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Title: High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila

Abstract

Recent observational work has indicated that mechanisms for accretion and outflow in Herbig Ae/Be star–disk systems may differ from magnetospheric accretion (MA) 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 MA 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,more » we find the observed line morphologies and variability are inconsistent with a scaled-up T Tauri MA scenario. We suggest that as magnetic field structure and strength change dramatically with increasing stellar mass from T Tauri to Herbig Ae/Be stars, so too may accretion and outflow processes.« less

Authors:
; ; ;  [1]; ; ;  [2]
  1. Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Avenue, Ann Arbor, MI 48109 (United States)
  2. Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)
Publication Date:
OSTI Identifier:
22679782
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 848; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; AUGER ELECTRON SPECTROSCOPY; CORRELATIONS; INCLINATION; MAGNETIC FIELDS; MASS TRANSFER; RADIANT HEAT TRANSFER; RESOLUTION; SPECTRA; STAR EVOLUTION; STELLAR WINDS; T TAURI STARS; VELOCITY

Citation Formats

Aarnio, Alicia N., Monnier, John D., Calvet, Nuria, Che, Xiao, Harries, Tim J., Kraus, Stefan, and Acreman, David. High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8997.
Aarnio, Alicia N., Monnier, John D., Calvet, Nuria, Che, Xiao, Harries, Tim J., Kraus, Stefan, & Acreman, David. High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila. United States. doi:10.3847/1538-4357/AA8997.
Aarnio, Alicia N., Monnier, John D., Calvet, Nuria, Che, Xiao, Harries, Tim J., Kraus, Stefan, and Acreman, David. Tue . "High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila". United States. doi:10.3847/1538-4357/AA8997.
@article{osti_22679782,
title = {High-cadence, High-resolution Spectroscopic Observations of Herbig Stars HD 98922 and V1295 Aquila},
author = {Aarnio, Alicia N. and Monnier, John D. and Calvet, Nuria and Che, Xiao and Harries, Tim J. and Kraus, Stefan and Acreman, David},
abstractNote = {Recent observational work has indicated that mechanisms for accretion and outflow in Herbig Ae/Be star–disk systems may differ from magnetospheric accretion (MA) 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 MA 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 find the observed line morphologies and variability are inconsistent with a scaled-up T Tauri MA scenario. We suggest that as magnetic field structure and strength change dramatically with increasing stellar mass from T Tauri to Herbig Ae/Be stars, so too may accretion and outflow processes.},
doi = {10.3847/1538-4357/AA8997},
journal = {Astrophysical Journal},
number = 1,
volume = 848,
place = {United States},
year = {Tue Oct 10 00:00:00 EDT 2017},
month = {Tue Oct 10 00:00:00 EDT 2017}
}