Rotational Evolution of Protoneutron Stars

Abstract

We study the rotational evolution of a protoneutron star with hyperons and nucleons or solely nucleons in its core due to the escape of the trapped neutrinos. It is found that at the early stage of its evolution, the stellar crust contracts significantly, consequently the star spins up. At the late stage, a the protoneutron star with hyperons, it keeps shrinking and spinning up till all the trapped neutrinos escape. Consequently, the distribution of the stellar initial spin periods is skewed toward shorter periods. For a protoneutron star with only nucleons, the expansion of its core dominates, and the stellar rotation slows down. After the neutrinos escape, the range of the spin periods is narrower than the initial one, but the distribution is still nearly uniform. If the hyperonic star is metastable, its rotational frequency accelerates distinguishedly before it collapses to a black hole.