why do supernovas result in a magnetar rather than a neutron star

Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter, and have a mass of about 1.4 solar masses. They are formed by the collapse of a star with a mass 10–25 times that of the Sun. --- Send in a voice message: https://podcasters.spotify.com/pod/show/david-nishimoto/message