Spitzer Observations of Dust Around R Coronae Borealis Stars

Details Spitzer Observations of Dust Around R Coronae Borealis Stars Spitzer Observations of Dust Around R Coronae Borealis Stars

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.9307c&link_type=abstract

American Astronomical Society, AAS Meeting #211, #93.07; Bulletin of the American Astronomical Society, Vol. 39, p.890

Astronomy and Astrophysics

Astronomy

Scientific paper

The RCB stars are rare hydrogen-deficient carbon-rich supergiants, all apparently single stars which are consistent with being post-AGB stars. Their rarity may stem from the fact that they are in an extremely rapid phase of their evolution or in an evolutionary phase that most stars do not undergo. Several evolutionary scenarios have been suggested to account for the RCB stars including, a merger of two white dwarfs, or a final helium shell flash in a Planetary Nebula (PN) central star. Therefore, in the RCB stars, the presence or absence of circumstellar material and the nature of this material provides a fossil record of previous evolutionary stages. We have mapped the shells around four RCB stars, R CrB, UW Cen, SU Tau, and V CrA, with MIPS at 24, 70 and 160 microns. We will model the dust shells using dust grains appropriate to the RCB stars to reproduce the observed morphology. While most RCB stars are relatively cool (<7000; K), a few are significantly hotter ( 20,000 K). Two of these stars, V348 Sgr and HV 2671 show similarities to the [WC] central stars of PNe such as CPD -56 8032. We have obtained IRS spectra of V348 Sgr and HV 2671. We will compare their IR spectra with those of the [WC] stars and the cooler RCB stars. CPD -56 8032 shows emission features of PAHs as well as crystalline silicates, indicating a dual dust chemistry. These systems may all be binaries in which the O-rich silicates are trapped in a disk as a result of a past mass transfer event, with the C-rich particles being widely distributed in the nebula as a result of recent ejections of C-rich material.
This work was supported by Spitzer Space Telescope contracts 1287678 and 1287524 issued by Caltech/JPL.

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