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Paper: A Photometric Analysis of R Coronae Borealis Stars in the Magellanic Clouds
Volume: 404, The Eighth Pacific Rim Conference on Stellar Astrophysics: A Tribute to Kam Ching Leung
Page: 267
Authors: Woollands, R.M.; Cottrell, P.L.
Abstract: R Coronae Borealis (RCB) stars exhibit a unique variability whereby they undergo enigmatic and rapid declines in brightness of up to several magnitudes. The period of a decline may take several weeks, whereas the recovery to maximum light may take months or even years. The accepted wisdom for the cause of these enigmatic declines is a phenomenon whereby dust is formed in the stellar atmosphere which reduces the brightness by as much as eight magnitudes (Clayton 1996). This is followed by dust dissipation which is known as the recovery phase. The photometric data used for this paper was collected at Mt John University Observatory (New Zealand), the Southern African Large Telescope (SALT) and the Las Campanas Observatory (Chile). In this paper we present some results from our ongoing UBVRI photometric analysis of 19 RCB stars (14 in the Large Magellanic Cloud and 5 in the Small Magellanic Cloud), with particular emphasis on LMC100.6 48589 that exhibited six declines and subsequent recoveries over five years. The literature reveals that constructing various colour magnitude diagrams for these stars shows that the recovery to normal light occurs along a line with a gradient of 3.1. Continued work in this field will enable the information to be compared with that of a dust extinction curve allowing the size of the dust particles in the stellar atmosphere to be determined.
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