A&A Supplement series, Vol. 129, May I 1998, 541-552
Received September 5; accepted October 27, 1997
Send offprint request: R.D. Oudmaijer e-mail: email@example.com
Imperial College of Science, Technology and Medicine, Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, UK
Kapteyn Astronomical Institute, P.O. Box 800, NL-9700 AV Groningen, The Netherlands
A high resolution optical spectrum of the post-red supergiant candidate IRC+10420 is presented. The Utrecht Echelle Spectrograph observations, with a total integration time of more than 9 hours, provide a spectral coverage from 3850 Å to 1 m, and a spectral resolution of 9 km s-1. The spectrum is shown, and an identification list of lines in the spectrum is provided. From a preliminary analysis of the spectrum we find that the spectral type of IRC+10420 has changed from F8I+ in 1973 to mid- to early A type now, confirming the results of Oudmaijer et al.\ (1996), who claimed a change in temperature based on photometric changes. It is shown that most of the emission lines in the spectrum of IRC+10420 are blue-shifted with respect to the systemic velocity traced by circumstellar rotational CO emission, while the (few) absorption lines - with the exception of some high excitation lines - are red-shifted by 25 km s-1, which may suggest infall of material onto the star. Finally, it is found that the interstellar extinction towards IRC+10420 as traced by the Diffuse Interstellar Bands is very large, with an inferred E(B-V) of 1.4 0.5 compared to a total E(B-V) of 2.4.
keywords: stars: circumstellar matter -- stars: emission-line, Be -- stars: individual: IRC+10420 -- stars: AGB and post-AGB -- stars: supergiants