Mid- and far-infrared properties of dynamical models of carbon-rich long-period variables

Autor(en)

W Windsteig, Ernst Dorfi, Susanne Höfner, Josef Hron, Franz Kerschbaum

Abstrakt

We have calculated spectral energy distributions and synthetic IRAS colours of carbon-rich long-period variables. On top of dynamical models for the stellar atmosphere and circumstellar envelope which consistently treat the time-dependent hydrodynamics, the formation of amorphous carbon grains and grey radiative transfer, frequency-dependent radiative transfer calculations have been carried out in the range between 1 œm and 290 œm. Calculating the IRAS colours we find that the models lie in regions I (stars without circumstellar shells) and VII (variable stars with carbon-rich circumstellar shells) of the IRAS two colour diagram in accordance with observational results for carbon stars. They form an almost linear sequence (near the black body line) reflecting the different mass loss rates. We compare our results to empirical formulae which link the mass loss rate to the observed flux at 60 œm. Furthermore, we have also investigated qualitatively the effects of dust with a-SiC grains and of detached shells. The SiC-contribution causes mainly a blue-shift of about 0.2 mag in the [12]-[25] colour. Adding a detached shell results in higher [25]-[60] values partly shifting the models into region VIa (non-variable stars with relatively cold dust at large distances) of the IRAS two colour diagram as expected from observations.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Universität Wien, University of Copenhagen

Journal

Astronomy & Astrophysics

Band

324

Seiten

617-623

Anzahl der Seiten

7

ISSN

0004-6361

Publikationsdatum

1997

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/fcf00413-682d-4ad3-97e6-e07cda3d8421