A Large Fraction of Hydrogen-rich Supernova Progenitors Experience Elevated Mass Loss Shortly Prior to Explosion
Rachel J. Bruch, Avishay Gal-Yam, Steve Schulze, Ofer Yaron, Yi Yang, Maayane Soumagnac, Mickael Rigault, Nora L. Strotjohann, Eran Ofek, Jesper Sollerman, Frank J. Masci, Cristina Barbarino, Anna Y. Q. Ho, Christoffer Fremling, Daniel Perley, Jakob Nordin, S. Bradley Cenko, S. Adams, Igor Adreoni, Eric C. Bellm, Nadia Blagorodnova, Mattia Bulla, Kevin Burdge, Kishalay De, Suhail Dhawan, Andrew J. Drake, Dmitry A. Duev, Alison Dugas, Matthew Graham, Melissa L. Graham, Ido Irani, Jacob Jencson, Emir Karamehmetoglu, Mansi Kasliwal, Young-Lo Kim, Shrinivas Kulkarni, Thomas Kupfer, Jingyi Liang, Ashish Mahabal, A. A. Miller, Thomas A. Prince, Reed Riddle, Y. Sharma, Roger Smith, Francesco Taddia, Kirsty Taggart, Richard Walters, Lin Yan
Abstract
Abstract Spectroscopic detection of narrow emission lines traces the presence of circumstellar mass distributions around massive stars exploding as core-collapse supernovae. Transient emission lines disappearing shortly after the supernova explosion suggest that the material spatial extent is compact and implies an increased mass loss shortly prior to explosion. Here, we present a systematic survey for such transient emission lines (Flash Spectroscopy) among Type II supernovae detected in the first year of the Zwicky Transient Facility survey. We find that at least six out of ten events for which a spectrum was obtained within two days of the estimated explosion time show evidence for such transient flash lines. Our measured flash event fraction (>30% at 95% confidence level) indicates that elevated mass loss is a common process occurring in massive stars that are about to explode as supernovae.