Abstract

OB stars in IC1613: crossing the frontier of the Magellanic Clouds

Miriam Garcia (IAC)

A. Herrero (IAC), S. Simon-Diaz (IAC), K. Uytterhoeven (IAC), N. Castro (NOA)

Very low metallicity massive stars are a key ingredient for our understanding of the early Universe because of their connection with the first stars, the reionization epoch and long-GRBs. Metallicity, in turn, plays a crucial two-fold role in the life of massive stars, by entering directly the equations of stellar structure and evolution and indirectly through the metallicity dependence of radiation-driven winds. However, the theoretical predictions for the evolution and the winds of blue massive stars have only be tested thouroughly down to SMC metallicities. We have secured VLT optical spectra of a sample of early-type massive stars in IC1613 as a first step towards the characterization of these objects beyond the Magellanic Clouds. IC1613 is a metal poor (~<0.1Zo) irregular galaxy of the Local Group that represents the next step towards low metallicities after the SMC. We are carrying out a systematic analysis of the blue massive stars in IC1613 with FASTWIND (and CMFGEN in the most extreme cases) to derive the stellar parameters. The project has already led to the discovery of two peculiar objects, one of them with stronger wind than expected at this metallicity. We present new results on an extended sample of about 15 O-stars.