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Limits on pair production and multizone Comptonization: the broad-band X/γ-ray spectrum of XTE J1550–564 revisited

Hjalmarsdotter, L.; Axelsson, M.; Done, C.

Limits on pair production and multizone Comptonization: the broad-band X/γ-ray spectrum of XTE J1550–564 revisited Thumbnail


Authors

L. Hjalmarsdotter

M. Axelsson



Abstract

At high luminosities black hole binaries show spectra with a strong disc component accompanied by an equally strong tail where at least some of the electrons are non-thermal. We reanalyse the simultaneous ASCA–RXTE–OSSE data from the 1998 outburst of XTE J1550–564, which span 0.7–1000 keV and remain the best data available of a black hole binary in this state. We reassess the importance of electron–positron pair production using a realistically high value of the source compactness for the first time. The lack of an observable annihilation line together with the observed γ-ray flux beyond 511 keV constrains the maximum electron Lorentz factor to be ≤10, and the slope of the injected electrons to ≤2.5. We also use the fast (10–50 Hz) variability spectrum to constrain the spatial dependence of the electron heating and acceleration. We find that the spectrum of the fast variability is consistent with being fully thermal, so that the observed non-thermal emission is produced from further out in the flow.

Citation

Hjalmarsdotter, L., Axelsson, M., & Done, C. (2016). Limits on pair production and multizone Comptonization: the broad-band X/γ-ray spectrum of XTE J1550–564 revisited. Monthly Notices of the Royal Astronomical Society, 456(4), 4354-4363. https://doi.org/10.1093/mnras/stv2909

Journal Article Type Article
Acceptance Date Dec 8, 2015
Online Publication Date Jan 15, 2016
Publication Date Mar 11, 2016
Deposit Date Mar 16, 2016
Publicly Available Date Mar 17, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 456
Issue 4
Pages 4354-4363
DOI https://doi.org/10.1093/mnras/stv2909

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.







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