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Astron. Astrophys. 335, 561-564 (1998)

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Spectroscopic orbit of the ex-eclipsing binary SS Lacertae in the young open cluster NGC 7209

Lina Tomasella 1 and Ulisse Munari 2

1 Osservatorio Astrofisico del Dipartimento di Astronomia, Università di Padova, I-36012 Asiago (VI), Italy
2 Osservatorio Astronomico di Padova, Sede di Asiago, I-36012 Asiago (VI), Italy

Received 5 February 1998 / Accepted 24 April 1998


The no-longer-eclipsing system SS Lac in the young open cluster NGC 7209 has been recently announced to show a constant radial velocity. Puzzled by this finding, we have monitored the system during 1997 obtaining 24 Echelle+CCD spectra over 8 orbital revolutions. Our spectra reveal a nice orbital motion with periodic splitting and merging of spectral lines from both components.

An accurate orbit has been derived, together with individual masses of the stars. SS Lac presents a moderately eccentric orbit and a probably full synchronization between stellar rotation and orbital revolution.

Key words: binaries: eclipsing – binaries: spectroscopic – stars: individual: SS Lacertae – open clusters: individual: NGC 7209

Send offprint requests to: U. Munari

© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998