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arXiv · 1401.2936

Torque reversals and pulse profile of the pulsar 4U 1626-67

Aru Beri·Chetana Jain·Biswajit Paul·Harsha Raichur
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Abstract

We review the pulse profile evolution of the unique accretion powered X-ray pulsar 4U 1626-67 over the last 40 years since its discovery. This pulsar showed two distinct eras of steady spin-up separated by a steady spin-down episode for about 18 years. In the present work, using data from different observatories active during each phase of spin-up and spin-down we establish a clear correlation between the accretion torque acting on this pulsar and its pulse profile. The energy resolved pulse profiles are identical in both the spin-up eras and quite different in the spin-down era, especially in the low energy band. This correlation, along with the already known feature of strong Quasi Periodic Oscillations (QPO) that was present only in the spin-down era, clearly establish two different accretion modes onto the neutron star which produce different pulse profiles and only one of which produces the QPOs.

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Aru Beri, Chetana Jain, Biswajit Paul, Harsha Raichur. 2014-01-13. Torque reversals and pulse profile of the pulsar 4U 1626-67. https://doi.org/10.1093/mnras%2Fstu087

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