Aperture synthesis imaging of the carbon AGB star R Sculptoris: Detection of a complex structure and a dominating spot on the stellar disk

摘要: We present near-infrared interferometry of the carbon-rich asymptotic giant branch (AGB) star R Sculptoris. The visibility data indicate a broadly circular resolved stellar disk with complex substructure. The observed AMBER squared values show drops at positions CO and CN bands, indicating that these lines form in extended layers above photosphere. are best fit by model without wind. PIONIER consistent same model. obtain Rosseland angular diameter 8.9+-0.3 mas, corresponding to radius 355+-55 Rsun, an effective temperature 2640+-80 K, luminosity log L/Lsun=3.74+-0.18. These parameters match evolutionary tracks initial mass 1.5+-0.5 Msun current 1.3+-0.7 Msun. reconstructed images exhibit structure within including dominant bright spot located western part disk. has H-band peak intensity 40% 60% average limb-darkening-corrected contrast between minimum maximum on is about 1:2.5. Our observations predictions dynamic atmosphere wind models, although models appear have circumstellar envelope too compared our observations. detected most likely caused convection cells, resulting large-scale shock fronts, their effects clumpy molecule dust formation seen against photosphere distances 2-3 radii.