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arXiv · 1512.00851

NuSTAR discovery of a cyclotron absorption line in the transient X-ray pulsar 2S 1553-542

Sergey S. Tsygankov·Alexander A. Lutovinov·Roman A. Krivonos·Sergey V. Molkov·Peter J. Jenke·Mark H. Finger·Juri Poutanen
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Abstract

We report results of a spectral and timing analysis of the poorly studied transient X-ray pulsar 2S 1553-542 using data collected with the NuSTAR and Chandra observatories and the Fermi/GBM instrument during an outburst in 2015. Properties of the source at high energies (>30 keV) are studied for the first time and the sky position had been essentially improved. The source broadband spectrum has a quite complicated shape and can be reasonably described by a composite model with two continuum components - a black body emission with the temperature about 1 keV at low energies and a power law with an exponential cutoff at high energies. Additionally an absorption feature at $\sim23.5$ keV is discovered both in phase-averaged and phase-resolved spectra and interpreted as the cyclotron resonance scattering feature corresponding to the magnetic field strength of the neutron star $B\sim3\times10^{12}$ G. Based on the Fermi/GBM data the orbital parameters of the system were substantially improved, that allowed us to determine the spin period of the neutron star P = 9.27880(3) s and a local spin-up $\dot P \simeq -7.5\times10^{-10}$ s s$^{-1}$ due to the mass accretion during the NuSTAR observations. Assuming accretion from the disk and using standard torque models we have estimated the distance to the system $d=20\pm4$ kpc.

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Sergey S. Tsygankov, Alexander A. Lutovinov, Roman A. Krivonos, Sergey V. Molkov, Peter J. Jenke, Mark H. Finger, Juri Poutanen. 2015-12-02. NuSTAR discovery of a cyclotron absorption line in the transient X-ray pulsar 2S 1553-542. https://doi.org/10.1093/mnras%2Fstv2849

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