TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1240 SUBJECT: pre-SN2002ap (SN/GRB?) imaging of M74 DATE: 02/02/02 17:47:21 GMT FROM: Paul Vreeswijk at U of Amsterdam Stephen Smartt, Enrico Ramirez-Ruiz, Institute of Astronomy, Cambridge; and Paul Vreeswijk, University of Amsterdam, report: UBVI images of M74 were taken with the Wide Field Camera on the Isaac Newton Telescope in July 2001, as part of the INT Wide Field Survey. At RA=1:36:24.00, DEC=15:45:13.6 (J2000), consistent with the radio position of SN2002ap (GCN No. 1237) to within 1.3", we detect an object with B=21.6, V=21.2, I=20.5 (with errors +/- 0.2mag). This is a fairly faint object in these short (120s) exposures, and the object shows some inconclusive evidence of being extended. At the spatial resolution of the images (~50 pc) the object could be an unresolved small cluster or HII region, or a predominantly bright star on a variable background. Assuming it is a single star, a distance modulus of 29.5 to M74, and Galactic extinction estimates from Schlegel et al. (1998; E(B-V)=0.07), we estimate absolute magnitudes of M_B = -8.2, M_V = -8.5, M_I = -9.1. The colours B-V=0.3, V-I=0.6 and absolute magnitudes are consistent with a very luminous early to mid F-type supergiant. The bolometric luminosity is approximately 10**5.3 L_solar, which would place the star in the Luminous Blue Variable region of the HR-diagram (Humphreys & Davidson 1994, PASP, 704, 1025), and suggest an initial mass of around 40 M_sol. We currently have no estimate of the internal reddening in the host galaxy, however note that any significant extinction would make the star intrinsically bluer and more luminous. Further astrometry and image shape analysis are required to confirm that the progenitor object is stellar, and we encourage monitoring of this very interesting supernova at all wavelengths. For an image of M74 and BVI zooms of the region around SN2002ap, see: http://www.science.uva.nl/~pmv/m74sn2002ap.gif