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Astron. Astrophys. 320, L37-L40 (1997)

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Letter to the Editor

Rapid X-ray variability of the superluminal source GRS1915+105

B. Paul 1, P.C. Agrawal 1, A.R. Rao 1, M.N. Vahia 1, J.S. Yadav 1, T.M.K. Marar 2, S. Seetha 2 and K. Kasturirangan 2

1 Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India
2 ISRO Satellite Centre, Airport Road, Vimanpura P.O. Bangalore 560 017, India.

Received 17 January 1997 / Accepted 7 February 1997


The superluminal X-ray transient source GRS 1915+105 was observed during July 20-29, 1996 with the Indian X-ray Astronomy Experiment (IXAE) on the Indian satellite IRS-P3 launched on March 21, 1996 from Shriharikota Range in India. During our observations covering the energy band 2-18 keV, we have seen strong erratic intensity variations on time scale of 0.1s - 10s. Quasi Periodic Oscillations (QPOs) in a frequency range of 0.62 to 0.82 Hz were detected with a rms fraction of about [FORMULA]. The rapid X-ray intensity variations in GRS1915+105 are similar to those observed in some other black hole binaries and thus provide further support for the hypothesis that this source is likely to be a black hole. We discuss the possible emission region and mechanism of the observed quasi-periodic oscillations. Comparing the observed QPOs with the ones observed in other neutron star and black-hole systems, we argue that GRS1915+105 is possibly a black-hole.

Key words: accretion, accretion disks - black hole physics - X-rays: stars - stars: individual - GRS 1915+105

Send offprint requests to: B. Paul, bpaul@tifrvax.tifr.res.in

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998