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NuSTAR discovery of a cyclotron absorption line in the transient X-ray pulsar 2S 1553-542
Tekijät: Tsygankov SS, Lutovinov AA, Krivonos RA, Molkov SV, Jenke PJ, Finger MH, Poutanen J
Kustantaja: OXFORD UNIV PRESS
Julkaisuvuosi: 2016
Journal: Monthly Notices of the Royal Astronomical Society
Tietokannassa oleva lehden nimi: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Lehden akronyymi: MON NOT R ASTRON SOC
Vuosikerta: 457
Numero: 1
Aloitussivu: 258
Lopetussivu: 266
Sivujen määrä: 9
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stv2849
We report the 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. The properties of the source at high energies (>30 keV) are studied for the first time and the sky position has been essentially improved. The source broad-band spectrum has a quite complicated shape and can be reasonably described by a composite model with two continuum components - a blackbody emission with the temperature about 1 keV at low energies and a power law with an exponential cut-off at high energies. Additionally, an absorption feature at similar to 23.5 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 similar to 3 x 10(12) G. Based on the Fermi/ GBM data, the orbital parameters of the system were substantially improved, which allowed us to determine the spin period of the neutron star P = 9.27880(3) s and a local spin-up. (P) over dot similar or equal to -7.5 x 10(-10) s s(-1) due to the mass accretion during the NuSTAR observations. Assuming accretion from the disc and using standard torque models, we estimated the distance to the system as d = 20 +/- 4 kpc.