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Astron. Astrophys. 339, 75-86 (1998)

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V 439 Cyg: the smallest LBV? *

V.F. Polcaro 1 and L. Norci 2

1 Istituto di Astrofisica Spaziale, Area di Ricerca di Roma-Tor Vergata, Via Fosso del Cavaliere, I-00133 Roma, Italy
2 Dunsink Observatory, Dublin Institute for Advanced Studies, Castleknock, Dublin, Ireland

Received 14 April 1998 / Accepted 22 June 1998

Abstract

The emission line star V 439 Cyg (MWC 1015) dramatically changed its spectrum from late to early type in a few decades with line variability present at various levels. The star is a member of the peculiar young open cluster Berkeley 87 that contains, besides V 439 Cyg, a few peculiar objects in a late stage of stellar evolution. A strong IR source is associated with the region surrounding V 439 Cyg. The star has a peculiar position in the cluster HR diagram possibly due to anomalous reddening. We have analysed a collection of historical observations and collected new spectroscopic and photometric data on this unique object. We find several indications suggesting that the star has passed, in the last decades, through an instability phase with several features of the LBV behaviour. We suggest that its spectral change could be accounted for in the light of recent stellar models.

Key words: stars: evolution – line: formation – line: identification – stars: mass-loss – stars: Wolf Rayet – stars: individual: V 439 Cyg (MWC1015)

* Based on data collected at the Bologna Astronomical Observatory, Loiano (Italy); Telescopio InfraRosso Italiano al Gornergrat (TIRGO), Gornergrat (Switzerland); Juan Sanchez Telescope (JST) and INT (Canary Inslands), Sharru Observatory, Covo (Italy) and on archive plates from the OHP

Send offprint requests to: V.F. Polcaro, (polcaro@saturn.ias.rm.cnr.it)

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© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998
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