Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
K.-H. Hofmann, Y.Y. Balega, M. Scholz,
and G. Weigelt:
Multi-wavelength bispectrum speckle
interferometry of R Leo and comparison with Mira star models
Astronomy and Astrophysics 376, 518-531 (2001)
Abstract.
We present diffraction-limited (30mas resolution) bispectrum
speckle interferometry of the Mira star R Leo with the 6m SAO
telescope.
The speckle interferograms were recorded through narrow-band
interference
filters with centre wavelength/bandwidth of 673nm/8nm
(strong TiO absorption band), 656nm/10nm, 699nm/6nm and 781nm/14nm
(moderate TiO absorption),
754nm/6nm (weak TiO absorption), and 1045nm/9nm (continuum).
The reconstructed images show that the average uniform-disk diameters
of
R Leo are 60.6masą3.0mas at 656nm, 75.6masą3.7mas at 673nm,
52.5masą2.5mas at 699nm, 48.7masą2.3mas at 754nm,
55.0masą2.7mas at 781nm, and 37.9masą4.0mas at 1045nm.
In all six observed wavelength bands the shape of R Leo shows no
significant asymmetry. We compare our observations with Mira star
models and check the
ability of monochromatic linear diameters for discriminating between
model representations of the observed star. Monochromatic
tau_lambda=1 radii were derived from the observed visibilities
by application of model-predicted center-to-limb variations of the
intensity.
Adopting the HIPPARCOS parallax
we derived from the 1045nm-observation a photospheric radius
(Rosseland tau_Ross=1 radius) of R Leo
of 417 Rsolą97Rsol (19.2masą2.0mas)
indicating pulsation in the first-overtone mode.
From JHKL photometry and the angular photospheric radius an effective
temperature of 2590ą180K at near maximum phase was obtained.
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