Date of Completion

Spring 5-1-2021

Project Advisor(s)

Jonathan Trump; Yasaman Homayouni; Kyungseon Joo; Richard Jones

University Scholar Major



Astrophysics and Astronomy


We report accretion-disk structure measurements for eight rapidly accreting supermassive black holes selected from the Sloan Digital Sky Survey Reverberation Mapping project sample. Reverberation mapping uses light echoes to measure disk size from the time lag between variability in the inner/hotter and outer/cooler disk emission. We use Hubble Space Telescope ultraviolet observations coordinated with optical monitoring from the Liverpool Telescope and Las Cumbres Observatory. We find ten significant UV/optical lags for five out of the eight total targets. Through these time lags, we study the accretion disk as a function of disk size, temperature profile and radiative efficiency. We find that the best-fit color profile for our sample matches the classic analytic model for a disk around a compact object. We find slightly larger disk sizes than expected, providing evidence for diffuse nebular emission from Balmer and FeII lines over discrete wavelength ranges. Our results overall are broadly consistent with the classic model but also support various theories pointing towards larger disk sizes in a subset of black holes. In the near future with new large time-domain surveys, the techniques we use in this work can be used on a larger scale to clearly determine the accuracy and reliability of this analytical model.