The systematic parallax errors inherent in the Gaia DR1 data presently limit the precision of our results. Inferred cluster ages are robust against models and are generally consistent with literature values. For all but one cluster, parallaxes derived by us agree with those presented in Gaia Collaboration (2017, A&A, 601, A19), while a discrepancy is found for NGC 2516 we provide evidence supporting our own determination. Lithium depletion boundary (LDB) ages are also determined using literature observations and the same models employed for the Bayesian analysis. Ages and reddening values are recovered through a Bayesian analysis using the 2MASS magnitudes and three sets of standard models. The first one relies on the astrometric selection of a sample of bona fide members, while the other one fits the parallax distribution of a larger sample of TGAS sources. We obtain cluster parallaxes using two methods. The Gaia-ESO Survey also provides the cluster chemical composition.
Cluster membership probabilities for the Gaia-ESO Survey targets are derived based on several spectroscopic tracers. We perform a homogeneous analysis of eight open clusters using the Gaia-DR1 TGAS catalogue for bright members and information from the Gaia-ESO Survey for fainter stars. The final, long-term goal is the exploitation of open clusters as age calibrators. We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. Determination and calibration of the ages of stars, which heavily rely on stellar evolutionary models, are very challenging, while representing a crucial aspect in many astrophysical areas. Our approach appears promising and demonstrates the potential of combining Gaia and ground-based spectroscopic datasets.Ībstract = "Context. Nevertheless, we have been able to place these eight clusters onto the same age scale for the first time, with good agreement between isochronal and LDB ages where there is overlap. Inferred cluster ages are robust against models and are generally consistent with literature values.Ĭonclusions.
Determination and calibration of the ages of stars, which heavily rely on stellar evolutionary models, are very challenging, while representing a crucial aspect in many astrophysical areas.Īims.
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