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|Title:||Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra||Authors:||Childress, Michael J.
Hillier, D. John
ELIAS DE LA ROSA, NANCY DEL CARMEN
Howell, D. Andrew
Jha, Saurabh W.
Mazzali, Paolo A.
Smith, Ken W.
Young, D. R.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||454||Issue:||4||First Page:||3816||Abstract:||The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of <SUP>56</SUP>Ni to <SUP>56</SUP>Co at early times, and the decay of <SUP>56</SUP>Co to <SUP>56</SUP>Fe from ̃60 d after explosion. We examine the evolution of the [Co III] λ5893 emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of <SUP>56</SUP>Co as a function of time. This result indicates both efficient local energy deposition from positrons produced in <SUP>56</SUP>Co decay and long-term stability of the ionization state of the nebula. We compile SN Ia nebular spectra from the literature and present 21 new late-phase spectra of 7 SNe Ia, including SN 2014J. From these we measure the flux in the [Co III] λ5893 line and remove its well-behaved time dependence to infer the initial mass of <SUP>56</SUP>Ni (M<SUB>Ni</SUB>) produced in the explosion. We then examine <SUP>56</SUP>Ni yields for different SN Ia ejected masses (M<SUB>ej</SUB> - calculated using the relation between light-curve width and ejected mass) and find that the <SUP>56</SUP>Ni masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s ̃ 0.7-0.9), M<SUB>Ni</SUB> is clustered near M<SUB>Ni</SUB> ≈ 0.4 M<SUB>☉</SUB> and shows a shallow increase as M<SUB>ej</SUB> increases from ̃1 to 1.4 M<SUB>☉</SUB>; at high stretch, M<SUB>ej</SUB> clusters at the Chandrasekhar mass (1.4 M<SUB>☉</SUB>) while M<SUB>Ni</SUB> spans a broad range from 0.6 to 1.2 M<SUB>☉</SUB>. This could constitute evidence for two distinct SN Ia explosion mechanisms.||Acknowledgments:||This research was conducted by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. BPS and IRS acknowledge support from the Australian Research Council Laureate Fellowship Grant FL0992131. ST acknowledges support by TRR33 ‘The Dark Universe’ of the German Research Foundation (DFG). DJH acknowledges support from NASA theory grant NNX14AB41G. KM is supported by a Marie Curie Intra-European Fellowship, within the 7th European Community Framework Programme (FP7). NER acknowledges the support from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 267251 ‘Astronomy Fellowships in Italy’ (AstroFIt). MF acknowledges support from the European Union FP7 programme through ERC grant number 320360. MS acknowledges support from the Royal Society and EU/FP7-ERC grant no. . AGY is supported by the EU/FP7 via ERC grant no. 307260, the Quantum Universe I-Core programme by the Israeli Committee for planning and budgeting and the ISF, by Minerva and ISF grants, by the Weizmann-UK ‘making connections’ programme, and by Kimmel and ARCHES awards. AMG acknowledges financial support by the Spanish Ministerio de Economía y Competitividad (MINECO) grant ESP2013-41268-R. The research leading to these results has received funding from the European Union's Seventh Framework Programme [FP7/2007-2013] under grant agreement no. 264895. SJS acknowledges funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement no.  and STFC grants ST/I001123/1 and ST/L000709/1. SWJ and YC acknowledge support from the National Science Foundation through grants AST-0847157 and PHY-1263280, respectively. Part of this research was conducted while John Hillier was a Distinguished Visitor at the Research School of Astronomy and Astrophysics at the Australian National University. This research is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile as part of PESSTO (the Public ESO Spectroscopic Survey for Transient Objects), ESO programme ID 188.D-3003. We thank Stefano Benetti and Massimo Della Valle for helpful comments. We also thank Ben Shappee for kindly providing spectra of SN 2011fe. We thank the referee Jeff Silverman for a careful review of this work with many insightful comments that greatly improved the paper. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has also made use of NASA's Astrophysics Data System (ADS).||URI:||http://hdl.handle.net/20.500.12386/24142||URL:||https://academic.oup.com/mnras/article/454/4/3816/994403||ISSN:||0035-8711||DOI:||10.1093/mnras/stv2173||Bibcode ADS:||2015MNRAS.454.3816C||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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