TY - GEN
T1 - Testing substellar models with dynamical mass measurements
AU - Dupuy, T. J.
AU - Liu, M. C.
AU - Ireland, M. J.
N1 - Copyright the Author(s) 2011. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
PY - 2011
Y1 - 2011
N2 - We have been using Keck laser guide star adaptive optics to monitor the orbits of ultracool binaries, providing dynamical masses at lower luminosities and temperatures than previously available and enabling strong tests of theoretical models. We have identified three specific problems with theory: (1) We find that model color-magnitude diagrams cannot be reliably used to infer masses as they do not accurately reproduce the colors of ultracool dwarfs of known mass. (2) Effective temperatures inferred from evolutionary model radii are typically inconsistent with temperatures derived from fitting atmospheric models to observed spectra by 100-300K. (3) For the only known pair of field brown dwarfs with a precise mass (3%) and age determination (≈25%), the measured luminosities are ∼2-3× higher than predicted by model cooling rates (i.e., masses inferred from Lbol and age are 20-30% larger than measured). To make progress in understanding the observed discrepancies, more mass measurements spanning a wide range of luminosity, temperature, and age are needed, along with more accurate age determinations (e.g., via asteroseismology) for primary stars with brown dwarf binary companions. Also, resolved optical and infrared spectroscopy are needed to measure lithium depletion and to characterize the atmospheres of binary components in order to better assess model deficiencies.
AB - We have been using Keck laser guide star adaptive optics to monitor the orbits of ultracool binaries, providing dynamical masses at lower luminosities and temperatures than previously available and enabling strong tests of theoretical models. We have identified three specific problems with theory: (1) We find that model color-magnitude diagrams cannot be reliably used to infer masses as they do not accurately reproduce the colors of ultracool dwarfs of known mass. (2) Effective temperatures inferred from evolutionary model radii are typically inconsistent with temperatures derived from fitting atmospheric models to observed spectra by 100-300K. (3) For the only known pair of field brown dwarfs with a precise mass (3%) and age determination (≈25%), the measured luminosities are ∼2-3× higher than predicted by model cooling rates (i.e., masses inferred from Lbol and age are 20-30% larger than measured). To make progress in understanding the observed discrepancies, more mass measurements spanning a wide range of luminosity, temperature, and age are needed, along with more accurate age determinations (e.g., via asteroseismology) for primary stars with brown dwarf binary companions. Also, resolved optical and infrared spectroscopy are needed to measure lithium depletion and to characterize the atmospheres of binary components in order to better assess model deficiencies.
UR - http://www.scopus.com/inward/record.url?scp=84921461073&partnerID=8YFLogxK
U2 - 10.1051/epjconf/20111604004
DO - 10.1051/epjconf/20111604004
M3 - Conference proceeding contribution
AN - SCOPUS:84921461073
T3 - EPJ Web of Conferences
BT - Research, science and technology of brown dwarfs and exoplanets
A2 - Martin, E. L.
A2 - Ge, J.
A2 - Lin, W.
PB - EDP Sciences
CY - Les Ullis, France
T2 - International Conference Held in Shangai on Occasion of a Total Eclipse of the Sun
Y2 - 20 July 2009 through 24 July 2009
ER -