NuSTAR observations of the supergiant X-ray pulsar IGR J18027-2016: accretion from the stellar wind and possible cyclotron absorption line

Abstract

We report on the first focused hard X-ray view of the absorbed supergiant system IGRJ18027-2016 performed with the NuSTAR observatory. The pulsations are clearly detected with a period of $P_{spin}=139.866(1)$ s and a pulse fraction of about 50-60% 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 $dP/dt\simeq 6\times 10^{-10}$ s/s. 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 ~23 keV. This energy corresponds to the magnetic field $B\simeq 3\times 10^{12}$ G at the surface of the neutron star, which is typical for X-ray pulsars.

8 pages, 8 figures, accepted to MNRAS

References in corpus (7)

• NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission
• The critical accretion luminosity for magnetized neutron stars
• The ephemeris, orbital decay, and masses of 10 eclipsing HMXBs
• The 1 - 50 keV spectral and timing analysis of IGR J18027-2016: an eclipsing, high mass X-ray binary
• Transient X-ray pulsar V0332+53: pulse phase-resolved spectroscopy and the reflection model
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