The Spectacular Ultraviolet Flash from the Peculiar Type Ia Supernova 2019yvq

Creators: Miller, A. A.; Magee, M. R.; Polin, A.; Maguire, K.; Zimmerman, E.; Yao, Y.; Sollerman, J.; Schulze, S.; Perley, D. A.; Kromer, M.; Dhawan, S.; Bulla, M.; Andreoni, I.; Bellm, E. C.; De, K.; Dekany, R.; Delacroix, A.; Fremling, C.; Gal-Yam, A.; Goldstein, D. A.; Golkhou, V. Z.; Goobar, A.; Graham, M. J.; Irani, I.; Kasliwal, M. M.; Kaye, S.; Kim, Y. -L.; Laher, R. R.; Mahabal, A. A.; Masci, F. J.; Nugent, P. E.; Ofek, E.; Phinney, E. S.; Prentice, S. J.; Riddle, R.; Rigault, M.; Rusholme, B.; Schweyer, T.; Shupe, D. L.; Soumagnac, M. T.; Terreran, G.; Walters, R.; Yan, L.; Zolkower, J.; Kulkarni, S. R.

Abstract

Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia (M_g ~ -18.5 mag at peak) yet featured very high absorption velocities (v ~ 15,000 km s⁻¹ for Si ii λ6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive ⁵⁶Ni is relatively low (we measure M₅₆_(Ni) = 0.31 ± 0.05 M_⊙ and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of ⁵⁶Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [Ca ii] emission, if it was a double detonation, or narrow [O i] emission, if it was due to a violent merger.

Additional Information

© 2020 The American Astronomical Society. Received 2020 May 14; revised 2020 June 3; accepted 2020 June 4; published 2020 July 23. The authors would like to thank the anonymous referee for helpful comments that have improved this paper. We thank R. Pakmor for useful conversations on WD explosions, D.M. Scolnic for sharing the results of the 2M++ model, and C.-C. Ngeow for providing constructive comments on an early draft. A.A. Miller is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). C.F. gratefully acknowledges support of his research by the Heising-Simons Foundation (#2018-0907). A.A. Mahabal acknowledges support from the NSF (1640818, AST-1815034). E.S.P. was funded in part by the Gordon and Betty Moore Foundation through grant GBMF5076. M.R. and Y.-L.K. have received funding from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (grant agreement No. 759194—USNAC). This work was supported by TCHPC (Research IT, Trinity College Dublin). Calculations were performed on the Kelvin cluster maintained by the Trinity Centre for High Performance Computing. This cluster was funded through grants from the Higher Education Authority, through its PRTLI program. This work was supported by the GROWTH project funded by the National Science Foundation under grant No 1545949. This work is based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration, including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. This research made use of TARDIS, a community-developed software package for spectral synthesis in SNe (Kerzendorf & Sim 2014). The development of TARDIS received support from the Google Summer of Code initiative and from ESA's Summer of Code in Space program. TARDIS makes extensive use of Astropy and PyNE. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. MMT Observatory access was supported by Northwestern University and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Partly based on observations made with the Nordic Optical Telescope, operated at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Software: astropy (Astropy Collaboration et al. 2013), CASTRO (Almgren et al. 2010), corner (Foreman-Mackey 2016), emcee (Foreman-Mackey et al. 2013), FRODOSpec L2 pipeline (Barnsley et al. 2012), LPipe (Perley 2019), matplotlib (Hunter 2007), pandas (McKinney 2010), pyraf-dbsp (Bellm & Sesar 2016), pysedm (Rigault et al. 2019) SALT2 (Guy et al. 2007), scikit-learn (Pedregosa et al. 2011), scipy (Virtanen et al. 2020), SEDONA (Kasen et al. 2006), sncosmo (Barbary et al. 2016), SNooPY (Burns et al. 2011), TARDIS (Kerzendorf & Sim 2014), and TURTLS (Magee et al. 2018).

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