Accretion-induced Collapse from Magnetic White Dwarf Binaries and Formation of Binary Millisecond Pulsars: Redbacks and Black Widows

Abstract

Redbacks (RBs) and black widows (BWs) are two peculiar classes of eclipsing millisecond pulsars (MSPs). The accretion-induced collapse (AIC) of an oxygen/neon/magnesium composition white dwarf to a neutron star has been suggested as one possible formation pathway for those two classes of MSPs. However, it is difficult to produce all known MSPs with the traditional AIC scenario. In this study by using the MESA stellar evolution code, we investigate the detailed pre-AIC evolution of magnetized white dwarf binaries with the magnetic confinement model where the high magnetic field strength of the white dwarf can confine the accreted matter in the polar caps. We find that the initial donor mass and orbital periods in our model can be lower than that of previous traditional AIC models. We also present post-AIC evolution models to form RBs and BWs with and without the spin down luminosity evaporation of MSPs. Under the magnetic confinement model and evaporative winds (with corresponding angular momentum loss from the surface of the donor star), the companion masses and orbital periods of all known RBs can be covered and a number of binaries can evolve to become BWs.

Formation of millisecond pulsars with long orbital periods by accretion-induced collapse of white-dwarfs

“…For more studies on the formation of MSPs from LMXBs, see, e.g. Podsiadlowski, Rappaport & Pfahl (2002), Nelemans & Jonker (2010), Chen et al (2013bChen et al ( , 2021, Lü et al (2017), Tauris (2018), Ablimit (2019), Chen, Liu & Wang (2020), Wang et al (2021), etc.…”

4FGL J1120.0-2204: A Unique Gamma-ray Bright Neutron Star Binary with an Extremely Low Mass Proto-White Dwarf

“…Although the number of spider MSPs has increased dramatically in recent years, binary evolution models predict these systems will not end up being the MSP-He white dwarf binaries that make up the bulk of the MSP binary population (e.g., Benvenuto et al 2012;Chen et al 2013). In contrast to redbacks in particular, systems with companions in the late stages of becoming a He white dwarf do not fill significant fractions of their Roche lobe since most of the companion envelope has either been accreted or ejected during MSP spin-up (e.g., Podsiadlowski et al 2002;Postnov & Yungelson 2014;Ablimit 2019). Such systems will not show substantial optical variability, and so have remained relatively elusive.…”

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

“…two-pole accreting) compared to nonmagnetic or weakly magnetized WDs (e.g., Schwope et al 2021). However, not just the AIC itself but also the highly magnetized WD binary evolution as the progenitor of AIC or SNe Ia still lack of direct observational evidence (e.g., Ablimit & Li 2015, 2019Ruiter et al 2019), and polar systems observed to date can not generate AIC/ SNe Ia, because they have very low mass donors or/and low mass WDs needed for producing SNe Ia or AIC (see below sections for more information). Theoretically, it has been studied that the magnetic field of the WD may play a key role in the evolution of CO (carbon/oxgen) WD binaries, and the CO WD even with a low mass companion can grow in mass and reach the Chandrasekhar limit mass to explode as a SN Ia if magnetic confinement is achieved (e.g., Ablimit & Maeda 2019a,b).…”

“…Theoretically, it has been studied that the magnetic field of the WD may play a key role in the evolution of CO (carbon/oxgen) WD binaries, and the CO WD even with a low mass companion can grow in mass and reach the Chandrasekhar limit mass to explode as a SN Ia if magnetic confinement is achieved (e.g., Ablimit & Maeda 2019a,b). The magnetic confinement model has been proposed to have the crucial effect on accreting and nuclear burning processes of the WD, and it is related to the magnetic field strength of the WD, mass transfer rate (mass of the donor) and mass of the WD (e.g., Livio 1983;Ablimit & Maeda 2019a;Ablimit 2019). Thus, in this study, we investigate the influence of the magnetic confinement model in the evolution of ONeMg WD + He star binaries.…”

“…In this work, we present detailed numerical calculations of the ONeMg WD + He star binaries by considering nonmagnetic and magnetic cases in the pre-AIC evolution (e.g., Ablimit 2019). The main goal of the work is to show the possible role of the magnetic confinement model in the WD + He star binary evolution.…”