External Compton emission from relativistic jets in Galactic black hole candidates and ultraluminous X-ray sources

Galactic binary systems that contain a black hole candidate show evidence of radio jets in their hard X-ray states. Unavoidably, photons from the companion star and/or the accretion disk are Compton-scattered by relativistic electrons in the jet, producing beamed X-rays and possibly gamma-rays. The importance of this process depends on the jet power and the Doppler boosting factor. For plausible values of these parameters, we show that the jet emission can contribute significantly to the hard state X-ray luminosity. Two sources - XTE J1118+480 and Cygnus X-1 - are modelled as representatives of black holes with low and high luminosity companion stars respectively. In XTE J1118+480, weak reflection features indicate that the jet emission is comparable to coronal emission. In Cygnus X-1, strong reflection features indicate coronal emission in the X-ray band, but the jet emission may emerge in the gamma-ray band. The absence of reflection features in the spectra of the ultraluminous compact X-ray sources in nearby galaxies suggests that they are dominated by jet emission. We show that a viable model for these sources is a stellar mass black hole with a high luminosity companion and a favourably oriented jet.

[1]  Harvard-Smithsonian Center for Astrophysics,et al.  Discovery of a Luminous, Variable, Off-Center Source in the Nucleus of M82 with the Chandra High-Resolution Camera , 2000, astro-ph/0009250.

[2]  J. Kotoku,et al.  A Possible X-Ray Periodicity at Several Tens of Hours of an Ultraluminous Compact X-Ray Source in IC 342 , 2001, astro-ph/0109385.

[3]  Sera Markoff,et al.  Population X: Are the super-Eddington X-ray sources beamed jets in microblazars or intermediate mass black holes? , 2002 .

[4]  Martí,et al.  Discovery of a high-energy gamma-ray-emitting persistent microquasar , 2000, Science.

[5]  Yasushi Fukazawa,et al.  Discovery of Spectral Transitions from Two Ultraluminous Compact X-Ray Sources in IC 342 , 2000, astro-ph/0011232.

[6]  C. Done,et al.  Probing the Inner Region of Cygnus X-1 in the Low/Hard State through Its X-Ray Broadband Spectrum , 2000, astro-ph/0010062.

[7]  M. B. Davies,et al.  Ultraluminous X-Ray Sources in External Galaxies , 2001 .

[8]  J. E. Pringle,et al.  Theory of black hole accretion disks , 1999 .

[9]  P. T. O'Brien,et al.  The identification of an optical counterpart to the super-Eddington X-ray source, NGC 5204 X-1 , 2001 .

[10]  R. Blandford,et al.  On the jets associated with galactic superluminal sources , 1995, astro-ph/9506137.

[11]  C. Dermer.  On the Beaming Statistics of Gamma-Ray Sources , 1995 .

[12]  Radiative Processes and Geometry of Spectral States of Black-Hole Binaries , 2000, astro-ph/0001078.

[13]  Ping Zhao,et al.  A Black Hole Greater Than 6 M☉ in the X-Ray Nova XTE J1118+480* , 2001 .

[14]  Felix Aharonian,et al.  Modelling of the non-thermal flares in the Galactic microquasar GRS 1915+105 , 1999 .

[15]  R. P. Fender,et al.  Giant repeated ejections from GRS 1915+105 , 2000 .

[16]  V. La Parola,et al.  The Ultraluminous M81 X-9 Source: 20 Years’ Variability and Spectral States , 2001, astro-ph/0103250.

[17]  M. McConnell,et al.  A High-Sensitivity Measurement of the MeV Gamma-Ray Spectrum of Cygnus X-1 , 2000, astro-ph/0001484.

[18]  K. Johnston,et al.  Radio emission from conical jets associated with X-ray binaries , 1988 .

[19]  A. Zezas,et al.  Chandra Observations of “The Antennae” Galaxies (NGC 4038/9) , 2001 .

[20]  Aya Kubota,et al.  The Nature of Ultraluminous Compact X-Ray Sources in Nearby Spiral Galaxies , 2000, astro-ph/0001009.

[21]  Sera Markoff,et al.  A jet model for the broadband spectrum of XTE J1118+480. Synchrotron emission from radio to X-rays in the , 2000, astro-ph/0010560.

[22]  A. Stirling,et al.  A relativistic jet from Cygnus X-1 in the low/hard X-ray state , 2001, astro-ph/0107192.

[23]  G. Fabbiano.  Chandra Observations of The Antennae Galaxies (NGC 4038/39) , 2001 .

[24]  A. Mastichiadis,et al.  The Beaming Pattern and Spectrum of Radiation from Inverse Compton Scattering in Blazars , 2001 .

[25]  R. Sunyaev,et al.  Near-infrared jets in the Galactic microquasar GRS1915+105 , 1996, Nature.

[26]  C. A. Haswell,et al.  Complete and Simultaneous Spectral Observations of the Black Hole X-Ray Nova XTE J1118+480 , 2001, astro-ph/0103051.

[27]  R. Fender.  Powerful jets from black hole X-ray binaries in low/hard X-ray states , 2000, astro-ph/0008447.

[28]  J. Grindlay,et al.  Synchrotron and inverse Compton emission from expanding sources in jets - Application to SS 433 , 1986 .