Magnetar formation through a convective dynamo in protoneutron stars

Raphaël Raynaud (1, 2) , Jérôme Guilet (1, 2) , Hans-Thomas Janka (3) , Thomas Gastine (4)

1 DAP - Département d'Astrophysique (ex SAP)
2 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
3 MPA - Max-Planck-Institut für Astrophysik
4 IPGP - Institut de Physique du Globe de Paris

The release of spin-down energy by a magnetar is a promising scenario to power several classes of extreme explosive transients. However, it lacks a firm basis because magnetar formation still represents a theoretical challenge. Using the first three-dimensional simulations of a convective dynamo based on a protoneutron star interior model, we demonstrate that the required dipolar magnetic field can be consistently generated for sufficiently fast rotation rates. The dynamo instability saturates in the magnetostrophic regime with the magnetic energy exceeding the kinetic energy by a factor of up to 10. Our results are compatible with the observational constraints on galactic magnetar field strength and provide strong theoretical support for millisecond protomagnetar models of gamma-ray burst and superluminous supernova central engines.

Mots clés: Dynamo action; Magnetars; Protoneutron star; Gamma Ray Bursts; Supernova core collapse; Convection

Domaines: Phénomènes cosmiques de haute energie [astro-ph.HE]; Astrophysique stellaire et solaire [astro-ph.SR]

Raphaël Raynaud, Jérôme Guilet, Hans-Thomas Janka, Thomas Gastine. Magnetar formation through a convective dynamo in protoneutron stars. Science Advances , 2020, 6 (eaay2732), ⟨10.1126/sciadv.aay2732⟩. ⟨hal-02428428⟩