Light curves of SN 1993J from the Keck Northeast Astronomy Consortium

Abstract

We present BVRI photometry of SN 1993J, as well as data on its likely progenitor. The post-explosion data were obtained with CCDs attached to telescopes (aperture size 0.4 to 0.6 m) on the campuses of the Keck Northeast Astronomy Consortium members by the authors and their students. Our data show that the supernova rose to a second maximum in all colors and has declined steadily since then. This is unlike either the plateau or linear version of the typical Type II light curve. Except for the initial peak, the light curve bears a strong resemblance to SNe Ib, supporting suggestions that this is a Type IIb event. The position of the supernova, as measured on our images, agrees to within 0.1 arcsec with the position of a faint, apparently stellar image on a CCD R image taken with the 0.9 m telescope at KPNO on 1992 October 2. The likely progenitor is also visible on B and I frames taken with the 0.9 m Burrell Schmidt telescope of the Warner and Swasey Observatory, Case Western Reserve University, at KPNO in 1993 February. Examination of a photograph of M81 taken on 1993 March 27.1 (UT) by an amateur astronomer allows us to set a constraint on its brightness at that time.