Calibrating models of ultralow-mass stars

Abstract

Evolutionary and atmospheric models have become available for young ultralow-mass objects. These models are being used to determine fundamental parameters from observational properties. TiO bands are used to determine effective temperatures in ultralow-mass objects, and together with Na- and K-lines to derive gravities at the substellar boundary. Unfortunately, model calibrations in (young) ultralow-mass objects are rare. As a first step towards a calibration of synthetic spectral features, I show molecular bands of TiO, which is a main opacity source in late M-dwarfs. The TiO $\epsilon$-band at 8450Åis systematically too weak. This implies that temperatures determined from that band are underestimated, and I discuss implications for determining fundamental parameters from high resolution spectra.

4 pages, accepted for AN, "Ultra low mass star formation and evolution"

References in corpus (5)

• L' and M' Photometry of Ultracool Dwarfs
• An Assessment of Dynamical Mass Constraints on Pre-Main Sequence Evolutionary Tracks
• Metallicity measurements using atomic lines in M and K dwarf stars
• Measuring Fundamental Parameters of Substellar Objects. I: Surface Gravities
• Measuring Fundamental Parameters of Substellar Objects. II: Masses and Radii

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• Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models: I. Parameter accuracy and benchmark stars
• A high resolution spectral atlas of brown dwarfs
• Photospheric properties and fundamental parameters of M dwarfs
• Detection of strong activity in the eclipsing binary brown dwarf 2MASSJ05352184-0546085 - A possible explanation for the temperature reversal
• Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy
• High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity Uncertainties