Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005hia....13..813m&link_type=abstract
Highlights of Astronomy, Vol. 13, as presented at the XXVth General Assembly of the IAU - 2003 [Sydney, Australia, 13 - 26 July
Astronomy and Astrophysics
Astronomy
Scientific paper
We present an analysis of optical high-resolution spectra of very young ultra-low mass stellar and substellar objects in Upper Scorpius and Taurus. We show that a multi-feature spectral analysis combined with the latest synthetic spectra can yield accurate surface gravities (+/- 0.25 dex) and effective temperatures (+/- 50K). This represents the most stringent observational constraint so far on gravity in young ultra-low mass objects. Combining our gravity and temperature results with observed and synthetic photometry and known cluster distance we also derive masses and radii for our objects. These are the first mass and radii measurements in young ultra-low mass objects that are INDEPENDENT of theoretical evolutionary tracks. We find that two of our faintest targets have planetary mass (~ 6 Jupiters). We also find that significant discrepancies exist between our results and the theoretical tracks for the coolest objects: our derived radii are substantially larger than predicted. Recent studies of M dwarf eclipsing binaries also show the theoretical radii to be underestimations. We conclude that high-resolution spectroscopy is invaluable for guiding the evolutionary modeling of young low-mass stars and brown dwarfs.
Basri Gibor
Jayawardhana Ray
Mohanty Subhanjoy
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