The Optical/Near-Infrared Light Curves of SN 2002ap for the First 140 Days after Discovery

Supernova (SN) 2002ap in M74 was observed in the UBVRIJHK bands for the first 40 days following its discovery (2002 January 29) until it disappeared as a result of solar conjunction and then in June after it reappeared. The magnitudes and dates of peak brightness in each band were determined. While the rate of increase of the brightness before the peak is almost independent of wavelength, the subsequent rate of decrease becomes smaller with wavelength from the U to the R bands and is constant at wavelengths beyond the I band. The photometric evolution is faster than in the well-known "hypernovae" SNe 1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The bolometric light curve of SN 2002ap for the full period of observations was constructed. The absolute magnitude is found to be much fainter than that of SN 1998bw but is similar to that of SN 1997ef, which lies at the faint end of the hypernova population. The bolometric light curve at the early epochs was best reproduced with the explosion of a C + O star that ejects 2.5 M_☉ with kinetic energy E_K = 4 × 10⁵¹ ergs. A comparison of the predicted brightness of SN 2002ap with that observed after solar conjunction may imply that γ-ray deposition at the later epochs was more efficient than in the model. This may be due to an asymmetric explosion.