高变红Ia型超新星中Na I D线的第二种情况（有勘误）
A Second Case of Variable Na I D Lines in a Highly-Reddened Type Ia Supernova (with Erratum)
摘要：
Ia型SN 2006 X最近的高分辨率光谱显示了时变和蓝移Na I D特征的存在，Patat等人解释为起源于祖先系统内的拱星物质。在SN 2006 X中观察到的变化引起总Na I D等效宽度的相对较大的变化（仅在两周内的$Δ\rm{EW}\approx 0.5 \unicode{x212B}$），这将在较低分辨率下可检测到。我们已经使用了一个大的数据集，包括2400低分辨率光谱的450 Ia型超新星（SNe Ia）获得的CfA超新星计划，以寻找可变的Na I D功能。在31个Ia型超新星（包括SN 2006 X）中，我们可以检测到类似的EW变化，只有一个（SN 1999 cl）显示出不同的Na I D特征，在类似的~10天时间尺度（$Δ\rm{EW} = 1.66 \pm 0.21 \unicode{x212B}$）内有更大的变化。有趣的是，SN 1999cl和SN 2006X都是我们样本中最红的两个天体，这增加了这种变化与尘埃环境有关的可能性。在SN 1999cl中观测到的Na I D等效宽度的巨大变化实际上是测量误差的结果。我们的新测量结果表明，在$0.43 \pm 0.14 \unicode{x212B}$，EW变化明显较低。虽然EW变化仍然具有统计学显著性（3.1 $σ$不同于零），但它现在低于原始论文中发表的蒙特卡罗模拟得出的0.5 $\unicode{x212B}$的检测阈值。因此，SN 1999cl在我们的研究中不应再被认为是一个显示可变Na I D线的天体。因此，在我们的样本中显示Na I D线的SNe Ia分数从原始研究中的$\sim$ 6%（2/31）变为修订分析中的$\sim$ 3%（1/31），SN 2006 X是我们的样本中唯一具有可变Na I D线的SNe Ia。
英文摘要：
(Original) Recent high-resolution spectra of the Type Ia SN 2006X have revealed the presence of time-variable and blueshifted Na I D features, interpreted by Patat et al. as originating in circumstellar material within the progenitor system. The variation seen in SN 2006X induces relatively large changes in the total Na I D equivalent width ($Δ\rm{EW}\approx 0.5 \unicode{x212B}$ in just over two weeks), that would be detectable at lower resolutions. We have used a large data set comprising 2400 low-resolution spectra of 450 Type Ia supernovae (SNe Ia) obtained by the CfA Supernova Program to search for variable Na I D features. Out of the 31 SNe Ia (including SN 2006X) in which we could have detected similar EW variations, only one other (SN 1999cl) shows variable Na I D features, with an even larger change over a similar ~10-day timescale ($Δ\rm{EW} = 1.66 \pm 0.21 \unicode{x212B}$). Interestingly, both SN 1999cl and SN 2006X are the two most highly-reddened objects in our sample, raising the possibility that the variability is connected to dusty environments. (Erratum) The large variation in the Na I D equivalent width observed in SN 1999cl results in fact from a measurement error. Our new measurements show that the EW variation is significantly lower, at $0.43 \pm 0.14 \unicode{x212B}$. While the EW variation remains statistically significant (3.1$σ$ different from zero), it is now below the detection threshold of 0.5 $\unicode{x212B}$ derived from the Monte Carlo simulations published in the original paper. As a result, SN 1999cl should no longer be considered as an object displaying variable Na I D lines in our study. The fraction of SNe Ia in our sample displaying Na I D lines thus goes from $\sim$6% (2/31) in the original study to $\sim$3% (1/31) in the revised analysis, SN 2006X being the only SN Ia in our sample with variable Na I D lines.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
