GW170817 showed that neutron star mergers not only emit gravitational waves but also can release electromagnetic signatures in multiple wavelengths. Within the first half of the third observing run of the Advanced LIGO and Virgo detectors, there have been a number of gravitational wave candidates of compact binary systems for which at least one component is potentially a neutron star. In this article, we look at the candidates S190425z, S190426c, S190510g, S190901ap, and S190910h, predicted to have potentially a non-zero remnant mass, in more detail. All these triggers have been followed up with extensive campaigns by the astronomical community doing electromagnetic searches for their optical counterparts; however, according to the released classification, there is a high probability that some of these events might not be of extraterrestrial origin. Assuming that the triggers are caused by a compact binary coalescence and that the individual source locations have been covered during the EM follow-up campaigns, we employ three different kilonova models and apply them to derive possible constraints on the matter ejection consistent with the publicly available gravitational-wave trigger information and the lack of a kilonova detection. These upper bounds on the ejecta mass can be related to limits on the maximum mass of the binary neutron star candidate S190425z and to constraints on the mass-ratio, spin, and NS compactness for the potential black hole-neutron star candidate S190426c. Our results show that deeper electromagnetic observations for future gravitational wave events near the horizon limit of the advanced detectors are essential.
Bibliographical noteFunding Information:
Michael Coughlin is supported by the David and Ellen Lee Postdoctoral Fellowship at the California Institute of Technology. Tim Dietrich acknowledges support by the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 749145, BNSmergers. Sarah Antier is supported by the CNES Postdoctoral Fellowship at Laboratoire Astroparticle et Cosmologie. MB acknowledges support from the G.R.E.A.T research environment funded by the Swedish National Science Foundation. Francois Foucart gratefully acknowledges support from NASA through grant no. 80NSSC18K0565 and from the NSF through grant no. PHY-1806278. The light-curve fitting/upper limits code used here is available at https://github.com/mcoughlin/gwemlightcurves.
- Gravitational waves
- Methods: statistical