High resolution spectroscopy of the post-red supergiant IRC+10420^*

I. The data

Imperial College of Science, Technology and Medicine, Blackett Laboratory, Prince Consort Road, London, SW7 2BZ, UK

Corresponding author: Send offprint request to: R.D. Oudmaijer e-mail: r.oudmaijer@ic.ac.uk

Received: 5 September 1997
Accepted: 27 October 1997

Abstract

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 Åto 1 μm, 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.