Résumé du preprint DAPNIA-02-109

Accretion ejection instability and QPO in the black hole binaries : 2.Relativistic effects
P. Varniere, J. Rodriguez, M. Tagger
The Accretion-Ejection Instability has been proposed to explain the
 low frequency Quasi-Periodic Oscillation (QPO) observed in
 low-mass X-Ray binaries, in particular Black-Hole candidates. Its
 frequency, typically a fraction of the Keplerian frequency at the disk
 inner radius, is exactly in the range indicated by observations. The
 variations of the frequency with the disk inner radius (extracted
 from spectral fits of the X-ray emission) might thus be a useful
 test. In this paper we discuss how changes in the rotation curve,
 due to relativistic effects when the disk approaches the central
 object, affect the physics of the instability, and thus this
 frequency-inner radius relation. We find that the relationship
 between the frequency of the mode and the Keplerian frequency at
 the inner disk radius (r_int) departs from the one obtained in a
Keplerian disk, when r_int approaches the last stable orbit. This
 might agree with the recently published results, showing a
 discrepancy between the behavior of the QPO in the micro quasar
 GRO J1655-40, compared to other sources such as XTE
 J1550-564 and GRS 1915+105. In a companion paper (Rodriguez
 et al. 2002, hereafter Paper I) we have presented detailed
 observational results for GRO J1655-40 and GRS 1915+105. We
 show how the opposite correlations found in these sources
 between the disk color radius (assumed to be close to its inner
 radius) and the QPO frequency could indeed be explained by our
 theoretical result. 


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