont, G.; Mason, K. O.; Cordova, F. A. +1 more
A partial eclipse of the X-ray flux from 2S 0921-630 has been recorded for the first time, using the EXOSAT satellite. The time of the X-ray eclipse agrees with an extrapolation of the ephemeris of optical dips in 2S 0921-630, strongly supporting the hypothesis that 2S 0921-630 is an eclipsing binary with a period of just over 9 day. The X-ray ecl…
Time-Resolved IUE Studies of Cataclysmic Variables. I. Eclipsing Systems of IP Peg, PG 1030 + 590, and V1315 AQL
Szkody, Paula
IUE time-resolved spectra of the high-inclination cataclysmic variables IP Peg, PG 1030+590, and V1315 Aql are analyzed in order to determine the characteristics of the disks, hotspots, and white dwarfs. The UV continuum flux distributions are generally flatter than systems of low inclination and high mass-transfer rate, and the white dwarfs/inner…
An EXOSAT observation of the bursting X-ray transient 4U 1608-52.
Stella, L.; White, N. E.; Barr, P. +1 more
An EXOSAT observation of the transient X-ray burster 4U 1608-52 detected the source in a low state. The spectrum of the persistent emission is a power law with a photon index of 1.9 similar to that from other X-ray burst sources. During the 5.5 hr exposure a double-peaked type I burst was seen. A detailed spectral analysis shows this to be caused …
EXOSAT observations of the 1983 outburst of the rapid burster : a newmode of behaviour.
Haberl, F.; Stella, L.; Parmar, A. N. +4 more
The results of three observations of the rapid burster (MXB 1730-335) made in August 1983 are reported. A new mode of behavior consisting of strong persistent emission at a level of about 5 microJY along with type I bursts recurring approximately every 80 minutes, is reported. No type II bursts were seen during this interval. The spectrum of the p…
Recurrent Episodic Mass Loss in a B2e Star: 66 Ophiuchi, 1982--1985
Sonneborn, George; Grady, C. A.; Wu, Chi-Chao +1 more
The results of three intensive ultraviolet monitoring campaigns for 66 Oph in September-October 1982, September 1983, and September 1984, supplemented by the available IUE archival data from April, 1982 to June, 1985 are reported. The stellar wind went through at least two and probably three episodes of weak-wind absorption. At wind minimum, the r…
Time Variability of Gamma Cassiopeiae in X-Rays
Frontera, F.; Costa, E.; Manzo, G. +3 more
A 22,000 s observation with EXOSAT of the X-ray source 4U 0053+60/Gamma Cassiopeiae reveals oscillations in the X-ray flux with a period of about 6000 s. The source also exhibits chaotic variability with time scales down to a few tens of seconds. This observation strengthens the hypothesis that the X-ray source is a neutron star in a wide orbit ar…
The Ultraviolet and Optical Emission-Line Spectrum of III ZW 77
Ferland, Gary J.; Osterbrock, Donald E.
The high-ionization Seyfert I galaxy III Zw 77 has been simultaneously observed over the satellite ultraviolet to near-IR spectral regions. As in other AGN, the continuous energy distribution shows a roughly power-law decline across much of the optical region and a flatter-than-unity spectral index in the near-UV. The equivalent widths of the Balm…
The interpretation of the UV light of elliptical galaxies.
Kjaergaard, P.
The UV spectra of the dwarf elliptical M 32 and the two Virgo giant ellipticals NGC 4472 and NGC 4649 are discussed using the spectrum synthesis technique in the whole wavelength region from 1500 A to 2.3 microns. For M 32, the UV spectrum may be explained in terms of evolved blue stars from a minor metal-poor component together with a small contr…
The final COS-B database - In-flight calibration of sensitivity and instrumental background behaviour
Strong, A. W.; Hermsen, W.; Lebrun, F. +3 more
This is one in a series of papers prepared in association with the release of the final COS-B database. Various aspects of the performance of the COS-B gamma-ray telescope are studied using in-flight data. First, the time-variation of the sensitivity and background over the 6.7 years of the mission is investigated. COS-B observed many regions of t…
The diffusion of gallium in main-sequence peculiar stars.
Artru, M. -C.; Alecian, G.
New observations of the gallium abundance in main-sequence peculiar stars are now available in the literature. The present paper analyses these new data in the framework of the diffusion processes. The radiative accelerations of gallium are computed, with up-to-date gallium line data, in various physical conditions of stable main-sequence star atm…