Year: 2011
Type: article
Abstract: We present convincing evidence of unburned carbon at photospheric velocities in new observations of five Type Ia supernovae (SNe Ia) obtained by the Nearby Supernova Factory. These SNe are identified by examining 346 spectra from 124 SNe obtained before +2.5 days relative to maximum. Detections are based on the presence of relatively strong C ii λ6580 absorption "notches" in multiple spectra of each SN, aided by automated fitting with the SYNAPPS code. Four of the five SNe in question are otherwise spectroscopically unremarkable, with ions and ejection velocities typical of SNe Ia, but spectra of the fifth exhibit high-velocity ( v > 20, 000 km s −1 ) Si ii and Ca ii features. On the other hand, the light curve properties are preferentially grouped, strongly suggesting a connection between carbon-positivity and broadband light curve/color behavior: three of the five have relatively narrow light curves but also blue colors and a fourth may be a dust-reddened member of this family. Accounting for signal to noise and phase, we estimate that 22 +10 − 6 % of SNe Ia exhibit spectroscopic C ii signatures as late as −5 days with respect to maximum. We place these new objects in the context of previously recognized carbon-positive SNe Ia and consider reasonable scenarios seeking to explain a physical connection between light curve properties and the presence of photospheric carbon. We also examine the detailed evolution of the detected carbon signatures and the surrounding wavelength regions to shed light on the distribution of carbon in the ejecta. Our ability to reconstruct the C ii λ6580 feature in detail under the assumption of purely spherical symmetry casts doubt on a "carbon blobs" hypothesis, but does not rule out all asymmetric models. A low volume filling factor for carbon, combined with line-of-sight effects, seems unlikely to explain the scarcity of detected carbon in SNe Ia by itself.
Source: The Astrophysical Journal
Authors: R. C. Thomas, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Baltay, S. Bongard, C. Buton, A. Canto, M. Childress, N. Chotard, Y. Copin, H. K. Fakhouri, E. Gangler, E. Y. Hsiao, M. Kerschhaggl, M. Kowalski, S. Loken, P. Nugent, K. Paech, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, D. Rabinowitz, M. Rigault, D. Rubin, K. Runge, R. Scalzo, G. Smadja, C. Tao, B. A. Weaver, C. Wu, (The Nearby Supernova Factory), P. J. Brown, P. A. Milne
Institutions: Lawrence Berkeley National Laboratory, Centre National de la Recherche Scientifique, Laboratoire de Physique Nucléaire et de Hautes Énergies, Institut National de Physique Nucléaire et de Physique des Particules, Université Paris Diderot, Université Pierre-et-Marie-Curie, Yale University, University of Bonn, University of California, Berkeley, Université de Lyon, Lyon 1 Université, Institute of Nuclear Physics of Lyon, Australian National University, Mount Stromlo Observatory, Centre de Recherche Astrophysique de Lyon, Centre de physique des particules de Marseille, Tsinghua University, New York University, Chinese Academy of Sciences, National Astronomical Observatories
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, Smithsonian Institution, U.S. Department of Energy, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Aspen Center for Physics, National Energy Research Scientific Computing Center, Deutsche Forschungsgemeinschaft, Centre National de la Recherche Scientifique, Office of Science, University of California, San Diego, Smithsonian Astrophysical Observatory, France-Berkeley Fund, Institut National de Physique Nucléaire et de Physique des Particules, Advanced Scientific Computing Research, High Energy Physics, Astrophysics Division
Awards: G1286236842, G1632040200, G1677143136, G1771655729, G1799333409, G1863003419, G196419191, G222768804, G3083819904, G3136028036, "FUNDING FOR SUPER-LOTIS TELESCOPE IN SUPPORT OF NASA SWIFT SATELLITE", G3685081974, G42916606, G4501827968, G498139845, G5076365615, G6024799018, G6447494072, G6649312515, G6652958823, G759921648, Supernovae and Supernova Cosmology, An Interdisciplinary Collaboration on Performance Aspects of a High Performance Wireless Research and Education Network, G969889393
OpenAlex ID: W2061948473