HEAD 2003 Meeting
Session 11. Black Holes Binaries III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[11.07] X-ray spectra and quasi-periodic oscillations observed in the low hard states of the microquasar GRS 1915+105

R. B. Fiorito (Catholic University of America), C. B. Markwardt (University of Maryland, NASA-GSFC), J. H. Swank (NASA-GSFC)

Low frequency (1 - 10 Hz) quasi-periodic oscillations (QPO's) have been observed from the black hole candidate GRS 1915+105 by the Rossi X-ray Timing Explorer in 1996 and 1997 when this source was in a low luminosity hard state. The frequency of the QPO's is generally observed to increase with the total x-ray intensity but the relationship is not unique. We have performed a spectral and temporal analysis of a representative number of 1996 and 1997 PCA and HEXTE observations. We find that the time averaged x-ray spectral flux for 1997 can be fit with a power law and a small (less than 20 % of the total flux) disk black body component. For 1996 the thermal flux component is weaker, i.e. less than 10 % of the total. A correlation between QPO frequency and power law flux and index is observed for each data set. However, a correlation between thermal flux and the QPO frequency is observed only for the 1997 data. No correlation between disk temperature and frequency is observed for either data set.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.