J/AJ/168/139 The Galactic bulge exploration. III. RRL FeHCaT (Kunder+, 2024)
The Galactic bulge exploration.
III. Calcium triplet metallicities for RR Lyrae stars.
Kunder A., Prudil Z., Skaggs C., Reggiani H., Nataf D.M., Hughes J.,
Covey K.R., Devine K.
<Astron. J., 168, 139 (2024)>
=2024AJ....168..139K 2024AJ....168..139K
ADC_Keywords: Stars, variable; Spectra, optical; Spectra, infrared; Abundances;
Milky Way; Equivalent widths
Keywords: Stellar populations ; RR Lyrae variable stars ; Distance indicators ;
Distance measure ; Metallicity ; Gaia ; Galactic bulge ;
Milky Way Galaxy ; Spectroscopy ; Infrared spectroscopy
Abstract:
RR Lyrae stars (RRLs) are excellent tracers of stellar populations for
old, metal-poor components in the the Milky Way and the Local Group.
Their luminosities have a metallicity dependence, but determining
spectroscopic [Fe/H] metallicities for RRLs, especially at distances
outside the solar neighborhood, is challenging. Using 40 RRLs with
metallicities derived from both Fe(II) and Fe(I) abundances, we verify
the calibration between the [Fe/H] of RRLs from the calcium triplet.
Our calibration is applied to all RRLs with Gaia Radial Velocity
Spectrometer (RVS) spectra in Gaia DR3 and to 80 stars in the inner
Galaxy from the BRAVA-RR survey. The coadded Gaia RVS RRL spectra
provide RRL metallicities with an uncertainty of 0.25 dex, which is a
factor of two improvement over the Gaia photometric RRL metallicities.
Within our Galactic bulge RRL sample, we find a dominant fraction with
low energies without a prominent rotating component. Due to the large
fraction of such stars, we interpret these stars as belonging to the
in situ metal-poor Galactic bulge component, although we cannot rule
out that a fraction of these belong to an ancient accretion event such
as Kraken/Heracles.
Description:
The ESO archive was used to access the RR Lyrae star (RRL) spectra
from the UVES (R∼40000) and XSHOOTER (R∼10000) instruments.
Additionally, spectra from the RAVE survey (R∼7500) were obtained for
a handful of RRLs with [Fe/H] in the Crestani+ (2021, J/ApJ/914/10)
compilation. In total, 68 spectra for 40 single-mode pulsators were
collected, and for each spectrum we obtained its S/N, resolution,
exposure, and observation time. The S/N of the RRL spectra varied
between 28 and 222, with a median centered at 69. The spectra
collected are listed in Table 1. See Section 2.
Individual photometric metallicities for Gaia RRLs presented in
Gaia DR3 come from the Specific Object Study (SOS) pipeline. We list
in Table 3 CaT metallicities derived for the Gaia RRLs with Radial
Velocity Spectrometer (RVS) spectra. See Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 133 68 RR Lyrae star spectra used to calibrate the EW
for CaII at 8498Å to [Fe/H] metallicity
table3.dat 71 175 The [Fe/H] metallicities of local RRLs from
Gaia RVS spectra using the equivalent width of
the 8498Å CaII line
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See also:
III/283 : RAVE 6th data release (Steinmetz+, 2020)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/358 : Gaia DR3 Part 4. Variability (Gaia Collaboration, 2022)
J/AJ/108/1016 : Kinematics of local RR lyrae stars. I. (Layden, 1994)
