Searching for magnetar binaries disrupted by core-collapse supernovae

Abstract

Core-collapse Supernovae (CCSNe) are considered the primary magnetar formation channel, with 15 magnetars associated with supernova remnants (SNRs). A large fraction of these should occur in massive stellar binaries that are disrupted by the explosion, meaning that $\sim 45~{{\%}}$ of magnetars should be nearby high-velocity stars. Here we conduct a multi-wavelength search for unbound stars, magnetar binaries, and SNR shells using public optical (uvgrizy −bands), infrared (J −, H −, K −, and Ks −bands), and radio (888 MHz, 1.4 GHz, and 3 GHz) catalogs. We use Monte Carlo analyses of candidates to estimate the probability of association with a given magnetar based on their proximity, distance, proper motion, and magnitude. In addition to recovering a proposed magnetar binary, a proposed unbound binary, and 13 of 15 magnetar SNRs, we identify two new candidate unbound systems: an OB star from the Gaia catalog we associate with SGR J1822.3-1606, and an X-ray pulsar we associate with 3XMM J185246.6+003317. Using a Markov-Chain Monte Carlo simulation that assumes all magnetars descend from CCSNe, we constrain the fraction of magnetars with unbound companions to $5\lesssim f_u \lesssim 24~{{\%}}$, which disagrees with neutron star population synthesis results. Alternate formation channels are unlikely to wholly account for the lack of unbound binaries as this would require $31\lesssim f_{nc} \lesssim 66~{{\%}}$ of magnetars to descend from such channels. Our results support a high fraction ($48\lesssim f_m \lesssim 86~{{\%}}$) of pre-CCSN mergers, which can amplify fossil magnetic fields to preferentially form magnetars.

VLBA Astrometry of the Fastest-spinning Magnetar Swift J1818.0−1607: A Large Trigonometric Distance and a Small Transverse Velocity

“…Despite these evidences in favor of magnetar production in mergers, the DNS merger scenario is disfavored for the bulk of the known Galactic magnetar population by their low Galactic latitudes (Olausen & Kaspi 2014). On the other hand, at least a fraction of Galactic magnetars are expected to come from CCSNe, given the 15 confirmed or proposed associations (see Table 1 of Sherman et al 2024) between Galactic magnetars and supernova remnants (SNRs) (e.g., Vasisht & Gotthelf 1997;Klose et al 2004;Gelfand & Gaensler 2007;Gaensler 2014;Borkowski & Reynolds 2017;Bailes et al 2021). For formation channels other than the CCSNe or the DNS merger channel, it remains unclear whether they would contribute to the birth of Galactic magnetars.…”