Discovery of a retrogradely rotating neutron star in the X-ray pulsar GX 301$-$2

Abstract

We report on the analysis of the spin evolution of a slow X-ray pulsar GX 301$-$2 along the orbit using long-term monitoring by Fermi/GBM. Based on the observationally confirmed accretion scenario and an analytical model for the accretion of angular momentum we demonstrate that in this system, the neutron star spins retrogradely, that is, in a direction opposite to the orbital motion. This first-of-a-kind discovery of such a system proves the principal possibility of retrograde rotation in accreting systems with suitable accretion torque, and might have profound consequences for our understanding of the spin evolution of X-ray pulsars, estimates of their initial spin periods, and the ultimate result of their evolution.

5 pages, 2 figures, accepted by MNRAS

References in corpus (8)

• Catalogue of high-mass X-ray binaries in the Galaxy ($4^{th}$ edition)
• Asymmetric Accretion Flows within a Common Envelope
• VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX301-2
• Stellar Wind Accretion in GX301-2: Evidence for a High-density Stream
• 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
• NuSTAR observations of the wind-fed X-ray pulsar GX 301--2 during an unusual spin-up event
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Cited by in corpus (5)

• X-ray polarimetry of the accreting pulsar GX 301-2
• Timing and spectral variability of high mass X-ray pulsar GX 301--2 over orbital phases observed by Insight-HXMT
• X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT
• On the spin-up events and spin direction of the X-ray pulsar GX 301-2
• Evolution of eccentric high-mass X-ray binaries. The case of GX 301-2