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Researchers conducted a spectroscopic survey of 32 FGK-type stars that host brown dwarf companions, using high-resolution optical spectra from the PEPSI spectrograph on the Large Binocular Telescope. They determined precise stellar parameters and chemical abundances for 11 elements, achieving temperature uncertainties of approximately 42 K and iron abundance precision of 0.03 dex. The analysis revealed significant variation in carbon-to-oxygen ratios among brown dwarf host stars and explored how stellar abundance ratios like Mg/Si and Ca/Al can inform predictions about cloud properties in their brown dwarf companions.
Why it matters
This work provides a uniform baseline of host star chemistry that supports current and future brown dwarf characterization efforts with JWST and other facilities. Understanding the chemical connection between stars and their substellar companions helps constrain brown dwarf formation mechanisms and atmospheric composition predictions.
Understand the Science
arXiv:2607.09851v2 Announce Type: replace
Abstract: We present results from a spectroscopic survey of 32 FGK stars hosting brown dwarfs, using high-resolution optical spectra (R = 130,000 and 50,000) obtained with the PEPSI spectrograph on the Large Binocular Telescope. The primary goal of this survey is to determine precise stellar parameters and abundances for 11 elements (C, O, Mg, Si, Ca, Al, Ti, Fe, Y, S, and N) in these systems. We employ spectral synthesis within the BACCHUS framework to derive precise stellar properties and elemental abundance ratios. For our average S/N $>$ 200 data, we achieve a typical error of 42 K in T$_mathrm{eff}$ and $sim$0.03 dex for [Fe/H]. We observe a significant dispersion from a solar C/O ratio among the sample of brown dwarf host stars that host primarily wide-orbit brown dwarfs. Using established theoretical chemical frameworks, we discuss the implications of the observed Mg/Si and Ca/Al ratios for cloud properties in the brown dwarf companions. Finally, we evaluate the applicability of the [Y/Mg] stellar clock for our sample and discuss the broader implications of our results. This work provides a timely and uniform abundance analysis of host stars, supporting extended wavelength brown dwarf observations in the era of JWST.