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A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522

Hemphill, Paul B. and Rothschild, Richard E. and Markowitz, Alex and Fürst, Felix and Pottschmidt, Katja and Wilms, Jörn (2014) A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522. Astrophysical Journal, 792 (1). Art. No. 14. ISSN 0004-637X. doi:10.1088/0004-637X/792/1/14.

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We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538–522. The broadband spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at 23.0 ± 0.4 keV and the iron Kα line at 6.426 ± 0.008 keV, as well as placing limits on the strengths of the iron Kβ line and the iron K edge. We track the evolution of the spectral parameters both in time and in luminosity, notably finding a significant positive correlation between cyclotron line energy and luminosity. A dip and spike in the light curve is shown to be associated with an order-of-magnitude increase in column density along the line of sight, as well as significant variation in the underlying continuum, implying the accretion of a overdense region of a clumpy stellar wind. We also present a phase-resolved analysis, with most spectral parameters of interest showing significant variation with phase. Notably, both the cyclotron line energy and the iron Kα line intensity vary significantly with phase, with the iron line intensity significantly out of phase with the pulse profile. We discuss the implications of these findings in the context of recent work in the areas of accretion column physics and cyclotron resonance scattering feature formation.

Item Type:Article
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URLURL TypeDescription Paper
Hemphill, Paul B.0000-0002-1676-6954
Fürst, Felix0000-0003-0388-0560
Pottschmidt, Katja0000-0002-4656-6881
Wilms, Jörn0000-0003-2065-5410
Additional Information:© 2014 American Astronomical Society. Received 2014 May 21; accepted 2014 July 2; published 2014 August 8. This research has made use of data and software obtained from NASA’s High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Goddard Space Flight Center and the Smithsonian Astrophysical Observatory. P.B.H. was supported by NASA grant NNX13AE68G.
Funding AgencyGrant Number
Subject Keywords:pulsars: individual (4U 1538-522); stars: magnetic field; stars: oscillations; X-rays: binaries; X-rays: stars
Issue or Number:1
Record Number:CaltechAUTHORS:20140925-074917192
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Official Citation:A Clumpy Stellar Wind and Luminosity-dependent Cyclotron Line Revealed by the First Suzaku Observation of the High-mass X-Ray Binary 4U 1538–522 Paul B. Hemphill et al. 2014 ApJ 792 14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50014
Deposited By: Ruth Sustaita
Deposited On:25 Sep 2014 15:27
Last Modified:10 Nov 2021 18:50

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