Broad-band observations of the Be/X-ray binary pulsar RX J0440.9+4431: Discovery of a cyclotron absorption line

: Tsygankov S, Krivonos R, Lutovinov A

: 2012

: Monthly Notices of the Royal Astronomical Society

: 421

: 3

: 2407

: 2413

: 7

: 0035-8711

DOI: https://doi.org/10.1111/j.1365-2966.2012.20475.x

We report the results of an analysis of data obtained with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), Swift and Rossi X-ray Timing Explorer (RXTE) observatories during the 2010 April and September outbursts of the X-ray pulsar RXJ0440.9+4431. The temporal and spectral properties of the pulsar in a wide energy band (0.6-120keV) were studied for the first time. We discovered a ∼32-keV cyclotron resonant scattering feature in the source spectrum that allowed us to estimate the magnetic field strength of the neutron star as B≃ 3.2 × 10 G. The estimate of the magnetic field strength was confirmed by a comprehensive analysis of the noise power spectrum of the source. Based on the recurrence time between Type I outbursts, the orbital period of the binary system can be estimated as ∼155d. We have shown that the pulse profile has a sinusoidal-like single-peaked shape and has practically no dependence on the source luminosity or energy band. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.