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arXiv · 1003.2217

Nearby Supernova Factory Observations of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor

R. A. Scalzo·G. Aldering·P. Antilogus·C. Aragon·S. Bailey·C. Bongard·C. Buton·M. Childress·N. Chotard·Y. Copin·H. K. Fakhouri·A. Gal-Yam·E. Gangler·S. Hoyer·M. Kasliwal·S. Loken·P. E. Nugent·R. Pain·E. Pecontal·R. Pereira·S. Perlmutter·D. Rabinowitz·A. Rau·G. Rigaudier·K. Runge·G. Smadja·C. Tao·R. C. Thomas·B. Weaver·C. Wu
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Abstract

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 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. 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. SN2007 if 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 \ion{Si}{2} velocity evolution to constrain the mass of the shell and the underlying SN ejecta, and demonstrate that SN2007 if 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 solar masses, with 1.6 +/- 0.1 solar masses of nickel-56 and with 0.3-0.5 solar masses 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 SNeIa.

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R. A. Scalzo, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Bongard, C. Buton, M. Childress, N. Chotard, Y. Copin, H. K. Fakhouri, A. Gal-Yam, E. Gangler, S. Hoyer, M. Kasliwal, S. Loken, P. E. Nugent, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, D. Rabinowitz, A. Rau, G. Rigaudier, K. Runge, G. Smadja, C. Tao, R. C. Thomas, B. Weaver, C. Wu. 2010-04-02. Nearby Supernova Factory Observations of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor. https://doi.org/10.1088/0004-637x%2F713%2F2%2F1073

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