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Title: The astrosphere of the asymptotic giant branch star CIT 6

We have discovered two extended half-ring structures in a far-ultraviolet image taken with the GALEX satellite of the well-known mass-losing carbon star CIT 6 (RW LMi). The northern (southern) ring is brighter (fainter) with a diameter of ∼15' (∼18'). These structures most likely represent the astrosphere resulting from the shock interaction of CIT 6's molecular wind with the warm interstellar medium (ISM), as it moves through the latter. These data provide a direct estimate of the size of CIT 6's circumstellar envelope that is a factor ∼20 larger than previous estimates based on CO millimeter-wave line data. We find that CIT 6 has been undergoing heavy mass-loss for at least 93,000 yr and the total envelope mass is 0.29 M {sub ☉} or larger, assuming a constant mass-loss rate of 3.2 × 10{sup –6} M {sub ☉} yr{sup –1}. Assuming that the shock front has reached a steady state and CIT 6's motion relative to the ISM is in the sky plane, we measure the termination-shock standoff distance directly from the image and find that CIT 6 is moving at a speed of about ≳39 (0.17 cm{sup –3}/n {sub ISM}){sup 1/2} km s{sup –1} through the ISM around it. However,more » comparisons with published numerical simulations and analytical modeling shows that CIT 6's forward shock (the northern ring) departs from the parabolic shape expected in steady state. We discuss several possible explanations for this departureþ.« less
Authors:
 [1] ;  [2]
  1. Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)
  2. Department of Physics, Occidental College, Los Angeles, CA 90041 (United States)
Publication Date:
OSTI Identifier:
22342244
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 148; Journal Issue: 4; 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 MONOXIDE; CARBON STARS; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; DISTANCE; FAR ULTRAVIOLET RADIATION; IMAGES; INTERACTIONS; MASS TRANSFER; SATELLITES; SKY; STEADY-STATE CONDITIONS; STELLAR WINDS; VELOCITY