Authors: K. Belczynski, M. Dominik, T. Bulik, R. O'Shaughnessy, C.L. Fryer, D.E. Holz
Date: 2 Apr 2010
Abstract: By combining advances in observational astrophysics with recent progress in stellar evolution, we show that there will be a remarkably high number of black holes with compact object (neutron star or black hole) companions in the local Universe. Data from the Sloan Digital Sky Survey (300,000 galaxies) indicates that recent star formation (within the last 1 billion years) is bimodal: half the stars form from gas with high amounts of metals (solar metallicity), and the other half form with small contribution of elements heavier than Helium (20% solar). Theoretical studies of mass loss derive significantly higher stellar-origin black hole masses (30-80 Msun) than previously estimated for sub-solar compositions. We combine these findings to estimate the probability for detection of gravitational waves arising from the inspiral of double compact objects. Our results show that a low metallicity environment significantly boosts the formation of double compact object binaries with at least one black hole. In particular, we find the gravitational-wave detection rate is increased by a factor of 20 if the metallicity is decreased from solar (as in all previous estimates) to a 50-50 mixture of solar and 10% solar metallicity. The current sensitivity of the largest instruments to double neutron-star binaries (VIRGO: 9 Mpc; LIGO: 18) is not high enough to ensure a first detection. However, our results indicate that if a future instrument increased the reach to 50-100Mpc, a detection of gravitational waves would be expected within the first year of observation. It was previously thought that binary neutron stars were the most likely source, but our results indicate that black-hole binaries are 25-times more likely. We are therefore truly on the cusp of seeing gravitational waves, and the first source ever to be seen is likely to be a black hole binary.
© M. Vallisneri 2012 — last modified on 2010/01/29
Tantum in modicis, quantum in maximis