Speaker
Description
The angular size of the innermost regions of AGN are generally too small to be resolved, thus we must rely on indirect techniques to probe these regions. Reverberation mapping measures time lags between light curves of different wavelengths to estimate size scales. In the simplest picture for continuum reverberation, variable X-rays from close to the black hole irradiate an optically thick, geometrically thin accretion disk driving variations at longer wavelengths - the inner hot disk 'sees' variations before the outer cooler disk. Thus, we expect time lags that increase with wavelength, with the lags on the other of ~1 day. Before Swift, it was technically challenging to obtain good enough light curves to measure such short lags with high confidence. But, the capability of Swift to perform sub-daily monitoring of AGN for in X-rays plus 6 UV/optical filters for many months revolutionized continuum reverberation mapping studies. High cadence, high S/N, multiband light curves obtained by Swift led to high significance measurements that time lags increase with wavelength. I will review continuum reverberation in AGN, and what we have learned about the innermost regions of AGN.
