Abstract

Contributed Talk - Splinter CloseBinaries   (MW-0250)

Circumstellar environments of recent mass transfer binaries in Westerlund 1

Cormac Larkin, Jonathan Mackey, Harim Jin, Thomas Haworth, Andreas Sander, Brian Reville, Morten Andersen, Amelia Bayo & the EWOCS Collaboration
ESO Garching, DIAS, MPA, QMUL, ZAH Uni Heidelberg & MPI Kernphysik

Westerlund 1 (Wd 1) is the most massive young stellar cluster in the Galaxy, and hosts a uniquely numerous and diverse nearby population of evolved massive stars including 24 Wolf-Rayet (WR) stars, several yellow and red supergiants, a luminous blue variable and over 100 OB supergiants. Wd 1’s high binary WR fraction of over 90% makes it an ideal laboratory for studying the effects of binary interactions in a large and coeval stellar population. In this talk I will introduce two systems which may soon become exemplary cases for our understanding of non-conservative mass transfer. The supergiant B[e] star Wd1-9 is a recently stripped massive binary system deeply embedded in a dense rotating circumstellar medium. I will present new MUSE data showing a striking bipolar photoevaporating outflow reminiscent of a protoplanetary disk wind, which strongly suggests the presence of a dense circumbinary disk/torus composed of non-conserved mass transfer material. I will also show how the unusual nebulosity around the WR+O binary system Wd1-72 can be explained by a recent (~10 kyr ago) non-conservative mass transfer event. These two systems are further evidence that short period WN systems are shaped by binary interactions, and quantitative study of their surrounding material could provide robust empirical constraints for mass transfer prescriptions used in population synthesis codes.