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Self-consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission

Steiner, James F. and García, Javier A. and Eikmann, Wiebke and McClintock, Jeffrey E. and Brenneman, Laura W. and Dauser, Thomas and Fabian, Andrew C. (2017) Self-consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission. Astrophysical Journal, 836 (1). Art. No. 119. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20170213-161331493

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Abstract

Continuum and reflection spectral models have each been widely employed in measuring the spins of accreting black holes. However, the two approaches have not been implemented together in a photon-conserving, self-consistent framework. We develop such a framework using the black hole X-ray binary GX 339–4 as a touchstone source, and we demonstrate three important ramifications. (1) Compton scattering of reflection emission in the corona is routinely ignored, but is an essential consideration given that reflection is linked to the regimes with strongest Comptonization. Properly accounting for this causes the inferred reflection fraction to increase substantially, especially for the hard state. Another important impact of the Comptonization of reflection emission by the corona is the downscattered tail. Downscattering has the potential to mimic the relativistically broadened red wing of the Fe line associated with a spinning black hole. (2) Recent evidence for a reflection component with a harder spectral index than the power-law continuum is naturally explained as Compton-scattered reflection emission. (3) Photon conservation provides an important constraint on the hard state's accretion rate. For bright hard states, we show that disk truncation to large scales R » R_(ISCO) is unlikely as this would require accretion rates far in excess of the observed Ṁ of the brightest soft states. Our principal conclusion is that when modeling relativistically broadened reflection, spectral models should allow for coronal Compton scattering of the reflection features, and when possible, take advantage of the additional constraining power from linking to the thermal disk component.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/836/1/119DOIArticle
http://iopscience.iop.org/article/10.3847/1538-4357/836/1/119/metaPublisherArticle
https://arxiv.org/abs/1701.03777arXivDiscussion Paper
ORCID:
AuthorORCID
García, Javier A.0000-0003-3828-2448
Additional Information:© 2017. The American Astronomical Society. Received 2016 August 15; revised 2017 January 5; accepted 2017 January 13; published 2017 February 13. J.F.S. has been supported by NASA Einstein Fellowship grant PF5-160144. We thank Ramesh Narayan and Charith Peris for helpful discussions, and the anonymous referee.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NASA Einstein FellowshipPF5-160144
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:accretion, accretion disks; black hole physics; stars: individual (GX 339–4) ; X-rays: binaries
Record Number:CaltechAUTHORS:20170213-161331493
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170213-161331493
Official Citation:James F. Steiner et al 2017 ApJ 836 119
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74278
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:14 Feb 2017 15:28
Last Modified:01 Mar 2017 05:24

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