High-resolution spectroscopy of the R Coronae Borealis star V Coronae Australis
Abstract
Optical high-resolution spectra of the R Coronae Borealis star V CrA at light maximum and during minimum light are discussed. Abundance analysis confirms previous results showing that V CrA has the composition of the small subclass of R Coronae Borealis (RCB) stars know as `minority' RCBs, i.e. the Si/Fe and S/Fe ratios are 100 times their solar values. A notable novel result for RCBs is the detection of the 1-0 Swan system 12C13C bandhead indicating that 13C is abundant: spectrum synthesis shows that 12C/13C is about 3-4. Absorption-line profiles are variable at maximum light with some lines showing evidence of splitting by about 10 kms-1. A spectrum obtained as the star was recovering from a deep minimum shows the presence of cool C2 molecules with a rotational temperature of about 1200K, a temperature suggestive of gas in which carbon is condensing into soot. The presence of rapidly outflowing gas is shown by blueshifted absorption components of the NaI D and KI 7698 Å resonance lines.
Based on observations obtained with (1) The Blanco 4-m Telescope at the Cerro Tololo Inter-American Observatory, which is operated by AURA, Inc., under contract to the National Science Foundation of USA and (2) The Harlan J. Smith Telescope of the W. J. McDonald Observatory of the University of Texas at Austin. E-mail: nkrao@iiap.res.in- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2008
- DOI:
- 10.1111/j.1365-2966.2007.12643.x
- arXiv:
- arXiv:0710.5030
- Bibcode:
- 2008MNRAS.384..477R
- Keywords:
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- circumstellar matter;
- stars: individual: R CrB;
- stars: variables: other;
- Astrophysics
- E-Print:
- 14 pages, 18 figures, 3 tables, accepted to MNRAS