J/ApJ/870/115 Reddening, distance modulus & Fe/H of RRLs in w Cen (Bono+, 2019)
On a new method to estimate the distance, reddening, and metallicity of
RR Lyrae stars using optical/near-infrared (B, V, I, J, H, K) mean magnitudes:
ω Centauri as a first test case.
Bono G., Iannicola G., Braga V.F., Ferraro I., Stetson P.B., Magurno D.,
Matsunaga N., Beaton R.L., Buonanno R., Chaboyer B., Dall'Ora M.,
Fabrizio M., Fiorentino G., Freedman W.L., Gilligan C.K., Madore B.F.,
Marconi M., Marengo M., Marinoni S., Marrese P.M., Martinez-Vazquez C.E.,
Mateo M., Monelli M., Neeley J.R., Nonino M., Sneden C., Thevenin F.,
Valenti E., Walker A.R.
<Astrophys. J., 870, 115-115 (2019)>
=2019ApJ...870..115B 2019ApJ...870..115B (SIMBAD/NED BibCode)
ADC_Keywords: Abundances, [Fe/H]; Clusters, globular; Photometry, UBV;
Reddening; Stars, distances; Stars, variable; Infrared sources
Keywords: globular clusters: individual: Centaurii; stars: distances;
stars: horizontal-branch; stars: variables: RR Lyrae
Abstract:
We developed a new approach to provide accurate estimates of the metal
content, reddening, and true distance modulus of RR Lyrae stars
(RRLs). The method is based on homogeneous optical (BVI) and
near-infrared (JHK) mean magnitudes and on predicted
period-luminosity-metallicity relations (IJHK) and absolute mean
magnitude-metallicity relations (BV). We obtained solutions for three
different RRL samples in ωCen: first overtone (RRc, 90),
fundamental (RRab, 80), and global (RRc+RRab) in which the period of
first overtones were fundamentalized. The metallicity distribution
shows a well defined peak at [Fe/H]~-1.98 and a standard deviation of
σ=0.54dex. The spread is, as expected, metal-poor ([Fe/H]≤-2.3)
objects. The current metallicity distribution is ∼0.3dex more
metal-poor than similar estimates for RRLs available in the
literature. The difference vanishes if the true distance modulus we
estimated is offset by -0.06/-0.07mag in true distance modulus. We
also found a cluster true distance modulus of
µ=13.720±0.002±0.030mag, where the former error is the
error on the mean and the latter is the standard deviation. Moreover,
we found a cluster reddening of E(B-V)=0.132±0.002±0.028mag
and spatial variations of the order of a few arcmin across the body of
the cluster. Both the true distance modulus and the reddening are
slightly larger than similar estimates available in the literature,
but the difference is within 1σ. The metallicity dependence of
distance diagnostics agrees with theory and observations, but firm
constraints require accurate and homogeneous spectroscopic
measurements.
Description:
We took advantage of the accurate and homogeneous optical (BVI) and
NIR (JHK) mean magnitudes for RR Lyrae stars (RRLs) in ω Cen to
develop a new algorithm (REDIME; REddening, DIstance modulus and
MEtallicity) to fully exploit the use of RRLs as distance indicators
and tracers of old stellar populations.
The RRLs hosted by ω Cen are roughly 200 and our group collected
during the last 15yr sizable samples of optical (UBVRI) and NIR (JHK)
time series (Braga+, 2016, J/AJ/152/170 and 2018, J/AJ/155/137). To
avoid possible systematics in applying REDIME we restricted the sample
to the 170 RRLs for which we have accurate optical and NIR mean
magnitudes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 127 170 Individual iron abundances, reddenings, and true
distance moduli for ωCen RR Lyrae stars (RRLs)
based on REDIME (REddening, DIstance modulus and
MEtallicity) algorithm
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See also:
J/AJ/119/1225 : Stroemgren photometry of Omega Cen and NGC 6397 (Hughes+, 2000)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/ApJ/640/L43 : Metallicities of RR Lyrae stars in Omega Cen (Sollima+, 2006)
