THE COMPLEX ACCRETION GEOMETRY OF GX 339-4 AS SEEN BY NuSTAR AND SWIFT

Fuerst F, Nowak MA, Tomsick JA, Miller JM, Corbel S, Bachetti M, Boggs SE, Christensen FE, Craig WW, Fabian AC, Gandhi P, Grinberg V, Hailey CJ, Harrison FA, Kara E, Kennea JA, Madsen KK, Pottschmidt K, Stern D, Walton DJ, Wilms J, Zhang WW (2015)

Publication Status: Published

Publication Type: Journal article

Publication year: 2015

Journal

Astrophysical Journal American Astronomical Society

Publisher: IOP PUBLISHING LTD

Book Volume: 808

Article Number: ARTN 122

Journal Issue: 2

DOI: 10.1088/0004-637X/808/2/122

Abstract

We present spectral analyses of five Nuclear Spectroscopic Telescope Array and Swift observations of GX 339-4 taken during a failed outburst during the summer of 2013. These observations cover Eddington luminosity fractions in the range approximate to 0.9%-6%. Throughout this outburst GX 339-4 stayed in the hard state and all five observations show similar X-ray spectra, with a hard power law with a photon index near 1.6, and significant contribution from reflection. Using simple reflection models we find unrealistically high iron abundances. Allowing for different photon indices for the continuum incident on the reflector relative to the underlying observed continuum results in a statistically better fit and reduced iron abundances. With a photon index around 1.3, the input power law on the reflector is significantly harder than that which is directly observed. We study the influence of different emissivity profiles and geometries and consistently find an improvement when using separate photon indices. The inferred inner accretion disk radius is strongly model dependent, but we do not find evidence for a truncation radius larger than 100 r(g) in any model. The data do not allow independent spin constraints, but the results are consistent with the literature (i.e., a > 0). Our best-fit models indicate an inclination angle in the range 40 degrees-60 degrees, consistent with limits on the orbital inclination but higher than reported in the literature using standard reflection models. The iron line around 6.4 keV is clearly broadened, and we detect a superimposed narrow core as well. This core originates from a fluorescent region outside the influence of the strong gravity of the black hole. Additionally, we discuss possible geometries.

Authors with CRIS profile

Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

California Institute of Technology (Caltech) US United States (USA) (US) University of Cambridge GB United Kingdom (GB) University of California, Berkeley US United States (USA) (US) Technical University of Denmark / Danmarks Tekniske Universitet (DTU) DK Denmark (DK) Université Fédérale de Toulouse Midi-Pyrénées FR France (FR) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot FR France (FR) University of Michigan US United States (USA) (US) Massachusetts Institute of Technology (MIT) US United States (USA) (US) University of Maryland, Baltimore County US United States (USA) (US) Pennsylvania State University (Penn State) US United States (USA) (US) Columbia University US United States (USA) (US) Durham University GB United Kingdom (GB)

How to cite

APA:

Fuerst, F., Nowak, M.A., Tomsick, J.A., Miller, J.M., Corbel, S., Bachetti, M.,... Zhang, W.W. (2015). THE COMPLEX ACCRETION GEOMETRY OF GX 339-4 AS SEEN BY NuSTAR AND SWIFT. Astrophysical Journal, 808(2). https://dx.doi.org/10.1088/0004-637X/808/2/122

MLA:

Fuerst, F., et al. "THE COMPLEX ACCRETION GEOMETRY OF GX 339-4 AS SEEN BY NuSTAR AND SWIFT." Astrophysical Journal 808.2 (2015).

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