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Abstract: Context. It has been suggested that convection in Red Supergiant RSG starsgives rise to large-scale granules causing observable surface inhomogeneities.This convection is also extremely vigorous, and suspected to be one of thecauses of mass-loss in RSGs. It must thus be understood in details. Evidencehas been accumulated that there are asymmetries in the photospheres of RSGs,but detailedstudies of granulation are still lacking. Interferometricobservations offer an exciting possibility to tackle this question, but theyare still often interpreted using smooth symmetrical limb-darkened intensitydistributions, or very simple spotted ad hoc models. Aims. We explore theimpact of the granulation on visibility curves and closure phases using theradiative transfer code OPTIM3D. We simultaneously assess how 3D simulations ofconvection in RSG with CO5BOLD can be tested against these observations.Methods. We use 3D radiative-hydrodynamics RHD simulations of convection tocompute intensity maps at various wavelengths and time, from which we deriveinterferometric visibility amplitudes and phases. We study their behaviour withtime, position angle, and wavelength, and compare them to observations of theRSG alpha Ori Results. We provide average limb-darkening coefficients for RSGs.We detail the prospects for the detection and characterization of granulationcontrast, size on RSGs. We demonstrate that our RHD simulations provide anexcellent fit to existing interferometric observation of alpha Ori, contrary tolimb darkened disks. This confirms the existence of large convective cells onthe surface of Betelgeuse.



Autor: A. Chiavassa, B. Plez, E. Josselin, B. Freytag

Fuente: https://arxiv.org/







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