IMPLICATION OF THE OBSERVED SPECTRAL CUTOFF ENERGY EVOLUTION IN XTE J1550-564

Journal Article · Wed Dec 01 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/724/2/1147· OSTI ID:21474486

Titarchuk, Lev ^[1]; Shaposhnikov, Nikolai ^[2]

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1. University of Ferrara, Physics Department, Via Saragat 1, 44100 Ferrara (Italy)
2. Goddard Space Flight Center, NASA, Astrophysics Science Division, Greenbelt, MD 20771 (United States)

The physical mechanisms responsible for the production of non-thermal emission in accreting black holes (BHs) should be imprinted in the observational appearances of the power-law tails in the X-ray spectra from these objects. Phenomenology of different spectral states exhibited by galactic BH binaries allows us to establish the physics of the photon upscattering under different accretion regimes. We revisit the data collected by the Rossi X-ray Timing Explorer from the BH X-ray binary XTE J1550-564 during two periods of X-ray activity in 1998 and 2000 focusing on the behavior of the high-energy cutoff of the power-law part of the spectrum. For the 1998 outburst, the transition from the low-hard state to the intermediate state was accompanied by a gradual decrease in the cutoff energy. This was followed by an extended minimum which then showed an abrupt reversal to a clear increasing trend as the source evolved to the very high and high-soft states. The 2000 outburst showed only the decreasing and extended minimum portions of this pattern. We attribute this difference in the cutoff energy behavior to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization. Namely, during the 1998 event the higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions, the bulk motion takes a leading role in boosting the input soft photons. Recent Monte Carlo simulations by Laurent and Titarchuk strongly support this scenario.

• OSTI ID: 21474486
• Journal Information: Astrophysical Journal, Vol. 724, Issue 2; Other Information: DOI: 10.1088/0004-637X/724/2/1147; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BLACK HOLES
COMPUTERIZED SIMULATION
MONTE CARLO METHOD
PHOTONS
STAR EVOLUTION
STARS
X RADIATION
X-RAY SPECTRA
BOSONS
CALCULATION METHODS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EVOLUTION
IONIZING RADIATIONS
MASSLESS PARTICLES
RADIATIONS
SIMULATION
SPECTRA