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Article overview
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Fundamental M-dwarf parameters from high-resolution spectra using PHOENIX ACES models: I. Parameter accuracy and benchmark stars | | Vera Maria Passegger
; Sebastian Wende-von Berg
; Ansgar Reiners
; | | Date: |
8 Jan 2016 | | Abstract: | M-dwarf stars are the most numerous stars in the Universe; they span a wide
range in mass and are in the focus of ongoing and planned exoplanet surveys. To
investigate and understand their physical nature, detailed spectral information
and accurate stellar models are needed. We use a new synthetic atmosphere model
generation and compare model spectra to observations. To test the model
accuracy, we compared the models to four benchmark stars with atmospheric
parameters for which independent information from interferometric radius
measurements is available. We used $chi^2$ -based methods to determine
parameters from high-resolution spectroscopic observations. Our synthetic
spectra are based on the new PHOENIX grid that uses the ACES description for
the equation of state. This is a model generation expected to be especially
suitable for the low-temperature atmospheres. We identified suitable spectral
tracers of atmospheric parameters and determined the uncertainties in $T_{
m
eff}$, $log{g}$, and [Fe/H] resulting from degeneracies between parameters and
from shortcomings of the model atmospheres. The inherent uncertainties we find
are {sigma}$T_{
m eff}$= 35 K, {sigma}$log{g}$ = 0.14, and {sigma}[Fe/H] =
0.11. The new model spectra achieve a reliable match to our observed data; our
results for $T_{
m eff}$ and $log{g}$ are consistent with literature values
to within 1{sigma}. However, metallicities reported from earlier photometric
and spectroscopic calibrations in some cases disagree with our results by more
than 3 {sigma}. A possible explanation are systematic errors in earlier
metallicity determinations that were based on insufficient descriptions of the
cool atmospheres. At this point, however, we cannot definitely identify the
reason for this discrepancy, but our analysis indicates that there is a large
uncertainty in the accuracy of M-dwarf parameter estimates. | | Source: | arXiv, 1601.1877 | | Services: | Forum | Review | PDF | Favorites | |
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