Radio Transients from the Accretion Induced Collapse of White Dwarfs

TL;DR

This paper proposes that accretion induced collapse of white dwarfs can produce detectable transient radio sources due to pulsar wind nebula emission from newly formed magnetars, offering a novel observational signature.

Contribution

It introduces the idea that AIC events can be identified through radio transients caused by magnetar-driven pulsar wind nebulae, a new detection method for these elusive phenomena.

Findings

Radio transients from AIC are potentially detectable with current radio surveys.

Estimated detection rate is about 4% of the Type Ia supernova rate.

Magnetar magnetic fields of ~2×10^14 G and initial spin periods of ~10 ms are sufficient for detection.

Abstract

It has long been expected that in some scenarios when a white dwarf (WD) grows to the Chandrasekhar limit, it can undergo an accretion induced collapse (AIC) to form a rapidly rotating neutron star. Nevertheless, the detection of such events has so far evaded discovery, likely because the optical, supernova-like emission is expected to be dim and short-lived. Here we propose a novel signature of AIC: a transient radio source lasting for a few months. Rapid rotation along with flux freezing and dynamo action can grow the WD's magnetic field to magnetar strengths during collapse. The spindown of this newly born magnetar generates a pulsar wind nebula (PWN) within the ~0.001-0.1Msun of ejecta surrounding it. Our calculations show that synchrotron emission from the PWN may be detectable in the radio, even if the magnetar has a rather modest magnetic field of ~2*10^14 G and an initial spin period of ~10 ms. An all-sky survey with a detection limit of 1 mJy at 1.4 GHz would see ~4(f/10^-2) above threshold at any given time, where f is the ratio of the AIC rate to Type Ia supernova rate. A similar scenario may result from binary neutron stars if some mergers produce massive neutron stars rather than black holes. We conclude with a discussion of the detectability of these types of radio sources in an era of facilities with high mapping speeds.