A Search for New Candidate Super-Chandrasekhar-Mass Type Ia Supernovae in the Nearby Supernova Factory Dataset
The Nearby Supernova Factory, :, R. Scalzo, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Baltay, S. Bongard, C. Buton, A. Canto, F. Cellier-Holzem, M. Ch… 展开作者
The Nearby Supernova Factory, :, R. Scalzo, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Baltay, S. Bongard, C. Buton, A. Canto, F. Cellier-Holzem, M. Childress, N. Chotard, Y. Copin, H. K. Fakhouri, E. Gangler, J. Guy, E. Y. Hsiao, M. Kerschhaggl, M. Kowalski, P. Nugent, K. Paech, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, D. Rabinowitz, M. Rigault, K. Runge, G. Smadja, C. Tao, R. C. Thomas, B. A. Weaver, C. Wu
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28 pages, 10 figures; v2, v3 small corrections to section 5.4. Accepted for publication in the Astrophysical Journal
We present optical photometry and spectroscopy of five type Ia supernovae discovered by the Nearby Supernova Factory selected to be spectroscopic analogues of the candidate super-Chandrasekhar-mass events SN 2003fg and SN 2007if. Their spectra are characterized by hot, highly ionized photospheres near maximum light, for which SN 1991T supplies the best phase coverage among available close spectral templates. Like SN 2007if, these supernovae are overluminous (-19.5 < M_V < -20) and the velocity of the Si II 6355 absorption minimum is consistent with being constant in time from phases as early as a week before, and up to two weeks after, $B$-band maximum light. We interpret the velocity plateaus as evidence for a reverse-shock shell in the ejecta formed by interaction at early times with a compact envelope of surrounding material, as might be expected for SNe resulting from the mergers of two white dwarfs. We use the bolometric light curves and line velocity evolution of these SNe to estimate important parameters of the progenitor systems, including nickel-56 mass, total progenitor mass, and masses of shells and surrounding carbon/oxygen envelopes. We find that the reconstructed total progenitor mass distribution of the events (including SN 2007if) is bounded from below by the Chandrasekhar mass, with SN 2007if being the most massive. We discuss the relationship of these events to the emerging class of super-Chandrasekhar-mass SNe Ia, estimate the relative rates, compare the mass distribution to that expected for double-degenerate SN Ia progenitors from population synthesis, and consider implications for future cosmological Hubble diagrams.
Evidence for sub-Chandrasekhar-mass progenitors of Type Ia supernovae at the faint end of the width-luminosity relation
低光度Ia型超新星（SNe Ia）的光变曲线演化速度更快，这表明它们可能是由质量低于克拉塞卡质量（$M_{\rm Ch}$）的白矮星（WD）的祖先爆炸造成的。在这里，我们提出了一维非LTE时间相关的辐射传输模拟的纯中心爆炸的碳氧WD与质量（$M_\rm{tot}$）之间的0.88 M $_{\odot}$和1.15 M $_{\odot}$，和一个$^{56}\rm{Ni}$产率之间的0.08 M $_{\odot}$和0.84 M $_{\odot}$。与$M_{\rm Ch}$模型相比，它们较低的喷出物密度导致早期光度更快地增加，并增强了$γ$射线逃逸分数超过最大光。因此，它们的热光变曲线显示较短的上升时间和较大的最大后下降率。此外，在给定的$^{56}\rm{Ni}$质量下，较高的$M(^{56}\rm{Ni})/M_\rm{tot}$比率增强了发光度较低的模型的光谱形成区域中的温度和电离水平，从而在最大光下产生更蓝的颜色，并且$B-V$颜色的最大后演化更快。对于在峰值时比$M_B\approx -18.5$等暗的次$M_{\rm Ch}$模型，较大的热辐射衰减和较快的颜色演变导致较大的$B$带最大后衰减率$ΔM_{15}(B)$。特别是，我们以前发表的所有$M_{\rm Ch}$模型（标准和脉动延迟爆轰）都局限于$ΔM_{15}(B) < 1.4$等，而$M_\rm{tot…
The Post-Merger Magnetized Evolution of White Dwarf Binaries: The Double-Degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs
