L-T序列中的硅酸盐云、SiO及分子趋势：褐矮星的JWST/MIRI LRS光谱库
Silicate Clouds, SiO, and Molecular Trends across the L-T Sequence: A JWST/MIRI LRS Spectral Library of Brown Dwarfs
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中文总结 AI 辅助
该研究利用JWST的MIRI LRS对23颗L0 - T6矮星进行观测，获得其5 - 14μm光谱，详细研究硅酸盐吸收等特征，首次在矮星中检测气相SiO吸收，发现多颗双星，还发现单场矮星比经验关系暗，所建光谱库为JWST MIRI光谱解释提供校准基础。
中文摘要 AI 辅助
我们展示了使用JWST的MIRI LRS进行的一项调查计划的结果，该计划获得了23颗L0 - T6矮星的5 - 14μm、R~100光谱。这个光谱类型范围涵盖了硅酸盐凝结云的形成、增长和沉降，以及褐矮星大气中甲烷和氨的出现。以前所未有的细节研究了L0光谱类型处硅酸盐吸收的初始出现以及该特征随光谱类型的演变。首次在矮星中检测到7.5 - 9.5μm气相SiO吸收，在M5.5 - L2.5矮星中通过结合斯皮策IRS和JWST光谱检测到。此前在K和M巨星中检测到该特征，这些巨星中的吸收比高重力M矮星更强。相比之下，低重力L矮星的SiO吸收比场重力L矮星弱。我们还证实了以前在斯皮策IRS观测中看到的水、氨和甲烷吸收随光谱类型的趋势。我们报告了在一颗T3.5矮星中可能检测到CS2，不过确认需要更高分辨率光谱。我们发现了两颗新分辨的双星，确认了两颗近等通量未分辨候选双星，并识别出另外两颗可能的不等通量双星。在考虑分辨和候选双星的污染后，我们发现单场矮星比现有经验关系暗约0.15 - 0.20星等。所展示的光谱库为未来解释JWST MIRI对褐矮星或直接成像或凌日系外行星的光谱提供了分光光度校准基础。
英文摘要
We present the results of a survey program with JWST's MIRI LRS that obtained 5$-$14 $μ$m R~100 spectra of twenty-three L0$-$T6 dwarfs. This spectral type range spans the formation, growth, and sedimentation of silicate condensate clouds, as well as the appearance of methane and ammonia in the atmospheres of brown dwarfs. The initial onset of silicate absorption at spectral type L0 as well as the evolution of this feature with spectral type are both examined in unprecedented detail. We detect 7.5$-$9.5 $μ$m gas-phase SiO absorption for the first time in dwarf stars, with detections in M5.5$-$L2.5 dwarfs from combined Spitzer IRS and JWST spectra. This feature has previously been detected in K and M giants, with stronger absorption in these giants than in higher-gravity M dwarfs. In contrast, low-gravity L dwarfs show weaker SiO absorption than field-gravity L dwarfs. We also confirm water, ammonia, and methane absorption trends with spectral type previously seen in Spitzer IRS observations. We report the possible detection of CS2 in a T3.5 dwarf, although confirmation would require higher-dispersion spectroscopy. We find two newly resolved binaries, confirm two near-equal flux unresolved candidate binaries, and identify two additional possible non-equal flux binaries. After accounting for contamination by resolved and candidate binaries, we find that single field dwarfs are ~0.15$-$0.20 mag underluminous compared to existing empirical relations. The presented spectral library offers a spectrophotometrically calibrated basis for future interpretation of JWST MIRI spectra of brown dwarfs or of directly imaged or transiting exoplanets.
