Abstract

Polarization of A/B stars in the Young cluster NGC 6611

Ariane Trudeau (Université de Montréal)

Ariane Trudeau,Pierre Bastien,François Ménard,Patrice Corporon,Nadine Manset, Frédérick Poidevin, Gaspard Duchêne and Jean-Louis Monin

Most stars form in groups in molecular cloud complexes. NGC 6611 is a particularly large open cluster which formed about 1 Myr ago. With polarimetry we want to probe the presence of circumstellar disks or envelopes through dust scattering and also the presence of magnetic fields within the cluster and in the foreground material through dichroic extinction by aligned grains. We present linear polarization measurements for 82 A/B stars with a limiting magnitude of V = 14 in red filters. While most of the observed stars show a red polarization of 2-4 %, mostly interstellar in origin, W80, W151 and the remarkable W188 display high polarizations partially due to the intracluster dust in the north-western part of NGC 6611. Eight of the 18 stars tested for polarimetric variability, including W188 and W231, show evidences of intrinsic polarization and 4 others may have an intrinsic polarization component. Relation between the frequency of circumstellar disks and the proximity of O stars is not clear and will need further investigation.

Mode of presentation: poster