The First NuSTAR Observation of 4U 1538-522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy

Hemphill PB, Rothschild RE, Cheatham DM, Furst F, Kretschmar P, Kühnel M, Pottschmidt K, Staubert R, Wilms J, Wolff MT (2019)

Publication Status: Published

Publication Type: Journal article

Publication year: 2019

Journal

Astrophysical Journal American Astronomical Society

Publisher: IOP PUBLISHING LTD

Book Volume: 873

Article Number: ARTN 62

Journal Issue: 1

DOI: 10.3847/1538-4357/ab03d3

Abstract

We have performed a comprehensive spectral and timing analysis of the first NuSTAR observation of the high-mass X-ray binary 4U 1538-522. The observation covers the X-ray eclipse of the source, plus the eclipse ingress and egress. We use the new measurement of the mid-eclipse time to update the orbital parameters of the system and find marginally significant evolution in the orbital period, with (P) over dot(orb)/P-orb = (-0.95 +/- 0.37) x 10(-6) yr(-1). The cyclotron line energy is found to be approximately 1.2 keV higher than RXTE measurements from 1997 to 2003, in line with the increased energy observed by Suzaku in 2012 and strengthening the case for secular evolution of 4U 1538-522's CRSF. We additionally characterize the behavior of the iron fluorescence and emission lines and line-of-sight absorption as the source moves into and out of eclipse.

Authors with CRIS profile

Matthias Bissinger Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

U.S. Naval Research Laboratory US United States (USA) (US) Eberhard Karls Universität Tübingen DE Germany (DE) University of Maryland, Baltimore County US United States (USA) (US) European Space Astronomy Centre (ESAC) ES Spain (ES) University of California, San Diego US United States (USA) (US) Massachusetts Institute of Technology (MIT) US United States (USA) (US)

How to cite

APA:

Hemphill, P.B., Rothschild, R.E., Cheatham, D.M., Furst, F., Kretschmar, P., Kühnel, M.,... Wolff, M.T. (2019). The First NuSTAR Observation of 4U 1538-522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy. Astrophysical Journal, 873(1). https://dx.doi.org/10.3847/1538-4357/ab03d3

MLA:

Hemphill, Paul B., et al. "The First NuSTAR Observation of 4U 1538-522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy." Astrophysical Journal 873.1 (2019).

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