There is irresistible observational evidence that binary systems of compact objects with at least one neutron star are progenitors of short gamma-ray bursts, as well as a production site for $r$-process elements, at least when some matter is ejected by the merger and an accretion disk is formed. The recent observations of gravitational waves in conjunction with electromagnetic counterparts fuel the need for models predicting the outcome of a given merger and the properties of the associated matter outflows as a function of the initial parameters of the binary. In this manuscript, we provide updated fitting formulas that estimate the disk mass for double neutron star binaries and ejecta masses for black hole–neutron star and double neutron star binaries, fitted to the results of numerical simulations. Our proposed fitting formulas improve on existing models by aiming for analytical simplicity, by covering a larger region of parameter space, and by accounting for regions of parameter space not covered by numerical simulations but with physically manifest merger outcomes.

• Received 18 February 2020
• Accepted 17 April 2020

DOI:https://doi.org/10.1103/PhysRevD.101.103002