The Highly Luminous Type Ibn Supernova ASASSN-14ms

Abstract

We present photometric and spectroscopic follow-up observations of the highly luminous Type Ibn supernova ASASSN-14ms, which was discovered on UT 2014-12-26.61 at $m_V\sim 16.5$. With a peak absolute $V$-band magnitude brighter than $-20.5$, a peak bolometric luminosity of $1.7\times 10^{44}$ ergs s${}^{-1}$, and a total radiated energy of $2.1\times 10^{50}$ ergs, ASASSN-14ms is one of the most luminous Type Ibn supernovae yet discovered. In simple models, the most likely power source for this event is a combination of the radioactive decay of ${}^{56}$Ni and ${}^{56}$Co at late times and the interaction of supernova ejecta with the progenitor's circumstellar medium at early times, although we cannot rule out the possibility of a magnetar-powered light curve. The presence of a dense circumstellar medium is indicated by the intermediate-width He I features in the spectra. The faint ($m_g\sim 21.6$) host galaxy SDSS J130408.52+521846.4 has an oxygen abundance below $12+\log (O/H)\lesssim 8.3$, a stellar mass of $M_{\ast }\sim 2.6\times 10^8{M}_{\odot }$, and a star formation rate of $\text{SFR}\sim 0.02$ $M_{\odot }$ yr${}^{-1}$.

12 pages, 2 tables, 6 figures. Photometric data presented in this submission are included as ancillary files. For a brief video explaining this paper, see https://www.youtube.com/watch?v=I9Maq9Q6u1g