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Astron. Astrophys. 362, 236-244 (2000)

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Spectroscopy of the candidate luminous blue variable at the center of the ring nebula G79.29+0.46

R.H.M. Voors 1,2, T.R. Geballe 3, L.B.F.M. Waters 4,5, F. Najarro 6 and H.J.G.L.M. Lamers 1,2

1 Astronomical Institute, University of Utrecht, Princetonplein 5, 3508 TA Utrecht, The Netherlands
2 SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
3 Gemini Observatory, 670 N. A'ohoku Place, Hilo, Hawaii 96720, USA
4 Astronomical Institute `Anton Pannekoek', University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
5 SRON Laboratory for Space Research, P.O. Box 800, 9700 AV Groningen, The Netherlands
6 CSIC Instituto de Estructura de la Materia, Dpto. Fisica Molecular, C/Serrano 121, 28006 Madrid, Spain

Received 23 March 2000 / Accepted 14 July 2000

Abstract

We report optical and near-infrared spectra of the central star of the radio source G79.29+0.46, a candidate luminous blue variable. The spectra contain numerous narrow (FWHM [FORMULA] 100 km s-1) emission lines of which the low-lying hydrogen lines are the strongest, and resemble spectra of other LBVc's and B[e] supergiants. A few prominent infrared lines are unidentified. The terminal wind speed is determined from H[FORMULA] to be 110 km s-1. The strength of H[FORMULA] implies the presence of a very dense wind. Extended emission from H[FORMULA] and [N II ] was detected but appears to be associated with the Cygnus X region rather than the radio source. Both diffuse interstellar bands and interstellar absorption lines are present in the optical spectrum of the central star, suggesting that there are both diffuse and molecular cloud components to the extinction and implying a minimum distance of 1 kpc and minimum luminosity of [FORMULA]105 L[FORMULA] for the star. The new spectra and their analysis indicate a low excitation, dense, and slowly expanding wind and support the LBVc classification.

Key words: stars: circumstellar matter – stars: early-type – stars: evolution – stars: individual: G79.29+0.46 – stars: mass-loss – stars: variables: general

Present address: KNMI (Royal Dutch Meteorological Institute), Sectie Astmospherische Samenstelling, Postbus 201, 3730 AE De Bilt, The Netherlands

Send offprint requests to: L.B.F.M. Waters (rensw@astro.uva.nl)

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100
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