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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

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 and Zhang, X (2019) 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. Astrophysical Journal, 887 (2). ISSN 0004-637X

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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. © 2019. The American Astronomical Society. All rights reserved.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0306 Physical Chemistry (incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
Date Deposited: 29 Jan 2020 10:43
Last Modified: 29 Jan 2020 10:43
DOI or Identification number: 10.3847/1538-4357/ab55ec
URI: http://researchonline.ljmu.ac.uk/id/eprint/12132

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