Early observations of the nearby Type Ia supernova SN 2015F
Early observations of the nearby Type Ia supernova SN 2015F
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DOI：
10.1093/mnras/stw2678
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发表时间：
2016-09
影响因子：
4.8
通讯作者：
R. Cartier;M. Sullivan;R. Firth;G. Pignata;P. Mazzali;P. Mazzali;K. Maguire;M. Childress;I. Arcavi;I. Arcavi;C. Ashall;B. Bassett;B. Bassett;S. Crawford;C. Frohmaier;L. Galbany;A. Gal-yam;G. Hosseinzadeh;G. Hosseinzadeh;D. Howell;D. Howell;C. Inserra;J. Johansson;E. Kasai;C. McCully;C. McCully;S. Prajs;S. Prentice;S. Schulze;S. Schulze;S. Smartt;K. Smith;Mathew Smith;S. Valenti;S. Valenti;D. Young
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文献类型：
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作者：
R. Cartier;M. Sullivan;R. Firth;G. Pignata;P. Mazzali;P. Mazzali;K. Maguire;M. Childress;I. Arcavi;I. Arcavi;C. Ashall;B. Bassett;B. Bassett;S. Crawford;C. Frohmaier;L. Galbany;A. Gal-yam;G. Hosseinzadeh;G. Hosseinzadeh;D. Howell;D. Howell;C. Inserra;J. Johansson;E. Kasai;C. McCully;C. McCully;S. Prajs;S. Prentice;S. Schulze;S. Schulze;S. Smartt;K. Smith;Mathew Smith;S. Valenti;S. Valenti;D. Young
我们目前的光度测定和时间序列光谱附近的Ia型超新星（SN Ia）SN 2015 F超过$-16$天，以$+80$天相对于最大的光，作为公共ESO瞬态天体光谱调查（PESSTO）的一部分。SN 2015 F是一个稍微次亮的Ia型超新星，衰减率为$\Delta m15（B）=1.35 \pm 0.03$ mag，位于正常和SN 1991 bg类事件之间的区域。我们密集采样的光度数据严格限制了第一道光的出现时间和早期光变曲线的形式。光谱表现出光球C II $\lambda 6580$吸收，直到$-4$天，和高速钙II是特别强的14000$公里s$^{-1}$，这表明混合在最外层的SN喷出物。虽然不寻常的超新星Ia光谱，包括V II的建模显着提高了光谱拟合。有趣的是，我们在6800\AA\处检测到一个吸收特征，它一直持续到最大光。我们对这条线的最佳解释是光球层Al II，这在SNe Ia中以前从未被声称过，尽管分离的高速C II物质也可能是原因。在这两种情况下，吸收材料似乎被限制在速度空间中的一个相对狭窄的区域。核合成的可检测量的Al II将反对低金属丰度的白色矮星祖先。我们还发现，这种6800 \AA\特征在其他正常的SN Ia事件中存在较弱，在SN 1991 bg类子类中很常见。
We present photometry and time-series spectroscopy of the nearby type Ia supernova (SN Ia) SN 2015F over $-16$ days to $+80$ days relative to maximum light, obtained as part of the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). SN 2015F is a slightly sub-luminous SN Ia with a decline rate of $\Delta m15(B)=1.35 \pm 0.03$ mag, placing it in the region between normal and SN 1991bg-like events. Our densely-sampled photometric data place tight constraints on the epoch of first light and form of the early-time light curve. The spectra exhibit photospheric C II $\lambda 6580$ absorption until $-4$ days, and high-velocity Ca II is particularly strong at $ 14000$ km s$^{-1}$, suggesting mixing in the outermost layers of the SN ejecta. Although unusual in SN Ia spectra, including V II in the modelling significantly improves the spectral fits. Intriguingly, we detect an absorption feature at $\sim$6800 \AA\ that persists until maximum light. Our favoured explanation for this line is photospheric Al II, which has never been claimed before in SNe Ia, although detached high-velocity C II material could also be responsible. In both cases the absorbing material seems to be confined to a relatively narrow region in velocity space. The nucleosynthesis of detectable amounts of Al II would argue against a low-metallicity white dwarf progenitor. We also show that this 6800 \AA\ feature is weakly present in other normal SN Ia events, and common in the SN 1991bg-like sub-class.