skip to main content

SciTech ConnectSciTech Connect

Title: ACCRETION VARIABILITY OF HERBIG Ae/Be STARS OBSERVED BY X-SHOOTER HD 31648 AND HD 163296

This work presents X-Shooter/Very Large Telescope spectra of the prototypical, isolated Herbig Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by timescales ranging from days to months. Each spectrum spans over a wide wavelength range covering from 310 to 2475 nm. We have monitored the continuum excess in the Balmer region of the spectra and the luminosity of 12 ultraviolet, optical, and near-infrared spectral lines that are commonly used as accretion tracers for T Tauri stars. The observed strengths of the Balmer excesses have been reproduced from a magnetospheric accretion shock model, providing a mean mass accretion rate of 1.11 × 10{sup –7} and 4.50 × 10{sup –7} M{sub ☉} yr{sup –1} for HD 31648 and HD 163296, respectively. Accretion rate variations are observed, being more pronounced for HD 31648 (up to 0.5 dex). However, from the comparison with previous results it is found that the accretion rate of HD 163296 has increased by more than 1 dex, on a timescale of ∼15 yr. Averaged accretion luminosities derived from the Balmer excess are consistent with the ones inferred from the empirical calibrations with the emission line luminosities, indicating that those can be extrapolated to HAemore » stars. In spite of that, the accretion rate variations do not generally coincide with those estimated from the line luminosities, suggesting that the empirical calibrations are not useful to accurately quantify accretion rate variability.« less
Authors:
;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)
  2. Departamento de Física Teórica, Módulo 15, Facultad de Ciencias, Universidad Autónoma de Madrid, P.O. Box 78, E-28049, Cantoblanco, Madrid (Spain)
  3. Centro de Astrobiología, Departamento de Astrofísica (CSIC-INTA), ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain)
  4. GAIA Science Operations Centre, ESA, European Space Astronomy Centre, P.O. Box 78, E-28691, Villanueva de la Cañada, Madrid (Spain)
  5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  6. School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom)
  7. Department of Planetary Science, Lunar and Planetary Lab, University of Arizona, 1629, E. University Boulevard, 85719, Tucson, AZ (United States)
Publication Date:
OSTI Identifier:
22270728
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 776; 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; ACCRETION DISKS; ASTRONOMY; ASTROPHYSICS; BALMER LINES; COMPARATIVE EVALUATIONS; HERBIG-HARO OBJECTS; INFRARED SPECTRA; LUMINOSITY; MASS; PROTOPLANETS; STAR ACCRETION; T TAURI STARS; TELESCOPES; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; VARIATIONS