The Reliability of the Low-latency Estimation of Binary Neutron Star Chirp Mass

The LIGO and Virgo Collaborations currently conduct searches for gravitational waves from compact binary coalescences in real time. For promising candidate events, a sky map and distance estimation are released in low latency to facilitate their electromagnetic follow-up. Currently, no information is released about the masses of the compact objects. Recently, Margalit & Metzger suggested that knowledge of the chirp mass of the detected binary neutron stars could be useful to prioritize the electromagnetic follow-up effort, and urged the LIGO-Virgo collaboration to release chirp mass information in low latency. One might worry that low-latency searches for compact binaries make simplifying assumptions that could introduce biases in the mass parameters: neutron stars are treated as point particles with dimensionless spins below 0.05 perfectly aligned with the orbital angular momentum. Furthermore, the template bank used to search for them has a finite resolution. In this paper we show that none of these limitations can introduce chirp mass biases larger than ∼10−3 M⊙. Even the total mass is usually accurately estimated, with biases smaller than 6%. The mass ratio and effective inspiral spins, on the other hand, can suffer from more severe biases.