Open AccessMultiwavelength diameters of nearby Miras and semiregular variables
Author(s) -
Ireland M. J.,
Tuthill P. G.,
Bedding T. R.,
Robertson J. G.,
Jacob A. P.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07651.x
Subject(s) - physics , stars , astrophysics , wavelength , circumstellar dust , angular diameter , brightness , telescope , aperture (computer memory) , interferometry , visibility , scattering , astronomy , optics , acoustics
We have used optical interferometry to obtain multiwavelength visibility curves for eight red giants over the wavelength range 650–1000 nm. The observations consist of wavelength‐dispersed fringes recorded with MAPPIT (Masked Aperture‐Plane Interference Telescope) at the 3.9‐m Anglo‐Australian Telescope. We present results for four Miras (R Car, o Cet, R Hya and R Leo) and four semiregular variables (R Dor, W Hya, L 2 Pup and γ Cru). All stars except γ Cru show strong variations of angular size with wavelength. A uniform‐disc model was found to be a poor fit in most cases, with Gaussian (or other more tapered) profiles preferred. This, together with the fact that most stars showed a systematic increase in apparent size towards the blue and a larger‐than‐expected linear size, even in the red, all point towards significant scattering by dust in the inner circumstellar environment. Some stars showed evidence for asymmetric brightness profiles, while L 2 Pup required a two‐component model, indicating an asymmetrical circumstellar dust shell.