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Title: | Rapid state transitions in the galactic black hole candidate source GRS 1915+105 |
Authors: | Rao, A.R. Yadav, J.S. Paul, Biswajit |
Keywords: | accretion disks stars: binaries black hole physics |
Issue Date: | Nov-2000 |
Publisher: | IOP Publishing Ltd. |
Citation: | Astronomy and Astrophysics, 2000, Vol. 544, p443-452 |
Abstract: | We examine the X-ray spectral and temporal behavior of the Galactic black hole candidate source GRS 1915+105 during its spectral state transition observed in 1997 March-August. The source was making a slow transition from a low hard state to a high soft state in about 3 months, and during this transition it was exhibiting a series of fast variations, which can be classified as bursts. During one type of burst, called the irregular burst, it was found that the source makes rapid transitions between two intensity states. We have analyzed the RXTE PCA data obtained on 1997 June 18 (when the source was making rapid state transitions) and compared the results with two sets of data each pertaining to the low hard state and high soft states. We find that the power density spectrum (PDS) during the burst shows remarkable similarity to that seen during the high soft state of the source. The PDS during the quiescence, on the other hand, is quite flat and is very similar to the PDS commonly seen during the canonical low hard state of black hole X-ray binaries. A low-frequency quasi-periodic oscillation at ~3 Hz is observed during the quiescence, a property seen during the low hard state of the source. The X-ray spectrum of the source during quiescence is similar to the spectrum seen during the low hard state of the source, and the spectra during the burst and high soft state are very similar to each other. These observations corroborate the suggestion made by Yadav and coworkers that during the irregular bursts the source shows spectral state variations at very fast timescales. We explain such fast state changes using the two component accretion flow model in which the accretion disk consists of a geometrically thin (and optically thick) standard disk coexisting with an advection-dominated hot thick disk. |
Description: | Open Access |
URI: | http://hdl.handle.net/2289/4887 |
ISSN: | 0004-637X 1538-4357 (Online) |
Alternative Location: | http://adsabs.harvard.edu/abs/2000ApJ...544..443R http://arxiv.org/abs/astro-ph/0007250 http://dx.doi.org/10.1086/317168 |
Copyright: | 2000 The American Astronomical Society |
Appears in Collections: | Research Papers (A&A) |
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2000_APJ_V544_p443.pdf Restricted Access | Open Access | 570.21 kB | Adobe PDF | View/Open Request a copy |
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