Type-IIn supernovae (SNe), which are characterized by strong interaction of their ejecta with the surrounding circumstellar matter (CSM), provide a unique opportunity to study the mass-loss history of massive stars shortly before their explosive death. We present the discovery and follow-up observations of a Type IIn SN, PTF 09uj, detected by the Palomar Transient Factory (PTF). Serendipitous observations by GALEX at ultraviolet (UV) wavelengths detected the rise of the SN light curve prior to the PTF discovery. The UV light curve of the SN rose fast, with a time scale of a few days, to a UV absolute AB magnitude of about -19.5. Modeling our observations, we suggest that the fast rise of the UV light curve is due to the breakout of the SN shock through the dense CSM (n~10^10 cm^-3). Furthermore, we find that prior to the explosion the progenitor went through a phase of high mass-loss rate (~0.1 solar mass per year) that lasted for a few years. The decay rate of this SN was fast relative to that of other SNe IIn.
@article{arxiv.1009.5378,
title = {Supernova PTF 09uj: A possible shock breakout from a dense circumstellar wind},
author = {E. O. Ofek and I. Rabinak and J. D. Neill and I. Arcavi and S. B. Cenko and E. Waxman and S. R. Kulkarni and A. Gal Yam and P. E. Nugent and L. Bildsten and J. S. Bloom and A. V. Filippenko and K. Forster and D. A. Howell and J. Jacobsen and M. M. Kasliwal and N. Law and C. Martin and D. Poznanski and R. M. Quimby and K. J. Shen and M. Sullivan and R. Dekany and G. Rahmer and D. Hale and R. Smith and J. Zolkower and V. Velur and R. Walters and J. Henning and K. Bui and D. McKenna},
journal= {arXiv preprint arXiv:1009.5378},
year = {2015}
}