Linking signatures of accretion with magnetic field measurements – line profiles are not significantly different in magnetic and non-magnetic Herbig Ae/Be stars
American Astronomical Society
© 2017. The American Astronomical Society. All rights reserved.
Herbig Ae/Be stars are young, pre-main-sequence stars that sample the transition in structure and evolution between low- and high-mass stars, providing a key test of accretion processes in higher-mass stars. Few Herbig Ae/Be stars have detected magnetic fields, calling into question whether the magnetospheric accretion paradigm developed for low-mass stars can be scaled to higher masses. We present He i 10830 ˚A line profiles for 64 Herbig Ae/Be stars with a magnetic field measurement in order to test magnetospheric accretion in the physical regime where its ecacy remains uncertain. Of the 5 stars with a magnetic field detection, 1 shows redshifted absorption, indicative of infall, and 2 show blueshifted absorption, tracing mass outflow. The fraction of redshifted and blueshifted absorption profiles in the non-magnetic Herbig Ae/Be stars is remarkably similar, suggesting that the stellar magnetic field does not a↵ect gas kinematics traced by He i 10830 ˚A. Line profile morphology does not correlate with the luminosity, rotation rate, mass accretion rate, or disk inclination. Only the detection of a magnetic field and a nearly face-on disk inclination show a correlation (albeit for few sources). This provides further evidence for weaker dipoles and more complex field topologies as stars develop a radiative envelope. The small number of magnetic Herbig Ae/Be stars has already called into question whether magnetospheric accretion can be scaled to higher masses; accretion signatures are not substantially di↵erent in magnetic Herbig Ae/Be stars, casting further doubt that they accrete in the same manner as classical T Tauri stars.
This is the author accepted manuscript. The final version is available from the American Astronomical Society via the DOI in this record.
Vol. 852 (1).