Observational constraints on the stellar radiation field impinging on transitional disk atmospheres

Judit Szulágyi, Ilaria Pascucci, P. Ábrahám, Dániel Apai, Jeroen Bouwman, A. Moór

Research output: Article

6 Citations (Scopus)

Abstract

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] 15.55μm 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.

Original languageEnglish
Article number47
JournalAstrophysical Journal
Volume759
Issue number1
DOIs
Publication statusPublished - nov. 1 2012

Fingerprint

stellar radiation
radiation distribution
atmospheres
atmosphere
stellar spectra
pre-main sequence stars
Indian spacecraft
x rays
protoplanetary disks
planets
hardness
shock
near infrared
ionization
outflow
planet
radiation
gases
gas

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Observational constraints on the stellar radiation field impinging on transitional disk atmospheres. / Szulágyi, Judit; Pascucci, Ilaria; Ábrahám, P.; Apai, Dániel; Bouwman, Jeroen; Moór, A.

In: Astrophysical Journal, Vol. 759, No. 1, 47, 01.11.2012.

Research output: Article

Szulágyi, Judit ; Pascucci, Ilaria ; Ábrahám, P. ; Apai, Dániel ; Bouwman, Jeroen ; Moór, A. / Observational constraints on the stellar radiation field impinging on transitional disk atmospheres. In: Astrophysical Journal. 2012 ; Vol. 759, No. 1.
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