The astrosphere of the asymptotic giant branch star CIT 6

Journal Article · Wed Oct 01 04:00:00 EDT 2014 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/148/4/74· OSTI ID:22342244

Sahai, Raghvendra ^[1]

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1. Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)

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, 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.

• OSTI ID: 22342244
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 4 Vol. 148; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
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