Luminosity and mass limits for the progenitor of the type Ic supernova 2004gt in NGC 4038

We report our attempts to locate the progenitor of the type Ic SN 2004gt in NGC 4038. We use high resolution HST ACS images of SN 2004gt and have compared them with deep pre-explosion HST WFPC2 F336W, F439W, F555W and F814W images. We identify the SN location on the pre-explosion frames with an accuracy of 5mas. We show that the progenitor is below the detection thresholds of all the pre-explosion images. These detection limits are used to place luminosity and mass limits on the progenitor, by comparing them with stellar evolution tracks on the Hertzsprung-Russell diagram. The progenitor of SN 2004gt seems to be restricted to a low-luminosity high-temperature star, either a single WC star with initial mass $>40M_{\odot}$ or a low mass star in a binary. The pre-explosion data cannot distinguish between the two scenarios.