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The Luminosity Calibration of the HR Diagram

Published online by Cambridge University Press:  14 August 2015

A.E. Gómez ,
X. Luri ,
M.O. Mennessier ,
J. Torra ,
F. Figueras  and
F. Royer
A.E. Gómez
Affiliation:
1 Observatoire de Paris-Meudon, D.A.S.G.A.L., CNRS URA 335 Pl. J. Janssen, 92195 Meudon Cedex, France
X. Luri
Affiliation:
1 Observatoire de Paris-Meudon, D.A.S.G.A.L., CNRS URA 335 Pl. J. Janssen, 92195 Meudon Cedex, France 3 Universitat de Barcelona Diagonal, 647, 08028 Barcelona, Spain
M.O. Mennessier
Affiliation:
2 Universite de Montpellier II Pl. E. Bataillon, 34095 Montpellier Cedex 5, France
J. Torra
Affiliation:
3 Universitat de Barcelona Diagonal, 647, 08028 Barcelona, Spain
F. Figueras
Affiliation:
3 Universitat de Barcelona Diagonal, 647, 08028 Barcelona, Spain
F. Royer
Affiliation:
1 Observatoire de Paris-Meudon, D.A.S.G.A.L., CNRS URA 335 Pl. J. Janssen, 92195 Meudon Cedex, France

Extract

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An extensive work on the luminosity calibration of the HR diagram has been performed using the LM method based on the Maximum Likelihood estimation (Luri et al. 1996). The method uses all available information: Hipparcos parallax and proper motion data as well as radial velocities and some measured spectroscopic or photometric parameters related to luminosity. On the other hand, the method takes into account the censorship of the sample and the errors of the data. Finally, it is able to identify and separate in a given sample, groups with different luminosity, kinematical or spatial characteristics providing not only the corresponding luminosity calibration relationship, but also improved individual absolute magnitude estimates.

In order to asses how reliable the luminosity calibrations based on the MK spectral classification are, the LM method has been applied to a sample of B to K stars with MK classification selected from the Hipparcos survey. All known binaries, variables and spectroscopically peculiar stars were removed from the sample. The final sample contains 22054 stars. Our results show that the relation between absolute magnitude and luminosity class has a large intrinsic dispersion. As a consequence, the assignation to a star of a mean absolute magnitude given by a MK classification calibration is a rough procedure. It is preferable to use the individual absolute magnitudes estimated using all the available information for each star, like the estimates provided by the LM method (Gómez et al. 1997).

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 11 , Issue 1: Highlights of Astronomy. As presented at the XXIIIrd General Assembly of the IAU (Part A), 1997 , 1998 , pp. 558
Copyright
Copyright © Kluwer 1998

References

Alvarez, R., Mennessier, M.O., Barthès, D., Luri, X., Mattei, J. (1997), A&A, in pressGoogle Scholar
Gómez, A.E., Luri, X., Mennessier, M.O.,Torra, J., Figueras, F. (1997), Hipparcos Venice’97, ESA SP-402, in pressGoogle Scholar
Luri, X., Mennessier, M.O., Figueras, F., Torra, J. (1997), A&AS, 117 pp. 405–415 Google Scholar
Mennessier, M.O., Luri, X., Figueras, F., Gómez, A.E., Grenier, S., Torra, J., North, P. (1997), A&A, in pressGoogle Scholar