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

December 2019 • 2019ApJ...887..169H

Authors • Ho, Anna Y. Q. • Goldstein, Daniel A. • Schulze, Steve • Khatami, David K. • Perley, Daniel A. • Ergon, Mattias • Gal-Yam, Avishay • Corsi, Alessandra • Andreoni, Igor • Barbarino, Cristina • Bellm, Eric C. • Blagorodnova, Nadia • Bright, Joe S. • Burns, E. • Cenko, S. Bradley • Cunningham, Virginia • De, Kishalay • Dekany, Richard • Dugas, Alison • Fender, Rob P. • Fransson, Claes • Fremling, Christoffer • Goldstein, Adam • Graham, Matthew J. • Hale, David • Horesh, Assaf • Hung, Tiara • Kasliwal, Mansi M. • Kuin, N. Paul M. • Kulkarni, S. R. • Kupfer, Thomas • Lunnan, Ragnhild • Masci, Frank J. • Ngeow, Chow-Choong • Nugent, Peter E. • Ofek, Eran O. • Patterson, Maria T. • Petitpas, Glen • Rusholme, Ben • Sai, Hanna • Sfaradi, Itai • Shupe, David L. • Sollerman, Jesper • Soumagnac, Maayane T. • Tachibana, Yutaro • Taddia, Francesco • Walters, Richard • Wang, Xiaofeng • Yao, Yuhan • Zhang, Xinhan

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 ({M}_g,{peak}=-20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity ({L}_bol}≳ 3× {10}⁴⁴ {erg} {{{s}}}^-1), the short rise time ({t}_rise}=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 ({T}_eff}≳ {{40,000}} {{K}}) spectra of a stripped-envelope SN. A retrospective search revealed luminous ({M}_g∼ {M}_r≈ -14 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 {L}_{{X}}< {10}⁴⁰ {erg} {{{s}}}^-1, and a limit on radio emission ν {L}_ν ≲ {10}³⁷ {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× {10}¹⁴ {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.

Links

• PREPRINT http://arxiv.org/abs/1904.11009
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2019ApJ...887..169H
• ELECTR https://doi.org/10.3847%2F1538-4357%2Fab55ec
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2019ApJ...887..169H
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/ab55ec/pdf
• PDF https://stacks.iop.org/0004-637X/887/169/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/887/169
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2019ApJ...887..169H
• DATA https://cda.harvard.edu/chaser?obsid=20319,20320
• DATA https://irsa.ipac.caltech.edu/bibdata/2019/H/2019ApJ...887..169H.html