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Astron. Astrophys. 320, 791-798 (1997)

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A spectroscopic study of the binary star [FORMULA]  Gem

G. Scholz 1, H. Lehmann 2, P. Harmanec 3, E. Gerth 1 and G. Hildebrandt 1

1 Astrophysikalisches Institut Potsdam, Telegrafenberg A 31, D-14473 Potsdam, Germany (gscholz@aip.de, egerth@aip.de, ghildebrandt@aip.de)
2 Thüringer Landessternwarte Tautenburg, Karl-Schwarzschild-Observatorium, D-07778 Tautenburg, Germany (lehm@tls-tautenburg.de)
3 Astronomický ústav, Akademie v d eské republiky, 251 65 Ond ejov, Czech Republic (hec@sunstel.asu.cas.cz)

Received 27 December 1995 / Accepted 2 August 1996

Abstract

Analysis of an extensive collection of 730 spectroscopic observations of the bright A0IV star [FORMULA]  Gem lead to the following conclusions:

(1) A new orbital solution is presented. Some hints of a small gradual increase of the systemic velocity were found but cannot be taken as real until confirmed by continuing observations. There is still no compelling evidence of the apsidal motion, however.

(2) A new, more accurate value of the projected rotational velocity of the primary, (10.2 [FORMULA] 0.2) km s-1, was derived from the 2 Å mm-1 spectrograms. Together with available estimates of the radius of the primary it sets up an upper limit of about one month on its rotational period. Period analyses of the O-C velocity deviations from the orbital solution revealed no significant periodic RV variations on time scales from 0 [FORMULA] 01 to 30 [FORMULA] 0 which we could assign to the rotation of the star or pulations as they are to expect in case that [FORMULA]  Gem is a member of the so-called Maia sequence.

(3) We confirm the existence of a strong global magnetic field in the atmosphere of [FORMULA]  Gem if we use an empirical correlation between the magnetic field strength and the relative differences of the equivalent widths of a pair of spectral lines belonging to the same multiplet but with different magnetic sensivity.

Key words: stars: standard – binaries: spectroscopic – binaries: visual – stars: individual: fl Gem

Send offprint requests to: G. Scholz

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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