Program: GN-2009A-Q-7

The first Pan-STARRS telescope, PS1, is now collecting survey data on a nightly basis, for the first time producing new transient detections. We expect to reach the milestone of Operational Readiness Review (ORR) before the end of the calendar year, and a ramping up of science production is now a primary component of the ORR push. One of the primary branches of the PS1 science strategy is the Medium Deep survey, which will detect thousands of Type Ia Supernovae (SN1a). This extraordinary yield from a single survey will allow us to put new constraints on the nature of Dark Energy and to improve our understanding of the progenitor systems that produce SN1a. Pan-STARRS will usher in a new epoch of object characterization by photometry alone, both by virtue of being deeper and broader than any survey before, but mostly by virtue of the time domain. Opportunities abound for using time information to discriminate between variable and static objects with the same colors. However, characterization by photometry alone (color and time variability) cannot be done without extensive training, and it takes spectroscopy to sort out all the different kinds of objects that Pan-STARRS will discover. Our baseline program will be spectroscopic observations of SN1a to identify them, obtain their redshifts, and characterize their host galaxies. Detection of hundreds of explosions per month easily provides targets for any given night allocated for spectroscopy, but the density on the sky is low enough that it is unlikely we will be able to observe two simultaneously. The Gemini North telescope can reach the depth necessary for spectroscopic characterization of the majority of PS1 SN candidates. We are requesting GMOS queue time with Target of Opportunity status to provide the flexibility needed to target the most interesting candidates as they are discovered.