Pseudo-photometric distances of 30 open clusters⋆
1
Laboratoire Lagrange, Observatoire de la Côte d’Azur, CNRS, Bld. de l’Observatoire, 06304 Nice, France
e-mail: alain.chelli@oca.eu
2
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
Received:
23
March
2018
Accepted:
5
June
2018
Aims. We demonstrate that reliable photometric distances of stellar clusters, and more generally of stars, can be obtained using pseudomagnitudes and rough spectral type without having to correct for visual absorption.
Methods. We determine the mean absolute pseudomagnitude of all spectral (sub)types between B and K. Distances are computed from the difference between the star’s observed pseudomagnitude and its spectral type’s absolute pseudomagnitude. We compare the distances of 30 open clusters thus derived against the distances derived from TGAS parallaxes.
Results. Our computed distances, up to distance modulus 12, agree within 0.1 mag rms with those obtained from TGAS parallaxes, proving excellent distance estimates. We show additionally that there are actually two markedly different distances in the cluster NGC 2264.
Conclusions. We suggest that the pseudomagnitude distance estimation method, which is easy to perform, can be routinely used in all large-scale surveys where statistical distances on a set of stars, such as an open cluster, are required.
Key words: stars: distances / methods: observational / methods: data analysis / techniques: photometric
Pseudo-photometric distances of selected stars are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A132
© ESO 2018
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.