G. Weigelt et al., FIRST DIFFRACTION-LIMITED SPECKLE MASKING OBSERVATIONS OF THE MIRA VARIABLE R-CAS WITH THE 6 M SAO TELESCOPE, Astronomy and astrophysics, 316(1), 1996, pp. 21-24
We present the first diffraction-limited speckle masking observations
of a Mira star with the Russian 6 m SAO telescope. At 700 and 714 nm w
avelength a resolution of 1,22 lambda/D = 30 milli-arcsec was achieved
. The reconstructed true images are the images with the highest resolu
tion obtained up to now in this wavelength region. The speckle interfe
rograms of R Cas were recorded through interference filters with cente
r wavelength/bandwidth of 714 nm/6 nm (strong TiO band absorption) and
700 nm/6 nm (moderate TiO absorption). The two reconstructed images s
how that the azimuthally averaged 700 and 714 nm uniform-disk diameter
s of R Gas are 36 mas +/- 2 mas and 49 mas +/- 2 mas, respectively. In
the 700 nm and 714 nm images the disks of R Cas are non-uniform and e
longated along position angle 52 degrees +/- 7 degrees and 57 degrees
+/- 7 degrees, respectively. The size (elliptical uniform disk fit) of
the elongated disks is about 33.3 mas x 38.7 mas (axial ratio 0.86) i
n the 700 nm pseudo-continuum filter and 42.3 mas x 55.6 mas (axial ra
tio 0.76) in the 714 nm TiO absorption band filter. We discuss briefly
theoretical aspects of these and previous observations.