A1 Refereed original research article in a scientific journal
NuSTAR observations of the supergiant X-ray pulsar IGR J18027-2016: accretion from the stellar wind and possible cyclotron absorption line
Authors: Lutovinov AA, Tsygankov SS, Postnov KA, Krivonos RA, Molkov SV, Tomsick JA
Publisher: OXFORD UNIV PRESS
Publication year: 2017
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 466
Issue: 1
First page : 593
Last page: 599
Number of pages: 7
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/stw3058
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/20667125
We report on the first focused hard X-ray view of the absorbed supergiant system IGR J18027-2016 performed with the Nuclear Spectroscopic Telescope Array observatory. The pulsations are clearly detected with a period of P-spin = 139.866(1)s and a pulse fraction of about 50-60 per cent at energies from 3 to 80 keV. The source demonstrates an approximately constant X-ray luminosity on a time-scale of more than dozen years with an average spin-down rate of P similar or equal to 6 x 10(-10) s s(-1). This behaviour of the pulsar can be explained in terms of the wind accretion model in the settling regime. The detailed spectral analysis at energies above 10 keV was performed for the first time and revealed a possible cyclotron absorption feature at energy similar to 23 keV. This energy corresponds to the magnetic field B similar or equal to 3 x 10(12) G at the surface of the neutron star, which is typical for X-ray pulsars.
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