Distance of the hypernova SN 2002ap via the expanding photosphere method

Abstract

New optical photometric and spectroscopic data of the bright hypernova SN 2002ap are presented. The obtained light curves as well as the optical spectra agree well with other published data series. The distance has been inferred by applying the Expanding Photosphere Method for the data around maximum. The derived 6.7 Mpc is in good agreement with recent photometric distances of M 74. However, the total (random plus systematic) uncertainty of the EPM-distance is at least ±4.5 Mpc (about 70%). The physical parameters of the SN have been determined via simplified analytic models of the light and velocity curves. It is confirmed that SN 2002ap was a less energetic hypernova, the kinetic energy was erg, and the reddening-free absolute bolometric magnitude reached -16.63 mag (corresponding to ), about 2 mag less than the prototype hypernova SN 1998bw.