The detection rate of inspiral and quasi-normal modes of Population III binary black holes which can confirm or refute the general relativity in the strong gravity region

Abstract

Using our population synthesis code, we found that the typical chirp mass defined by (m 1 m 2 ) 3/5 /(m 1 + m 2 ) 1/5 of Population III (Pop III) binary black holes (BH-BHs) is ∼ 30 M ⊙ with the total mass of ∼ 60 M ⊙ so that the inspiral chirp signal as well as quasi normal mode (QNM) of the merging black hole (BH) are interesting targets of KAGRA. The detection rate of the coalescing Pop III BH-BHs is ∼180 events yr.33) · Err sys in our standard model where SFR p , f b and Err sys are the peak value of the Pop III star formation rate, the binary fraction and the systematic error with Err sys = 1 for our standard model, respectively. To evaluate the robustness of chirp mass distribution and the range of Err sys , we examine the dependence of the results on the unknown parameters and the distribution functions in the population synthesis code. We found that the chirp mass has a peak at ∼ 30 M ⊙ in most of parameters and distribution functions as well as Err sys ranges from 0.046 to 4. Therefore, the detection rate of the coalescing Pop III BH-BHs ranges about 8.3 − 720 events yrThe minimum rate corresponds to the worst model which we think unlikely so that unless (SFR p /(10 −2.5 M ⊙ yr1, we expect the Pop III BH-BHs merger rate of at least one event per year by KAGRA. Nakano, Tanaka & Nakamura (2015) show that if S/N of QNM is larger than 35, we can confirm or refute the General Relativity (GR) more than 5 sigma level. In our standard model, the detection rate of Pop III BH-BHs whose S/N is larger than 35 is 3.2 events yr −1 (SFR p /(10 −2.5 M ⊙ yr −1 Mpc −3 )) · ([f b /(1 + f b )]/0.33) · Err sys . Thus, there is a good chance to check whether GR is correct or not in the strong gravity region.

Upper Limits on the Rates of Binary Neutron Star and Neutron Star–black Hole Mergers From Advanced Ligo’s First Observing Run

“…For example, a calculation prior to the start of O1 predicted 0.0005-4 detections of BNS signals during O1 (Aasi et al 2016). Some works, however, predicted that BBH mergers would be the most promising candidates (Dominik et al 2015;Belczynski et al 2016;Kinugawa et al 2016).…”

Gravitational wave background from Population III binary black holes consistent with cosmic reionization

“…The origin of such massive and compact BBHs are of astrophysical interest, and several pathways have been proposed for their formation. One channel is massive binary evolution in a metal-poor environment (Bond & Carr 1984;Belczynski, Bulik & Rudak 2004;Kulczycki et al 2006;Dominik et al 2012;Kinugawa et al 2014Kinugawa et al , 2016Belczynski et al 2016), including rapid rotation and tides (Mandel & de Mink 2016), or assisted by accretion discs in active galactic nuclei (Bartos et al 2016;Stone, Metzger & Haiman 2016). Alternative formation channels include stellar collisions in dense clusters (e.g.…”

How to confirm the existence of population III stars by observations of gravitational waves

“…In Refs. [3,4], Pop III binaries tend to become BH-BH binaries which merge within the Hubble time. The typical mass of Pop III BH-BH binaries is ∼ 30 M which does not depend on the binary parameters and the initial distribution functions.…”

“…As an example of Pop III model, we use Kinugawa's models [4]. An employed model in this paper is the standard model (the flat initial mass function model) with the heavier initial mass range and the conservative core-merger criterion during the common envelope phase.…”

“…To explain the existence of such high mass black holes, there are some scenarios. One of the possible origins of GW150914 is the Population III (Pop III) stars, i.e., the zero metal stars formed first after the big bang [3,4]. While Population I (Pop I) stars and Population II (Pop II) stars with nonzero metal are observed electromagnetically, the existence of Pop III stars has not been confirmed yet by electromagnetic wave observations.…”