Optical studies of SN 2009jf: A type Ib supernova with an extremely slow decline and aspherical signature

Optical $UBVRI$ photometry and medium resolution spectroscopy of the type Ib supernova SN 2009jf, during the period $sim -15$ to +250days with respect to the $B$ maximum are reported. The light curves are broad, with an extremely slow decline. The early post-maximum decline rate in the $V$ band is similar to SN 2008D, however, the late phase decline rate is slower than other studied type Ib supernovae. With an absolute magnitude of $M_{V} = -17.96pm0.19$ magnitude at peak, SN 2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via $^{56}$Ni $rightarrow$ $^{56}$Co chain indicate that $sim {0.17}^{+0.03}_{-0.03}$ M$_{odot}$ of $^{56}$Ni was ejected during the explosion. He,I 5876 AA line is clearly identified in the first spectrum of day $sim -15$, at a velocity of $sim 16000$ km sec$^{-1}$. The [O,I] 6300-6364 AA line seen in the nebular spectrum has a multi-peaked and asymmetric emission profile, with the blue peak being stronger. The estimated flux in this line implies $ga 1.34$ M$_odot$ oxygen was ejected. The slow evolution of the light curves of SN 2009jf indicates the presence of a massive ejecta. The high expansion velocity in the early phase and broader emission lines during the nebular phase suggest it to be an explosion with a large kinetic energy. A simple qualitative estimate leads to the ejecta mass of M$_{rm ej} = 4-9$ M$_odot$, and kinetic energy E$_{rm K} = 3-8 times 10^{51}$ erg. The ejected mass estimate is indicative of an initial main-sequence mass of $ga 20- 25$ M$_odot$.