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Context: Recent spectropolarimetric observations of Herbig Ae/Be stars have yielded new arguments in favour of a fossil origin for the magnetic fields of intermediate mass stars. Aims: To study the evolution of these magnetic fields, and their impact on the evolution of the angular momentum of these stars during the pre-main sequence phase, we observed Herbig Ae/Be members of young open clusters of various ages. Methods: We obtained high-resolution spectropolarimetric observations of Herbig Ae/Be stars belonging to the young open clusters NGC 6611 (< 6 Myr), NGC 2244 (~1.9 Myr), and NGC 2264 (~8 Myr), using ESPaDOnS at theCanada-France-Hawaii Telescope. Results: Here we report the discovery of strong magnetic fields in two massive pre-main sequence cluster stars. We detected, for the first time, a magnetic field in a pre-main sequence rapid rotator: the 10.2 Msun Herbig B1.5e star W601 (NGC 6611; v sin i ~ 190 km/s). Our spectropolarimetric observations yield a longitudinal magnetic field larger than 1 kG, and imply a rotational period shorter than 1.7 days. The spectrum of this very young object (age ~ 0.017 Myr) shows strong and variable lines of He and Si. We also detected a magnetic field in the 12.1 Msun B1 star OI 201 (NGC 2244; v sin i = 23.5 km/s). The Stokes V profile of this star does not vary over 5 days, suggesting a long rotational period, a pole-on orientation, or aligned magnetic and rotation axes. OI 201 is situtated near the Zero-Age Main Sequence on the HR diagram, and exhibits normal chemical abundances and no spectrum variability.
NGC 6611 is the massive young cluster (2-3 Myr) that ionises the Eagle Nebula. We present very deep photometric observations of the central region of NGC 6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850L
We present in this paper the first near infrared study of the young open cluster NGC 2244, which is well known for its partially embedded nature in the Rosette Nebula. Based on the spatially complete 2 Micron All Sky Survey, the young OB cluster indi
The young open cluster NGC 6611 includes among its candidate members a class of peculiar objects with interesting properties: blue stars with infrared IR excesses. These stars show excesses in IR bands, signature of the presence of a circumstellar di
As part of the ongoing effort to characterize the low-mass (sub)stellar population in a sample of massive young clusters, we have targeted the ~2 Myr old cluster NGC 2244. The distance to NGC 2244 from Gaia DR2 parallaxes is 1.59 kpc, with errors of
We present IZJHKL photometry of the core of the cluster NGC 6611 in the Eagle Nebula. This photometry is used to constrain the Initial Mass Function (IMF) and the circumstellar disk frequency of the young stellar objects. Optical spectroscopy of 258