Modeling T Tauri Winds from Heiλ10830 Profiles

The high opacity of He I 10830 makes it an exceptionally sensitive probe ofthe inner wind geometry of accreting T Tauri stars. In this line blueshiftedabsorption below the continuum results from simple scattering of stellarphotons, a situation which is readily modeled without definite knowledge of thephysical conditions and recourse to multi-level radiative transfer. We presenttheoretical line profiles for scattering in two possible wind geometries, adisk wind and a wind emerging radially from the star, and compare them toobserved He I 10830 profiles from a survey of classical T Tauri stars. Thecomparison indicates that subcontinuum blueshifted absorption is characteristicof disk winds in ~30% of the stars and of stellar winds in ~40%. We furtherconclude that for many stars the emission profile of helium likely arises instellar winds, increasing the fraction of accreting stars inferred to haveaccretion-powered stellar winds to ~60%. Stars with the highest disk accretionrates are more likely to have stellar wind than disk wind signatures and lesslikely to have redshifted absorption from magnetospheric funnel flows. Thissuggests the possibility that when accretion rates are high, disks can extendcloser to the star, magnetospheric accretion zones can be reduced in size andconditions arise that favor radially outflowing stellar winds.Comment: 41 pages, 11 figures. Accepted by Astrophysical Journa