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Title: Photoionization Models for the Inner Gaseous Disks of Herbig Be Stars: Evidence against Magnetospheric Accretion?

Abstract

We investigate the physical properties of the inner gaseous disks of three hot Herbig B2e stars, HD 76534, HD 114981, and HD 216629, by modeling CFHT-ESPaDOns spectra using non-LTE radiative transfer codes. We assume that the emission lines are produced in a circumstellar disk heated solely by photospheric radiation from the central star in order to test whether the optical and near-infrared emission lines can be reproduced without invoking magnetospheric accretion. The inner gaseous disk density was assumed to follow a simple power-law in the equatorial plane, and we searched for models that could reproduce observed lines of H i (H α and H β ), He i, Ca ii, and Fe ii. For the three stars, good matches were found for all emission line profiles individually; however, no density model based on a single power-law was able to reproduce all of the observed emission lines. Among the single power-law models, the one with the gas density varying as ∼10{sup −10}( R {sub *}/ R ){sup 3} g cm{sup −3} in the equatorial plane of a 25 R {sub *} (0.78 au) disk did the best overall job of representing the optical emission lines of the three stars. This modelmore » implies a mass for the H α -emitting portion of the inner gaseous disk of ∼10{sup −9} M {sub *}. We conclude that the optical emission line spectra of these HBe stars can be qualitatively reproduced by a ≈1 au, geometrically thin, circumstellar disk of negligible mass compared to the central star in Keplerian rotation and radiative equilibrium.« less

Authors:
; ;  [1]
  1. Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada)
Publication Date:
OSTI Identifier:
22663761
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 836; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; AUGER ELECTRON SPECTROSCOPY; DENSITY; EMISSION; GASES; MASS; PHOTOIONIZATION; RADIANT HEAT TRANSFER; ROTATION; SIMULATION; SPECTRA; STARS

Citation Formats

Patel, P., Sigut, T. A. A., and Landstreet, J. D., E-mail: ppatel54@uwo.ca. Photoionization Models for the Inner Gaseous Disks of Herbig Be Stars: Evidence against Magnetospheric Accretion?. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA5C3F.
Patel, P., Sigut, T. A. A., & Landstreet, J. D., E-mail: ppatel54@uwo.ca. Photoionization Models for the Inner Gaseous Disks of Herbig Be Stars: Evidence against Magnetospheric Accretion?. United States. doi:10.3847/1538-4357/AA5C3F.
Patel, P., Sigut, T. A. A., and Landstreet, J. D., E-mail: ppatel54@uwo.ca. Mon . "Photoionization Models for the Inner Gaseous Disks of Herbig Be Stars: Evidence against Magnetospheric Accretion?". United States. doi:10.3847/1538-4357/AA5C3F.
@article{osti_22663761,
title = {Photoionization Models for the Inner Gaseous Disks of Herbig Be Stars: Evidence against Magnetospheric Accretion?},
author = {Patel, P. and Sigut, T. A. A. and Landstreet, J. D., E-mail: ppatel54@uwo.ca},
abstractNote = {We investigate the physical properties of the inner gaseous disks of three hot Herbig B2e stars, HD 76534, HD 114981, and HD 216629, by modeling CFHT-ESPaDOns spectra using non-LTE radiative transfer codes. We assume that the emission lines are produced in a circumstellar disk heated solely by photospheric radiation from the central star in order to test whether the optical and near-infrared emission lines can be reproduced without invoking magnetospheric accretion. The inner gaseous disk density was assumed to follow a simple power-law in the equatorial plane, and we searched for models that could reproduce observed lines of H i (H α and H β ), He i, Ca ii, and Fe ii. For the three stars, good matches were found for all emission line profiles individually; however, no density model based on a single power-law was able to reproduce all of the observed emission lines. Among the single power-law models, the one with the gas density varying as ∼10{sup −10}( R {sub *}/ R ){sup 3} g cm{sup −3} in the equatorial plane of a 25 R {sub *} (0.78 au) disk did the best overall job of representing the optical emission lines of the three stars. This model implies a mass for the H α -emitting portion of the inner gaseous disk of ∼10{sup −9} M {sub *}. We conclude that the optical emission line spectra of these HBe stars can be qualitatively reproduced by a ≈1 au, geometrically thin, circumstellar disk of negligible mass compared to the central star in Keplerian rotation and radiative equilibrium.},
doi = {10.3847/1538-4357/AA5C3F},
journal = {Astrophysical Journal},
number = 2,
volume = 836,
place = {United States},
year = {Mon Feb 20 00:00:00 EST 2017},
month = {Mon Feb 20 00:00:00 EST 2017}
}