A. C. Fabian

TL;DR: In this article, the authors presented an X-ray study of eight black holes in the low-hard state and found that a thermal disc with a colour temperature consistent with L ∝ T 4 is clearly detected in all eight sources, down to ≈5 x 10 −4 L Edd.

TL;DR: In this paper, the authors investigated the stability of the warm absorber to isobaric perturbations under the assumptions of thermal and photoionization equilibrium and showed that there is a remarkably small range of ionization parameters, i.e.,

TL;DR: In this article, the authors present and discuss the X-ray luminosity function (XLF) of the ROSAT Brightest Cluster sample (BCS), an Xray flux limited sample of clusters of galaxies in the northern hemisphere compiled from ROSAT All-Sky Survey data.

Abstract: We observed the Galactic black hole GX 339-4 with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for 75 ksec during the decline of its 2002-2003 outburst. The sensitivity of this observation provides an unprecedented glimpse of a Galactic black hole at about a tenth of the luminosity of the outburst peak. The continuum spectrum is well described by a model consisting of multicolor disk blackbody (kT = 0.6 keV) and power-law (Gamma = 2.5) components. X-ray reflection models yield improved fits. A strong, relativistic Fe K-alpha emission line is revealed, indicating that the inner disk extends to the innermost stable circular orbit. The breadth of the line is sufficient to suggest that GX 339-4 may harbor a black hole with significant angular momentum. Absorption lines from H-like and He-like O, and He-like Ne and Mg are detected, as well as lines which are likely due to Ne II and Ne III. The measured line properties make it difficult to associate the absorption with the coronal phase of the interstellar medium. A scenario wherein the absorption lines are due to an intrinsic AGN-like warm-absorber geometry -- perhaps produced by a disk wind in an extended disk-dominated state -- may be more viable. We compare our results to Chandra observations of the Galactic black hole candidate XTE J1650-500, and discuss our findings in terms of prominent models for Galactic black hole accretion flows and connections to supermassive black holes.

TL;DR: In this article, the authors present and discuss the X-ray luminosity function (XLF) of the ROSAT Brightest Cluster sample (BCS), an Xray flux limited sample of clusters of galaxies in the northern hemisphere compiled from ROSAT All-Sky Survey data.