J/A+A/312/111 : [Fe/H] from RR Lyrae light curves (Jurcsik+, 1996)
J/A+A/330/515 : RR Lyrae parallaxes & proper motions (Fernley+ 1998)
J/ApJS/197/29 : Chemical compositions of 11 RR Lyrae (For+, 2011)
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
J/MNRAS/435/3206 : Properties of field RR Lyrae variables (Dambis+, 2013)
J/MNRAS/447/2404 : Equivalent width of 21 RR Lyrae stars (Pancino+, 2015)
J/ApJ/821/L25 : Bulge RR Lyrae RV Assay (BRAVA-RR) (Kunder+, 2016)
J/ApJ/844/L4 : PS1 RRab for tracing outer Virgo overdensity (Sesar+, 2017)
J/ApJ/848/68 : Abund. & RVs of stable and Blazhko RRc stars (Sneden+, 2017)
J/AJ/154/85 : CTIO/DECam photometry of RR Lyrae stars in M5 (Vivas+, 2017)
J/MNRAS/481/1195 : GaiaDR2 RR Lyrae stars as standard candles (Muraveva+, 2018)
J/MNRAS/484/4833 : Oosterhoff dichotomy in Galactic bulge (Prudil+, 2019)
J/MNRAS/493/5195 : Milky Way halo stars ages and kinematics (Das+, 2020)
J/ApJS/247/68 : Probing the Gal. halo with RR Lyrae stars. I. (Liu+, 2020)
J/MNRAS/492/3408 : Galactic disc RR Lyrae stars (Prudil+, 2020)
J/ApJ/914/10 : Field RR Lyrae as Gal. probes. III. Abund. (Crestani+, 2021)
J/ApJ/908/20 : Field RR Lyrae as galactic probes. II. (Crestani+, 2021)
J/ApJ/920/33 : Fe/H estimation of RR Lyrae from I- LC (Dekany+, 2021)
J/MNRAS/502/4074 : Period-luminosity-metallicities of RRLs (Muhie+, 2021)
J/ApJ/912/144 : Metallicity of Gal. RR Lyrae from LCs (Mullen+, 2021)
J/A+A/648/A78 : Orphan stream RR Lyrae and non-variables (Prudil+, 2021)
J/ApJS/261/33 : Phot. metallicity prediction of RR Lyrae (Dekany+, 2022)
J/A+A/674/A18 : Gaia DR3. The RR Lyrae sample (Clementini+, 2023)
J/MNRAS/530/3391 : Pristine Inner Gal. Survey VIII (Ardern-Arentsen+, 2024)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Gaia DR3 identifier
21- 25 F5.2 [-] [Fe/H] [-2.5/-0.16] Metallicity from
Crestani+ 2021, J/ApJ/914/10
27- 30 F4.2 [-] e_[Fe/H] [0/0.2] Uncertainty in [Fe/H]
32- 40 F9.7 d Per [0.26/0.71] Pulsation period
42- 55 F14.6 d M0 Time of maximum brightness, M0
57- 70 F14.6 d HJD Time spectra was taken
72- 75 A4 --- Type Type of single-mode RRL ("RRab" or "RRc")
77-103 A27 --- File Spectra name from archive
105-107 I3 --- SN [28/221] Signal-to-noise ratio
109-113 I5 --- Res [1512/56990] Resolution
115-122 A8 --- Inst Instrument used ("XSHOOTER", "UVES" or "rave")
124-128 F5.1 0.1nm EW [391/863] Measured equivalent width; Angstroms
130-133 F4.1 0.1nm e_EW [1/33] Uncertainty in EW
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Gaia Gaia DR3 identifier
21- 29 F9.5 deg RAdeg Right ascension (J2000)
31- 39 F9.5 deg DEdeg Declination (J2000)
41- 43 I3 10-13m EW [265/991] CaT equivalent width
45- 46 I2 10-13m e_EW [3/57] Uncertainty in EW
48- 52 F5.2 [-] [Fe/H] [-2.8/-0.01] Metallicity
54- 57 F4.2 [-] e_[Fe/H] [0.14/0.3] Uncertainty in [Fe/H]
59- 61 I3 --- SN [18/179] Signal-to-noise ratio
63- 64 I2 --- Nep [5/54] Number of clean Gaia epochs
66- 71 F6.3 mag Gmag [9.56/13.14] Apparent Gaia DR3 G magnitude
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History:
From electronic version of the journal
References:
Prudil et al. Paper I. 2024A&A...684A.176P 2024A&A...684A.176P
Prudil et al. Paper II. 2024A&A...685A.153P 2024A&A...685A.153P Cat. J/A+A/685/153
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Feb-2025