2006/08/31 by V. C. Geers, Vincent Geers, J.‐C. Augereau +15 · 9 citations
Chemistry · Physics and Astronomy · #Abundance (ecology) #Accretion (finance) #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Feature (linguistics) #Herbig Ae/Be star #K-type main-sequence star #Low Mass #Molecular Spectroscopy and Structure #Optics #Physics #Radiative transfer #Spectral line #Spitzer Space Telescope #Stars #Stellar, planetary, and galactic studies #T Tauri star #astro-ph
paper · pdf · doi:10.1051/0004-6361:20064830
20 pages, 15 figures, accepted for publication in A&A
arxiv created 2006/09/06 · openalex publication_date 2006/11/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/02
Aims.We search for Polycyclic Aromatic Hydrocarbon (PAH) features towards young low-mass (T Tauri) stars and compare them with surveys of intermediate mass (Herbig Ae/Be) stars. The presence and strength of the PAH features are interpreted with disk radiative transfer models exploring the PAH feature dependence on the incident UV radiation, PAH abundance and disk parameters.<BR /> Methods: .Spitzer Space Telescope 5-35 mum spectra of 54 pre-main sequence stars with disks were obtained, consisting of 38 T Tauri, 7 Herbig Ae/Be and 9 stars with unknown spectral type.<BR /> Results: .Compact PAH emission is detected towards at least 8 sources of which 5 are Herbig Ae/Be stars. The 11.2 mum PAH feature is detected in all of these sources, as is the 6.2 mum PAH feature for the 4 sources for which short wavelength data are available. However, the 7.7 and 8.6 mum features appear strongly in only 1 of these 4 sources. Based on the 11.2 mum feature, PAH emission is observed towards at least 3 T Tauri stars, with 14 tentative detections, resulting in a lower limit to the PAH detection rate of 8%. The lowest mass source with PAH emission in our sample is <ASTROBJ>T Cha</ASTROBJ> with a spectral type G8. All 4 sources in our sample with evidence for dust holes in their inner disk show PAH emission, increasing the feature/continuum ratio. Typical 11.2 mum line intensities are an order of magnitude lower than those observed for the more massive Herbig Ae/Be stars. Measured line fluxes indicate PAH abundances that are factors of 10-100 lower than standard interstellar values. Conversely, PAH features from disks exposed to stars with Teff&leq; 4200 K without enhanced UV are predicted to be below the current detection limit, even for high PAH abundances. Disk modeling shows that the 6.2 and 11.2 mum features are the best PAH tracers for T Tauri stars, whereas the 7.7 and 8.6 mum bands have low feature over continuum ratios due to the strongly rising silicate emission.<BR />