A&A Supplement series, Vol. 129, May I 1998, 541-552
Received September 5; accepted October 27, 1997
R.D. Oudmaijer
Send offprint request: R.D. Oudmaijer e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
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