Discovery of magnetic fields in the very young, massive stars W601 (NGC 6611) and OI 201 (NGC 2244)

Abstract

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.

Accepted for publication as a letter in A&A

References in corpus (4)

• The VLT-FLAMES Survey of Massive Stars: Stellar parameters and rotational velocities in NGC3293, NGC4755 and NGC6611
• Correlation between the spatial distribution of the circumstellar disks and the massive stars in the open cluster NGC 6611. Compiled catalog and cluster parameters
• Mass segregation in very young open clusters -- A case study of NGC 2244 and NGC 6530
• The magnetic field of the pre-main sequence Herbig Ae star HD 190073

Cited by in corpus (9)

• MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars
• Magnetic fields and chemical peculiarities of the very young intermediate-mass binary system HD 72106
• Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey
• A JVLA survey of the high frequency radio emission of the massive magnetic B- and O-type stars
• Early-type objects in NGC6611 and Eagle Nebula
• Detection of Magnetic Massive Stars in the Open Cluster NGC 3766
• NGC 6611 601: A hot pre-main sequence spectroscopic binary containing a centrifugal magnetosphere host star
• The MiMeS Project: Magnetism in Massive Stars
• Discovery of fossil magnetic fields in the intermediate-mass pre-main sequence stars