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Title: Low extreme-ultraviolet luminosities impinging on protoplanetary disks

The amount of high-energy stellar radiation reaching the surface of protoplanetary disks is essential to determine their chemistry and physical evolution. Here, we use millimetric and centimetric radio data to constrain the extreme-ultraviolet (EUV) luminosity impinging on 14 disks around young (∼2-10 Myr) sun-like stars. For each object we identify the long-wavelength emission in excess to the dust thermal emission, attribute that to free-free disk emission, and thereby compute an upper limit to the EUV reaching the disk. We find upper limits lower than 10{sup 42} photons s{sup –1} for all sources without jets and lower than 5 × 10{sup 40} photons s{sup –1} for the three older sources in our sample. These latter values are low for EUV-driven photoevaporation alone to clear out protoplanetary material in the timescale inferred by observations. In addition, our EUV upper limits are too low to reproduce the [Ne II] 12.81 μm luminosities from three disks with slow [Ne II]-detected winds. This indicates that the [Ne II] line in these sources primarily traces a mostly neutral wind where Ne is ionized by 1 keV X-ray photons, implying higher photoevaporative mass loss rates than those predicted by EUV-driven models alone. In summary, our results suggestmore » that high-energy stellar photons other than EUV may dominate the dispersal of protoplanetary disks around sun-like stars.« less
Authors:
;  [1] ;  [2] ; ;  [3] ; ;  [4]
  1. Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States)
  2. Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States)
  3. SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043 (United States)
  4. Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia)
Publication Date:
OSTI Identifier:
22370347
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; 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; DUSTS; EMISSION; EXTREME ULTRAVIOLET RADIATION; KEV RANGE; LUMINOSITY; MASS TRANSFER; NEON; PHOTONS; PROTOPLANETS; STAR EVOLUTION; STELLAR RADIATION; STELLAR WINDS; SUN; SURFACES; WAVELENGTHS; X RADIATION