Detection of a cyclotron line in SXP 15.3 during its 2017 outburst

Abstract

We report the results of AstroSat and NuSTAR observations of the Be/X-ray binary pulsar SXP 15.3 in the Small Magellanic Cloud during its outburst in late 2017, when the source reached a luminosity level of ~ 10^{38} erg s^{-1}, close to the Eddington limit. The unprecedented broadband coverage of the source allowed us to perform timing and spectral analysis between 3 and 80 keV. The pulse profile exhibits a significant energy dependence, and morphs from a double peaked profile to a single broad pulse at energies >15 keV. This can be explained by a spectral hardening during an intensity dip seen between the two peaks of the pulse profile. We detect a Cyclotron Resonance Scattering Feature (CRSF) at ~5 keV in the X-ray spectrum, independent of the choice of the continuum model. This indicates a magnetic field strength of 6x10^{11} G for the neutron star.

5 pages, 6 figures, accepted for publication in MNRAS Letters

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• Probing the Cyclotron line characteristics of 4U 1538-522 using AstroSat-LAXPC
• Neutron Stars and Black Holes in the Small Magellanic Cloud: The SMC NuSTAR Legacy Survey
• An X-ray high-frequency quasi-periodic oscillation in NGC 1365
• Meta-analysis of Electron Cyclotron Resonance Absorption Features Detected in High-Mass X-ray Binaries
• NuSTAR observation of GRO J1744-28 at low mass accretion rate
• An X-ray view of the 2021 outburst of SXP 15.6: constraints on the binary orbit and magnetic field of the Neutron Star
• Measuring the magnetic dipole moment and magnetospheric fluctuations of accretion-powered pulsars in the Small Magellanic Cloud with an unscented Kalman filter
• LAXPC instrument onboard AstroSat: Five exciting years of new scientific results specially on X-ray Binaries
• Disentangling the neighbouring pulsars SXP 15.3 and SXP 305
• Discovery of a magnetar candidate X-ray pulsar in the Large Magellanic Cloud
• Monte-Carlo simulations on possible collimation effects of outflows to fan-beamed emission of ultraluminous accreting X-ray pulsars
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