Black holes and neutron stars are the final products of the collapsed cores of massive stars.
We now detect neutron stars and black holes merging via the detection of gravitational waves.
What is the mass spectrum of these objects?
Is their formation associated with a kick?
How do pairs of compact objects form?
I use multiwavelength, multi epoch spectroscopy to hunt for compact objects in the Local Universe.
Notable relevant publications:
Shenar et al. 2022, A&A, 665, 148: "Characterization of hidden companions in 51 single-lined spectroscopic binaries"
Janssens, Shenar et al. 2022, A&A, 658, 129: "Uncovering astrometric black holes with Gaia"