2008CBET.1213....1P

G. Pojmanski, Warsaw University Observatory; and J. L. Prieto, K. Z. Stanek, and J. F. Beacom, Ohio State University, report the detection of SN 2007sr in several V-band images obtained by the "All-Sky Automated Survey (ASAS) for Nearby Supernovae" before the announced discovery date (2007 Dec. 18.53 UT; cf. CBET 1172). The supernova is absent in ASAS images obtained on Dec. 1.36 (limiting mag 14.0) but is clearly detected in images obtained after Dec. 7.35. The measured V-band magnitudes (± 0.1 mag) are as follows: 2007 Dec. 7.35, 13.46; 14.36, 12.70; 18.35, 12.83; 22.34, 12.91; 26.33, 13.08; 2008 Jan. 3.32, 13.58; 7.35, 13.62; 11.37, 13.87; 15.31, 13.84. ASAS data show that this nearby type-Ia supernova (CBET 1173, 1174) had peaked around Dec. 14 UT and was therefore detected about 7 days before peak. A formal fit to the ASAS V-band light curve, using the template-fitting method of Prieto et al. (2006, Ap.J. 647, 501), gives the time of maximum as Dec. 16 at V = 12.79, with a light-curve decline rate after 15 days (delta_m15) of 0.8-0.9 mag. Using the calibrated peak absolute magnitudes for a type-Ia supernovae in the Hubble flow with similar decline rates from Prieto et al. (using H_0 = 72 km/s/Mpc), a distance modulus to NGC 4038 of 32.0 mag (25 Mpc) is estimated, after correcting for Galactic extinction in the line-of-sight (A_V = 0.15 mag; Schlegel et al. 1998, Ap.J. 500, 525).