Different Types of X-ray Variability Observed in Micro-Quasar 
                   GRS 1915+105 with the IXAE

P.C.Agrawal,S.Naik,B.Paul,A.R.Rao and J.S.Yadav

Tata Institute of Fundamental Research,
     Homi Bhabha Road, Colaba, Mumbai - 400 005 , India


   The galactic micro-quasar source GRS 1915+105 has been observed with
the Indian X-ray Astronomy Experiment ( IXAE ) several times over a period
extending from 1996 to 2000. This source  has been observed in different  
luminosity states and exhibits a rich variety of random and regular x-ray
variability over a wide time scale. The micro-quasar also shows a unique
variability characteristic namely the occurence of quasi-regular x-ray
bursts with period ranging from 20 s to about 100 s which have slow rise
and fast decay. The x-ray spectrum of these bursts is hardest near the end
of decay. In the low-hard state and bright-soft state with rapid
variability , the source exhibits quasi-periodic oscillations (QPOs) with
variable frequency which is luminosity dependent. Regular x-ray intensity
dips have been detected following the occurence of a giant radio
outburst. The source made a transition from a low state to bright state in
1999 and from a soft-bright state to a hard-low state in 2000 in less than
100 minutes during the IXAE observations. Details of this and other
variability characteristics of the source will be presented in this paper.