The extended atmosphere and evolution of the RV Tau star, R Scuti
Abstract
We analyze ISO/SWS spectra of the RV Tau star R Scuti. The infrared spectra are dominated by H2O emission bands. The near- and mid-infrared excess is attributed to H2O; the dust contribution is less important. We also identify CO, SiO and CO2 bands. The various molecular emission bands originate from an extended atmosphere, an atmosphere above the photosphere. The extended atmosphere of R Sct is formed from matter which gradually have lifted up from the photosphere through the pulsations of the star. In contrast to the abundant molecules around the star, the silicate dust feature is weak and the dust mass-loss rate is only dot Md=10-11 Msun yr-1. This implies that there might be a process to inhibit dust formation from molecules. RV Tau stars are commonly considered as post-AGB stars. While a detached dust envelope around R Sct is consistent with such an interpretation, we show that its period evolution is slower than expected. We argue that R Sct may be a thermal-pulsing AGB star, observed in a helium-burning phase. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) with the participation of ISAS and NASA. The SWS is a joint project of SRON and MPE.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2002
- DOI:
- 10.1051/0004-6361:20020391
- arXiv:
- arXiv:astro-ph/0203234
- Bibcode:
- 2002A&A...387.1022M
- Keywords:
-
- stars: AGB and post-AGB;
- stars: atmospheres;
- stars: circumstellar matter;
- infrared: stars;
- stars: variables: general;
- stars: individual: R Sct;
- Astrophysics
- E-Print:
- 10 pages, 7 figures, accepted by A&