Paper detail

The first month of evolution of the slow rising type II-P SN 2013ej in M74

We present early photometric and spectroscopic observations of SN 2013ej, a bright type IIP supernova in M74. SN 2013ej is one of the closest SNe ever discovered. The available archive images and the early discovery help to constrain the nature of its progenitor. The earliest detection of this explosion was on 2013 July 24.14 UT and our spectroscopic monitoring began on July 27.73 UT, continuing almost daily for two weeks with the LCOGT FLOYDS spectrographs. Daily optical photometric monitoring was achieved with the LCOGT 1m network, and were complemented by UV data from SWIFT and near-infrared spectra from PESSTO and IRTF. The data from our monitoring campaign show that SN 2013ej experienced a 10-day rise before entering into a well defined plateau phase. This unusually long rise time for a type IIP has been seen previously in SN 2006bp and SN 2009bw. A relatively rare strong absorption blue-ward of Hα is present since our earliest spectrum. We identify this feature as Si ii, rather than high velocity Hα as sometimes reported in the literature.