Hipparcos, VLA and CCD Observations of CYG OB2 No. 5

Contreras, M. E.; Rodriguez, L. F.; Tapia, M.; Cardini, D.; Badiali, M.; Emanuele, A.; Persi, P.
Bibliographical reference

Proceedings of the ESA Symposium `Hipparcos - Venice '97', 13-16 May, Venice, Italy, ESA SP-402 (July 1997), p. 401-404

Advertised on:
8
1997
Number of authors
7
IAC number of authors
0
Citations
3
Refereed citations
3
Description
Cyg OB2 No. 5 (BD+40deg4220; V729 Cyg) is known to be a contact binary system formed by two O-type stars. For this object a 6-cm radio emission has been detected at the optical position as well as an additional weak non-thermal radio source located at ~ 0.9 arcsec to the north east of the contact binary. It has been suggested that this radio component was possibly a third stellar object in the system. This was the first time that a radio companion was observed to be associated with the contact binary system. In this work we present new radio, CCD and Hipparcos observations that provide the basis for a plausible explanation of the origin of the non-thermal radiation emitted by the `third' component of this system and its nature.