An Upper Mass Limit for the Progenitor of the Type II-P Supernova SN 1999[CLC]gi[/CLC]

Masses and progenitor evolutionary states of TypeII supernovae remain almostunconstrained by direct observations. Only one robust observation of aprogenitor (SN1987A) and one plausible observation (SN1993J) are available.Neither matched theoretical predictions and in this Letter we report limits ona third progenitor (SN1999gi). The Hubble Space Telescope has imaged the siteof the TypeII-P supernova SN1999gi with the WFPC2 in two filters (F606W andF300W) prior to explosion. The distance to the host galaxy (NGC3184) of 7.9Mpcmeans that the most luminous, massive stars are resolved as single objects inthe archive images. The supernova occurred in a resolved, young OB association2.3kpc from the centre of NGC3184 with an association age of about 4Myrs.Follow-up images of SN1999gi with WFPC2 taken 14 months after discoverydetermine the precise position of the SN on the pre-explosion frames. An upperlimit of the absolute magnitude of the progenitor is estimated (M_v >= -5.1).By comparison with stellar evolutionary tracks this can be interpreted as astellar mass, and we determine an upper mass limit of 9(+3/-2)M_solar. Wediscuss the possibility of determining the masses or mass limits for numerousnearby core-collapse supernovae using the HST archive enhanced by our currentSNAP programme.Comment: To appear in ApJ Letters, 16 pages, 3 figure