Survey of Extreme Black Hole Outbursts with ~100y of DASCH Data

The Digital Access to a Sky Century @ Harvard (DASCH) project has now scanned and done full photometric/astrometric reductions on half the sky (Galactic latitudes b = 0 - 90deg) when data release DR6 is enabled in December. The speaker will review the overall project, briefly, and then present initial results on the search for historic outbursts from black hole low mass X-ray binaries (BH-LMXBs) all of which are transients. This was one of the primary motivations for undertaking DASCH, and already yields interesting new results on the outburst Duty Cycles which constrain the BH-LMXB population and thus formation mechanisms. He will also discuss some examples of long-term AGN variability (3C273, OJ287 and others) which enable the study of extreme flares to be conducted on days to decades timescales.