Ia型超新星2023vjh：一颗具有异常暗淡光变曲线的特殊类1991bg超新星
The type Ia supernova 2023vjh: a peculiar 1991bg-like SN with unusually faint light curves
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中文总结 AI 辅助
研究Ia型超新星2023vjh，通过观测其光变曲线形状参数、光谱演化等，发现它属快速下降、亚光度超新星，比模型预测和其他同类超新星暗，可能受星周物质影响，光变曲线拟合等分析表明有较大红化，模型存在局限性。
中文摘要 AI 辅助
我们展示了与椭圆星系MCG+04-10-013相关的类1991bg Ia型超新星（SN）2023vjh的观测结果。其光变曲线形状参数（$\Delta m_{15}(B)=1.89 \pm 0.01$ 星等和 $s_{BV} = 0.45 \pm 0.03$）以及光谱演化，使其稳固地属于快速下降、亚光度Ia型超新星类别。近峰值光谱显示出Si II、Ca II和Ti II的显著特征，与冷光球一致，并将SN 2023vjh置于分类图的“冷”和极冷区域。此外，三个晚期近红外（NIR）光谱显示出Ca II NIR三线态、Fe II和Co II吸收，但没有明显的H波段断裂。尽管SN 2023vjh落在分类图中与其他充分研究的类91bg事件相同的区域，但它在该类别中显示出一些偏差。特别是，它系统地比爆炸模型预测的更暗，且比其他充分研究的类91bg超新星更暗。光变曲线拟合和基于颜色的分析表明有相对较大的红化（$E(B-V)_{宿主}\sim$ 0.2 - 0.35星等），这对类91bg超新星来说是不寻常的。然而，其光谱中缺乏可检测的Na I D吸收，以及它与被动宿主星系中心的大投影距离（6.8 kpc），表明视线方向上的星际消光最小。SN 2023vjh似乎比典型的类91bg超新星更暗，并且可能受到星周物质（CSM）的影响。与爆炸模型和替代消光处方的比较表明，包括类似CSM的消光可改善蓝波段的一致性，但i波段的残余差异可能反映了模型的局限性。
英文摘要
We present observations of the 1991bg-like type Ia supernova (SN) 2023vjh, associated with the elliptical galaxy MCG+04-10-013. Its light-curve shape parameters ($Δm_{15}(B)=1.89 \pm 0.01$ mag and $s_{BV} = 0.45 \pm 0.03$), together with its spectroscopic evolution, place it firmly within the class of fast-declining, subluminous SNe Ia. The near-peak spectra show prominent features of Si II, Ca II, and Ti II, consistent with a cool photosphere, and place SN 2023vjh within the "cool" and extreme cool regions on the classification diagrams. In addition, the three late-phase near-infrared (NIR) spectra display the Ca II NIR triplet, Fe II, and Co II absorptions, but no obvious $H$-band break. Although SN 2023vjh falls in the same regions of the classification diagrams as other well-studied 91bg-like events, it shows some deviation within this class. In particular, it is systematically fainter than predicted by explosion models and fainter than other well-studied 91bg-like SNe. Light-curve fitting and color-based analyses indicate a relatively large reddening ($E(B-V)_{host}\sim$ 0.2 - 0.35 mag), which is unusual for 91bg-like SNe. Yet, the lack of detectable Na I D absorption in its spectra, along with its large projected distance from the center of its passive host galaxy (6.8 kpc), suggests that interstellar extinction along the line of sight is minimal. SN 2023vjh appears to be fainter than typical 91bg-like SNe, and it could be affected by circumstellar material (CSM). Comparisons with explosion models and alternative extinction prescriptions show that including CSM-like extinction improves agreement in the blue bands, but residual discrepancies in the $i$-band may reflect limitations in the model.
