Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Electronic Refereed Journal Article (HTML)
· Full Refereed Journal Article (PDF/Postscript)
· arXiv e-print (arXiv:0910.4099)
· References in the article
· SIMBAD Objects (5)
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
Discovery of Photon Index Saturation in the Black Hole Binary GRS 1915+105
Authors:
Titarchuk, Lev; Seifina, Elena
Affiliation:
AA(Dipartimento di Fisica, Università di Ferrara, Via Saragat 1, I-44100 Ferrara, Italy ; ICRANET Piazzale d. Repubblica 10-12 65122 Pescara, Italy ; George Mason University Fairfax, VA 22030, USA ; US Naval Research Laboratory, Code 7655, Washington, DC 20375, USA ; Goddard Space Flight Center, NASA, Code 663, Greenbelt MD 20771, USA ; ), AB(Moscow State University/Sternberg Astronomical Institute, Universitetsky Prospect 13, Moscow, 119992, Russia )
Publication:
The Astrophysical Journal, Volume 706, Issue 2, pp. 1463-1483 (2009). (ApJ Homepage)
Publication Date:
12/2009
Origin:
IOP
ApJ Keywords:
accretion, accretion disks, black hole physics, radiation mechanisms: non-thermal, stars: individual: GRS 1915+105
DOI:
10.1088/0004-637X/706/2/1463
Bibliographic Code:
2009ApJ...706.1463T

Abstract

We present a study of the correlations between spectral, timing properties, and mass accretion rate observed in X-rays from the Galactic black hole (BH) binary GRS 1915+105 during the transition between hard and soft states. We analyze all transition episodes from this source observed with the Rossi X-ray Timing Explorer, coordinated with Ryle Radio Telescope observations. We show that broadband energy spectra of GRS 1915+105 during all these spectral states can be adequately presented by two bulk motion Comptonization (BMC) components: a hard component (BMC1, photon index Γ1 = 1.7-3.0) with turnover at high energies and soft thermal component (BMC2, Γ2 = 2.7-4.2) with characteristic color temperature <=1 keV, and the redskewed iron-line (LAOR) component. We also present observable correlations between the index and the normalization of the disk "seed" component. The use of "seed" disk normalization, which is presumably proportional to mass accretion rate in the disk, is crucial to establish the index saturation effect during the transition to the soft state. We discovered the photon index saturation of the soft and hard spectral components at values of lsim4.2 and 3, respectively. We present a physical model which explains the index-seed photon normalization correlations. We argue that the index saturation effect of the hard component (BMC1) is due to the soft photon Comptonization in the converging inflow close to the BH and that of soft component is due to matter accumulation in the transition layer when mass accretion rate increases. Furthermore, we demonstrate a strong correlation between equivalent width of the iron line and radio flux in GRS 1915+105. In addition to our spectral model components we also find a strong feature of "blackbody (BB)-like" bump whose color temperature is about 4.5 keV in eight observations of the intermediate and soft states. We discuss a possible origin of this "BB-like" emission.
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)
   

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints