Non-periodic type I Be/X-ray binary outbursts

Abstract

Type I Be/X-ray binary outbursts are driven by mass transfer from a Be star decretion disc to a neutron star companion during each orbital period. Treiber et al. (2021) recently observed non-periodic type I outbursts in RX J0529.8-6556 that has unknown binary orbital properties. We show that non-periodic type I outbursts may be temporarily driven in a low eccentricity binary with a disc that is inclined sufficiently to be mildly unstable to Kozai-Lidov oscillations. The inclined disc becomes eccentric and material is transferred to the neutron star at up to three locations in each orbit: when the neutron star passes the disc apastron or one of the two nodes of the disc. The timing and magnitude of each vary with the disc argument of periapsis and longitude of the ascending node that precess in opposite directions. Calculating the orbital period of the RX J0529.8-6556 system is non-trivial but we suggest it maybe >300 day, longer than previous estimates.

Accepted for publication in ApJL

References in corpus (14)

• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• Accretion disc viscosity: how big is alpha?
• The Kozai-Lidov Mechanism in Hydrodynamical Disks
• Giant Outbursts in Be/X-ray Binaries
• Tidal Torques on Misaligned Disks in Binary Systems
• Autoregressive Times Series Methods for Time Domain Astronomy
• The Kozai-Lidov Mechanism in Hydrodynamical Disks. II. Effects of binary and disk parameters
• On the Spin Period Distribution in Be/X-ray Binaries
• Misaligned accretion disc formation via Kozai-Lidov oscillations
• AutoRegressive Planet Search: Application to the Kepler Mission
• On the neutron star-disc interaction in Be/X-ray binaries
• Growth and Dissipation of Be Star Discs in Misaligned Binary Systems
• Sustained Kozai-Lidov oscillations in misaligned circumstellar gas disks
• RX J0529.8-6556: a BeXRB pulsar with an evolving optical period and out of phase X-ray outbursts