Short gamma-ray bursts and gravitational-wave observations from eccentric compact binaries

Abstract

Mergers of compact binaries, such as binary neutron stars (BNSs), neutron star-black hole binaries (NSBHs), and binary black holes (BBHs), are expected to be the best candidates for the sources of gravitational waves (GWs) and the leading theoretical models for short gamma-ray bursts (SGRBs). Based on the observations of SGRBs, we could derive the merger rates of these compact binaries, and study the stochastic GW backgrounds (SGWBs) or the co-detection rates of GWs associate with SGRBs (GW-SGRBs). But before that, the most important thing is to derive the GW spectrum from a single GW source. Usually, GW spectrum from a circular orbit binary is assumed. However, observations of the large spatial offsets of SGRBs from their host galaxies imply that SGRB progenitors may be formed by the dynamical processes, and will merge with residual eccentricities (e r ). The orbital eccentricity has important effect on GW spectra, and therefore on the SGWB and GW-SGRB co-detection rate. Our results show that the power spectra of the SGWBs from eccentric compact binaries are greatly suppressed at low frequencies (e.g., f 1 Hz). Especially, SGWBs from binaries with high residual eccentricities (e.g., e r 0.1 for BNSs) will hard to be detected (above the detection frequency of ∼ 100 Hz). For the co-detection rates of GW-SGRB events, they could be ∼ 1.4 times higher than the circular case within some particular ranges of e r (e.g., 0.01 e r 0.1 for BBH), but greatly reduced for high residual eccentricities (e.g., e r > 0.1 for BNSs). In general, the BBH progenitors produce 200 and 10 times higher GW-SGRB events than the BNS and NSBH progenitors, respectively. Therefore, binaries with low residual eccentricities (e.g., 0.001 e r 0.1) and high total masses will easier to be detected by aLIGO. However, only a small fraction of BBHs could be SGRB progenitors (if they can produce SGRBs), because the predicted GW-SGRB event rate (60∼100 per year) is too high compared with the recent observations, unless they merge with high residual eccentricities (e.g., e r > 0.7).

Dynamical ejecta and nucleosynthetic yields from eccentric binary neutron-star mergers

“…For the sensitivity and instrumental characteristics of adLIGO the numbers suggest so far that GW detections from eccentric sources are expected to be rare at best. In particular, highly eccentric binary neutron stars are extremely difficult to detect for the detector characteristics of adLIGO [29] mainly due to missing signal power at frequencies around ∼ 100 Hz where the detector performs best.…”

Kilonova rates from spherical and axisymmetrical models

“…However, the power-law delay model has been shown to be inconsistent with the observations (e.g. Tan et al 2018). We used the formula for the lognormal time delay model they give to simulate the redshift distribution for our kilonova samples (Eq.…”

“…There are numerous works which give an estimation for KN rates for the future sky surveys (e.g. Wollaeger et al (2018); Tan et al (2018); Pol et al (2018); Scolnic et al (2018); Mapelli & Giacobbo (2018); Chruslinska et al (2018); Kruckow et al (2018);Jin et al (2018); Vigna-Gómez et al (2018); Eldridge et al (2019); Cao et al (2018); Dominik et al (2013); Sun et al (2015); Sadowski et al (2008); Cowperthwaite et al (2019) (hereafter C19)). When calculating these rates one has to take into account the short gammaray burst (sGRB) rate determined from observations (e.g.…”

Stochastic gravitational-wave background from spin loss of black holes

“…[26,36]), which is reasonable for current ground detectors, since the overlap reduction function modified the most sensitive band to 10-50 Hz. Our fiducial QNM model is constructed as follows: (i) we assume R m (z) to be proportional to the cosmic star formation rates ( [37]) with a constant time delay (3.65 Gyr) between the star formation and binary black hole merger [38] and normalized to R m (0) = 28 Gpc −3 yr −1 (see detail in [39]). (ii) we adopt a uniform distribution for 10M < M 1,2 < 30M for θ = (M 1 , M 2 ), (iii) we adopt (dE/d f ) IMR [36] for the IMR parts of the waveform superimpose (dE SD /d f ) QNM directly as an additional contribution.…”