Type Ia supernovae are thought to be the result of a thermonuclear runaway in carbon/oxygen white dwarfs, but it is uncertain whether the explosion is triggered by accretion from a non-degenerate companion star or by a merger with another white dwarf. Observations of a supernova immediately following the explosion provide unique information on the distribution of ejected material1 and the progenitor system. Models predict2 that the interaction of supernova ejecta with a companion star or circumstellar debris lead to a sudden brightening lasting from hours to days. Here we present data for three supernovae that are likely to be type Ia observed during the Kepler mission3 with a time resolution of 30 minutes. We find no signatures of the supernova ejecta interacting with nearby companions. The lack of observable interaction signatures is consistent with the idea that these three supernovae resulted from the merger of binary white dwarfs or other compact stars such as helium stars.
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We thank M. Still, M. Fanelli, and S. Gezari for useful conversations, M. Graham, P. Kelly, K. Clubb, and O. Fox for assistance with the observations and reductions of the host-galaxy spectra, D. Scolnic for help with PSNID, and F. Bianco for sending us time series of the companion shock models integrated over the Kepler bandpass. D. Thilker kindly provided the SDSS magnitudes for the supernova host galaxies. R.P.O. and E.J.S. were, in a small part, supported by Kepler GO3 and GO4 grants NNX12AC95G and NNX13AC27G. P.M.G. was partly supported by Kepler grants NNX12AC89G and NNX11AG95G. A.V.F. and B.E.T. were supported by NSF grant AST-1211916, the TABASGO Foundation, and the Christopher R. Redlich Fund. Some of the data presented herein were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. This work is based in part on observations obtained at the Gemini Observatory (program IDs GN-2013A-Q-4 and GS-2013A-Q-115) which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
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The Astrophysical Journal (2019)