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A& A Supplement series, Vol. 121, January 1997, 201 - 209

Received October 10, 1995; accepted April 13, 1996

Separating the spectra of binary stars

I.  A simple method: Secondary reconstruction

S. Ferlugatex2html_wrap1245, L. Floreanotex2html_wrap1247, U. Bravartex2html_wrap1249 - C. Bédalotex2html_wrap1251

Send offprint request: Steno Ferluga  (Internet e-mail:

tex2html_wrap1253  Dept.of Astronomy, Univ.of Trieste - via G.B. Tiepolo 11, I-34131 Trieste, Italy
tex2html_wrap1255  INFN, Trieste - Padriciano 99, I-34012 Trieste, Italy
tex2html_wrap1257  Dept.of Physics, Univ.of Trieste - via A.Valerio 2, I-34127 Trieste, Italy.


We present a practical method for the analysis of spectroscopic binaries, reconstructing the lines of the two components of the system. We show that the problem of the separation of binary spectra can be solved in an easy way, under most common conditions.

One pair of observations may be sufficient, if taken at different orbital phases of the system, preferably at opposite quadratures. The separation procedure is discussed analytically, and a technique is described, which allows to restore the secondary lines in few steps. An algorithm is also provided, which derives the radial velocity of the secondary star, by directly analysing a difference line-profile obtained from the two input spectra.

The efficiency of the method is tested, by reconstructing artificial line-profiles and simulated binary spectra as well. Then the procedure is applied to the eclipsing binary IZPer, revealing for the first time its faint secondary spectrum.

keywords: methods: data analysis -- binaries: spectroscopic -- stars: individual: IZ Per

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