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Strong Near-infrared Carbon Absorption in the Transitional Type Ia SN 2015bp

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DOI

  • S. D. Wyatt, University of Arizona
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  • D. Sand, University of Arizona
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  • E. Y. Hsiao, Observatories of the Carnegie Institution for Science
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  • C. R. Burns, Carnegie Institution of Washington
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  • S. Valenti, University of California at Davis
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  • K. A. Bostroem, University of California at Davis
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  • M. Lundquist, University of Arizona
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  • L. Galbany, University of Granada
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  • J. Lu, Florida State University
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  • C. Ashall, Florida State University
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  • T. R. Diamond, Private Astronomer: Tiaradiamond@gmail.com
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  • A. V. Filippenko, University of California at Berkeley
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  • M. L. Graham, University of Washington
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  • P. Hoeflich, Florida State University
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  • R. P. Kirshner, Harvard University, Gordon and Betty Moore Foundation
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  • K. Krisciunas, Texas A and M University
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  • G. H. Marion, University of Texas at Austin
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  • N. Morrell, Carnegie Observatories, Las Campanas Observatory, La Serena, Chile
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  • S. E. Persson, Observatories of the Carnegie Institution for Science
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  • M. M. Phillips, Carnegie Observatories, Las Campanas Observatory, La Serena, Chile
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  • M. D. Stritzinger
  • N. B. Suntzeff, Texas A and M University
  • ,
  • F. Taddia
Unburned carbon is potentially a powerful probe of Type Ia supernova (SN) explosion mechanisms. We present comprehensive optical and near-infrared (NIR) data on the "transitional" Type Ia SN 2015bp. An early NIR spectrum (t= - 9.9 days with respect to B-band maximum) displays a striking C I 1.0693 μm line at 11.9 × 103 km s−1, distinct from the prominent Mg II 1.0927 μm feature, which weakens toward maximum light. SN 2015bp also displays a clear C II 6580 Å notch early (t= - 10.9 days) at 13.2 × 103 km s−1, consistent with our NIR carbon detection. At MB = - 18.46, SN 2015bp is less luminous than a normal SN Ia and, along with iPTF 13ebh, is the second member of the transitional subclass to display prominent early-time NIR carbon absorption. We find it unlikely that the C I feature is misidentified He I 1.0830 μm because this feature grows weaker toward maximum light, while the helium line produced in some double-detonation models grows stronger at these times. Intrigued by these strong NIR carbon detections, but lacking NIR data for other SNe Ia, we investigated the incidence of optical carbon in the sample of nine transitional SNe Ia with early-time data (t ≲ −4 days). We find that four display C II 6580 Å, while two others show tentative detections, in line with the SN Ia population as a whole. We conclude that at least ∼50% of transitional SNe Ia in our sample do not come from sub-Chandrasekhar-mass explosions due to the clear presence of carbon in their NIR and optical spectra



Original languageEnglish
Article number57
JournalAstrophysical Journal
Volume914
Issue1
Number of pages16
ISSN0004-637X
DOIs
Publication statusPublished - Jun 2021

    Research areas

  • ABSOLUTE MAGNITUDES, CHANDRASEKHAR-MASS EXPLOSIONS, DOUBLE-DETONATION, LIGHT CURVES, OPTICAL-SPECTRA, PROGENITOR SYSTEMS, PROJECT-II, SUPERNOVA FACTORY OBSERVATIONS, SYSTEMATIC UNCERTAINTIES, TIME-SERIES

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