Detection of Cyclotron Resonance Scattering Feature in High Mass X-ray Binary Pulsar SMC X-2

Abstract

We report broadband spectral properties of the high mass X-ray binary pulsar SMC X-2 by using three simultaneous $NuSTAR$ and $Swift$/XRT observations during its 2015 outburst. The pulsar was significantly bright, reaching a luminosity up to as high as $\sim$5.5$\times$10${}^{38}$~ergs~s${}^{-1}$ in 1-70 keV range. Spin period of the pulsar was estimated to be 2.37 s. Pulse profiles were found to be strongly luminosity dependent. The 1-70 keV energy spectrum of the pulsar was well described with three different continuum models such as (i) negative and positive power-law with exponential cutoff, (ii) Fermi-Dirac cutoff power-law and (iii) cutoff power-law models. Apart from the presence of an iron line at $\sim$6.4 keV, a model independent absorption like feature at $\sim$27 keV was detected in the pulsar spectrum. This feature was identified as a cyclotron absorption line and detected for the first time in this pulsar. Corresponding magnetic field of the neutron star was estimated to be $\sim$2.3$\times$10${}^{12}$ G. The cyclotron line energy showed a marginal negative dependence on the luminosity. The cyclotron line parameters were found to be variable with pulse phase and interpreted as due to the effect of emission geometry or complicated structure of the pulsar magnetic field.

5 Pages, 5 figures, 2016, MNRAS, 461, L97-L101

References in corpus (4)

• A model for cyclotron resonance scattering features
• A Further Study of the Luminosity-Dependent Cyclotron Resonance Energies of the Binary X-ray Pulsar 4U0115+63 with RXTE
• Spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud
• An Investigation of Be/X-ray Pulsars with OGLE-III Data

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