Convection in A and F Stars


The treatment of convection within stellar atmospheres and interiors is of fundamental importance in our modelling of stars and stellar evolution. Most models use the phenomenological mixing-length theory, which has many drawbacks, including the free parameter of mixing length which can be adjusted at will. The Canuto & Mazzitelli turbulent convection theory, however, has no such free parameter and attempts to provide a more-realistic treatment within the 1-d framework.

I am collaborating with Friedrich Kupka (Max Plank Institue for Astrophysics) on the treatment of convection within stellar atmospheres. This work has involved the comparison of the Canuto & Mazzitelli theory with standard mixing length theory. Results using Strömgren photometry indicated that the Canuto & Mazzitelli theory is marginally superior to mixing-length. My former Ph.D. student Rebecca Gardiner studied the use of Balmer lines as diagnostics of stellar convection, finding that none of the current analytical treatments are sufficient for stars with effective temperatures around 8000K. Her findings raise significant concerns with the use of 1-d model atmospheres in the studies of A and F stars.

I recented presented a review talk on Observations of convection in A-type stars at IAU Symposium 224 The A-star puzzle in Poprad, Slovakia. A copy of the written paper is available via ADS.

During the Trieste Workshop on ATLAS12 and Related Codes it gave a presentation on the Different convection models in ATLAS.