Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992apjs...82..285h&link_type=abstract
Astrophysical Journal Supplement v.82, p.285
Astronomy and Astrophysics
Astronomy
91
Stars: Chromospheres, Stars: Emission-Line, Be, Stars: Pre-Main-Sequence
Scientific paper
We present optical emission-line data for a sample of 32 Herbig Ae/Be stars. Many of the Herbig stars have line spectra similar to the "classical" (strong Hα) T Tauri stars. The Herbig stars with the most T Tauri-like characteristics are the ones that also have direct evidence for outflow in their spectra, e.g., P Cygni profiles or broad or blueshifted forbidden lines. Among the similarities derived from the Ca II triplet lines are space densities of ≳1011-3, column densities of Nβ ≳ 1021 cm-3, and optically thick emitting areas that can be several times larger than the stars. The triplet line profiles also suggest similar dynamical environments. Some Herbig stars have the distinctive Ca II triplet signature observed in the T Tauri stars, where 8498 Å has the largest peak height but the narrowest width of the three. We interpret this in terms of increasing velocities and decreasing triplet source functions outward through the emitting gas.
Based on these similarities we suggest that the models developed for classical T Tauri star winds/envelopes could also apply to many of the Herbig stars. We favor the model discussed in our accompanying paper on the T Tauri stars; e.g., where the strong and broad emission lines form in dense turbulent regions that are generated at a star-accretion disk boundary layer and reside primarily near the disk plane. This conflicts with previous models of Herbig star envelopes that invoke the star as the driving force behind the winds and dense line-emitting gas.
We also estimate the Ca II emissivity from dense envelopes near hot stars using photoionization calculations. We find that the Ca II lines of most Herbig stars could form very near the photosphere. Therefore, the T Tauri star models of dense turbulent envelopes near the star might apply directly. However, the early B stars require more extended high-density regions. Their sometimes double-peaked line profiles and general spectral similarity to the classical Be stars suggest that the lines form inside the disks. The profile peak-to-peak velocities and the photoionization models (if ne ≳ 1011 cm-3) both imply emission from within a few tens of stellar radii.
Hamann Fred
Persson Eric S.
No associations
LandOfFree
Emission-Line Studies of Young Stars. II. The Herbig Ae/Be Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Emission-Line Studies of Young Stars. II. The Herbig Ae/Be Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Emission-Line Studies of Young Stars. II. The Herbig Ae/Be Stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1766318