SPECTROSCOPIC BINARIES
b Aur
- Introduction
Spectrum of b Aur
The two components of b Aur have the same spectral class and almost the same luminosity
(Dm=0,13 mag).
For this reason the lines belonging to both components can be easily observed.
The lines appear periodically doubled because of the Doppler effect. The maximum separation corresponds to
a relative speed of the two components of 107.5+111.5 Km/sec that gives 3,27 Å for Mg II 4481 Å line.
The spectrum in the picture 1 shows the situation almost at the maximum of separation of the lines.
With a program that can do peak fitting it is possible to find the line separation with a precision that can be
better than 1/5 th of pixel, thus 0,15 Å that at this working wavelenght correspond to 9 Km/sec.
Working in the red can improve the results of a factor 2.
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Picture 1: A small part of the spectrum of b Aur centered on the Hg line,
recorded with 0,7 Å resolution and 5 minutes exposure. The black stripe shows the original image on the CCD.
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Introduction
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