低光度Ia型超新星2022xkq的JWST MIRI/MRS观测与光谱模型
JWST MIRI/MRS Observations and Spectral Models of the Under-luminous Type Ia Supernova 2022xkq
AI总结：
本研究利用JWST MIRI获取低光度Ia型超新星2022xkq的中红外光谱，发现其特有谱线特征，通过模拟约束爆炸白矮星质量与爆炸机制，证明中红外观测结合建模对研究SN Ia物理的强大能力。
摘要：
我们展示了低光度Ia型超新星（SN Ia）2022xkq的JWST中红外光谱，该光谱由中红外仪器（MIRI）的中分辨率光谱仪在爆炸后约130天获取。我们识别出了SN Ia观测中首批14微米以上的中红外谱线。我们发现了低光度SN Ia特有的特征，包括：稳定Ni的孤立发射、[Ti II]的强混合线，以及[Ar]和[Co]中单电离与双电离物种的大比值。与相似阶段的正常光度SN Ia光谱对比显示，[Co III] 11.888微米特征的宽度与超新星光变曲线形状之间存在初步趋势。利用非LTE多维辐射流体模拟和观测到的电子俘获元素，我们约束了爆炸白矮星的质量。最佳拟合模型表明，SN 2022xkq符合近钱德拉塞卡质量白矮星（抛射物质量≈1.37倍太阳质量）的偏中心延迟爆轰爆炸，该白矮星具有高中心密度（中心密度≥2.0×10^9克每立方厘米），观测视角为赤道方向，爆炸产生了0.324倍太阳质量的56Ni和≥0.06倍太阳质量的58Ni。观测到的谱线宽度与整体丰度分布一致；窄的稳定Ni谱线表明中心区域几乎没有混合，支持亚音速碳燃烧的中心点火，随后在单点开始偏中心DDT（延迟爆轰转变）。额外的观测可能会进一步约束物理机制，揭示包括Cr和Mn在内的其他物种的存在。我们的工作证明了结合MIRI的全波段覆盖与详细建模，能够以前所未有的水平阐明SN Ia的物理机制。
英文摘要：
We present a JWST mid-infrared spectrum of the under-luminous Type Ia Supernova (SN Ia) 2022xkq, obtained with the medium-resolution spectrometer on the Mid-Infrared Instrument (MIRI) $\sim130$ days post-explosion. We identify the first MIR lines beyond 14 $μ$m in SN Ia observations. We find features unique to under-luminous SNe Ia, including: isolated emission of stable Ni, strong blends of [Ti II], and large ratios of singly ionized to doubly ionized species in both [Ar] and [Co]. Comparisons to normal-luminosity SNe Ia spectra at similar phases show a tentative trend between the width of the [Co III] 11.888 $μ$m feature and the SN light curve shape. Using non-LTE-multi-dimensional radiation hydro simulations and the observed electron capture elements we constrain the mass of the exploding white dwarf. The best-fitting model shows that SN 2022xkq is consistent with an off-center delayed-detonation explosion of a near-Chandrasekhar mass WD (M$_{\rm ej}$ $\approx 1.37$ M$_{\odot}$) of high-central density ($ρ_c \geq 2.0\times10^{9}$ g cm$^{-3}$) seen equator on, which produced M($^{56}$Ni) $= 0.324$ M$_{\odot}$ and M($^{58}$Ni) $\geq 0.06$ M$_{\odot}$. The observed line widths are consistent with the overall abundance distribution; and the narrow stable Ni lines indicate little to no mixing in the central regions, favoring central ignition of sub-sonic carbon burning followed by an off-center DDT beginning at a single point. Additional observations may further constrain the physics revealing the presence of additional species including Cr and Mn. Our work demonstrates the power of using the full coverage of MIRI in combination with detailed modeling to elucidate the physics of SNe Ia at a level not previously possible.
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