Long-duration Gamma-ray Burst Progenitors and Magnetar Formation

Abstract

Millisecond magnetars produced in the center of dying massive stars are one prominent model to power gamma-ray bursts (GRBs). However, their detailed nature remains a mystery. To explore the effects of the initial mass, rotation rate, wind mass loss, and metallicity on the GRB progenitors and the newborn magnetar properties, we evolve 227 of $10-30~M_\odot$ single star models from the pre-main-sequence to core collapse by using the stellar evolution code MESA. The pre-supernova properties, the compactness parameter, and magnetar characteristics of models with different initial parameters are presented. The compactness parameter remains a non-monotonic function of the initial mass and initial rotation rate when the effects of vary metallicity and ``Dutch'' wind scale factor are taken into account. We find that the initial rotation rate and mass play the dominant roles in whether a star can evolve into a GRB progenitor. The minimum rotation rate necessary to generate a magnetar gradually reduces as the initial mass increases. The greater the initial metallicity and ``Dutch'' wind scale factor, the larger the minimum rotation rate required to produce a magnetar. In other words, massive stars with low metallicity are more likely to harbor magnetars. Furthermore, we present the estimated period, magnetic field strength, and masses of magnetars in all cases. The typical rotational energy of these millisecond magnetars is sufficient to power long-duration GRBs.