On the magnetic fields of Be/X-ray pulsars in the Small Magellanic Cloud

Abstract

We explore the possibility to explain the properties of the Be/X-ray pulsars observed in the Small Magellanic Cloud within the magnetic levitation accretion scenario. This implies that their X-ray emission is powered by a wind-fed accretion onto a neutron star (NS) which captures matter from a magnetized stellar wind. The NS in this case is accreting matter from a non-keplerian magnetically levitating disc (ML-disc) which is surrounding its magnetosphere. This allows us to explain the observed periods of the pulsars in terms of spin equilibrium without the need of invoking dipole magnetic fields outside the usual range ~ 10^11- 10^13 G inferred from cyclotron features of Galactic high mass X-ray binaries. We find that the equilibrium period of a NS, under certain conditions, depends strongly on the magnetization of the stellar wind of its massive companion and, correspondingly, on the magnetic field of the massive companion itself. This may help to explain why similar NSs in binaries with similar properties rotate with different periods yielding a large scatter of periods of the accretion-powered pulsar observed in SMC and our galaxy.

6 pages, 1 figure, Published in MNRAS 454, 3760-3765 (2015)

References in corpus (9)

• Spin period change and the magnetic fields of neutron stars in Be X-ray binaries in the Small Magellanic Cloud
• Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs
• The origin of long-period X-ray pulsars
• Signs of magnetic accretion in young Be/X-ray pulsar SXP 1062
• Signs of Magnetic Accretion in the X-ray Pulsar Binary GX 301-2
• Burst Fluence Distributions of Soft Gamma Repeaters 1806-20 and 1900+14 in the RXTE PCA era
• Signs of magnetic accretion in X-ray pulsars
• Spin evolution of long-period X-ray pulsars
• A scenario of the formation of isolated X-ray pulsars with anomalously long period

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• Spectral and timing analysis of BeXRB eRASSU J050810.4-660653 recently discovered in the Large Magellanic Cloud (LMC)
• On the origin of super-global spin-up trends of X-ray pulsars in HMXB systems
• MAD-Accretion Scenario in High-Mass X-Ray Binaries with Neutron Stars
• Spectral and Timing properties of the recently discovered Be/X-ray pulsar eRASSUJ 052914.9-662446
• Super-critical accretion of BeXRB SXP 15.3