THE OPTICAL/NEAR-INFRARED LIGHT CURVES OF SN 2002ap FOR THE FIRST 1.5 YEARS AFTER DISCOVERY

摘要

Late-time BVRIJHK 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~(-1) between days 130 and 230 to 0.014 mag day~(-1) between days 270 and 580. To reproduce the late-time light curve, a dense core must be added to the one-dimensional hypernova model that best fits the early-time observations, bringing the ejecta mass from 2.5 to 3 solar mass without much change in the kinetic energy, which is 4 x 10~(51) 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] 1.646 and 1.608 μm 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.