EDP Sciences
Free Access
Volume 372, Number 3, June IV 2001
Page(s) 793 - 802
Section Cosmology (including clusters of galaxies)
DOI https://doi.org/10.1051/0004-6361:20010574
Published online 15 June 2001

A&A 372, 793-802 (2001)
DOI: 10.1051/0004-6361:20010574

Spectral differences between the radio-loud and radio-quiet low-hard states of GRS 1915+105: Possible detection of synchrotron radiation in X-rays

S. V. Vadawale1, A. R. Rao1 and S. K. Chakrabarti2

1  Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India
2  S.N. Bose National Center for Basic Sciences, Salt Lake, Calcutta 700 091, India

(Received 22 December 2000 / Accepted 28 March 2001 )

The Galactic microquasar GRS 1915+105 exhibits several episodes of steady X-ray emission characterized by a hard power-law spectrum and intense Quasi Periodic Oscillations. It is known that there are two types of such low-hard states, one with steady radio emission and the other without any significant radio emission. We present the results of a detailed X-ray spectroscopic study of GRS 1915+105, using data from the Rossi X-ray Timing Explorer obtained during various episodes of the low-hard states of the source. We show that there are distinct X-ray spectral differences between the radio-quiet and radio-loud low-hard states of the source. The X-ray spectra of the radio-quiet low-hard state is best described by a model consisting of a multicolor disk-blackbody and a Comptonized component, whereas the X-ray spectra of radio-loud low-hard state requires a model consisting of three components: a multicolor disk-blackbody, a Comptonized component and a power-law, for statistically and physically acceptable fits. We attempt to model the presence of this additional power-law component as due to synchrotron radiation which is responsible for the radio and infrared radiation from the source. We show that a simple adiabatically expanding jet model for the synchrotron radiation can account for the observed X-ray flux for reasonable values of the magnetic field and the mass outflow rate. This is the first report of detection of the synchrotron radiation in the X-ray band for this source.

Key words: accretion, accretion disks -- black hole physics -- stars: winds, outflows -- stars: individual: GRS1915+105 -- X-rays: stars

Offprint request: S. V. Vadawale, santoshv@tifr.res.in

SIMBAD Objects

© ESO 2001

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.