Anna Y.Q. Ho, California Institute of Technology
S. R. Kulkarni, California Institute of Technology
Daniel A. Perley, Liverpool John Moores University
S. Bradley Cenko, NASA Goddard Space Flight Center
Alessandra Corsi, Texas Tech University
Steve Schulze, Weizmann Institute of Science Israel
Ragnhild Lunnan, Stockholms universitet
Jesper Sollerman, Stockholms universitet
Avishay Gal-Yam, Weizmann Institute of Science Israel
Shreya Anand, California Institute of Technology
Cristina Barbarino, Stockholms universitet
Eric C. Bellm, University of Washington
Rachel J. Bruch, Weizmann Institute of Science Israel
Eric Burns, NASA Goddard Space Flight Center
Kishalay De, California Institute of Technology
Richard Dekany, California Institute of Technology
Alexandre Delacroix, California Institute of Technology
Dmitry A. Duev, California Institute of Technology
Dmitry D. Frederiks, Ioffe Institute
Christoffer Fremling, California Institute of Technology
Daniel A. Goldstein, California Institute of Technology
V. Zach Golkhou, University of Washington
Matthew J. Graham, California Institute of Technology
David Hale, California Institute of Technology
Mansi M. Kasliwal, California Institute of Technology
Thomas Kupfer, Kavli Institute for Theoretical Physics
Russ R. Laher, Infrared Processing & Analysis Center
Julia Martikainen, Helsingin Yliopisto
Frank J. Masci, Infrared Processing & Analysis Center
James D. Neill, California Institute of Technology
Anna Ridnaia, Ioffe Institute
Ben Rusholme, Infrared Processing & Analysis Center
Volodymyr Savchenko, Université de Genève

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We present optical, radio, and X-ray observations of SN 2020bvc (=ASASSN-20bs, ZTF 20aalxlis), a nearby broad-line (BL) Type Ic supernova (SN) and the first double-peaked Ic-BL discovered without a gamma-ray burst (GRB) trigger. Our observations show that SN 2020bvc shares several properties in common with the Ic-BL SN 2006aj, which was associated with the low-luminosity gamma-ray burst (LLGRB) 060218. First, the 10 GHz radio luminosity is brighter than ordinary core-collapse SNe but fainter than LLGRB SNe such as SN 1998bw (associated with LLGRB 980425). We model our VLA observations (spanning 13-43 days) as synchrotron emission from a mildly relativistic (v 0.3c) forward shock. Second, with Swift and Chandra, we detect X-ray emission (L X 1041 erg that is not naturally explained as inverse Compton emission or part of the same synchrotron spectrum as the radio emission. Third, high-cadence (6× night-1) data from the Zwicky Transient Facility (ZTF) show a double-peaked optical light curve, the first peak from shock cooling of extended low-mass material (mass SN 2020bvc is the first double-peaked Ic-BL SN discovered without a GRB trigger, so it is noteworthy that it shows X-ray and radio emission similar to LLGRB SNe. For four of the five other nearby (z ≲ 0.05) Ic-BL SNe with ZTF high-cadence data, we rule out a first peak like that seen in SN 2006aj and SN 2020bvc, i.e., that lasts 1 day and reaches a peak luminosity M -18. Follow-up X-ray and radio observations of Ic-BL SNe with well-sampled early optical light curves will establish whether double-peaked optical light curves are indeed predictive of LLGRB-like X-ray and radio emission.

Publication Source (Journal or Book title)

Astrophysical Journal