학술논문
Evidence for Late-stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-lined Ic Supernova: Pre-explosion Emission and a Rapidly Rising Luminous Transient
Document Type
article
Author
Ho, AYQ; Goldstein, DA; Schulze, S; Khatami, DK; Perley, DA; Ergon, M; Gal-Yam, A; Corsi, A; Andreoni, I; Barbarino, C; Bellm, EC; Blagorodnova, N; Bright, JS; Burns, E; Cenko, SB; Cunningham, V; De, K; Dekany, R; Dugas, A; Fender, RP; Fransson, C; Fremling, C; Goldstein, A; Graham, MJ; Hale, D; Horesh, A; Hung, T; Kasliwal, MM; M. Kuin, NP; Kulkarni, SR; Kupfer, T; Lunnan, R; Masci, FJ; Ngeow, CC; Nugent, PE; Ofek, EO; Patterson, MT; Petitpas, G; Rusholme, B; Sai, H; Sfaradi, I; Shupe, DL; Sollerman, J; Soumagnac, MT; Tachibana, Y; Taddia, F; Walters, R; Wang, X; Yao, Y; Zhang, X
Source
Astrophysical Journal. 887(2)
Subject
Language
Abstract
We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 ± 0.1 mag hr-1) and luminous (Mg,peak = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (Lbol ≳ 3 × 1044 erg s-1), the short rise time (trise = 3 days in g band), and the blue colors at peak (g-r ∼ -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (Teff ≳ 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (Mg ∼ Mr ≈ mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E γ,iso < 4.9 × 10 48 erg, a limit on X-ray emission LX < 1040 erg s-1, and a limit on radio emission ν Lν ≲ 1037 erg s-1. Taken together, we find that the early (< 10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 M⊙) at large radii (3 × 1014 cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (> 10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.