Astron. Astrophys. 339, L61-L64 (1998)

Letter to the Editor

Fitting the unusual UV extinction curve of V348 Sgr

Setsuko Wada ¹, Alan T. Tokunaga ², Chihiro Kaito ³ and Seiji Kimura <sup>3

1</sup> Department of Chemistry, University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan
² Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822, USA
³ Department of Physics, University of Ritsumeikan, Kusatsu, Shiga 525-8577, Japan

Received 17 August 1998 / Accepted 5 October 1998

Abstract

We have produced new types of carbonaceous condensates from the ejecta of a hydrocarbon plasma. These condensates are named Quenched Carbonaceous Composites (QCC). There are various types of QCC formed around the center of the ejecta that show an absorption feature in the spectral range 220-250 nm. The QCC with an absorption feature at 220 nm is composed of onion-like spherules; that with an absorption feature at 230-240 nm are composed of polyhedral particles; and that with an absorption feature at 250 nm is composed of ribbons with bent graphitic layers. The 240-250 nm absorption feature of the hot evolved star V348 Sgr can be matched by the ribbon-like QCC, suggesting that this type of QCC may be present in the circumstellar shell of this star.

Key words: stars RCB stars-carbon: laboratory dust, extinction

Send offprint requests to: S. Wada

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Contents

• 1. Introduction
• 2. Experiment and results
  • 2.1. Production of QCC with different types of source gas mixtures
  • 2.2. High resolution imaging of QCC samples
  • 2.3. Comparison to the UV absorption of V348 Sgr
• 3. Discussion
• 4. Conclusions
• References

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998
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