DISTORTED CYCLOTRON LINE PROFILE IN CEP X-4 AS OBSERVED BY NuSTAR

Fuerst F, Pottschmidt K, Miyasaka H, Bhalerao V, Bachetti M, Boggs SE, Christensen FE, Craig WW, Grinberg V, Hailey CJ, Harrison FA, Kennea JA, Rahoui F, Stern D, Tendulkar SP, Tomsick JA, Walton DJ, Wilms J, Zhang WW (2015)

Publication Status: Published

Publication Type: Journal article, other

Publication year: 2015

Journal

Astrophysical Journal Letters American Astronomical Society

Publisher: American Astronomical Society

Book Volume: 806

DOI: 10.1088/2041-8205/806/2/L24

Abstract

We present spectral analysis of Nuclear Spectroscopic Telescope Array and Swift observations of Cep X-4 during its outburst in 2014. We observed the source once during the peak of the outburst and once during the decay, finding good agreement in the spectral shape between the observations. We describe the continuum using a power law with a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to describe the shape of the CRSF accurately, leaving significant deviations at the red side of the line. We characterize this asymmetry with a second absorption feature around 19 keV. The line energy of the CRSF, which is not influenced by the addition of this feature, shows a small but significant positive luminosity dependence. With luminosities between (1-6) x 10(36) erg s(-1), Cep X-4 is below the theoretical limit where such a correlation is expected. This behavior is similar to Vela X-1 and we discuss parallels between the two systems.

Authors with CRIS profile

Jörn Wilms Professur für Astronomie und Astrophysik

Involved external institutions

National Aeronautics and Space Administration (NASA)

United States (USA) (US) California Institute of Technology (Caltech)

United States (USA) (US) University of California, Berkeley

United States (USA) (US) European Southern Observatory (ESO)

Germany (DE) Pennsylvania State University (Penn State)

United States (USA) (US) Columbia University

United States (USA) (US) Massachusetts Institute of Technology (MIT)

United States (USA) (US) Technical University of Denmark / Danmarks Tekniske Universitet (DTU)

Denmark (DK) INAF-Osservatorio Astronomico di Cagliari

Italy (IT) Inter-University Centre for Astronomy and Astrophysics (IUCAA)

India (IN) University of Maryland, Baltimore County (UMBC)

United States (USA) (US)

How to cite

APA:

Fuerst, F., Pottschmidt, K., Miyasaka, H., Bhalerao, V., Bachetti, M., Boggs, S.E.,... Zhang, W.W. (2015). DISTORTED CYCLOTRON LINE PROFILE IN CEP X-4 AS OBSERVED BY NuSTAR. Astrophysical Journal Letters, 806. https://doi.org/10.1088/2041-8205/806/2/L24

MLA:

Fuerst, F., et al. "DISTORTED CYCLOTRON LINE PROFILE IN CEP X-4 AS OBSERVED BY NuSTAR." Astrophysical Journal Letters 806 (2015).

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