A More Stringent Constraint on the Mass Ratio of Binary Neutron Star Merger GW170817

Abstract

Recently, the LIGO-Virgo collaboration reported their first detection of gravitational wave (GW) signals from a low mass compact binary merger GW170817, which is most likely due to a double neutron star (NS) merger. With the GW signals only, the chirp mass of the binary is precisely constrained to 1.188 +0.004 −0.002 M , but the mass ratio is loosely constrained in the range 0.4 − 1, so that a very rough estimation of the individual NS masses (1.36 M < M 1 < 2.26 M and 0.86 M < M 2 < 1.36 M ) was obtained. Here we propose that if one can constrain the dynamical ejecta mass through performing kilonova modeling of the optical/IR data, by utilizing an empirical relation between the dynamical ejecta mass and the mass ratio of NS binaries, one may place a more stringent constraint on the mass ratio of the system. For instance, considering that the red "kilonova" component is powered by the dynamical ejecta, we reach a tight constraint on the mass ratio in the range of 0.46 − 0.59. Alternatively, if the blue "kilonova" component is powered by the dynamical ejecta, the mass ratio would be constrained in the range of 0.53 − 0.67. Overall, such a multi-messenger approach could narrow down the mass ratio of GW170817 system to the range of 0.46 − 0.67, which gives a more precise estimation of the individual NS mass than pure GW signal analysis, i.e. 1.61 M < M 1 < 2.11 M and 0.90 M < M 2 < 1.16 M .

Kilonovae

“…2017b; Dietrich and Ujevic 2017; Gao et al. 2017)However, a small NS radius may be in tension with the creation of a large accretion disk needed to produce the red KN ejecta (Radice et al. 2018c)…”

GLADE: A galaxy catalogue for multimessenger searches in the advanced gravitational-wave detector era

“…Abbott et al 2017c), one can refine the parameter estimations for the GW source with priors derived from the EM counterpart and properties of the host (see e.g. Guidorzi et al 2017;Gao et al 2017;Abbott et al 2019a), or use GW parameter estimations to draw conclusions on the EM source (e.g. Rezzolla et al 2018), the host (e.g.…”

The Gravitational-wave physics II: Progress

“…For example, we have carefully studied the evolution of NS-WD binaries, especially on the orbital evolution of ultra-compact Xray binaries and its GW radiation [623,624]. We have investigated in details about the EM properties of BNS and NS-BH mergers and the constraints on the merger products and equation of state (EOS) of NSs that can be obtained from both GW and EM observations of GW170817, the first GW source with multi-wavelength EM counterparts detected [625][626][627][628][629]. We have studied the formation and evolution of stellar BBHs (sBBHs) and BNSs and its relation to the properties of the host galaxies of BBH mergers [630], and we predicted the SGWBs resulting from sBBHs and BNSs [631].…”