SN 2020bvc: A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart
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.
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Ho, A., Kulkarni, S., Perley, D., Cenko, S., Corsi, A., Schulze, S., Lunnan, R., Sollerman, J., Gal-Yam, A., Anand, S., Barbarino, C., Bellm, E., Bruch, R., Burns, E., De, K., Dekany, R., Delacroix, A., Duev, D., Frederiks, D., Fremling, C., Goldstein, D., Golkhou, V., Graham, M., Hale, D., Kasliwal, M., Kupfer, T., Laher, R., Martikainen, J., Masci, F., Neill, J., Ridnaia, A., Rusholme, B., & Savchenko, V. (2020). SN 2020bvc: A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart. Astrophysical Journal, 902 (1) https://doi.org/10.3847/1538-4357/aba630