NuSTAR discovery of a cyclotron absorption line in the transient X-ray pulsar 2S 1553-542

Abstract

We report results of a spectral and timing analysis of the poorly studied transient X-ray pulsar 2S 1553-542 using data collected with the NuSTAR and Chandra observatories and the Fermi/GBM instrument during an outburst in 2015. Properties of the source at high energies (>30 keV) are studied for the first time and the sky position had been essentially improved. The source broadband spectrum has a quite complicated shape and can be reasonably described by a composite model with two continuum components - a black body emission with the temperature about 1 keV at low energies and a power law with an exponential cutoff at high energies. Additionally an absorption feature at $\sim 23.5$ keV is discovered both in phase-averaged and phase-resolved spectra and interpreted as the cyclotron resonance scattering feature corresponding to the magnetic field strength of the neutron star $B\sim 3\times 10^{12}$ G. Based on the Fermi/GBM data the orbital parameters of the system were substantially improved, that allowed us to determine the spin period of the neutron star P = 9.27880(3) s and a local spin-up $\dot{P}\simeq -7.5\times 10^{-10}$ s s${}^{-1}$ due to the mass accretion during the NuSTAR observations. Assuming accretion from the disk and using standard torque models we have estimated the distance to the system $d=20\pm 4$ kpc.

10 pages, 9 figures, 2 tables, accepted for publication in MNRAS

References in corpus (7)

• NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission
• The critical accretion luminosity for magnetized neutron stars
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• INTEGRAL observations of Her X-1
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• The X-ray properties of Be/X-ray pulsars in quiescence
• NuSTAR observation of LS 5039
• NuSTAR observations of the supergiant X-ray pulsar IGR J18027-2016: accretion from the stellar wind and possible cyclotron absorption line
• Correlation between the luminosity and spin-period changes during outbursts of 12 Be binary pulsars observed by the MAXI/GSC and the Fermi/GBM
• Spectral and Timing Analysis of the accretion-powered pulsar 4U 1626-67 observed with Suzaku and NuSTAR
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• 2S1553-542: a Be/X-ray binary pulsar on the far side of the Galaxy
• Radius of the neutron star magnetosphere during disk accretion
• Catalog of the Galactic population of X-ray pulsars in High-mass X-ray binary systems
• Accreting on the edge: a luminosity-dependent cyclotron line in the Be/X-ray Binary 2S 1553-542 accompanied by accretion regimes transition
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• Discovery of cyclotron and narrow Fe K${}_{\alpha }$ lines in HMXB GRO J1750-27
• Study of the X-ray Pulsar XTE J1946+274 with NuSTAR
• The gravitational Higgs mechanism and resulting smoking gun effects
• Temporal and spectral study of the X-ray pulsar 2S 1553-542 during the 2021 outburst
• Spectral properties of the Be/X-ray pulsar 2S 1553-542 during Type II outbursts
• Study of recently discovered Be/X-ray pulsar MAXI J0655-013 using NuSTAR