Diffraction-limited speckle interferometry and modeling of the circumstellar envelope of R CrB at maximum and minimum light

Details Diffraction-limited speckle interferometry and modeling of the circumstellar envelope of R CrB at maximum and minimum light Diffraction-limited speckle interferometry and modeling of the circumstellar envelope of R CrB at maximum and minimum light

2002-01-04

arxiv.org/abs/astro-ph/0201049v1

Astronomy & Astrophysics 380, 212-220 (2001)

Astronomy and Astrophysics

Astrophysics

9 pages including 10 PostScript figures, also available from http://www.mpifr-bonn.mpg.de/div/ir-interferometry/publications.h

Scientific paper

10.1051/0004-6361:20011369

We present the first speckle interferometric observations of R CrB, the prototype of a class of peculiar stars which undergo irregular declines in their visible light curves. The observations were carried out with the 6m telescope at the Special Astrophysical Observatory near maximum light (V=7, 1996 Oct. 1) and at minimum light (V=10.61, 1999 Sep. 28). A spatial resolution of 75mas was achieved in the K-band. The dust shell around R CrB is partially resolved, and the visibility is approximately 0.8 at a spatial frequency of 10 cycles/arcsec. The two-dimensional power spectra obtained at both epochs do not show any significant deviation from circular symmetry. The visibility function and spectral energy distribution obtained near maximum light can be simultaneously fitted with a model consisting of the central star and an optically thin dust shell with density proportional to r^-2. The inner boundary of the shell is found to be 82Rstar (19mas) with a temperature of 920K. However, this simple model fails to simultaneously reproduce the visibility and spectral energy distribution obtained at minimum light. We show that this discrepancy can be attributed to thermal emission from a newly formed dust cloud.

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