The bright Type IIP SN 2009bw, showing signs of interaction★

Abstract

We present photometry and spectroscopy of the type IIP supernova 2009bw in\nUGC 2890 from few days after the outburst to 241 days. The light curve of SN\n2009bw during the photospheric phase is similar to that of normal SNe IIP but\nwith brighter peak and plateau (Mmax R = -17.82 mag, Mplateau R = -17.37 mag).\nThe luminosity drop from the photospheric to the nebular phase is one of the\nfastest ever observed, ~2.2 mag in about 13 days. The radioactive tail of the\nbolometric light curve indicates that the amount of ejected 56 Ni is \\approx\n0.022 M\\odot. The photospheric spectra reveal high velocity lines of H{\\alpha}\nand H{\\beta} until about 105 days after the shock breakout, suggesting a\npossible early interaction between the SN ejecta and pre-existent circumstellar\nmaterial, and the presence of CNO elements. By modeling the bolometric light\ncurve, ejecta expansion velocity and photospheric temperature, we estimate a\ntotal ejected mass of 8-12M\\odot, a kinetic energy of ~0.3 foe and an initial\nradius of ~ 3.6 - 7 \\times 10^13 cm.\n