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Living on a Flare: Relativistic Reflection in V404 Cyg Observed by NuSTAR During its Summer 2015 Outburst

Walton, D. J. and Mooley, K. and King, A and Tomsick, J. A. and Miller, J. M. and Dauser, T. and García, J. and Bachetti, M. and Brightman, M. and Fabian, A. C. and Forster, K. and Fürst, F. and Gandhi, P. and Grefenstette, B. W. and Harrison, F. A. and Madsen, K. K. and Meier, D. L. and Middleton, M. J. and Natalucci, L. and Rahoui, F. and Rana, V. and Stern, D. (2017) Living on a Flare: Relativistic Reflection in V404 Cyg Observed by NuSTAR During its Summer 2015 Outburst. Astrophysical Journal, 839 (2). Art. No. 110. ISSN 1538-4357. doi:10.3847/1538-4357/aa67e8.

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We present first results from a series of NuSTAR observations of the black hole X-ray binary V404 Cyg obtained during its summer 2015 outburst, primarily focusing on observations during the height of this outburst activity. The NuSTAR data show extreme variability in both the flux and spectral properties of the source. This is partly driven by strong and variable line-of-sight absorption, similar to previous outbursts. The latter stages of this observation are dominated by strong flares, reaching luminosities close to Eddington. During these flares, the central source appears to be relatively unobscured and the data show clear evidence for a strong contribution from relativistic reflection, providing a means to probe the geometry of the innermost accretion flow. Based on the flare properties, analogies with other Galactic black hole binaries, and also the simultaneous onset of radio activity, we argue that this intense X-ray flaring is related to transient jet activity during which the ejected plasma is the primary source of illumination for the accretion disk. If this is the case, then our reflection modeling implies that these jets are launched in close proximity to the black hole (as close as a few gravitational radii), consistent with expectations for jet launching models that tap either the spin of the central black hole, or the very innermost accretion disk. Our analysis also allows us to place the first constraints on the black hole spin for this source, which we find to be a* > 0.92 (99% statistical uncertainty, based on an idealized lamp-post geometry).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Walton, D. J.0000-0001-5819-3552
Mooley, K.0000-0002-2557-5180
Tomsick, J. A.0000-0001-5506-9855
Dauser, T.0000-0003-4583-9048
García, J.0000-0003-3828-2448
Bachetti, M.0000-0002-4576-9337
Brightman, M.0000-0002-8147-2602
Fabian, A. C.0000-0002-9378-4072
Forster, K.0000-0001-5800-5531
Fürst, F.0000-0003-0388-0560
Gandhi, P.0000-0003-3105-2615
Grefenstette, B. W.0000-0002-1984-2932
Harrison, F. A.0000-0003-2992-8024
Madsen, K. K.0000-0003-1252-4891
Middleton, M. J.0000-0002-8183-2970
Natalucci, L.0000-0002-6601-9543
Rahoui, F.0000-0001-7655-4120
Rana, V.0000-0003-1703-8796
Stern, D.0000-0003-2686-9241
Additional Information:© 2017 The American Astronomical Society. Received 2016 September 2; revised 2017 March 6; accepted 2017 March 17; published 2017 April 21. The authors thank the anonymous reviewer for suggestions that helped to improve the manuscript. D.J.W., P.G., and M.J.M. acknowledge support from STFC Ernest Rutherford fellowships (grant ST/J003697/2). K.P.M. acknowledges support from the Hintze Foundation. A.L.K. acknowledges support from NASA through an Einstein Postdoctoral Fellowship (grant number PF4-150125) awarded by the Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. A.C.F. acknowledges support from ERC Advanced Grant 340442. L.N. wishes to acknowledge the Italian Space Agency (ASI) for Financial support by ASI/INAF grant I/037/12/0-011/13. This research has made use of data obtained with NuSTAR, a project led by Caltech, funded by NASA and managed by NASA/JPL, and has utilized the NUSTARDAS software package, jointly developed by the ASDC (Italy) and Caltech (USA). This research has also made use of data from AMI, which is supported by the ERC, and we thank the AMI staff for scheduling these radio observations. Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, AMI - Arcminute MicroKelvin Imager.
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/J003697/2
Hintze FoundationUNSPECIFIED
NASA Einstein FellowshipPF4-150125
European Research Council (ERC)340442
Agenzia Spaziale Italiana (ASI)I/037/12/0-011/13
Subject Keywords:black hole physics – X-rays: binaries – X-rays: individual (V404 Cyg)
Issue or Number:2
Record Number:CaltechAUTHORS:20161117-111407065
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72120
Deposited By: Ruth Sustaita
Deposited On:17 Nov 2016 19:31
Last Modified:11 Nov 2021 04:56

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