MIT Astrophysics Colloquium 2/15/2022 — Observing Black Hole Shadows Via Self-lensing Tomography (speaker: Jordy Davelaar, Columbia University, Flatiron Institute)
Tuesday February 15, 2022 4:00 pm
via Zoom and in-person for individuals in MIT's Covid Pass system with a valid health attestation
Abstract: In 2019 the Event Horizon Telescope (EHT) collaboration published the first direct image of a black hole shadow. This result signaled the arrival of event horizon scale observations that will allow us to test our knowledge of gravity and plasma physics around compact objects. Although the EHT uses unprecedented resolution, only two potential supermassive black holes are thought to be resolvable. In my talk, I will show that by using self-lensing properties of supermassive black hole binaries, it is possible to extract black hole shadow sizes from sources inaccessible by high-resolution VLBI techniques. The method relies on viewing the orbital plane close to edge-on; in this case, the black holes align twice per orbit with respect to the line of sight and generate a self-lensing flare (SLF). In this SLF, we explicitly identified a feature associated with the size of the shadow of the lensed black hole. This new method will potentially increase the number of observable black hole shadows when large time-domain surveys, such as LSST by the Vera Rubin Observatory, will start their operations.