The Magnetized White Dwarf + Helium star Binary Evolution with Accretion-induced Collapse

Abstract

Accretion-induced collapse (AIC) from oxygen/neon/magnesium composition white dwarf (ONeMg WD) + stripped helium (He) star binaries is one promising channel to form peculiar neutron star objects. It has been discussed that the WD's magnetic field may alter the accretion phase in the WD binary evolution. By considering non-magnetic and sufficiently magnetized WDs, we investigate the evolution of ONeMg WD + He star binaries with detailed stellar evolution and binary population synthesis simulations. The role of the magnetically confined accretion in the possible formation pathway for like millisecond pulsars (MSPs) and magnetars is also studied. Comparing with the case of spherically symmetric accretion, the mass accumulation efficiency of the WDs is enhanced at low mass transfer rate under the magnetic confinement model. The initial parameter space of the potential AIC progenitor systems moves toward shorter orbital period and lower donor mass (but not so significantly) due to the effect of the magnetic confinement. This also allows final MSPs to have lower-mass WD companions and shorter orbital periods. There is no significant difference between the Galactic birthrates of the AIC derived with and without the magnetic confinement, which implies that the magnetic field of the WD does not dramatically change the number of ONeMg WD + He star binaries which can produce AIC. It is worth noting that these conclusions can be applied for the CO (carbon/oxgen) WD + He star binaries as progenitors of type Ia supernovae, because the accretion phases of ONeMg WDs and CO WDs are similar. The Galactic rate of magnetars possibly formed via AIC of highly magnetized WDs is 0.34 × 10 −4 yr −1 .

Where are the magnetar binary companions? Candidates from a comparison with binary population synthesis predictions

“…However, some contribution from other channels cannot be excluded. For example, accretion or merger induced collapse magnetars are predicted on theoretical grounds (Duncan & Thompson 1992;Levan et al 2006;Margalit et al 2019;Gautam et al 2021;Ablimit 2021), and are a possible explanation for FRB202001E, which resides in a globular cluster (Kirsten et al 2021;Lu et al 2021). If the majority of magnetars are born in core-collapse events, it is still uncertain whether this is a typical outcome, or if it requires specific pre-collapse conditions (this is largely dependent on how rapidly their magnetic fields decay, Nakano et al 2015;Beniamini et al 2019).…”

“…There are, however, magnetars for which there is no obvious association with recent star formation despite a relatively clear sightline (see e.g., SGR 0501+4516 which lies in the Galactic anti-centre direction). Putative non-core-collapse production channels include binary neutron star mergers and the accretion or merger induced collapse of ONe white dwarfs resulting in magnetars (Duncan & Thompson 1992;Levan et al 2006;Ablimit 2021).…”

Assessing the complexity of orbital parameters after asymmetric kick in binary pulsars

“…It has been studied that the magnetized WDs can grow in mass with low accretion rates (Ablimit & Maeda 2019). Ablimit (2021b) showed that the channel of magnetized ONe or CO) WD + stripped helium star binaries can produces MSPs, magnetars and type Ia supernovae (SNe Ia which are thermonuclear explosions of CO WDs that have grown to the Chandrasekhar limit).…”