tokens: Acknowledgments We thank Emily Levesque for helpful conversations and V. Ashely Villar for access to their SN 2010da spectra. We are grateful to our anonymous referee for a thoughtful and constructive review. The supernova research of AVF’s group at U.C. Berkeley is supported by Gary Cynthia Bengier, the Richard Rhoda Goldman Fund, the Christopher R. Redlich Fund, the TABASGO Foundation and NSF grant AST–1211916. Some of AVF’s work was completed at the Aspen Center for Physics, which is supported by NSF grant PHY-1066293; he thanks the Center for its hospitality during the black holes workshop in 2016 June and July. This research makes use of observations from the Las Cumbres Observatory (LCO) network and is supported by National Science Foundation (NSF) grant AST-1313484. This research is based in part on observations made at the W. M. Keck Observatory; we are grateful to the Keck staff for their assistance, and we extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration (NASA); it was made possible by the generous financial support of the W. M. Keck Foundation. We thank Daniel Perley and Brad Cenko for the use of, and assistance with, their Keck LRIS imaging and spectroscopy reduction pipeline. 5 We also thank WeiKang Zheng, Kelsey Clubb, Brad Tucker, Patrick Kelly and Isaac Shivvers for their assistance with the observations. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This work has made use of the Weizmann Interactive Supernova Data Repository (Yaron Gal-Yam 2012 ) at http://wiserep.weizmann.ac.il .
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