Magnetars, Gamma-ray Bursts, and Very Close Binaries

TL;DR

This paper explores a potential common evolutionary pathway for binary systems leading to gamma-ray bursts, magnetars, and close binaries, emphasizing the role of tidal synchronization and natal kicks.

Contribution

It proposes a unified scenario linking binary evolution to the formation of magnetars and gamma-ray bursts, with analysis of binary fractions and natal velocities.

Findings

Calculated formation rate of rapidly rotating neutron stars aligns with magnetar formation estimates.

The binary fraction among young neutron stars exceeds observational data unless large perpendicular velocities are assumed.

Magnetar natal kicks must be significant and oriented perpendicular to the orbital plane.

Abstract

We consider the possible existence of a common channel of evolution of binary systems, which results in a gamma-ray burst during the formation of a black hole or the birth of a magnetar during the formation of a neutron star. We assume that the rapid rotation of the core of a collapsing star can be explained by tidal synchronization in a very close binary. The calculated rate of formation of rapidly rotating neutron stars is qualitatively consistent with estimates of the formation rate of magnetars. However, our analysis of the binarity of newly-born compact objects with short rotational periods indicates that the fraction of binaries among them substantially exceeds the observational estimates. To bring this fraction into agreement with the statistics for magnetars, the additional velocity acquired by a magnetar during its formation must be primarily perpendicular to the orbital plane before the supernova explosion, and be large.