Observations of the quiescent x-ray transients GRS 1124-684 (=GU Mus) and Cen x-4 (=V822 Cen) taken with ULTRACAM on the VLT
Shahbaz, T., Dhillon, V. S., Marsh, T. R., Casares, J., Zurita, C. and Charles, P. A.. (2010) Observations of the quiescent x-ray transients GRS 1124-684 (=GU Mus) and Cen x-4 (=V822 Cen) taken with ULTRACAM on the VLT. Monthly Notices of the Royal Astronomical Society, Vol.403 (No.4). pp. 2167-2175. ISSN 0035-8711Full text not available from this repository.
Official URL: http://dx.doi.org/10.1111/j.1365-2966.2010.16262.x
We present high time-resolution multicolour optical observations of the quiescent X-ray transients GRS 1124-684 (=GU Mus) and Cen X-4 (=V822 Cen) obtained with ULTRACAM. Superimposed on the secondary stars' ellipsoidal modulation in both objects are large flares on time-scales of 30-60 min as well as several distinct rapid flares on time-scales of a few minutes, most of which show further variability and unresolved structure. Not significant quasi-periodic oscillations are observed and the power density spectra of GRS 1124-684 and Cen X-4 can be described by a power law. From the colour-colour diagrams of the flare events, for GRS 1124-684 we find that the flares can be described by hydrogen gas with a density of N-H similar to 1024 nucleons cm(-2), a temperature of similar to 8000 K and arising from a radius of similar to 0.3 R-circle dot. Finally we compile the values for the transition radius (the radius of the hot advection-dominated accretion flow) estimated from quasi-periodic oscillations and/or breaks in the power density spectrum for a variety of X-ray transients in different X-ray states. As expected, we find a strong correlation between the bolometric luminosity and the transition radius.
|Item Type:||Journal Article|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Science > Physics|
|Journal or Publication Title:||Monthly Notices of the Royal Astronomical Society|
|Official Date:||21 April 2010|
|Number of Pages:||9|
|Page Range:||pp. 2167-2175|
|Access rights to Published version:||Restricted or Subscription Access|
|Funder:||Spanish Ministry of Science and Technology, Spanish MEC, STFC|
|Grant number:||AYA2007-66887, CSD2006-00070, PP/D002370/1|
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