Affiliation:
1. Sabancı University, 34956, Orhanlı Tuzla, İstanbul, Turkey
Abstract
ABSTRACT
We have extended the analytical model proposed earlier to estimate the inner disc radius of accreting neutron stars in the strong-propeller (SP) phase, and the conditions for the transitions between the strong and weak propeller (WP) phases (Ertan 2017, 2018) to the WP (accretion with spin-down) and the spin-up (SU) phases, and the torque reversals during the WP/SU transitions. The model can account for some basic observed properties of these systems that are not expected in conventional models: (1) accretion on to the star at low X-ray luminosities and the transitions to the SP phase (no accretion) at critical accretion rates much lower than the rate required for the spin-up/spin-down transition, (2) ongoing accretion throughout a large range of accretion rates while the source is spinning down (WP phase), and (3) transitions between the spin-up and spin-down phases with comparable torque magnitudes, without substantial changes in the mass-flow rate. Our results indicate that the magnitudes of the torques on either side of the torque reversal have a ratio similar for different systems independently of their spin periods, magnetic dipole moments, and accretion rates during the transitions. Estimated torque reversal properties in our model are in agreement with the observed torque reversals of 4U 1626–67.
Funder
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
6 articles.
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1. Typical X-Ray Outburst Light Curves of Aql X-1;The Astrophysical Journal;2024-01-31
2. Neutron Stars in Low-mass X-ray Binaries;Turkish Journal of Astronomy and Astrophysics;2023-12-31
3. Evolution of the long-period pulsar PSR J0901−4046;Monthly Notices of the Royal Astronomical Society: Letters;2022-12-23
4. Evolution of the long-period pulsar GLEAM-X J162759.5–523504.3;Monthly Notices of the Royal Astronomical Society: Letters;2022-04-01
5. The torque reversals of 4U 1626–67;Astronomy & Astrophysics;2022-01-25