Optical Observations of the Rapidly Expanding Type Ia Supernova 2007gi
T. Zhang, X. Wang, W. Li, A. V. Filippenko, L. Wang, X. Zhou, P. J. Brown, J. M. Silverman, T. N. Steele, M. Ganeshalingam, J. Li, J. Deng, T. Li, Y. Qiu, M. Zhai, R. Shang
本文介绍了NGC 4036中Ia型超新星2007 gi的光学光度学和光谱。SN 2007 gi的特徴是中等质量元素（Si、Ca和S）的极高速（HV）特征，膨胀速度（$v_{\rm exp}$）接近$\sim$ 15，500 km s $^{-1}$，接近最大亮度（相比之下，超新星Ia的$\sim$ 10，600 km s $^{-1}$具有正常的$v_{\rm exp}$）。SN 2007 gi的$B$波段峰值星等为13.25 $\pm$ 0.04等，衰减率为$Δm_{15}(B)$（真）= 1.33 $\pm$ 0.09等。SN 2007 gi的$B$波段光变曲线显示出在星云相有一个有趣的两阶段演化，在$t = 60$ -90天期间的衰减率为1.16 $\pm$ 0.05 mag（100天）$^{-1}$，此后为1.61 $\pm0.04$ mag（100天）$^{-1}$。在HV SN Ia 2006 X中也观察到了这种行为，可能是由超新星喷出物与HV SN Ia周围的星周物质（CSM）相互作用引起的。基于一打的$R$带（或未过滤）的超新星Ia的光变曲线的样本，我们确认，HV事件可能有一个更快的上升时间比正常的$v_{\rm exp}$的最大值。
英文摘要：
We present optical photometry and spectra for the Type Ia supernova (SN Ia) 2007gi in the nearby galaxy NGC 4036. SN 2007gi is characterized by extremely high-velocity (HV) features of the intermediate-mass elements (Si, Ca, and S), with expansion velocities ($v_{\rm exp}$) approaching $\sim$15,500 km s$^{-1}$ near maximum brightness (compared to $\sim$10,600 km s$^{-1}$ for SNe Ia with normal $v_{\rm exp}$). SN 2007gi reached a $B$-band peak magnitude of 13.25$\pm$0.04 mag with a decline rate of $Δm_{15}(B)$(true) = 1.33$\pm$0.09 mag. The $B$-band light curve of SN 2007gi demonstrated an interesting two-stage evolution during the nebular phase, with a decay rate of 1.16$\pm$0.05 mag (100 days)$^{-1}$ during $t = 60$--90 days and 1.61$\pm0.04$ mag (100 days)$^{-1}$ thereafter. Such a behavior was also observed in the HV SN Ia 2006X, and might be caused by the interaction between supernova ejecta and circumstellar material (CSM) around HV SNe Ia. Based on a sample of a dozen well-observed $R$-band (or unfiltered) light curves of SNe Ia, we confirm that the HV events may have a faster rise time to maximum than the ones with normal $v_{\rm exp}$.
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Ia超新星的前身是单简并还是双简并白矮星系统一直是一个备受争议的话题。为了解决Ia型第谷超新星遗迹（SNR）SN 1572的起源，我们进行了$^{12}$ CO J=2-1映射和使用IRAM 30米望远镜对遗迹进行3毫米线测量。我们表明，第谷是包围着一个clusterous分子泡在当地的标准的$\sim 61$公里的$^{-1}$的速度为$\sim 4.5$公里的$^{-1}$，并有一个质量为$\sim 220$ M $_\odot$（在距离为2.5千秒差距）。增强的$^{12}$ CO J=2-1线发射相对于$^{12}$ CO J=1-0发射和可能的线加宽（在速度范围$-64$到$-60$ km s $^{-1}$）被发现在东北边界的SNR，在那里的壳变形和减速。这些功能，结合膨胀的分子泡和第谷之间的形态对应关系，表明SNR是与泡沫在速度范围$-66$到$-57$ km s $^{-1}$。最合理的起源膨胀的泡沫是快速流出（速度为数百公里秒$^{-1}$）驱动的WD附近，因为它吸积的物质从一个非退化的伴星。在低密度风吹气泡中，信噪比一直在扩大，冲击波刚刚到达分子腔壁。在低密度风吹气泡中，信噪比一直在扩大，冲击波刚刚到达分子腔壁。这是第一次明确检测到Ia型SNR的祖先驱动的膨胀气泡，这构成了Ia型SN的单一简并祖先的证据。
Early Spectral Evolution of the Rapidly Expanding Type Ia SN 2006X
We present optical spectroscopic and photometric observations of Type Ia supernova (SN) 2006X from --10 to +91 days after the $B$ -band maximum. This SN exhibits one of the highest expansion velocity ever published for SNe Ia. At premaximum phases, the spectra show strong and broad features of intermediate-mass elements such as Si, S, Ca, and Mg, while the O{ \sc i} $λ$ 7773 line is weak. The extremely high velocities of Si{ \sc ii} and S{ \sc ii} lines and the weak O{ \sc i} line suggest that an intense nucleosynthesis might take place in the outer layers, favoring a delayed detonation model.…
