Title: Optical and near-infrared nebular-phase spectroscopy of SN 2024ggi: constraints on the structure of the inner ejecta, progenitor mass, and dust Show Chinese title

Title: SN 2024ggi 的光学和近红外星云相光谱学：对内抛射物结构、前身星质量及尘埃的限制

Abstract: We present optical and near-infrared (NIR) spectroscopic observations of the nearby Type II supernova SN\,2024ggi from 250 and 420 days after the explosion. Comparing the evolution of the [\ion{O}{1}] at 6300, 6363 \text{\AA} doublet normalized to the continuum with spectral models from the literature, we estimate a progenitor star zero-age main-sequence mass ($M_{\mathrm{ZAMS}}$) of $\approx 14$ M$_\odot$. This value is consistent with $M_{\mathrm{ZAMS}}$ reported in the literature from independent methodologies. The nebular spectra are used to study the structure of the inner ejecta. The broad H$\alpha$ line has a full-width at half maximum (FWHM) of $\simeq 3900$ km s$^{-1}$, with small deviations from a symmetric Gaussian profile centred at zero velocity, and the [\ion{O}{1}] doublet is blue-shifted by $\approx -940$ km s$^{-1}$. In the NIR, the nebular spectra reveal double-peaked emission features of \ion{Mg}{1} and [\ion{Fe}{2}] lines, suggesting a bipolar distribution of intermediate mass and iron peak elements in the line-of-sight. Such a double-peaked feature in these NIR lines has not been previously reported. No corresponding asymmetries are observed in the hydrogen lines, suggesting that the asymmetry is mostly confined to intermediate mass and iron peak elements in the innermost core of the supernova ejecta. Additionally, we detect first-overtone carbon monoxide (CO) emission at $2.3$ $\mu$m from 250 to 319 days in the NIR. Show Chinese abstract

Abstract: 我们提供了对近邻的II型超新星SN 2024ggi在爆炸后250天和420天的光学和近红外（NIR）光谱观测。 将[\ion{O}{1}]在6300、6363\text{\AA }双线相对于连续谱的演化与文献中的光谱模型进行比较，我们估计前身恒星零年龄主序质量（$M_{\mathrm{ZAMS}}$）为 $\approx 14$M$_\odot$。 这个值与文献中从独立方法得出的$M_{\mathrm{ZAMS}}$相一致。 利用行星状光谱研究了内部抛射物的结构。 宽的H$\alpha$线的半高全宽（FWHM）为$\simeq 3900$ km s$^{-1}$，其偏离以零速度为中心的对称高斯轮廓有小的偏差，而[\ion{O}{1}]双线蓝移了$\approx -940$ km s$^{-1}$。 在近红外波段，行星状光谱显示出\ion{Mg}{1}和 [\ion{Fe}{2}] 线的双峰发射特征，表明中等质量元素和铁峰元素在视线方向上呈双极分布。 这些近红外线中的双峰特征此前尚未有报道。 在氢线中未观察到相应的不对称性，表明这种不对称性主要局限于超新星爆发物质最内层核心中的中等质量元素和铁峰元素。 此外，我们在近红外波段从250天到319天检测到一阶泛音一氧化碳（CO）发射，波长为$2.3$ $\mu$ m。