Name/Affiliation: Laura Venuti (Institut de Planetologie et d'Astrophysique de Grenoble)
Accretion variability in the young open cluster NGC 2264
We present the results of an extensive u-band accretion survey of the young open cluster NGC 2264 (3 Myr). Performed at CFHT/MegaCam as a part of an international coordinated monitoring campaign (involving Spitzer, CoRoT, CFHT, VLT/Flames and several other instruments), the survey provided simultaneous UV+optical photometric monitoring over two full weeks for about 750 young stars (of which about 40% accreting) within the cluster, in order to probe accretion from the direct diagnostics of the UV excess, measured over the reference flux level of non-accreting cluster members. We investigate accretion properties over the stellar mass range 0.1-1.5 Mo and infer evidence for a huge variety of accretion regimes, with a significant spread in Macc values around an average correlation of Macc with stellar mass. Little contribution to this spread arises from stellar variability over week timescales; we explore and discuss the origin of this large intrinsic spread in accretion properties, which may take contribution from an intrinsic evolutionary spread throughout the cluster, and additionally be associated to a multiplicity of accretion mechanisms, as well as to a diversity in the initial properties of individual systems.