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Sub-Chandrasekhar White Dwarf Mergers as the Progenitors of Type Ia Supernovae

van-Kerkwuk, Marten H. and Chang, Philip and Justham, Stephen (2010) Sub-Chandrasekhar White Dwarf Mergers as the Progenitors of Type Ia Supernovae. Astrophysical Journal Letters, 722 (2). L157-L161. ISSN 2041-8205.

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Type Ia supernovae (SNe Ia) are generally thought to be due to the thermonuclear explosions of carbon–oxygen white dwarfs (COWDs) with masses near the Chandrasekhar mass. This scenario, however, has two long-standing problems. First, the explosions do not naturally produce the correct mix of elements, but have to be finely tuned to proceed from subsonic deflagration to supersonic detonation. Second, population models and observations give formation rates of near-Chandrasekhar WDs that are far too small. Here, we suggest that SNe Ia instead result from mergers of roughly equal-mass CO WDs, including those that produce sub-Chandrasekhar mass remnants. Numerical studies of such mergers have shown that the remnants consist of rapidly rotating cores that contain most of the mass and are hottest in the center, surrounded by dense, small disks. We argue that the disks accrete quickly, and that the resulting compressional heating likely leads to central carbon ignition. This ignition occurs at densities for which pure detonations lead to events similar to SNe Ia. With this merger scenario, we can understand the type Ia rates and have plausible reasons for the observed range in luminosity and for the bias of more luminous supernovae toward younger populations. We speculate that explosions of WDs slowly brought to the Chandrasekhar limit—which should also occur—are responsible for some of the “atypical” SNe Ia.

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Chang, Philip0000-0002-2137-2837
Additional Information:© 2010 The American Astronomical Society. Received 2010 June 22; accepted 2010 September 10; published 2010 September 28. This work was triggered by coffee-time astro-ph discussions at KIAA. We thank the referee for constructive criticism, Yanqin Wu for her insistence that rotation was important, Carles Badenes,Ray Carlberg,Avishay Gal-Yam, Andy Howell, Rubina Kotak, Kelly Lepo, Yuri Levin, Dany Maoz, and Ken Shen for interesting discussions, and Enrique García-Berro and Pablo Lorén-Aguilar for providing details on their merger simulations. We are grateful to Bill Paxton for making mesa publicly available and for setting it up such that parts can be used separately and “what if” experiments are easy to execute. M.H.vK. and P.C. thank KIAA and Caltech Astronomy for their hospitality. This research made extensive use of NASA’s ADS.
Subject Keywords:binaries: close; supernovae: general; white dwarfs
Issue or Number:2
Classification Code:PACS: 97.20.Rp; 97.60.Bw; 97.10.Cv; 98.58.Mj; 97.10.Ri
Record Number:CaltechAUTHORS:20101101-134624990
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Official Citation:Marten H. van Kerkwijk et al 2010 ApJ 722 L157 doi: 10.1088/2041-8205/722/2/L157
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20623
Deposited By: Ruth Sustaita
Deposited On:01 Nov 2010 21:24
Last Modified:03 Oct 2019 02:12

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