T. Mineo, E. Massaro, A. D'Ai, F. Massa, M. Feroci, G. Ventura, P. Casella, C. Ferrigno, T. Belloni
BeppoSAX observed GRS 1915+105 on October 2000 with a long pointing lasting
about ten days. During this observation the source was mainly in the rho class
characterized by busts with recurrence time between 40 and 100 s. We identified
five segments in the burst structure and accumulated the average spectra of
these segments during each satellite orbit. We present a detailed spectral
analysis aimed at determining variations along the burst and understanding the
physical process that produces them. MECS, HPGSPC and PDS spectra have been
compared with several models, and under the assumption that a single model is
able to fit all spectra, we find that the combination of a multi-temperature
blackbody disk plus an hybrid corona is able to give a consistent physical
explanation of the source behavior. The variations of KT_el, tau, KT_in and
R_in exhibit properties either of correlation or anti-correlation with the
count rate in the range 1.6-10 keV. The strongest variations are detected along
the burst segments: almost all parameters exhibit significant variations in the
segments with the highest fluxes (Pulse) with the exception of R_in that varies
continuously and reaches the maximum just before the peak.The flux of the
multi-temperature disk strongly increases in the Pulse and simultaneously the
corona contribution is significantly reduced. The disk luminosity increases in
the Pulse and the R_in-T_in correlation can be better interpreted with the slim
disk model and the reduction of the the corona luminosity at the bursts could
indicate its condensation on the disk.
View original:
http://arxiv.org/abs/1110.5199
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