The Optical/Near-Infrared Light Curves of SN 2002ap for the First 1.5 Years after Discovery

Late-time BV RIJHK photometry of the peculiar Type Ic SN 2002ap, taken between 2002 June 12 and 2003 August 29 with the MAGNUM telescope, is presented. The light curve decline rate is derived in each band and the color evolution is studied through comparison with nebular spectra and with SN 1998bw. Using the photometry, the OIR bolometric light curve is built, extending from before light maximum to day 580 after explosion. The light curve has a late-time shape strikingly similar to that of the hypernova SN 1998bw. The decline rate changes from 0.018 mag/day between day 130 and 230 to 0.014 mag/day between day 270 and 580. To reproduce the late-time light curve, a dense core must be added to the 1-D hypernova model that best fits the early-time observations, bringing the ejecta mass from 2.5 M⊙ to 3 M⊙ without much change in the kinetic energy, which is 4× 10 ergs. This is similar to the case of other hypernovae and suggests asymmetry. A large H-band bump developed in the spectral energy distribution after ∼ day 300, probably caused by strong [Si I] 1.646μm and 1.608μm emissions. The near-infrared flux contribution increased simultaneously from < 30% to > 50% at day 580. The near-infrared light curves were compared with those of other Type Ib/c supernovae, among which SN 1983I seems similar to SN 2002ap both in the near-infrared and in the optical. Subject headings: supernovae: general—supernovae: individual (SN 2002ap)—supernovae: photometry Correspondence author’s address: National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, China; [email protected] Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan Department of Astronomy, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Department of Earth Science and Astronomy, Graduate School of Arts and Science, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan Research Center for the Early Universe, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Osservatorio Astronomico, Via Tiepolo 11, 34131 Trieste, Italy Max-Planck-Institut für Astrophysik, KarlSchwarzschild-Strasse 1, 85748 Garching, Germany National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Institute of Space and Astronomical Science, Japan