Title: Needles in the Haystack: Discovering Transients in between Novae and Supernovae


For the past several decades, there has existed a glaring six-magnitude luminosity gap between the brightest novae and faintest supernovae. To find optical transients that are fainter and faster than supernovae and rarer than novae, we designed a systematic search --- the "Palomar Transient Factory". Theorists predict a variety of mechanisms to produce transients in the gap and observers have the best chance of finding them in the local universe. Here I will present discoveries and unique physics of cosmic explosions that bridge this gap between novae and supernovae. This small number of intensively followed-up discoveries sets the stage for population studies with the upcoming "Large Synoptic Survey Telescope". This effort works towards building a complete inventory of transients in the local universe (d < 200 Mpc). It better prepares us for the search for potential electromagnetic counterparts to events in the emerging fields of gravitational wave, neutrinos, UHECR and TeV astronomy.