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

by Juhani Mönkkönen (University of Turku)

Wednesday 15 Apr 2020, 13:30 → 14:30 Europe/Stockholm

https://stockholmuniversity.zoom.us/j/530682073

https://arxiv.org/abs/2003.14347

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.

retrograde_spin_gx301_2.pdf