The case for asymmetric dust around a C-rich asymptotic giant branch star |
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| Authors: | Michael W Feast Patricia A Whitelock Freddy Marang |
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| Institution: | Astronomy Department, University of Cape Town, 7701, Rondebosch, South Africa;South African Astronomical Observatory, PO Box 9, 7935, Observatory, South Africa |
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| Abstract: | JHKL observations of the mass-losing carbon Mira variable IRAS 15194–5115 (II Lup) extending over about 18 yr are presented and discussed. The pulsation period is 575 d and has remained essentially constant over this time span. The star has undergone an extensive obscuration minimum during this time. This is complex and, like such minima in similar objects (e.g. R For), does not fit the model predictions of a simple long-term periodicity. Together with the high-resolution observations of Lopez et al., the results suggest that the obscuration changes are caused by the formation of dust clouds of limited extent in the line of sight. This is an R Coronae Borealis-type (RCB-type) model. The effective reddening law at J and H is similar to that found for R For. |
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| Keywords: | stars: AGB and post-AGB stars: carbon circumstellar matter stars: mass-loss stars: variables: other infrared: stars |
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