J/AJ/133/1447 : Light curves of variable stars in ωCen (Weldrake+, 2007)
J/MNRAS/384/1583 : JHK light curves of RR Lyr (Sollima+, 2008)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/AJ/142/187 : HST observations of 7 Pop. II variable stars (Benedict+, 2011)
J/ApJS/197/29 : Chemical compositions of 11 RR Lyrae (For+, 2011)
J/MNRAS/422/2116 : BHB and RR Lyrae towards Anticentre and NGP (Kinman+, 2012)
J/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013)
J/ApJ/794/107 : Distance to NGC6822 Spitzer/FourStar Photometry (Rich+, 2014)
J/MNRAS/439/3765 : RR Lyrae in 15 Galactic globular clusters (Dambis+, 2014)
J/PASP/126/521 : UBVRIJHK photometry of RR Lyrae in M4 (Stetson+, 2014)
J/A+A/574/A15 : RR Lyrae in omega Cen (Fernandez-Trincado+, 2015)
J/AJ/149/99 : VVV globulars. I. 2MASS-GC 02, Terzan 10 (Alonso-Garcia+, 2015)
J/ApJ/814/71 : Carina project IX: UBVI data Carina variables (Coppola+, 2015)
J/MNRAS/447/2404 : Equivalent width of 21 RR Lyrae stars (Pancino+, 2015)
J/AJ/152/170 : RRLs in globulars. IV. UBVRI phot. in Omega Cen (Braga+, 2016)
J/ApJ/832/176 : Classical Cepheids in MCs. I. LMC disk (Inno+, 2016)
J/A+A/604/A120 : omega Cen RR Lyrae and SX Phoenicis stars (Navarrete+, 2017)
J/AJ/153/154 : LMC NIR survey. IV. Type II Cepheid variables (Bhardwaj+, 2017)
J/AJ/154/85 : CTIO/DECam photometry of RR Lyrae stars in M5 (Vivas+, 2017)
J/AJ/154/231 : Multi-epoch multi-band photometry of B1-392 (Saha+, 2017)
J/ApJ/838/107 : Distances to RRab stars from WISE and Gaia (Sesar+, 2017)
J/ApJ/848/68 : Abundances & RVs of stable & Blazhko RRc stars (Sneden+, 2017)
J/AJ/155/137 : RRLs in globulars. V. ωCentauri NIR phot. (Braga+, 2018)
J/ApJ/864/57 : Abundances of field & GC RR Lyrae. I. NGC3201 (Magurno+, 2018)
J/AJ/158/105 : IR photometry of field RR Lyrae variable stars (Layden+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Variable identification (1)
7 I1 --- Mode [0/1] Pulsation mode: 0=RRab (80 occurrences;
1=RRc (90 occurrences)
9- 18 F10.6 deg RAdeg [201/203] Right ascension (J2000) (1)
20- 29 F10.6 deg DEdeg [-47.7/-47.2] Declination (J2000) (1)
31 I1 --- Nmag [3/6] Number of mean magnitudes adopted for the
REDIME solution
33- 37 F5.2 [-] [Fe/H]c [-2.5/-1.2]? Decimal exponant of mean iron
abundance based on RRc (2)
39- 42 F4.2 [-] e_[Fe/H]c [0.05/1.4]? Uncertainty on [Fe/H]c
44- 47 F4.2 mag E(B-V)c [0.05/0.2]? Reddening based on RRc
49- 52 F4.2 mag e_E(B-V)c [0.01/0.03]? Uncertainty on E(B-V)c
54- 58 F5.2 mag DMc [13.4/13.9]? True distance modulus µ based on
RRc
60- 63 F4.2 mag e_DMc [0.02/0.2]? Uncertainty on DMc
65- 69 F5.2 [-] [Fe/H]ab [-2.5/-1.2]? Decimal exponant of mean iron
abundance based on RRab (2)
71- 74 F4.2 [-] e_[Fe/H]ab [0.05/1.5]? Uncertainty on [Fe/H]ab
76- 79 F4.2 mag E(B-V)ab [0.07/0.21]? Reddening based on RRab
81- 84 F4.2 mag e_E(B-V)ab [0.01/0.09]? Uncertainty on E(B-V)ab
86- 90 F5.2 mag DMab [13.4/13.9]? True distance modulus µ based on
RRab
92- 95 F4.2 mag e_DMab [0.02/0.2]? Uncertainty on DMab
97-101 F5.2 [-] [Fe/H]g [-3.4/-1.2] Decimal exponant of mean iron
abundance based on global REDIME solution (2)
103-106 F4.2 [-] e_[Fe/H]g [0.01/0.3] Uncertainty on [Fe/H]g
108-111 F4.2 mag E(B-V)g [0.06/0.3] Reddening based on global REDIME
solution
113-116 F4.2 mag e_E(B-V)g [0.01/0.06] Uncertainty on E(B-V)g
118-122 F5.2 mag DMg [13.6/13.8] True distance modulus µ based on
global REDIME solution
124-127 F4.2 mag e_DMg [0.01/0.09] Uncertainty on DMg
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Note (1): From Braga+, 2016, J/AJ/152/170 (<Cl* NGC 5139 SAW VNNN> in Simbad).
Note (2): Based on NIR (J,H,K) PL relations.
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS] 02-Mar-2020