The SPHINX M dwarf Spectral Grid. II. New Model Atmospheres and Spectra to Derive Fundamental Properties of mid-to-late type M-dwarfs
NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Arizona State University（亚利桑那州立大学）；Boston University（波士顿大学）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；American Museum of Natural History（美国自然历史博物馆）
Aishwarya R. Iyer, Michael R. Line, Philip S. Muirhead, Jonathan J. Fortney, Jacqueline K. Faherty
备注：
VERSION 2: ACCEPTED TO APJ. 20 pages and 17 figures in main text, 12 pages and 4 figures in appendix. Link provided to additional supplementary figures on Zenodo and Github repository for model-grid files
M-dwarfs are the most dominant stars in the Galaxy. Their interiors and atmospheres exhibit complex processes including dust condensation, convective feedback, and magnetic activity-driven heterogeneity. Standard stellar characterization methods often struggle to capture these coupled effects. Part I of this series introduced SPHINX I, a validated grid of self-consistent radiative-convective model atmospheres and spectra for M-dwarfs with up-to-date molecular opacities suitable for early-to-mid M-dwarfs. Here, we present SPHINX II, which extends the model grid to cover mid-to-late type M-dwarfs, including both gray and physically motivated condensate cloud treatments and shorter convective mixing lengths. We validate SPHINX II using 39 benchmark FGK+M binary systems observed with SpeX IRTF (Mann et al. 2014) and apply it to 32 mid-to-late-type M-dwarfs from the SpeX Prism Library. SPHINX II yields improved fits that are statistically consistent with empirical benchmarks, achieving precisions of 0.078 dex in metallicity and 0.13 dex in C/O. Across the model grid, condensate cloud mass peaks between 2100-2400 K, decreasing sharply toward both cooler and hotter temperatures. We find the onset of the cloud-free regime around 2900 K, and below 2100 K, we see formation of deep/buried clouds. As a case study, we also model Trappist-1 and show that even mass-limited silicate grains subtly modify its emergent spectrum, suppressing near-infrared flux and reddening the mid-infrared slope via shallow cloud formation near 1e-2 bar. In sum, SPHINX II provides an improved framework for constraining the fundamental properties of mid-to-late M-dwarfs.
Inspecting Cloudy Substellar Atmospheres with JWST MIRI Synthetic Magnitudes from Spitzer Mid-infrared Spectra
Department of Physics, Graduate Center, City University of New York（纽约市立大学研究生中心物理系）；Department of Astronomy, Columbia University（哥伦比亚大学天文学系）；Department of Astrophysics, American Museum of Natural History（美国自然历史博物馆天体物理学系）；School of Physics, Trinity College Dublin, The University of Dublin（都柏林三一学院物理学院，都柏林大学）；Department of Physics and Astronomy, Western University（韦仕敦大学物理与天文系）；Institute for Earth and Space Exploration, Western University（韦仕敦大学地球与太空探索研究所）；Department of Physics and Astronomy, Hunter College, City University of New York（纽约市立大学亨特学院物理与天文系）
The Hawaii Infrared Parallax Program. VI. The Fundamental Properties of 1000+ Ultracool Dwarfs and Planetary-mass Objects Using Optical to Mid-IR SEDs and Comparison to BT-Settl and ATMO 2020 Model Atmospheres
