Scalzo, R. A. and Aldering, G. and Antilogus, P. and Aragon, C. and Bailey, S. and Baltay, C. and Bongard, S. and Buton, C. and Childress, M. and Chotard, N. and Copin, Y. and Fakhouri, H. K. and Gal-Yam, A. and Gangler, E. and Hoyer, S. and Kasliwal, M. and Loken, S. and Nugent, P. and Pain, R. and Pécontal, E. and Pereira, R. and Perlmutter, S. and Rabinowitz, D. and Rau, A. and Rigaudier, G. and Runge, K. and Smadja, G. and Tao, C. and Thomas, R. C. and Weaver, B. and Wu, C. (2010) Nearby Supernova Factory Observations of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor. Astrophysical Journal, 713 (2). pp. 1073-1094. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100604-110604313
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We present photometric and spectroscopic observations of SN 2007if, an overluminous (M_V = –20.4), red (B – V = 0.16 at B-band maximum), slow-rising (t_(rise) = 24 days) type Ia supernova (SN Ia) in a very faint (M_g = –14.10) host galaxy. A spectrum at 5 days past B-band maximum light is a direct match to the super-Chandrasekhar-mass candidate SN Ia 2003fg, showing Si II and C II at ~9000 km s^(–1). A high signal-to-noise co-addition of the SN spectral time series reveals no Na I D absorption, suggesting negligible reddening in the host galaxy, and the late-time color evolution has the same slope as the Lira relation for normal SNe Ia. The ejecta appear to be well mixed, with no strong maximum in I band and a diversity of iron-peak lines appearing in near-maximum-light spectra. SN 2007if also displays a plateau in the Si II velocity extending as late as +10 days, which we interpret as evidence for an overdense shell in the SN ejecta. We calculate the bolometric light curve of the SN and use it and the Si II velocity evolution to constrain the mass of the shell and the underlying SN ejecta, and demonstrate that SN 2007if is strongly inconsistent with a Chandrasekhar-mass scenario. Within the context of a "tamped detonation" model appropriate for double-degenerate mergers, and assuming no host extinction, we estimate the total mass of the system to be 2.4 ± 0.2 M_☉, with 1.6 ± 0.1 M_☉ of ^(56)Ni and with 0.3-0.5 M_☉ in the form of an envelope of unburned carbon/oxygen. Our modeling demonstrates that the kinematics of shell entrainment provide a more efficient mechanism than incomplete nuclear burning for producing the low velocities typical of super-Chandrasekhar-mass SNe Ia.
|Additional Information:||© 2010 American Astronomical Society. Received 2009 December 15; accepted 2010 March 3; published 2010 March 30. The authors are grateful to the technical and scientific staffs of the University of Hawaii 2.2 m telescope, the W. M. Keck Observatory, and Palomar Observatory, to the QUEST-II collaboration, and to HPWREN for their assistance in obtaining these data. 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. The authors 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 work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231; by a grant from the Gordon & Betty Moore Foundation; and in France by support from CNRS/IN2P3, CNRS/INSU, and PNC. R.S. acknowledges support from National Science foundation grant 0407297. Y.C. acknowledges support from a Henri Chretien International Research Grant administrated by the American Astronomical Society, and from the France-Berkeley Fund. A.G.-Y. is supported by the Israeli Science Foundation, an EU Seventh Framework Programme Marie Curie IRG fellowship and the Benoziyo Center for Astrophysics, Minerva program, a research grant from the Peter and Patricia Gruber Awards, and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Director, Office of Science, Office of Advanced Scientific Computing Research, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank them for generous allocation of storage and computing time. HPWREN is funded by National Science Foundation Grant Number ANI-0087344, and the University of California, San Diego. IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. The spectra of SN 1999ee were obtained through the SUSPECT Supernova Spectrum Archive, an online database maintained at the University of Oklahoma, Norman. We thank Andy Howell for providing photometry and the near-maximum spectrum of SN 2003fg, and Masayuki Yamanaka for providing Si ii and C ii velocity measurements derived from SN 2009dc spectra. The SMARTS 1.3 m observing queue receives support from NSF grant AST-0707627. We thank John Holtzman and Jon Cough for their assistance in photometrically monitoring our SN candidates with the NMSU 1 m telescope.We thank Dan Birchall for his assistance in collecting data with SNIFS, and for his helpful commentary on, and proofreading of, the manuscript. We also thank Charles Bailyn, Richard Pogge, and Kevin Krisciunas for their assistance in characterizing the ANDICAM system throughput, and Daniel Kasen and Alan Calder for helpful discussions. Facilities: UH:2.2m, Hale(PO:5.0m), PO:1.2m, CTIO:1.5m|
|Subject Keywords:||supernovae: general; supernovae: individual (SNe 2003fg, 2006gz, 2007if, 2009dc); white dwarfs|
|Classification Code:||PACS: 97.60.Bw; 97.10.Nf; 97.10.Cv; 97.10.Ri; 95.85.Kr.|
|Official Citation:||R. A. Scalzo et al 2010 ApJ 713 1073 doi: 10.1088/0004-637X/713/2/1073|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||04 Jun 2010 20:27|
|Last Modified:||26 Dec 2012 12:06|
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