The progenitor mass of the magnetar SGR1900+14

TL;DR

This study estimates the progenitor mass of the magnetar SGR 1900+14 as approximately 17 solar masses, challenging the idea that only very massive stars can produce magnetars and suggesting alternative formation mechanisms.

Contribution

The paper provides the first direct measurement of a magnetar's progenitor mass that is significantly lower than previous estimates, questioning existing theories about magnetar origins.

Findings

Progenitor mass of SGR 1900+14 is about 17 solar masses.

Magnetars can originate from less massive stars than previously thought.

Alternative models like fossil fields or binary evolution are supported.

Abstract

Magnetars are young neutron stars with extreme magnetic fields (B > 10^{14}-10^{15}G). How these fields relate to the properties of their progenitor stars is not yet clearly established. However, from the few objects associated with young clusters it has been possible to estimate the initial masses of the progenitors, with results indicating that a very massive progenitor star (M_prog >40Msun) is required to produce a magnetar. Here we present adaptive-optics assisted Keck/NIRC2 imaging and Keck/NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and report that the initial progenitor star mass of the magnetar was a factor of two lower than this limit, M_prog=17 \pm 2 Msun. Our result presents a strong challenge to the concept that magnetars can only result from very massive progenitors. Instead, we favour a mechanism which is dependent on more than just initial stellar mass for the production of these extreme magnetic fields, such as the "fossil-field" model or a process involving close binary evolution.