2024/07/09 by Andrew Gould, Gould, Andrew · 1 citation
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #FOS: Physical sciences #Relativity and Gravitational Theory
paper · pdf · doi:10.48550/arxiv.2407.06484
openalex publication_date 2024/07/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The Roman microlensing program can detect and fully characterize black holes (BHs) that are in orbit with about 30 million solar-type and evolved stars with periods up to the mission lifetime P0.2au, i.e., P> 10 d (M/M_\odot)-1/2, where M is the BH mass. For BH companions of about 150 million later (fainter) main-sequence stars, the threshold of detection is a>0.2 au × 10^(H\rm Vega-18.5)/5. The present Roman scheduling creates a "blind spot" near periods of P=3.5 yr due to a 2.3-year gap in the data. It also compromises the characterization of BHs in eccentric orbits with periods P>3 yr and peribothra within a year of the mission midpoint. I show that one can greatly ameliorate these issues by making a small adjustment to the Roman observing schedule. The present schedule aims to optimize proper-motion measurements, but the adjustment proposed here would degrade these by only 4%-9%. For many cases of P>90 d BHs, there will be discrete and/or continuous degeneracies. For G-dwarf and evolved sources, it will be straightforward to resolve these by radial-velocity (RV) follow-up observations, but such observations will be more taxing for fainter sources. Many BH-binaries in orbits of 5 yr