Discovery of photon index saturation in the black hole binary GRS 1915+105

Details Discovery of photon index saturation in the black hole binary GRS 1915+105 Discovery of photon index saturation in the black hole binary GRS 1915+105

2009-10-21

arxiv.org/abs/0910.4099v1

Astronomy and Astrophysics

Astrophysics

High Energy Astrophysical Phenomena

33 pages, 16 figures, accepted for publication in ApJ, on December 10, 2009, v. 707

Scientific paper

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 RXTE, coordinated with Ryle Radio Telescope (RT) observations. We show that broad-band 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 Gamma_1=1.7-3.0) with turnover at high energies and soft thermal component (BMC2, Gamma_2=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 4.2 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 BH and that of soft component is due to matter accumulation in the transition layer when mass accretion rate increases. In addition to our spectral model components we also find a strong feature of "blackbody-like" bump which color temperature is about 4.5 keV in eight observations of the intermediate and soft states. We discuss a possible origin of this "blackbody-like" emission.

Affiliated with

Also associated with

No associations

Rating

Discovery of photon index saturation in the black hole binary GRS 1915+105 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Discovery of photon index saturation in the black hole binary GRS 1915+105, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Discovery of photon index saturation in the black hole binary GRS 1915+105 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-144353