Space Weather & Heliophysics

Cool And Data-Driven: An Exploration Of Optical Cool Dwarf Chemistry With Both Data-Driven And Physical Models

By Keith Cowing
Status Report
February 23, 2024
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Cool And Data-Driven: An Exploration Of Optical Cool Dwarf Chemistry With Both Data-Driven And Physical Models
Spectra recovery for a representative set of benchmark stars with the WiFeS blue arm for 4 000 < ๐œ† < 5 400 ร… at Rโˆผ3 000, with observed spectra in black and Cannon model spectra in red. We generate model spectra from our fully-trained three-label Cannon model at the adopted (rather than best-fit) benchmark labels. The vertical red bars correspond to H-๐›ฝ, H-๐›พ, and H-๐›ฟ from the hydrogen Balmer series which were masked out to avoid emission features. The stars are sorted by their Gaia (๐ต๐‘ƒ โˆ’ ๐‘…๐‘ƒ) colour to show a smooth transition in spectral features across the parameter space considered. -- astro-ph.SR

Detailed chemical studies of F/G/K — or Solar-type — stars have long been routine in stellar astrophysics, enabling studies in both Galactic chemodynamics, and exoplanet demographics.

However, similar understanding of the chemistry of M and late-K dwarfs — the most common stars in the Galaxy — has been greatly hampered both observationally and theoretically by the complex molecular chemistry of their atmospheres. Here we present a new implementation of the data-driven \textit{Cannon} model, modelling Teff, logg, [Fe/H], and [Ti/Fe] trained on low-medium resolution optical spectra (4000โˆ’7000 angstrom) from 103 cool dwarf benchmarks.

Alongside this, we also investigate the sensitivity of optical wavelengths to various atomic and molecular species using both data-driven and theoretical means via a custom grid of MARCS synthetic spectra, and make recommendations for where MARCS struggles to reproduce cool dwarf fluxes.

Under leave-one-out cross-validation, our Cannon model is capable of recovering Teff, logg, [Fe/H], and [Ti/Fe] with precisions of 1.4\%, ยฑ0.04dex, ยฑ0.10dex, and ยฑ0.06dex respectively, with the recovery of [Ti/Fe] pointing to the as-yet mostly untapped potential of exploiting the abundant — but complex — chemical information within optical spectra of cool stars.

Adam D. Rains, Thomas Nordlander, Stephanie Monty, Andrew R. Casey, Bรกrbara Rojas-Ayala, Maruลกa ลฝerjal, Michael J. Ireland, Luca Casagrande, Madeleine McKenzie

Comments: 24 pages, 14 figures, 4 tables. Accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2402.14639 [astro-ph.SR] (or arXiv:2402.14639v1 [astro-ph.SR] for this version)
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Submission history
From: Adam Rains
[v1] Thu, 22 Feb 2024 15:36:39 UTC (12,326 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Naโ€™Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) ๐Ÿ––๐Ÿป