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20 April 2024 |
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Article overview
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Metal-Rich RRc stars in the Carnegie RR Lyrae Survey | | Christopher Sneden
; George W.Preston
; Juna A. Kollmeier
; Jeffrey D. Crane
; Nidia Morrell
; Jose L. Prieto
; Stephen A. Shectman
; Dorota M. Skowron
; Ian B. Thompson
; | | Date: |
1 Dec 2017 | | Abstract: | We describe and employ a stacking procedure to investigate abundances derived
from the low S/N spectra obtained in the Carnegie RR Lyrae Survey (CARRS;
Kollmeier et al. 2013). We find iron metallicities that extend from [Fe/H] ~
-2.5 to values at least as large as [Fe/H] ~ -0.5 in the 274-spectrum CARRS RRc
data set. We consider RRc sample contamination by high amplitude solar
metallicity delta Scuti stars (HADS) at periods less than 0.3 days, where
photometric discrimination between RRc and delta Scuti stars has proven to be
problematic. We offer a spectroscopic discriminant, the well-marked
overabundance of heavy elements, principally [Ba/H], that is a common, if not
universal, characteristic of HADS of all periods and axial rotations. No bona
fide RRc stars known to us have verified heavy-element overabundances. Three
out of 34 stars in our sample with [Fe/H] > -0.7 exhibit anomalously strong
features of Sr, Y, Zr, Ba, and many rare earths. However, carbon is not
enhanced in these three stars, and we conclude that their elevated n-capture
abundances have not been generated in interior neutron-capture nucleosynthesis.
Contamination by HADS appears to be unimportant, and metal-rich RRc stars occur
in approximately the same proportion in the Galactic field as do metal-rich
RRab stars. An apparent dearth of metal-rich RRc is probably a statistical
fluke. Finally we show that RRc stars have a similar inverse period-metallicity
relationship as has been found for RRab stars. | | Source: | arXiv, 1712.0159 | | Services: | Forum | Review | PDF | Favorites | |
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