HIPS AGaiN/Gorjian

The HIPS AGaiN (Hidden in Plain Sight AGaiN) team will be using archival surveys for stellar variability to detect variability in active galactic nuclei (AGN) in the background.

Current theoretical modelling of the accretion disks around the supermassive black holes (SMBH) at the centers of galaxies, known as active galactic nuclei (AGN), does not match well to that determined by observations. A way to measure the unresolved accretion disk size is through reverberation mapping (RM) of short timeframe variable AGN.   Unfortunately, there is a very small sample size of candidate AGN with known short-term variability. These objects have short-period emission events where variations in high energy/short wavelength light close to the SMBH travel outward and are absorbed at larger radii of the accretion disk and re-emitted at lower energy/longer wavelengths. The time delay between initial detection of these variations and the later detections at longer wavelengths provides a way to measure the diameter of the accretion disk.  Measuring the size of the accretion disk can be used to derive its luminosity so the AGN can then be used as a standard candle. This in turn can be used to determine the Hubble constant over the vast distances over which the AGN can be observed. In this research we will identify AGN with measurable short-term variability at wavelengths of 3.6 and 4.5 microns over the period of days to weeks which can then be used as targets for RM monitoring to help determine their accretion disk sizes. We propose to create a catalog of reliable AGN candidates with observed short-term variability for lightcurve analysis and reverberation mapping using the Young Stellar Object VARiability survey (YSOVAR) conducted by the Spitzer Space Telescope of multiple star forming regions.