04/07/2021
By Nicholas Sorabella

The Kennedy College of Science, Department of Physics & Applied Physics, invites you to attend a master's thesis defense by Nick Sorabella entitled "Self-Lensing Binary Systems: A New Pathway to Measure Compact Object Masses."

The defense will be held on April 19 at 1 p.m. via Zoom. Please contact Silas Laycock for meeting information if you are interested in attending.

Abstract: This work examines the feasibility of using gravitational lensing to measure the mass of compact objects in eclipsing binary systems, specifically X-ray binary systems (XRBs) and supermassive black hole (SMBH) binary systems. We investigate which kind of XRB would be most conducive for viewing the effect, by modeling the amplification curves and determining if any feature of an XRB system could potentially hinder observation of such a signal. We examine the effect of accretion disks and stellar winds, as well as the compact object mass, binary separation, and companion spectral type. Generally speaking, the lensing signal is strongest when the angular size subtended by the companion is small, favoring relatively compact companion stars, although, evolved massive stars (such as certain WR stars) have signals that are feasibly detectable. Interestingly, the self-lensing signal is stronger in binaries with large separations, which is the opposite of the case for all other techniques. Thus, a dedicated self-lensing survey would complement X-ray and radial-velocity techniques, by extending the parameter space for discovery of compact objects. At the same time, a self-lensing survey offers the possibility of revealing a large population of non-accreting compact objects in galactic binary systems. Finally, we apply our extended source self-lensing model to Spikey, the first self-lensing SMBH binary candidate, to test the effect the observed wavelength and inclination of the orbit have on the predicted signal.