The Dusty AGB Star RS CrB: First Mid-Infrared Interferometric Observations with the Keck Telescopes

• Published in: The Astrophysical journal 2005-12, Vol.634 (2), p.L169-L172
• Main Authors: Mennesson, B, Koresko, C, Creech-Eakman, M. J, Serabyn, E, Colavita, M. M, Akeson, R, Appleby, E, Bell, J, Booth, A, Crawford, S, Dahl, W, Fanson, J, Felizardo, C, Garcia, J, Gathright, J, Herstein, J, Hovland, E, Hrynevych, M, Johansson, E, Le Mignant, D, Ligon, R, Millan-Gabet, R, Moore, J, Neyman, C, Palmer, D, Panteleeva, T, Paine, C, Ragland, S, Reder, L, Rudeen, A, Saloga, T, Shao, M, Smythe, R, Summers, K, Swain, M, Tsubota, K, Tyau, C, Vasisht, G, Wizinowich, P, Woillez, J
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 1538-4357; 0004-637X; 1538-4357
• DOI: 10.1086/498864

We report interferometric observations of the semiregular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long-baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner. The light was dispersed by a low-resolution spectrometer, allowing simultaneous measurement of the source visibility and intensity spectra from 8 to 12 kM. The interferometric observations allow a nonambiguous determination of the dust shell spatial scale and relative flux contribution. Using a simple spherically symmetric model, in which a geometrically thin shell surrounds the stellar photosphere, we find that 630% to 670% of the overall mid-infrared flux - depending on the wavelength - originates from 7-8 stellar radii. The derived shell opacity profile shows a broad peak around 11 km (t 0.06), characteristic of Mg-rich silicate dust particles.