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Title: iPTF15dtg: a double-peaked Type Ic supernova from a massive progenitor

Type Ic supernovae (SNe Ic) arise from the core-collapse of H- (and He-) poor stars, which could either be single Wolf-Rayet (WR) stars or lower-mass stars stripped of their envelope by a companion. Their light curves are radioactively powered and usually show a fast rise to peak (~10-15 d), without any early (in the first few days) emission bumps (with the exception of broad-lined SNe Ic) as sometimes seen for other types of stripped-envelope SNe (e.g., Type IIb SN 1993J and Type Ib SN 2008D). Here, we have studied iPTF15dtg, a spectroscopically normal SN Ic with an early excess in the optical light curves followed by a long (~30 d) rise to the main peak. It is the first spectroscopically-normal double-peaked SN Ic to be observed. Our aim is to determine the properties of this explosion and of its progenitor star. Methods. Optical photometry and spectroscopy of iPTF15dtg was obtained with multiple telescopes. The resulting light curves and spectral sequence are analyzed and modeled with hydrodynamical and analytical models, with particular focus on the early emission. iPTF15dtg is a slow rising SN Ic, similar to SN 2011bm. Hydrodynamical modeling of the bolometric properties reveals a large ejecta mass (~10 Mmore » ) and strong 56Ni mixing. The luminous early emission can be reproduced if we account for the presence of an extended (≳500 R ), low-mass (≳0.045 M ) envelope around the progenitor star. Alternative scenarios for the early peak, such as the interaction with a companion, a shock-breakout (SBO) cooling tail from the progenitor surface, or a magnetar-driven SBO are not favored. In conclusion, the large ejecta mass and the presence of H- and He-free extended material around the star suggest that the progenitor of iPTF15dtg was a massive (≳35 M ) WR star that experienced strong mass loss.« less
 [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [5] ;  [1] ;  [6] ;  [3] ; ORCiD logo [7]
  1. Stockholm Univ. (Sweden). Oskar Klein Centre, Dept. of Astronomy
  2. Texas Tech Univ., Lubbock, TX (United States). Dept. of Physics
  3. Weizmann Inst. of Science, Rehovot (Israel). Dept. of Particle Physics & Astrophysics
  4. California Inst. of Technology (CalTech), Pasadena, CA (United States). Dept. of Astronomy
  5. California Inst. of Technology (CalTech), La Canada Flintridge, CA (United States). Jet Propulsion Lab.
  6. California Inst. of Technology (CalTech), Pasadena, CA (United States). Cahill Center for Astrophysics
  7. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0004-6361; TRN: US1800385
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 592; Journal ID: ISSN 0004-6361
EDP Sciences
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; National Science Foundation (NSF); Knut and Alice Wallenberg Foundation
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; Astronomy and Astrophysics; supernovae general
OSTI Identifier: