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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



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ID: 660638.0, MPI für Astronomie / Publikationen_mpia
Observational Constraints on the Stellar Radiation Field Impinging on Transitional Disk Atmospheres
Authors:Szulágyi, Judit; Pascucci, Ilaria; Ábrahám, Péter; Apai, Dániel; Bouwman, Jeroen; Moór, Attila
Date of Publication (YYYY-MM-DD):2012
Title of Journal:The Astrophysical Journal
Journal Abbrev.:ApJ
Volume:759
Issue / Number:1
Start Page:id 47
Review Status:not specified
Audience:Not Specified
Abstract / Description:Mid-infrared atomic and ionic line ratios measured in spectra of pre-main-sequence stars are sensitive indicators of the hardness of the radiation field impinging on the disk surface. We present a low-resolution Spitzer IRS search for [Ar II] at 6.98 μm, [Ne II] at 12.81 μm, and [Ne III] 15.55 μm lines in 56 transitional disks. These objects, characterized by reduced near-infrared but strong far-infrared excess emission, are ideal targets to set constraints on the stellar radiation field onto the disk, because their spectra are not contaminated by shock emission from jets/outflows or by molecular emission lines. After demonstrating that we can detect [Ne II] lines and recover their fluxes from the low-resolution spectra, here we report the first detections of [Ar II] lines toward protoplanetary disks. We did not detect [Ne III] emission in any of our sources. Our [Ne II]/[Ne III] line flux ratios combined with literature data suggest that a soft-EUV or X-ray spectrum produces these gas lines. Furthermore, the [Ar II]/[Ne II] line flux ratios point to a soft X-ray and/or soft-EUV stellar spectrum as the ionization source of the [Ar II] and [Ne II] emitting layer of the disk. If the soft X-ray component dominates over the EUV, then we would expect larger photoevaporation rates and, hence, a reduction of the time available to form planets.
Free Keywords:circumstellar matter; infrared: stars; protoplanetary disks; stars: pre-main sequence
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://cdsads.u-strasbg.fr/abs/2012ApJ...759...47S [ID No:1]
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