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Mon. Not. R. Astron. Soc. 000, 1--?? (1999) Printed 18 February 2000 (MN L A T E X style file v1.4) Modelling nearIR spectra and midIR dust emission of

Summary: Mon. Not. R. Astron. Soc. 000, 1--?? (1999) Printed 18 February 2000 (MN L A T E X style file v1.4)
Modelling near­IR spectra and mid­IR dust emission of
Mira variables at different phases
A. Lobel 1 , S. Bagnulo 2 , J.G. Doyle 3 and C. Power 3
1 Harvard­Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
2 Institut f¨ur Astronomie, Universit¨at Wien, T¨urkenschanzstrasse 17, A­1180 Wien, Austria
3 Armagh Observatory, College Hill Armagh BT61 9DG, N. Ireland
Received date, Accepted date
We model the spectral changes of late oxygen­rich Miras observed in different pul­
sation phases. From a combination of variable near­IR spectra and UKIRT spectro­
photometry of the 9:7 ¯m silicate dust emission feature in different phases we study
the influence of the changing atmospherical circumstances on the conditions in the
circumstellar dust shell. From a detailed modelling of TiO and VO bands in the
near­IR spectra we determine changes of the effective temperature and the effective
atmospheric acceleration of the central star. The corresponding model spectral energy
distribution is redistributed through the dust shell by means of radiative transfer cal­
culations in order to perform a detailed modelling of shape changes observed in the
silicate feature. We show that the latter are mainly caused by changes in the flux
distribution of the incident radiation field with stellar pulsation, whereas intensity


Source: Armagh Observatory


Collections: Physics