The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE: Minimizing cyclotron line biases

Kühnel M, Kreykenbohm I, Ferrigno C, Pottschmidt K, Marcu-Cheatham DM, Fuerst F, Rothschild RE, Kretschmar P, Klochkov D, Hemphill P, Hertel D, Müller S, Sokolova-Lapa E, Oruru B, Grinberg V, Martinez-Nunez S, Torrejon JM, Becker PA, Wolff MT, Ballhausen R, Schwarm FW, Wilms J (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Book Volume: 634

DOI: 10.1051/0004-6361/201935666

Abstract

We present an analysis of X-ray spectra of the high-mass X-ray binary 4U 0115+634 as observed with Suzaku and RXTE in 2011 July, during the fading phase of a giant X-ray outburst. We used a continuum model consisting of an absorbed cutoff power law and an ad hoc Gaussian emission feature centered around 8.5 keV, which we attribute to cyclotron emission. Our results are consistent with a fundamental cyclotron absorption line centered at similar to 10.2 keV for all observed flux ranges. At the same time we rule out significant influence of the 8.5 kev Gaussian on the parameters of the cyclotron resonant scattering feature, which are not consistent with the cyclotron line energies or the depths of previously reported flux-dependent descriptions. We also show that some continuum models can lead to artificial line-like residuals in the analyzed spectra, which are then misinterpreted as unphysically strong cyclotron lines. Specifically, our results do not support the existence of a previously claimed additional cyclotron feature at similar to 15 keV. Apart from these features, we find for the first time evidence for a He-like FeXXV emission line at similar to 6.7 keV and weak H-like FeXXVI emission close to similar to 7.0 keV.

Authors with CRIS profile

Involved external institutions

Massachusetts Institute of Technology (MIT) United States (USA) (US) University of Geneva / Université de Genève (UNIGE) Switzerland (CH) University of Maryland, Baltimore County United States (USA) (US) European Space Astronomy Centre (ESAC) Spain (ES) University of California, San Diego United States (USA) (US) Eberhard Karls Universität Tübingen Germany (DE) Makerere University Uganda (UG) Universidad de Cantabria (UC) Spain (ES) University of Alicante / Universidad de Alicante / Universitat d'Alacant Spain (ES) George Mason University United States (USA) (US) U.S. Naval Research Laboratory United States (USA) (US)

How to cite

APA:

Kühnel, M., Kreykenbohm, I., Ferrigno, C., Pottschmidt, K., Marcu-Cheatham, D.M., Fuerst, F.,... Wilms, J. (2020). The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE: Minimizing cyclotron line biases. Astronomy & Astrophysics, 634. https://dx.doi.org/10.1051/0004-6361/201935666

MLA:

Kühnel, Matthias, et al. "The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE: Minimizing cyclotron line biases." Astronomy & Astrophysics 634 (2020).

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