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Title: FIRST DETECTION OF ULTRAVIOLET EMISSION FROM A DETACHED DUST SHELL: GALAXY EVOLUTION EXPLORER OBSERVATIONS OF THE CARBON ASYMPTOTIC GIANT BRANCH STAR U Hya

We present the discovery of an extended ring of ultraviolet (UV) emission surrounding the asymptotic giant branch (AGB) star U Hya in archival observations performed by the Galaxy Evolution Explorer. This is the third discovery of extended UV emission from a carbon AGB star and the first from an AGB star with a detached shell. From imaging and photometric analysis of the FUV and NUV images, we determined that the UV ring has a radius of ∼110'', thus indicating that the emitting material is likely associated with the detached shell seen in the infrared. We find that scattering of the central point source of NUV and FUV emission by the dust shell is negligible. Moreover, we find that scattering of the interstellar radiation field by the dust shell can contribute at most ∼10% of the FUV flux. Morphological and photometric evidence suggests that shocks caused by the star's motion through space and, possibly, shock-excited H{sub 2} molecules are the most likely origins of the UV flux. In contrast to previous examples of extended UV emission from AGB stars, the extended UV emission from U Hya does not show a bow-shock-like structure, which is consistent with a lower space velocity andmore » lower interstellar medium density. This suggests the detached dust shell is the source of the UV-emitting material and can be used to better understand the formation of detached shells.« less
Authors:
 [1] ; ;  [2] ;  [3]
  1. Florida State University, Tallahassee, FL 32306 (United States)
  2. Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37240-1807 (United States)
  3. Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala (Sweden)
Publication Date:
OSTI Identifier:
22364658
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 798; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMPTOTIC SOLUTIONS; CARBON; DENSITY; DETECTION; GALACTIC EVOLUTION; GALAXIES; GIANT STARS; HYDROGEN; IMAGES; MOLECULES; PHOTON EMISSION; SCATTERING; SHOCK WAVES; ULTRAVIOLET RADIATION