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Title: X-ray variability of GRS 1915+105 during the low-hard state observed with the Indian X-ray astronomy experiment (IXAE)
Authors: Paul, Biswajit
Agrawal, P.C.
Rao, A.R.
Vahia, M.N.
Yadav, J.S.
Marar, T.M.K.
Seetha, S.
Kasturirangan, K.
Keywords: Accretion Disks
Black Hole Physics
X-Rays: Stars
Grs 1915+105
Issue Date: Feb-1998
Publisher: EDP Sciences
Citation: Astronomy and Astrophysics Supplement Series, 1998, Vol. 128, p145-151
Abstract: The galactic superluminal transient X-ray source GRS 1915+105 was observed with the pointed proportional counters (PPCs) onboard the Indian satellite IRS-P3 during 1996 July 23-27. We report here details of the behavior of this source during the relatively quiet and low luminosity state. Large intensity variations by a factor of 2 to 3, generally seen in black-hole candidates, are observed at a time scale of 100 ms to few seconds. No significant variation is detected over larger time scale of minute or more. The intensity variations are described as sum of shots in the light curve, and the number distribution of the shots are found to be exponential function of the fluence and duration of the shots. The cross correlation spectrum between 6-18 keV and 2-6 keV X-rays is found to have asymmetry signifying a delay of the hard X-rays by about 0.2 to 0.4 s. This supports the idea of hard X-rays being generated by Compton up-scattering from high energy clouds near the source of soft X-rays. Very strong and narrow quasi periodic oscillations in the frequency range 0.62 to 0.82 Hz are observed. We discuss about a model which explains a gradual change in the QPO frequencies with corresponding changes in the mass accretion rate of the disk.
Description: Open Access
ISSN: 0365-0138
Alternative Location:
Copyright: 1998 EDP Sciences
Appears in Collections:Research Papers (A&A)

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