R144 and DR1 - two extraordinary Wolf-Rayet stars
I will present recent results on two Wolf-Rayet stars, R144 in the LMC, and DR1 in IC1613. The first is the brightest Wolf-Rayet star in the LMC, and for that reason has long be suspected to be a binary, although radial velocity variations have not been observed in earlier research. Using multi-epoch X-Shooter observations, we have now identified R144 as a double-lined spectroscopic binary. Mass estimates based on its luminosity suggest a present day mass content of 200-300 solar masses, making it the most massive binary system known to date.
The second object, DR1, is one of the only eight known oxygen sequence Wolf-Rayet stars. These stars are usually seen as the successors of WC stars, where the high-excitation oxygen emission is the result of an enhanced surface abundance, as helium-burning products are being revealed by the strong stellar wind. Alternatively, the oxygen emission might be purely due to a higher stellar temperature. Modeling the spectrum of DR1 suggest that the latter is the case, as the surface abundances are not enhanced compared to WC stars.
Frank Tramper
Thursday 30 May 2013, 12:00
Location: C4.174