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Characterizing X-Ray and Radio Emission in the Black Hole X-Ray Binary V404 Cygni During QuiescenceWe present results from multi-wavelength simultaneous X-ray and radio observations of the black hole X-ray binary V404 Cyg in quiescence. Our coverage with NuSTAR provides the very first opportunity to study the X-ray spectrum of V404 Cyg at energies above 10 keV. The unabsorbed broadband (0.3-30 keV) quiescent luminosity of the source is 8.9 x 10(exp 32) erg per sec for a distance of 2.4 kpc. The source shows clear variability on short timescales (an hour to a couple of hours) in the radio, soft X-ray, and hard X-ray bands in the form of multiple flares. The broadband X-ray spectra obtained from XMM-Newton and NuSTAR can be characterized with a power-law model having a photon index of gamma = 2.12 +/- 0.07 (90% confidence errors); however, residuals at high energies indicate spectral curvature significant at a 3 sigma confidence level with the e-folding energy of the cutoff as 20(sub -7)(sup +20) keV. Such curvature can be explained using synchrotron emission from the base of a jet outflow. Radio observations using the VLA reveal that the spectral index evolves on very fast timescales (as short as 10 minutes), switching between optically thick and thin synchrotron emission, possibly due to instabilities in the compact jet or stochastic instabilities in the accretion rate. We explore different scenarios to explain this very fast variability.
Document ID
20170003072
Document Type
Reprint (Version printed in journal)
Authors
Rana, Vikram (California Inst. of Tech. Pasadena, CA, United States)
Loh, Alan (Centre National de la Recherche Scientifique Gif-sur-Yvette, France)
Corbel, Stephane (Centre National de la Recherche Scientifique Gif-sur-Yvette, France)
Tomsick, John A. (California Univ. Berkeley, CA, United States)
Chakrabarty, Deepto (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Walton, Dominic J. (California Inst. of Tech. Pasadena, CA, United States)
Barret, Didier (Toulouse Univ. France)
Boggs, Steven E. (California Univ. Berkeley, CA, United States)
Christensen, Finn E. (Technical Univ. of Denmark Lyngby, Denmark)
Craig, William (California Univ. Berkeley, CA, United States)
Stern, Daniel (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Zhang, William W. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
April 6, 2017
Publication Date
April 19, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 821
Issue: 2
ISSN: 2041-8205
Subject Category
Astronomy
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN40855
Funding Number(s)
CONTRACT_GRANT: ANR-10-LABX-0023
CONTRACT_GRANT: NNG08FD60C
CONTRACT_GRANT: ANR-12-BS05-0009
CONTRACT_GRANT: NNX14AF08G
CONTRACT_GRANT: ANR-11-IDEX-0005-02
Distribution Limits
Public
Copyright
Other
Keywords
accretion disks
accretion