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An X-Ray and Optical Study of the Supernova Remnant W44
Rho, Jeonghee; Hester, J. Jeff; Schlegel, Eric M. +1 more
We report the results of a 8000 s observation of the supernova remnant W44 using the ROSAT Position Sensitive Proportional Counter (PSPC). The image shows the same centrally peaked morphology observed by the Einstein IPC and contrasts with the shell-like radio morphology. The eastern limb shows a lack of X-ray emission within the radio shell, prob…
The Discovery of 8.7 Second Pulsations from the Ultrasoft X-Ray Source 4U 0142+61
Mereghetti, S.; Stella, L.; Israel, G. L.
We discovered a periodicity at about 8.7s from the X--ray sources 4U0142+61, previously considered a possible black hole candidate on the basis of its ultrasoft spectrum. The pulsations are visible only in the 1--4 keV energy range, during an observation obtained with the EXOSAT satellite in August 1984. A search for delays in the pulse arrival ti…
The X-Ray Spectra of Blazars Observed with EXOSAT
Giommi, Paolo; Barr, Paul; Sambruna, Rita M. +3 more
A systematic analysis of the X-ray spectra (0.1-10 keV) of all blazars observed with EXOSAT is presented. The objects include 16 X-ray-selected BL Lac objects (XBLs), five radio-selected BL Lac objects (RBLs), and five highly polarized quasars (HPQs). Comparing the results of single-power-law fits for the different classes, we find that XBLs have …
Elemental Abundances of the Supernova Remnant G292.0+1.8: Evidence for a Massive Progenitor
Singh, K. P.; Hughes, John P.
We present a comprehensive nonequilibrium ionization (NEI) analysis of X-ray spectral data from the Einstein Observatory and EXOSAT for the supernova remnant G292.0+1.8. The spectra are well described by a single-temperature, single-timescale NEI model with kT = 1.64-0.19+0.29 keV and net = (5.55-1.12
X-Ray Emission from a Simulated Cluster of Galaxies
Katz, Neal; Tsai, John C.; Bertschinger, Edmund
Using the 1993 cluster simulation of Katz & White, we analyze the intracluster medium and investigate the accuracy of the standard hydrostatic method for determining cluster masses. We show that the simulated cluster gas is in hydrostatic equilibrium with a subsonic flow toward the center. Inside a radius of ∼100 kpc, this flow is in a steady …
Weak Soft X-Ray Excesses Need Not Result from the High-Frequency Tail of the Optical/Ultraviolet Bump in Active Galactic Nuclei
Czerny, Bozena; Zycki, Piotr T.
The broad-band ROSAT/EXOSAT X-ray spectra of six Seyfert 1 galaxies are fitted by a model consisting of a direct power law and a component due to reflection/reprocessing from a partially ionized, optically thick medium. The reflected spectrum contains emission features from various elements in the soft X-ray range. In all objects but one (Mrk 335)…
The X-Ray Selected Cataclysmic Variables H0459+246 and H0857-242
Buckley, D. A. H.; Schwartz, D. A.; Tuohy, I. R. +5 more
We report the discovery of two cataclysmic variables located with the assistance of X-ray positions from the HEAO 1 Modulation Collimator and the Large-Area Sky Survey. Each case is distinguished by evidence of two periodic modulations that appear to represent the orbital period and the spin period of the white dwarf, respectively. The first case,…
X-Ray Continuum and Iron K Emission Line from the Radio Galaxy 3C 390.3
Elvis, M.; Fabbiano, G.; Hayashida, K. +8 more
X-ray properties of the radio galaxy 3C 390.3 were investigated using the EXOSAT and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model w…
X-Ray Spectral Study of Two X-Ray Binaries: 4U 1957+11 and 2S 1543-624
Kraft, Ralph P.; Apparao, Krishna M. V.; Singh, Kulinder P.
The X-ray observations of two binary systems, 4U 1957+11 and 2S 1543-624, by the High Eccentric Lunar Occultation Satellite (EXOSAT) satellite are analyzed. The continuum spectra are best fitted by a superposition of a blackbody spectrum (kT approximately = 1 keV) and emission from a Comptonized region, consistent with the spectra of low-mass X-ra…
Disk-Overflow Accretion in GK Persei?
Hellier, Coel; Livio, Mario
We reanalyze the 1983 European X-ray Observatory Satellite (EXOSAT) observations of GK Per during an outburst to investigate the approximately 5000 s quasiperiodic modulation. We find that the spectral behavior is reminiscent of dipping low-mass X-ray binaries and note that the time scale is characteristic of the radius where an accretion stream o…