NOAO > Observing Info > Approved Programs > 2012A-0222
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NOAO > Observing Info > Approved Programs > 2012A-0222 |
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PI: Geoffrey Clayton, Louisiana State University, gclayton@fenway.phys.lsu.edu
Address: Dept. of Physics & Astronomy, Baton Rouge, LA, 70803, USA
CoI: Tom Geballe, Gemini Observatory - North
CoI: Doug Welch, McMaster University
CoI: Patrick Tisserand, Mount Stromlo Observatory
CoI: Ben Sugerman, Goucher College
CoI: Howard Bond, Space Telescope Science Institute
Title: The Natural Coronographs of R Coronae Borealis Stars
Abstract:
The R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich
supergiants. Two evolutionary scenarios have been suggested, a double
degenerate merger of two white dwarfs (WDs), or a final helium shell flash.
The evidence pointing toward a WD merger or a final flash origin for RCB
stars is contradictory. A few show far-IR shells, cometary knots, or
significant lithium in their atmospheres, consistent with a fossil planetary
nebula (PN), supporting the scenario that RCB stars may be a product of a
final flash. However, the high mass of the stars and their high 18O and
fluorine abundances are more consistent with being the product of a WD
merger. We are proposing a TOO program to take advantage of the natural
coronograph of a deep decline in two RCB stars to obtain images with
Gemini/GMOS to look for the presence of old PN shells that will help
distinguish between the evolutionary scenarios. We will also use Monte Carlo
radiative transfer models to investigate the dust scattering in the fossil
shell. If the progenitors of RCB stars are close WD binaries, then they may
be low-mass analogs of more-massive binaries destined to become Type Ia SNe.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360
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NOAO > Observing Info > Approved Programs > 2012A-0222 |
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