J/AJ/155/45 Metal-rich RRc stars in the Carnegie RR Lyrae Survey (Sneden+, 2018)
Metal-rich RRc stars in the Carnegie RR Lyrae Survey.
Sneden C., Preston G.W., Kollmeier J.A., Crane J.D., Morrell N.,
Prieto J.L., Shectman S.A., Skowron D.M., Thompson I.B.
<Astron. J., 155, 45-45 (2018)>
=2018AJ....155...45S 2018AJ....155...45S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Spectroscopy ; Abundances, [Fe/H] ; Photometry
Keywords: methods: observational - stars: abundances - stars: atmospheres -
stars: variables: delta Scuti - stars: variables: RR Lyrae -
techniques: spectroscopic
Abstract:
We describe and employ a stacking procedure to investigate abundances
derived from the low signal-to-noise ratio spectra obtained in the
Carnegie RR Lyrae Survey (CARRS). 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 δ Scuti stars (HADS) at periods
less than 0.3 days, where photometric discrimination between RRc and
δ 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.
Description:
The Kollmeier et al. 2013ApJ...775...57K 2013ApJ...775...57K (K13) sample began with the
RRc variables identified in the All Sky Automated Survey catalog
(ASAS; Pojmanski et al. 2002-2005, Cat. II/264 and references therein;
http://www.astrouw.edu.pl/asas/).
The spectra for the K13 snapshot RR Lyrae survey were gathered in 2011-12
with the echelle spectrograph of the Las Campanas Observatory 2.5 m
du Pont Telescope. The spectrograph configuration was identical to that
employed in a series of papers on the velocities, Hα profiles,
metallicities, and relative abundance ratios of RR Lyrae stars (For et al.
2011, J/ApJS/194/38; J/ApJS/197/29, Govea et al. 2014, J/ApJ/782/59,
Chadid et al. 2017ApJ...835..187C 2017ApJ...835..187C, Sneden et al. 2017ApJ...848...68S 2017ApJ...848...68S).
The spectrograph with a 1.5x4.0 arcsec aperture delivered resolving power
R=λ/Δλ∼27000 at 5000 Å. The spectral coverage was
λλ 3400-9000, with wavelength gaps in the CCD order coverage
beginning at λ 7100 Å and growing with increasing wavelength. In
practice, the useful spectral domain for this work was limited to
λλ 3900-7000 Å.
There were 274 observed spectra, and with 13 stars observed twice, the
total number of stars was 261.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 274 RRc Program Stars
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See also:
II/264 : ASAS Variable Stars in Southern hemisphere (Pojmanski+, 2002-2005)
J/AcA/48/35 : All Sky Automated Survey variable stars (Pojmamski 1998)
J/AcA/50/177 : All Sky Automated Survey Catalog (Pojmanski+, 2000)
J/MNRAS/358/30 : Automated classification of ASAS variables (Eyer+, 2005)
J/MNRAS/377/1263 : Multiperiodic RR Lyrae in ASAS catalog (Szczygiel+, 2007)
J/AcA/59/137 : ASAS Galactic fundamental mode RR Lyrae stars
(Szczygiel+, 2009)
J/ApJS/194/38 : Radial velocities of 11 field RR Lyrae (For+, 2011)
J/ApJS/197/29 : Chemical compositions of 11 RR Lyrae (For+, 2011)
J/ApJ/782/59 : Abundances of 8 RR Lyrae subclass C variable stars
(Govea+, 2014)
J/MNRAS/445/1584 : AB-type RR Lyrae stars from ASAS and WASP (Skarka, 2014)
http://www.astrouw.edu.pl/asas/ : ASAS catalog homepage
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- ASAS Star name in the ASAS Catalog
(ASAS JHHMMSS+DDMM.m in Simbad)
14- 15 A2 --- n_ASAS [_12 ] Note on ASAS (1)
17- 24 F8.6 d Per [0.218941/0.42262] Pulsation period in the ASAS
Catalog
26- 33 F8.3 d HJD0 [1869.05/2788.84] Epoch of maximum light
(HJD-2450000)
35- 39 F5.2 mag Vmax [8.16/13.63] Approximate V magnitude at maximum
light
41- 44 F4.2 mag Vamp [0.05/1.4] Approximate V magnitude amplitude
46- 49 F4.1 --- S/N [4.6/59.9] Mean signal-to-noise ratio near 4600
and 5200Å
51- 55 F5.2 [Sun] [Fe/H] [-2.78/0.04] Metallicity estimate from
Kollmeier et al. (2013ApJ...775...57K 2013ApJ...775...57K)
57- 58 I2 --- Stack [1/28]? Number of co-added stack to which star
belongs
60- 61 A2 --- n_Stack [no ] Note on Stack (2)
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Note (1): Star names ending in "_N", where N=1 or 2, denote duplicate
observations of the same ASAS target.
Note (2): Note as follows:
no = A probable δ Scuti star, exluded from the stack mean.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 24-Sep-2018