Program: GS-2010A-Q-11

Two reasons motivate us to build a complete inventory of transients in the local universe (d < 200 Mpc). First, there exists a glaring six-magnitude luminosity gap between the brightest novae and faintest supernovae, especially on short timescales. 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. Second, the budding fields of gravitational waves, neutrinos, ultra high energy cosmic rays and TeV astronomy are also limited to ~100 Mpc horizon either due to instrumental sensitivity or physical effects. The Palomar Transient Factory (PTF) is now fully operational and has proven to be an extremely efficient transient discovery and classification machine. We systematically target local galaxy-light concentrations over a large area (~18000 galaxies) and are unique in our depth (m < 21) and cadence (1-day). We also have a multi-wavelength follow-up program (Optical/NIR at Palomar and Keck, UV/X-ray with Swift, radio with EVLA). The most crucial information needed after discovery is the spectrum. A spectrum can help unambiguously identify a transient by revealing its distance, physical state and composition. Gemini's unique rapid response capability, queue scheduling and availability of a sensitive spectrograph at almost all times is ideally suited to this program. Here we propose for nine rapid-response target-of-opportunity triggers on the Gemini-South (4 hrs) and Gemini-North telescopes (3 hrs).