Double Compact Objects as Low-frequency Gravitational Wave Sources - AstrophysicsReport as inadecuate

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Abstract: We study the Galactic field population of double compact objects NS-NS,BH-NS, BH-BH binaries to investigate the number if any of these systems thatcan potentially be detected with LISA at low gravitational-wave frequencies. Wecalculate the Galactic numbers and physical properties of these binaries andshow their relative contribution from the disk, bulge and halo. Although theGalaxy hosts 10^5 double compact object binaries emitting low-frequencygravitational waves, only a handful of these objects in the disk will bedetectable with LISA, but none from the halo or bulge. This is because the bulkof these binaries are NS-NS systems with high eccentricities and long orbitalperiods weeks-months causing inefficient signal accumulation small number ofsignal bursts at periastron passage in 1 yr of LISA observations renderingthem undetectable in the majority of these cases. We adopt two evolutionarymodels that differ in their treatment of the common envelope phase that is amajor and still mostly unknown process in the formation of close doublecompact objects. Depending on the adopted evolutionary model, our calculationsindicate the likely detection of about 4 NS-NS binaries and 2 BH-BH systemsmodel A; likely survival of progenitors through CE or only a couple of NS-NSbinaries model B; suppression of the double compact object formation due to CEmergers.

Author: Krzysztof Belczynski, Matthew Benacquista, Tomasz Bulik


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