Search Publications
The X-Ray Spectral Properties of Accretion Disks in X-Ray Binaries
Stella, L.; Parmar, A. N.; White, N. E.
Using EXOSAT observations, the spectral properties of the persistent emission from a number of X-ray burst sources, high-luminosity low-mass X-ray binaries (LMXRB), and galactic black hole candidates are compared with various models for X-ray emission from an accretion disk surrounding a compact object in a binary system. These models include the …
Measurements of the Gas Temperature and Iron Abundance Distribution in the Coma Cluster
Hughes, John P.; Gorenstein, P.; Fabricant, D.
The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. We find evidence at greater than 95% confidence for a higher temperature in the center of the cluster than in a position approximately 45' off-center. No difference in iron abundance…
4U 1626-67: The Binary with the Smallest Known Mass Function
van der Klis, M.; Verbunt, F.; Rappaport, S. +3 more
The pulsating X-ray source 4U 1626-67 is an accreting neutron star in a binary system with a very low mass companion. The authors observed the source with EXOSAT continuously for 23 hr on 1986 March 30 - 31 UT. These observations allow them to set a stringent upper limit on the projected semimajor axis of the orbit of the neutron star. The corresp…
Hard X-Ray Emission from a Type 2 Seyfert Galaxy (NGC 1068)
Elvis, Martin; Lawrence, A.
EXOSAT observations of the type 2 Seyfert galaxy NGC 1068 have detected a source in the 2-10 keV range with a flux density at 2 keV of 0.6 microJy. It has a flat (α_E_ = 0.62 +/- 0.25) power-law spectrum similar to type 1 Seyferts; Combined with Low Energy EXOSAT filter data and Einstein IPC observations, these data show that spectral curvature is…
EXOSAT Observations of the Cassiopeia A Supernova Remnant
White, N. E.; Jansen, F.; Smith, A. +3 more
The young supernova remnant Cas A has been observed with the European X-ray observatory satellite Exosat. The remnant was observed with all instruments covering the range from 0.5 to 25 KeV. It is shown here that the emission from the remnant cannot be described by a two-temperature isothermal plasma in collisional ionization equilibrium. A simple…
Contemporaneous X-Ray and VLBI Radio Observations of the Quasar NRAO 140
Marscher, Alan P.
The quasar NRAO 140 was observed at various times between 1978 and 1985 at X-ray energies using HEAO I, the Einstein Observatory, and EXOSAT. The author also observed this source a number of times with multifrequency VLBI between 1980 and 1984. In this paper, the author combines new observations with those previously published to present a time hi…
EXOSAT Observations of the Supernova Remnant G109.1-1.0 and the X-Ray Pulsar 1E 2259+586
van der Klis, M.; Robba, N. R.; Smith, A. +1 more
The authors report on the EXOSAT observation of the supernova remnant (SNR) G109.1-1.0+1E 2259+586 system. The spatial distribution of the X-ray emission as derived from the low-energy (<2 keV) data is very similar to that obtained from the Einstein Observatory. The various components of the source (SNR shell, pulsar, and jet) have different sp…
Quasi-periodic Oscillations in the X-Ray Flux of the Rapid Burster (MXB 1730-335)
Haberl, F.; Stella, L.; Parmar, A. N. +3 more
The authors report on the results of an EXOSAT observation of the "Rapid Burster" in 1985 August during an active state. Forty 1 - 10 minute long type 2 bursts were detected together with persistent emission. Quasi-periodic oscillations (QPO) were observed in 23 bursts with frequencies between 2 and 5 Hz. The average frequency of the QPO during th…
The Discovery of the 2 Hour Modulated X-Ray Source EXO 033319-2554.2, an AM Herculis System
Tagliaferri, G.; Stella, L.; Giommi, P. +2 more
The authors report the discovery of EXO 033319-2554.2, a soft X-ray source with 100% modulation of its soft X-ray flux, found during a systematic analysis of all of the EXOSAT soft X-ray data. The soft X-ray light curve, which has an on-off behavior, shows a period of 127.7±3.0 minutes. The bright part of the cycle lasts 0.55 in phase and is cut b…
X-Ray Spectrum and Variability of the Black Hole Candidate LMC X-3
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +4 more
LMC X-3 was observed on seven occasions in 1983-1984 with the EXOSAT satellite covering various orbital phases. No phase related variability was detected, while the X-ray flux increased gradually by ~ 30% in two weeks. Analysis of the short term variability in terms of autocorrelation reveals a minimum time scale of 600 s, with an rms amplitude of…