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Properties of AGN coronae in the NuSTAR era

Fabian, A. C. and Lohfink, A. and Kara, E. and Parker, M. L. and Vasudevan, R. and Reynolds, C. S. (2015) Properties of AGN coronae in the NuSTAR era. Monthly Notices of the Royal Astronomical Society, 451 (4). pp. 4375-4383. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20160128-135737582

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Abstract

The focusing optics of NuSTAR have enabled high signal-to-noise ratio spectra to be obtained from many X-ray bright active galactic nuclei (AGN) and galactic black hole binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness–temperature (Θ − ℓ) diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://mnras.oxfordjournals.org/content/451/4/4375PublisherArticle
http://dx.doi.org/10.1093/mnras/stv1218DOIArticle
Additional Information:© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 May 27. Received 2015 May 26. In original form 2015 April 27. First published online July 1, 2015. We thank Julien Malzac for a discussion and the referee for helpful comments. ACF and AL acknowledge support from ERC Advanced Grant FEEDBACK. CSR thanks the Simons Foundation Fellows Program (US) and the Sackler Fellowship Program (Cambridge) for support, and is grateful to the Institute of Astronomy (Cambridge) for its hospitality during a six month visit in which this work was conducted.
Group:NuSTAR
Funders:
Funding AgencyGrant Number
European Research Council (ERC)FEEDBACK
Simons FoundationUNSPECIFIED
Sackler Fellowship Program (Cambridge)UNSPECIFIED
Record Number:CaltechAUTHORS:20160128-135737582
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160128-135737582
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64056
Collection:CaltechAUTHORS
Deposited By: Joy Painter
Deposited On:28 Jan 2016 22:25
Last Modified:28 Jan 2016 22:34

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