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Extended Dust Shells around Carbon Stars in the Infrared and in Optical Light

Published online by Cambridge University Press:  25 May 2016

Hideyuki Izumiura
Affiliation:
Okayama Astrophysical Observatory, NAOJ, Kamogata, Asakuchi, Okayama 719-0232, Japan
L.B.F.M. Waters
Affiliation:
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, NL-1098 SJ Amsterdam, The Netherlands
T. De Jong
Affiliation:
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, NL-1098 SJ Amsterdam, The Netherlands
C. Loup
Affiliation:
Institut d'Astrophysique de Paris, CNRS, 75014 Paris, France
O. Hashimoto
Affiliation:
Gunma Astronomical Observatory, 1-18-7 Ohotomo, Maebashi, Gunma 371, Japan

Abstract

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We investigate the structure of extended dust shells around optical carbon stars in the far-infrared and in optical light. In the optical we have discovered that R Scl and U Ant are associated with circularly extended emission, the radii of which are about 20″ and 58″, respectively. The emission is probably scattered light of the central star by dust grains in their circumstellar shells. In the far-infrared we have discovered a double shell structure surrounding U Ant in high resolution IRAS images, which is direct evidence of a periodic change of mass-loss on a time-scale of the order of 104 years in the AGB evolution. Relating the two shells to two consecutive thermal pulses allows for a self-consistent determination of the interpulse period, core-mass, luminosity, and distance. Direct mapping of Y CVn at 90 and 160 μm with ISOPHOT on board ISO has revealed a very extended detached dust shell around this star. The mass-loss rate is found to have decreased drastically by two orders of magnitude 1.4×104 years ago, which should be an important clue to the understanding of J-type stars.

Type
Session IX — Circumstellar Emission and Environment
Copyright
Copyright © Kluwer 2000 

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