The progenitor system of the compact binary merger GW190425 had a total mass of 3.4 ^ { +0.3 } _ { -0.1 } M _ { \sun } ( 90th-percentile confidence region , with individual component masses of m _ { 1 } = 2.02 ^ { +0.58 } _ { -0.34 } and m _ { 2 } = 1.35 ^ { +0.26 } _ { -0.27 } M _ { \sun } ) as measured from its gravitational wave signal .
This mass is significantly different from the Milky Way ( MW ) population of binary neutron stars ( BNSs ) that are expected to merge in a Hubble time and from that of the first BNS merger , GW170817 .
Here we explore the expected electromagnetic signatures of such a system .
We make several astrophysically motivated assumptions to further constrain the parameters of GW190425 .
By simply assuming that both components were NSs , we reduce the possible component masses significantly , finding m _ { 1 } = 1.85 ^ { +0.27 } _ { -0.19 } M _ { \sun } and m _ { 2 } = 1.47 ^ { +0.16 } _ { -0.18 } M _ { \sun } .
However if the GW190425 progenitor system was a NS-black hole merger , we find best-fitting parameters m _ { 1 } = 2.19 ^ { +0.21 } _ { -0.17 } M _ { \sun } and m _ { 2 } = 1.26 ^ { +0.10 } _ { -0.08 } M _ { \sun } .
For a well-motivated BNS system where the lighter NS has a mass similar to the mass of non-recycled NSs in MW BNS systems , we find m _ { 1 } = 2.03 ^ { +0.15 } _ { -0.14 } M _ { \sun } and m _ { 2 } = 1.35 \pm 0.09 M _ { \sun } , corresponding to only 7 % mass uncertainties and reducing the 90th-percentile mass range to 32 % and 34 % the size of the original range , respectively .
For all scenarios , we expect a prompt collapse of the resulting remnant to a black hole .
Examining detailed models with component masses similar to our best-fitting results , we find the electromagnetic counterpart to GW190425 is expected to be significantly redder and fainter than that of GW170817 .
We find that almost all reported observations used to search for an electromagnetic counterpart for GW190425 were too shallow to detect the expected counterpart .
If the LIGO-Virgo Collaboration promptly provides the chirp mass , the astronomical community can adapt their observations to improve the likelihood of detecting a counterpart for similarly “ high-mass ” BNS systems .