Speaker
Description
Active Galactic Nuclei (AGNs) are compact regions powered by the accretion of matter onto the supermassive black holes (SMBHs) at the centers of galaxies. In general relativity, the black hole singularities are hidden behind event horizons, beyond which light cannot escape. However, motivated by the information paradox, a variety of other solutions have been posited that do not have an event horizon, ranging from black hole foils (e.g., gravastars, fuzzballs, etc.) to naked singularities. In this work, we compare the spectral energy distributions (SEDs) of 106 AGNs obtained from the BAT AGN Spectroscopic Survey (BASS) to those predicted by accretion-powered thermal surface emission models that are typical of black hole alternatives. In no source do we detect the excess surface emission, and we find that in 38 AGN, upon assuming that the emission is compact, the observed SED is inconsistent with the presence of excess surface emission. Therefore strongly suggests the presence of an event horizon in those cases. For most of the unconstrained AGN, the constraint is dominated by uncertainty in the source properties (e.g., black hole mass, distance, luminosity, etc.) or variability in the SED from the accretion flow itself, and thus these could benefit from future multiwavelength observations.
| Keyword-1 | Event Horizons |
|---|---|
| Keyword-2 | Surface Emission |
| Keyword-3 | AGNs |