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The Luminosity Determination

Published online by Cambridge University Press:  30 March 2016

A.E. Gómez  and
C. Turon
A.E. Gómez
Affiliation:
DASGAL/URA 335 du CNRS, Observatoire de Paris-Meudon 92195 Meudon Cedex, FRANCEe-mail: anita@obspm.fr
C. Turon
Affiliation:
DASGAL/URA 335 du CNRS, Observatoire de Paris-Meudon 92195 Meudon Cedex, FRANCEe-mail: anita@obspm.fr

Extract

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The Hertzprung-Russel (HR) diagram luminosity calibration relies basically on three kinds of data: trigonometric parallaxes, kinematical data (proper motions and radial velocities) and cluster distances obtained by the zero-age main sequence fitting procedure. The most fundamental method to calculate the absolute magnitude is the use of trigonometric parallaxes, but up to now, accurate data only exist for stars contained in a small volume around the sun. Individual absolute magnitudes are obtained using trigonometric parallaxes or photometric and spectroscopic calibrations. In these calibrations the accuracy on the absolute magnitude determination ranges from ±0.m2 in the main sequence to ±0m5 in the giant branch. On the other hand, trigonometric parallaxes, kinematical data or cluster distances have been used to make statistical calibrations of the absolute magnitude. The standard error on the mean absolute magnitude calibrations ranges from ±0m3 to ±0m6 on the mean sequence, from ±0m5 to ±0m7 on thegiant branch and is of about 1m for supergiants.

Future improvements in the absolute magnitude determination will depend on the improvement of the basic data from the ground and space. A brief overview of the new available data is presented. In particular, the analysis of the first 30 months data of the Hipparcos mission (H30) (from the 37 months data of the whole mission) allows to perform a statistical evaluation of the improvements expected in the luminosity determination.

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 10: Highlights of Astronomy. As presented at the XXIInd General Assembly of the IAU, 1994 , 1995 , pp. 399 - 402
Copyright
Copyright © Kluwer 1995

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