Journal article

Publication Details

Author(s): 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
Journal: Astrophysical Journal Letters
Publisher: American Astronomical Society
Publication year: 2015
Volume: 806
ISSN: 2041-8205
eISSN: 2041-8213


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.

FAU Authors / FAU Editors

Wilms, Jörn Prof. Dr.
Professur für Astronomie und Astrophysik

External institutions with authors

California Institute of Technology (Caltech)
Columbia University
European Southern Observatory (ESO)
INAF-Osservatorio Astronomico di Cagliari
Inter-University Centre for Astronomy and Astrophysics (IUCAA)
Massachusetts Institute of Technology (MIT)
National Aeronautics and Space Administration (NASA)
Pennsylvania State University (Penn State)
Technical University of Denmark / Danmarks Tekniske Universitet (DTU)
University of California, Berkeley
University of Maryland, Baltimore County

How to cite

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://dx.doi.org/10.1088/2041-8205/806/2/L24

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


Last updated on 2019-23-08 at 08:33