SN 2020bvc: A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart

• Published in: The Astrophysical journal 2020-10, Vol.902 (1), p.86
• Main Authors: Ho, Anna Y. Q., Kulkarni, S. R., Perley, Daniel A., Cenko, S. Bradley, Corsi, Alessandra, Schulze, Steve, Lunnan, Ragnhild, Sollerman, Jesper, Gal-Yam, Avishay, Anand, Shreya, Barbarino, Cristina, Bellm, Eric C., Bruch, Rachel J., Burns, Eric, De, Kishalay, Dekany, Richard, Delacroix, Alexandre, Duev, Dmitry A., Frederiks, Dmitry D., Fremling, Christoffer, Goldstein, Daniel A., Golkhou, V. Zach, Graham, Matthew J., Hale, David, Kasliwal, Mansi M., Kupfer, Thomas, Laher, Russ R., Martikainen, Julia, Masci, Frank J., Neill, James D., Ridnaia, Anna, Rusholme, Ben, Savchenko, Volodymyr, Shupe, David L., Soumagnac, Maayane T., Strotjohann, Nora L., Svinkin, Dmitry S., Taggart, Kirsty, Tartaglia, Leonardo, Yan, Lin, Zolkower, Jeffry
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Astrophysics; Cooling curves; Core-collapse supernovae; Gamma ray bursts; Gamma rays; High energy astrophysics; Light curve; Luminosity; Radio emission; Radio observation; Radio transient sources; Radioactive decay; Shock cooling; Supernova; Supernovae; Surveys; Synchrotrons; Transient sources; Type Ic supernovae; type lc supernovae; X-ray emissions; X-ray transient sources
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/aba630

We present optical, radio, and X-ray observations of SN 2020bvc (=ASASSN-20bs, ZTF 20aalxlis), a nearby ( z = 0.0252 ; d  = 114 Mpc) 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 ( L radio ≈ 10 37 erg s − 1 ) 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 ≳ 0.3 c ) forward shock. Second, with Swift and Chandra, we detect X-ray emission ( L X  ≈ 10 41 erg s − 1 ) 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 M e < 10 − 2 M ⊙ at radius R e  > 10 12 cm) and the second peak from the radioactive decay of 56 Ni . 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.