ULTRACAM observations of the black hole X-ray transient XTE J1118+480 in quiescence
Abstract
We present high time-resolution multicolour observations of the quiescent soft X-ray transient XTE J1118+480 obtained with ULTRACAM. Superimposed on the double-humped continuum g'- and i'-band light curves are rapid flare events which typically last a few minutes. The power density spectrum of the light curves can be described by a broken power-law model with a break frequency at ~2 mHz or a power-law model plus a broad quasi-periodic oscillation at ~2 mHz. In the context of the cellular automaton we estimate the size of the quiescent advection-dominated accretion flow (ADAF) region to be ~104 Schwarzschild radii, similar to that observed in other quiescent black hole X-ray transients, suggesting the same underlying physics. The similarities between the low/hard and quiescent-state power density spectrum suggest a similar origin for the optical and X-ray variability, most likely from regions at or near the ADAF.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2005
- DOI:
- 10.1111/j.1365-2966.2005.09361.x
- arXiv:
- arXiv:astro-ph/0507511
- Bibcode:
- 2005MNRAS.362..975S
- Keywords:
-
- accretion;
- accretion discs;
- binaries: close;
- stars: individual: XTE J1118+480;
- Astrophysics
- E-Print:
- 9 pages, 6 figures, accepted by MNRAS