Accurate computation of stellar masses in double and multiple stars

Resumo

Our aim is to show how the precise determination of orbits with both photometric and spectral data of binary systems can be used to obtain accurate stellar masses –even of each component in many cases. Firstly, we proceed to calculate orbital elements by means of the Docobo’s method [9] preferably using high-quality speckle measurements. If the system possesses a well-determined Hipparcos trigonometric parallax, we can calculate system mass from Kepler’s Third Law. If not, we will need to collect information about visual magnitudes and spectral classification. This information together with updated mass-luminosity calibrations for main-sequence and subgiant stars can be handled according to the algorithm of Baize-Romani [3] in order to obtain the dynamical parallax as well as the mass ratio of the components, and from these, the individual masses. In this paper we apply this methodology to some selected binaries discovered by W. S. Finsen using his eyepiece interferometer, one of his greatest achievements in binary stars research. We also discuss some political issues concerning his fierce opposition and negative predictions as Director of the Republic Observatory (R.O., Johannesburg) regarding the South African Government’s decision to close the R.O. and amalgamate it with the Cape Observatory (Cape Town) and the Radcliffe Observatory (Pretoria) into what became known as the South African Astronomical Observatory (SAAO) in 1974.