SN2019dge: a Helium-rich Ultra-Stripped Envelope Supernova

Creators: Yao, Yuhan; De, Kishalay; Kasliwal, Mansi M.; Ho, Anna Y. Q.; Schulze, Steve; Li, Zhihui; Kulkarni, S. R.; Fruchter, Andrew; Rubin, David; Perley, Daniel A.; Fuller, Jim; Piro, Anthony L.; Fremling, C.; Bellm, Eric C.; Burruss, Rick; Duev, Dmitry A.; Feeney, Michael; Gal-Yam, Avishay; Golkhou, V. Zach; Graham, Matthew J.; Helou, George; Kupfer, Thomas; Laher, Russ R.; Masci, Frank J.; Miller, Adam A.; Rusholme, Ben; Shupe, David L.; Smith, Roger; Sollerman, Jesper; Soumagnac, Maayane T.; Zolkower, Jeffry

Abstract

We present observations of ZTF18abfcmjw (SN2019dge), a helium-rich supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈0.33 M_⊙) and low kinetic energy (≈1.3 × 10⁵⁰ erg). Early-time (<4 days after explosion) photometry reveals evidence of shock cooling from an extended helium-rich envelope of ~0.1 M_⊙ located ~1.2 × 10¹³ cm from the progenitor. Early-time He II line emission and subsequent spectra show signatures of interaction with helium-rich circumstellar material, which extends from ≳ 5 × 10¹³ cm to 2 × 10¹⁶ cm. We interpret SN2019dge as a helium-rich supernova from an ultra-stripped progenitor, which originates from a close binary system consisting of a mass-losing helium star and a low-mass main-sequence star or a compact object (i.e., a white dwarf, a neutron star, or a black hole). We infer that the local volumetric birth rate of 19dge-like ultra-stripped SNe is in the range of 1400–8200 Gpc⁻³ yr⁻¹ (i.e., 2%–12% of core-collapse supernova rate). This can be compared to the observed coalescence rate of compact neutron star binaries that are not formed by dynamical capture.

Additional Information

© 2020 The American Astronomical Society. Received 2020 May 27; revised 2020 July 23; accepted 2020 July 27; published 2020 August 31. We thank Takashi Moriya, Thomas Tauris, David Khatami, Dan Kasen, Sterl Phinney, and Wenbin Lu for valuable discussions during this work. We thank Lin Yan for sharing spectra of SN1993J and Gaia16apd. Y.Y. thanks the instructors and organizers of the GROWTH summer school for teaching techniques in time-domain data analysis. This study made use of the open supernova catalog (Guillochon et al. 2017). C.F. gratefully acknowledges support of his research by the Heising-Simons Foundation (#2018-0907). This work was supported by the GROWTH project funded by the National Science Foundation under PIRE 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. Software: astropy (Astropy Collaboration et al. 2013), corner (Foreman-Mackey 2016), CIGALE (Boquien et al. 2019), emcee (Foreman-Mackey et al. 2013), LAMBDAR (Wright et al. 2016), Lpipe (Perley 2019), matplotlib (Hunter 2007), pandas (McKinney 2010), pyneb (Luridiana et al. 2015), pyraf-dbsp (Bellm & Sesar 2016), scipy (Virtanen et al. 2020), simsurvey (Feindt et al. 2019), sncosmo (Barbary et al. 2016), ztfquery (Rigault 2018).

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