Blue super giants are stars that are too bright and too big. Stellar models predict that they should be very rare and yet we find many of them. We don’t know if they are regular main sequence stars burning hydrogen, whether they are in the helium burning phase or whether they are on verge of exploding…. the progenitor of supernova 1987a was a blue supergiant. In this paper lead by Catherine McEnvoy and Philip Dufton (Belfast) we investigate the properties of blue super giants in the Tarantula survey. Never before we had such a well studied set of these stars. From this sample we learn that we have under estimated how big and cool massive stars get on the main sequence. An extension down to 20,000 K is suggested.
“The VLT-FLAMES Tarantula Survey XX: Atmospheric Parameters and Nitrogen Abundances to investigate the Role of binarity and the width of the Main Sequence” C.M. McEvoy, P. L. Dufton, C. J. Evans, V. M. Kalari, N. Markova, S. Simón-Díaz, J. Vink, N. Walborn, P. A. Crowther, A. de Koter, S. E. de Mink, P. R. Dunstall, V. Hénault-Brunet, A. Herrero, N. Langer, D. J. Lennon, J. Maíz Apellániz, F. Najarro,, J. Puls, H. Sana, F. R. N. Schneider, W. D. Taylor, accpeted for publication in Astronomy and Astrophysics