Photometric and spectroscopic data of the energetic Type Ic supernova ( SN ) 2002ap are presented , and the properties of the SN are investigated through models of its spectral evolution and its light curve .
The SN is spectroscopically similar to the “ hypernova ” SN 1997ef .
However , its kinetic energy [ \sim ( 4 - 10 ) \times 10 ^ { 51 } erg ] and the mass ejected ( 2.5–5 M _ { \odot } ) are smaller , resulting in a faster-evolving light curve .
The SN synthesized \sim 0.07 M _ { \odot } of ^ { 56 } Ni , and its peak luminosity was similar to that of normal SNe .
Brightness alone should not be used to define a hypernova , whose defining character , namely very broad spectral features , is the result of a high kinetic energy .
The likely main-sequence mass of the progenitor star was 20–25 M _ { \odot } , which is also lower than that of both hypernovae SNe 1997ef and 1998bw .
SN 2002ap appears to lie at the low-energy and low-mass end of the hypernova sequence as it is known so far .
Observations of the nebular spectrum , which is expected to dominate by summer 2002 , are necessary to confirm these values .