Binary Neutron Star Impostors & Event GW190814

In the first part of this talk I will address the following question: can we distinguish a binary black hole undergoing a merger from a binary neutron star if the individual compact companions have masses that fall inside the so-called mass gap of $3-5\ M_\odot$? For neutron stars, achieving such masses typically requires extreme compactness. I therefore will present general relativistic initial data and evolution simulations of binary neutron stars-the impostors- initially in quasiequilibrium circular orbits and supported by an EOS near the causal limit that exhibit extreme compactness. I will compare their gravitational waveforms with those of merging black hole binaries of the same mass. In the second part I will discuss event GW190814 of a merging binary having a $\sim 23 M_\odot$ black hole and a $\sim 2.6 M_\odot$ compact companion. I will explore some consequences of the assumption that the secondary was a neutron star.