High cadence, high resolution spectroscopic observations of Herbig stars HD 98922 and V1295 Aquila
American Astronomical Society
© 2017. The American Astronomical Society. All rights reserved.
Recent observational work has indicated mechanisms for accretion and out ow in Herbig Ae/Be star-disk systems may di er from magnetospheric accretion as it is thought to occur in T Tauri star-disk systems. In this work, we assess the temporal evolution of spectral lines probing accretion and mass loss in Herbig Ae/Be systems and test for consistency with the magnetospheric accretion paradigm. For two Herbig Ae/Be stars, HD 98922 (B9e) and V1295 Aql (A2e), we have gathered multi- epoch ( years) and high cadence ( minutes) high resolution optical spectra to probe a wide range of kinematic processes. Employing a line equivalent width evolution correlation metric introduced here, we identify species co-evolving (indicative of common line origin) via novel visualization. We interferometrically constrain often problematically degenerate parameters, inclination and inner disk radius, allowing us to focus on the structure of the wind, magnetosphere, and inner gaseous disk in radiative transfer models. Over all timescales sampled, the strongest variability occurs within the blueshifted absorption components of the Balmer series lines; the strength of variability increases with the cadence of the observations. Finally, high resolution spectra allow us to probe substructure within the Balmer series' blueshifted absorption components: we observe static, low-velocity features and time-evolving features at higher velocities. Overall we nd the observed line morphologies and variability are inconsistent with a scaled-up T Tauri magnetospheric accretion scenario. We suggest that as magnetic eld structure and strength change dramatically with increasing stellar mass from T Tauri to Herbig Ae/Be stars, so too may accretion and out ow processes.
This is the author accepted manuscript. The final version is available from American Astronomical Society via the DOI in this record.
Vol. 848 (1), article 18