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Astron. Astrophys. 340, 415-418 (1998)

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The RS CVn binary XY UMa as a member of a triple system

D. Chochol 1, T. Pribulla 1, M. Teodorani 2, L. Errico 2, A.A. Vittone 2, L. Milano 3, 4 and F. Barone 3, 4

1 Astronomical Institute of the Slovak Academy of Sciences, SK-059 60 Tatranská Lomnica, Slovakia
2 Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131, Napoli, Italy
3 Dipartimento di Scienze Fisiche, Universita di Napoli "Federico II", Via Cinthia, I-80126, Napoli, Italy
4 Instituto Nazionale di Fisica Nucleare, Via Cinthia, I-80126, Napoli, Italy

Received 6 August 1998 / Accepted 15 September 1998


New minima of the short period RS CVn binary system XY UMa taken in 1997-98 follow the light-time orbit with a 30.5 years period. An inferior conjunction of the third body with mass 0.23 [FORMULA] 0.03 [FORMULA] occurred in 1979. It is suggested that the light-curves of XY UMa taken in 1978-79 were affected by the eclipse of the binary system by a dusty envelope of the protostellar object responsible also for the observed infrared excess. There is no correlation between the long-term brightness variations of the system and the minima times in the O-C diagram, so its explanation by the Applegate mechanism proposed recently by Erdem & Güdür (1998) is brought into question.

Key words: binaries: eclipsing – stars: individual: XY Uma – stars: pre-main sequence – stars: magnetic fields

Send offprint requests to: D. Chochol, (chochol@auriga.ta3.sk)

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© European Southern Observatory (ESO) 1998

Online publication: November 9, 1998