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A Binary-Induced Pinwheel Outflow from the Extreme Carbon Star, AFGL 3068

Published online by Cambridge University Press:  15 December 2006

Mark Morris
Affiliation:
Dept. of Physics & Astronomy, University of California, Los Angeles, CA 90095-1547, USA email: morris@astro.ucla.edu
Raghvendra Sahai
Affiliation:
Jet Propulsion Laboratory/Calif. Inst. of Technology, MS 183-900, Pasadena, CA 91109, USA
Keith Matthews
Affiliation:
California Institute of Technology, Mail Code 105-24, Pasadena, CA 91125, USA
Judy Cheng
Affiliation:
Dept. of Physics & Astronomy, The Johns Hopkins Univ., Baltimore, MD 21218, USA
Jessica Lu
Affiliation:
Dept. of Physics & Astronomy, University of California, Los Angeles, CA 90095-1547, USA email: morris@astro.ucla.edu
Mark Claussen
Affiliation:
National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801, USA
Carmen Sánchez-Contreras
Affiliation:
Dpto. de Astrofísica Molecular e Infrarroja, IEM-CSIC, Serrano 121, 28006 Madrid, Spain
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Abstract

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The extreme carbon star, AFGL 3068, is losing mass at a rate in excess of 10$^{-4}$ M$_{\odot}$ yr$^{-1}$, and has so far been detected only in the infrared because it is hidden by a thick dust photosphere having a color temperature of $\sim$300K. Using the ACS camera on HST, we have imaged AFGL 3068 with broad-band filters at 0.6 and 0.8 $\mu$m and find a thin, apparently continuous spiral arc winding 4 or 5 times around the location of the star, from angular radii of 2 to 10 arcsec. We interpret this as the projection of nested spiral shells such as were predicted to occur when the mass-losing star is a member of a binary system. In this case, the illumination is presumably provided by ambient galactic starlight. Subsequent near-IR observations with the NIRC2 camera on the Keck II telescope using adaptive optics reveal that AFGL 3068 has two components separated by 0.11 arcsec, or 109 AU at a distance of 1 kpc. One very red component is presumably the mass-losing carbon star, while the other component is apparently a much bluer companion. Assuming each component has mass M(M$_{\odot}$), and ignoring the projection of the separation vector, we find the binary period to be 810 M$^{-0.5}$ yrs, strikingly comparable to the 710-yr separation of the shells obtained from the known outflow velocity of 14.7 km s$^{-1}$.

Type
Contributed Papers
Copyright
© 2006 International Astronomical Union