We present photometry and spectroscopy of the type IIP supernova 2009bw in UGC 2890 from few days after the outburst to 241 days .
The light curve of SN 2009bw during the photospheric phase is similar to that of normal SNe IIP but with brighter peak and plateau ( M _ { R } ^ { max } = -17.82 mag , M _ { R } ^ { plateau } = -17.37 mag ) .
The luminosity drop from the photospheric to the nebular phase is one of the fastest ever observed , \sim 2.2 mag in about 13 days .
The radioactive tail of the bolometric light curve indicates that the amount of ejected ^ { 56 } Ni is \approx 0.022 M _ { \odot } .
The photospheric spectra reveal high velocity lines of H \alpha and H \beta until about 105 days after the shock breakout , suggesting a possible early interaction between the SN ejecta and pre-existent circumstellar material , and the presence of CNO elements .
By modeling the bolometric light curve , ejecta expansion velocity and photospheric temperature , we estimate a total ejected mass of \sim 8 - 12 M _ { \odot } , a kinetic energy of \sim 0.3 foe and an initial radius of \sim 3.6 - 7 \times 10 ^ { 13 } cm .