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

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Optical UBVRI photometry and medium resolution spectroscopy of the type Ib supernova SN 2009jf, during the period -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 Mᵥ = -17.96±0.19 magnitude at peak, SN 2009jf is a normally bright supernova. The peak bolometric luminosity and the energy deposition rate via ⁵⁶Ni → ⁵⁶Co chain indicate that 0.17⁺⁰.⁰³₋₀.₀₃ M of ⁵⁶Ni was ejected during the explosion. HeI 5876 Å line is clearly identified in the first spectrum of day -15, at a velocity of 16000 km sec⁻¹. The [OI] 6300-6364 Å 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 1.34 M 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 ej = 4-9 M, and kinetic energy E K = 3-8 × 10⁵¹ erg. The ejected mass estimate is indicative of an initial main-sequence mass of 20- 25 M.