Studying very metal pool massive stars in I Zw 18 with new models: “Pop III imposters” ?

12 Sep
Screen Shot 2015-09-12 at 1.29.07 AMDorottya Szecsi’s new paper presents an extensive grid of models of massive stars for the galaxy with the inspiring name “I Zw 18”. With a metal content being 50 times lower than in the neighbourhood of the Sun, this galaxy is a unique opportunity to study massive stars that are more similar to the earliest generations of stars in the Universe.
Szecsi presents discusses the models that evolve “chemically homogeneously”. These models reach extreme temperatures. and become “Transparent Wind Ultraviolet INtense stars (TWUIN stars)”.  These provide an attractive explanation to the large observed He II ionizing photon flux, previously interpreted as a sign for Population III stars.
Low-metallicity massive single stars with rotation. Evolutionary models applicable to I Zwicky 18, D. Szécsi, N. Langer, S.-C. Yoon, D. Sanyal, S. E. de Mink, C.J. Evans, T. Dermine