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Title: Early Observations of the Type Ia Supernova iPTF 16abc: A Case of Interaction with Nearby, Unbound Material and/or Strong Ejecta Mixing

Early observations of Type Ia supernovae (SNe Ia) provide a unique probe of their progenitor systems and explosion physics. Here we report the intermediate Palomar Transient Factory (iPTF) discovery of an extraordinarily young SN Ia, iPTF 16abc. By fitting a power law to our early light curve, we infer that first light for the SN, that is when the SN could have first been detected by our survey, occurred only $$0.15\pm_{0.07}^{0.15}$$ days before our first detection. In the $$\sim$$24 hr after discovery, iPTF 16abc rose by $$\sim$$2 mag, featuring a near-linear rise in flux for $$\gtrsim$$3 days. Early spectra show strong C II absorption, which disappears after $$\sim$$7 days. Unlike the extensivelyobserved SN Ia SN 2011fe, the $$(B-V)_0$$ colors of iPTF 16abc are blue and nearly constant in the days after explosion. We show that our early observations of iPTF 16abc cannot be explained by either SN shock breakout and the associated, subsequent cooling or the SN ejecta colliding with a stellar companion. Instead, we argue that the early characteristics of iPTF 16abc, including (i) the rapid, near-linear rise, (ii) the nonevolving blue colors, and (iii) the strong C II absorption, are the result of either ejecta interaction with nearby, unbound material or vigorous mixing of radioactive 56Ni in the SN ejecta, or a combination of the two. Finally, in the next few years, dozens of very young normal SNe Ia will be discovered, and observations similar to those presented here will constrain the white dwarf explosion mechanism.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [6] ;  [7] ; ORCiD logo [7] ; ORCiD logo [8] ; ORCiD logo [9] ;  [7] ; ORCiD logo [10] ; ORCiD logo [10] ; ORCiD logo [4] ; ORCiD logo [11] ; ORCiD logo [4] ; ORCiD logo [12] ; ORCiD logo [10] ; ORCiD logo [13] ; ORCiD logo [9] more »;  [9] ; ORCiD logo [4] « less
  1. Northwestern Univ., Evanston, IL (United States). Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Dept. of Physics and Astronomy; Adler Planetarium, Chicago, IL (United States)
  2. Univ. of Washington, Seattle, WA (United States). eScience Inst. and Astronomy Dept.
  3. Observatories of the Carnegie Inst. for Science, Pasadena, CA (United States)
  4. California Inst. of Technology, Pasadena, CA (United States). Division of Physics, Mathematics, and Astronomy
  5. California Inst. of Technology, Pasadena, CA (United States). Jet Propulsion Lab.
  6. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Univ. of Maryland, College Park, MD (United States). Joint Space-Science Inst.
  7. Stockholm Univ. (Sweden). Oskar Klein Centre, Dept. of Physics
  8. Space Telescope Science Inst., Baltimore, MD (United States)
  9. Stockholm Univ. (Sweden). Oskar Klein Centre, Dept. of Astronomy
  10. Las Cumbres Observatory, Goleta, CA (United States); Univ. of California, Santa Barbara, CA (United States). Dept. of Physics
  11. California Inst. of Technology, Pasadena, CA (United States). Infrared Processing and Analysis Center
  12. California Inst. of Technology, Pasadena, CA (United States)
  13. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231; 1545949
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 852; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; methods: observational; supernovae: general; supernovae: individual (iPTF 16abc; SN 2011fe); surveys
OSTI Identifier:
1456978