Paper: astro-ph/0508462
Date: Mon, 22 Aug 2005 20:04:26 GMT (783kb)

Title: The Spin Periods and Rotational Profiles of Neutron Stars at Birth

Authors: Christian D. Ott (1), Adam Burrows (2), Todd A. Thompson (3), Eli
Livne (4), Rolf Walder (2) ((1) Max-Planck-Institut fuer Gravitationsphysik,
Albert-Einstein-Institut, Potsdam, Germany, (2) Department of Astronomy and
Steward Observatory, The University of Arizona, Tucson (3) Astronomy
Department and Theoretical Astrophysics Center, The University of California,
Berkeley, (4) Racah Institute of Physics, The Hebrew University, Jerusalem,
Israel)

Comments: Submitted to ApJ. 38 pages, including 25 color figures.
High-resolution figures available from the authors upon request
\\
We present results from an extensive set of one- and two-dimensional
radiation-hydrodynamic simulations of the supernova core collapse, bounce, and
postbounce phases, and focus on the protoneutron star (PNS) spin periods and
rotational profiles as a function of initial iron core angular velocity, degree
of differential rotation, and progenitor mass. For the models considered, we
find a roughly linear mapping between initial iron core rotation rate and PNS
spin. The results indicate that the magnitude of the precollapse iron core
angular velocities is the single most important factor in determining the PNS
spin. Differences in progenitor mass and degree of differential rotation lead
only to small variations in the PNS rotational period and profile. Based on our
calculated PNS spins, at ~ 200-300 milliseconds after bounce, and assuming
angular momentum conservation, we estimate final neutron star rotation periods.
We find periods of one millisecond and shorter for initial central iron core
periods of below ~ 10 s. This is appreciably shorter than what previous studies
have predicted and is in disagreement with current observational data from
pulsar astronomy. After considering possible spindown mechanisms that could
lead to longer periods we conclude that there is no mechanism that can robustly
spin down a neutron star from ~ 1 ms periods to the "injection" periods of tens
to hundreds of milliseconds observed for young pulsars. Our results indicate
that, given current knowledge of the limitations of neutron star spindown
mechanisms, precollapse iron cores must rotate with periods around 50-100
seconds to form neutron stars with periods generically near those inferred for
the radio pulsar population.

\\ ( http://arXiv.org/abs/astro-ph/0508462 , 783kb)