Search Publications
The EXOSAT High Galactic Latitude Survey
Tagliaferri, G.; Beuermann, K.; Branduardi-Raymont, G. +9 more
A survey of serendipitous sources performed in the very soft X-ray band (0.05-2.0 keV) using the EXOSAT imaging telescopes is presented. The survey covers 783 square degrees of high Galactic latitude sky and includes 210 serendipitous sources which define a complete (flux-limited) sample. An extensive program of optical and radio observations toge…
Accretion Mechanisms in the Be/X-Ray Transient System A0535+26
Stella, L.; Motch, C.; Janot-Pacheco, E. +1 more
We present four EXOSAT observations of the Be/X-ray transient pulsar HDE 245770/A0535+26 obtained at various phases of the 111d period. On all occasions, a faint X-ray flux is detected from the source (Fx = 1.5-3.0 × 10-10 ergs cm-2 s-1) which corresponds to Lx (1-20 keV) = 2.5 × 10…
Shot Model Parameters for Cygnus X-1 through Phase Portrait Fitting
Swank, J. H.; Szymkowiak, A. E.; Lochner, James C.
Shot models for systems having about 1/f power density spectrum are developed by utilizing a distribution of shot durations. Parameters of the distribution are determined by fitting the power spectrum either with analytic forms for the spectrum of a shot model with a given shot profile, or with the spectrum derived from numerical realizations of t…
Coordinated X-Ray, Ultraviolet, and Optical Observations of 3C 120
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +5 more
The results of 14 observations with EXOSAT and 10 quasi-simultaneous observations with IUE of the Seyfert galaxy 3C 120 are reported. On few epochs, quasi-simultaneous optical spectrophotometry was also obtained, allowing us to derive the energy distribution from the optical to the X-ray band in different intensity states. The X-ray spectra are we…
The Orbital Ephemeris and Eclipse Transitions of the Low-Mass X-Ray Binary EXO 0748-676
Parmar, A. N.; Verbunt, F.; Corbet, R. H. D. +1 more
Using the eclipses as fiducial markers, an updated ephemeris for EXO 0748 - 676 is derived and evidence is found that between February 1985 and March 1989 the 3.82-h orbital period of EXO 0748 - 676 decreased with a time scale of -5 x 10 to the 6th yr. The sense of this change is the same as that predicted by simple models for the evolution of low…
The Discovery of an X-Ray Burst and a Study of Aperiodic Variability from SMC X-1
Stella, L.; White, N. E.; Angelini, L.
The aperiodic X-ray variability of the 0.7 s X-ray pulsar SMC X-1 is investigated using five EXOSAT observations made in 1984 October and November. During the first observation an X-ray burst was observed, where the source count rate increased by a factor of ~ 3 in less than ~ 0.7 s, and then erratically decayed to the preburst level over ~ 80 s. …
On the X-Ray--emitting Boundary Layer of the Dwarf Nova VW Hydri
Mauche, Christopher W.; Polidan, Ronald S.; Wade, Richard A. +2 more
The temperature and luminosity of the boundary layer of VW Hyi are constrained to kT(BL) of about 10.5 eV, and L(BL) of about 6 x 10 to the 32nd (d/65 pc)squared ergs/sec. This is based on Voyager far- and extreme-ultraviolet spectrophotometry and a measurement of the column density of neutral hydrogen, combined with Exosat LE filter observations.…
The X-Ray Properties of GX 301-2 (4U 1223-62)
Haberl, F.
The X-ray luminosity of the X-ray binary pulsar GX 301 - 2 exhibits a strong maximum near periastron passage of the neutron star, or phase 0, but with the peak 0.05 in phase before. During the interval between phase 0.9 and 0.25, during periods when the absorption was high, the X-ray spectra indicate a strong low-energy excess that may be modeled …
Persistence and Change in the Soft X-Ray Spectrum of the Quasar PG 1211+143
Elvis, Martin; Wilkes, Belinda J.; Giommi, P. +1 more
Two Einstein and three EXOSAT observations of PG 1211 + 143 over a 6 year baseline show that strong steep-spectrum low-energy X-ray emission is a persistent feature of this quasar. EXOSAT observations of PG 1211 + 143 detected a factor of 2.3 increase in its steep soft X-ray (C-band) flux in 18 days. The bulk of the soft X-ray emission of PG 1211 …
X-Ray Emission from Hybrid-Chromosphere Stars
Brown, Alexander; Drake, Stephen A.; Linsky, Jeffrey L. +1 more
The observations of hybrid stars made by the Exosat X-ray satellite are considered, and emphasis is placed on the hybrid star alpha TrA. Attention is focused on the determination of the column density of IS hydrogen toward the stars in order to interpret X-ray observations of stellar coronal emission. The coronal properties of alpha TrA are discus…