Photometric Typing Analyses of Three Young Supernovae Observed with the Robotic Palomar 60 Inch Telescope

We present photometric typing analyses of three young supernovae observedwith the Robotic 60-inch Telescope at Palomar Observatory (P60). Thisrepresents the first time that such photo-typing has been attempted, in a blindfashion, on newly-discovered supernovae. For one of the target supernovae,SN2004cs, our photometry provided the first constraint on the SN type, which wepredicted would be type Ia. To the contrary, however, our subsequent Keckspectroscopy shows it to be an unusual type II supernova. For each of the othertwo supernovae, SN2004dh (type II) and SN2004dk (type Ib), our photo-typingresults are consistent with the known type of the event as determined fromground-based spectroscopy; however, the colors of SN2004dk are also consistentwith a type Ic or type II classification. We discuss our approach to thechallenges of photo-typing - contamination by host galaxy light and the unknownphotometric quality of the data - in the case where it is desirable to completethe analysis with just one night of observations. The growing interest in theproperties and behavior of very young supernovae, and the increased discoveryrate for such events, mean that prompt photo-typing analyses can provide usefulinput to observational campaigns. Our results demonstrate the value andfeasibility of such a project for P60, at the same time illustrating its chiefinherent shortcoming: an inability to identify new and unusual events as suchwithout later spectroscopic observations.Comment: PASP in press; AASTeX; 13 pages, 4 figures; minor changes as per referee repor