Gravitational Wave Emission from Core Collapse of Massive Stars

We derive estimates for the characteristics of gravitational radiation fromstellar collapse, using recent models of the core-collapse of Chandrasekharmass white dwarfs (accretion induced collapse), core-collapse supernovae andcollapsars, and the collapse of very massive stars (~> 300 Msun). We studygravitational-wave emission mechanisms using several estimation techniques,including two-dimensional numerical computation of quadrupole wave emission,estimates of bar-mode strength, estimates of r-mode emission, and estimates ofwaves from black hole ringing. We also review the rate at which the relevantcollapses are believed to occur, which has a major impact on their relevance asastrophysical sources. Although the latest supernova progenitor simulationsproduce cores rotating much slower than those used in the past, we find thatbar-mode and r-mode instabilities from core-collapse supernovae remain amongthe leading candidate sources for LIGO-II. Accretion induced collapse (AIC) ofa white dwarf could produce gravitational-wave signals similar to those fromcore-collapse. In the models that we examine, such collapses are not unstableto bar modes; we note that models recently examined by Liu and Lindblom, whichhave slightly more angular momentum, are certainly unstable to bar formation.Because AIC events are probably 1,000 times less common than core-collapsesupernovae, the typical AIC event will be much further away, and thus theobserved waves will be much weaker. In the most optimistic circumstances, wefind it may be possible to detect gravitational waves from the collapse of 300Msun Population III stars.Comment: 48 pages including 11 figures, to appear in ApJ. New version incorporates several helpful comments; also corrects some errors in the displayed LIGO noise curve, and several typo