The Accretion-Ejection Instability: Observational Tests

QPOs are commonly considered to originate in the disks of X-ray binaries. One thus expects, and most often observes, that the QPO frequency decreases as the disk inner radius increases. However Sobczak et al. (1999) pointed out an opposite behavior in the case of GRO J1655-40. This might prove usefull in testing the theory of the Accretion-Ejection Instability (see contributions by Caunt, Tagger and Varniere, these proceedings). At the same time, Merloni, Fabian, and Ross (1999) showed that, when fitting the sources spectra with the standard model (multicolor blackbody+ power law), severe distorsions could be due to the vertical structure of the disk. In that view we re-did the spectral analysis of the observations in which Sobczak et al. found QPO’s.