A SEARCH FOR FAST OPTICAL TRANSIENTS IN THE Pan-STARRS1 MEDIUM-DEEP SURVEY: M-DWARF FLARES, ASTEROIDS, LIMITS ON EXTRAGALACTIC RATES, AND IMPLICATIONS FOR LSST. - Berger, E.; Leibler, C. N.; Chornock, R.; Rest, A.; Foley, R. J.; Soderberg, A. M.; Price, P. A.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Huber, M. E.; Magnier, E. A.; et al. (Astrophysical Journal, 2013)