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Title: SWIFT J1910.2-0546: A possible black hole binary with a retrograde spin or truncated disk

We present the first results from a long (51 ks) XMM-Newton observation of the Galactic X-ray binary SWIFT J1910.2-0546 in an intermediate state, obtained during its 2012 outburst. A clear, asymmetric iron emission line is observed and physically motivated models are used to fully describe the emission-line profile. Unlike other sources in their intermediate spectral states, the inner accretion disk in SWIFT J1910.2-0546 appears to be truncated, with an inner radius of r {sub in} =9.4{sub −1.3}{sup +1.7} r {sub g} at a 90% confidence limit. Quasi-periodic oscillations are also found at approximately 4.5 and 6 Hz, which correlates well with the break frequency of the underlying broad-band noise. Assuming that the line emission traces the innermost stable circular orbit, as would generally be expected for an intermediate state, the current observation of SWIFT J1910.2-0546 may offer the best evidence for a possible retrograde stellar mass black hole with a spin parameter a < – 0.32cJ/GM{sup 2} (90% confidence). Although this is an intriguing possibility, there are also a number of alternative scenarios which do not require a retrograde spin. For example, the inner accretion disk may be truncated at an unusually high luminosity in this case, potentially suffering frequentmore » evaporation/condensation, or it could instead be persistently evacuated through mass loss in a relativistic jet. Further observations are required to distinguish between these different interpretations.« less
Authors:
; ; ; ; ;  [1] ;  [2]
  1. Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48109 (United States)
  2. Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22341886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; APPROXIMATIONS; ASYMMETRY; BLACK HOLES; EMISSION; EVAPORATION; INTERMEDIATE STATE; IRON; LUMINOSITY; MASS TRANSFER; ORBITS; OSCILLATIONS; PERIODICITY; RELATIVISTIC RANGE; SPIN; STELLAR WINDS; X RADIATION