2006ApJ...640..459G -
Astrophys. J., 640, 459-465 (2006/March-3)
On the nature of the ultraluminous X-ray transient in Cen A (NGC 5128).
GHOSH K.K., FINGER M.H., SWARTZ D.A., TENNANT A.F. and WU K.
Abstract (from CDS):
We combine nine ROSAT, nine Chandra, and two XMM-Newton observations of the Cen A galaxy to obtain the X-ray light curve of 1RXH J132519.8-430312 (=CXOU J132519.9-430317) spanning 1990-2003. The source reached a peak 0.1-2.4 keV flux FX>10–12 ergs/cm2/s during a 10 day span in 1995 July. The inferred peak isotropic luminosity of the source therefore exceeded 3x1039 ergs/s, which places the source in the class of ultraluminous X-ray sources. Coherent pulsations at 13.264 Hz are detected during a second bright episode (FX>3x10–13 ergs/cm2/s) in 1999 December. The source is detected and varies significantly within three additional observations but is below the detection threshold in seven observations. The X-ray spectrum in 1999 December is best described as a cutoff power law or a disk blackbody (multicolored disk). We also detect an optical source, mF555W∼24.1 mag, within the Chandra error circle of 1RXH J132519.8-430312 in Hubble Space Telescope images taken 195 days before the nearest X-ray observation. The optical brightness of this source is consistent with a late O or early B star at the distance of Cen A. If the optical source is the counterpart, then the X-ray and optical behavior of 1RXH J132519.8-430312 is similar to the transient Be/X-ray pulsar A0538-66.
Abstract Copyright:
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Journal keyword(s):
galaxies: individual (Cen A) - X-Rays: Binaries - X-rays: individual (1RXH J132519.8-430312)
Simbad objects:
9
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