TiO Absorption in Mira Variables

Details TiO Absorption in Mira Variables TiO Absorption in Mira Variables

Dec 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aas...189.9602c&link_type=abstract

American Astronomical Society, 189th AAS Meeting, #96.02; Bulletin of the American Astronomical Society, Vol. 28, p.1398

Astronomy and Astrophysics

Astronomy

Scientific paper

We probe the atmospheres of Mira variables as observed from 7000 Angstroms to 8000 Angstroms . \ The spectra are dominated by the TiO gamma -system and void of any intense hydrogen-series emission lines. \ The TiO features may be produced in a layer somewhat far from the photosphere. \ Haniff et al. (1992, AJ, 103, 1662) present optical aperture synthetic images of Mira's photosphere at 6500 Angstroms , 7007 Angstroms , and within a TiO bandhead at 7099 Angstroms , with the star phase 0.94. \ They find asymmetry in the images, with the TiO image one and a half times larger than the photospheric images. \ Also, narrowband speckle interferometric measurements taken in the TiO 7120 Angstroms bandhead and outside at 7400 Angstroms by Labeyrie et al. (1977, ApJ Letters, 218, L75) shows that the diameters of R Leo and Mira are twice as large in the TiO feature than outside of it. \ So, a model atmosphere, based on the spectra observed between 7000 Angstroms to 8000 Angstroms , provides parameters such as Teff and g in an atmospheric layer far from the photosphere. The primary aim of this paper is to present model atmosphere parameters calculated for synthetic spectra modeling new low resolution spectra (120 Angstroms /mm) taken over the spectral range from 7,000 Angstroms to 8,000 Angstroms of three Mira variables. \ Spectra were taken at two different phases. \ By taking spectra at different phases we can further probe the effects the pulsation mechanism has on the atmosphere parameters. \ For example, Wing (1967, unpublished Ph.D. Thesis, University of California, Berkley)\ found the TiO bands strengthen as the temperature decreases. Model atmosphere parameters are compared at the two phases. The authors gratefully acknowledge support from NSF grant AST-9500756 and an NSF REU Supplement grant.

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