J/AJ/163/239 Periods & mag of RR Lyrae stars in globular clusters (Ngeow+, 2022)
Zwicky Transient Facility and globular clusters: the RR Lyrae.
Ngeow C.-C., Bhardwaj A., Dekany R., Duev D.A., Graham M.J., Groom S.L.,
Mahabal A.A., Masci F.J., Medford M.S., Riddle R.
<Astron. J., 163, 239 (2022)>
=2022AJ....163..239N 2022AJ....163..239N
ADC_Keywords: Clusters, globular; Stars, variable; Photometry; Optical;
Reddening; Abundances, [Fe/H]
Keywords: Globular star clusters ; RR Lyrae variable stars ;
Distance indicators ; Wide-field telescopes ; Sky surveys
Abstract:
Based on time-series observations collected from the Zwicky Transient
Facility (ZTF), we derived period-luminosity-metallicity (PLZ) and
period-Wesenheit-metallicity (PWZ) relations for RR Lyrae located in
globular clusters. We have applied various selection criteria to
exclude RR Lyrae with problematic or spurious light curves. These
selection criteria utilized information on the number of data points
per light curve, amplitudes, colors, and residuals on the
period-luminosity and/or period-Wesenheit relations. Due to blending,
a number of RR Lyrae in globular clusters were found to be anomalously
bright and have small amplitudes of their ZTF light curves. We used
our final sample of ∼750 RR Lyrae in 46 globular clusters covering a
wide metallicity range (-2.36dex<[Fe/H]←0.54dex) to derive PLZ and
PWZ relations in the gri bands. In addition, we have also derived the
period-color-metallicity and, for the first time, the
period-Q-index-metallicity relations, where the Q-index is
extinction-free by construction. We have compared our various
relations to empirical and theoretical relations available in the
literature and found a good agreement with most studies. Finally, we
applied our derived PLZ relation to a dwarf galaxy, Crater II, and
found that its true distance modulus should be larger than the most
recent determination.
Description:
The Updated Catalog of Variable Stars in Globular Clusters
(Clement+2001; Clement2017, V/150) was used to select RR Lyrae in
globular clusters. We first selected globular clusters that are
visible from the Palomar Observatory in California, US (i.e.,
dec>-30°), and contain at least one RR Lyrae, either type RR0
(aka RRab, or fundamental mode) or RR1 (aka RRc, or first-overtone
mode).
The Zwicky Transient Facility (ZTF) is a dedicated time-domain
wide-field synoptic sky survey aimed at exploring the transient
universe. It utilizes the Palomar 48inch Samuel Oschin Schmidt
telescope to observe the northern sky in customized gri filters.
Observing time and the data right of ZTF was divided into three
high-level surveys: partner surveys, public surveys, and California
Institute of Technology (Caltech) surveys.
The ZTF gri-band light curves were extracted for our sample of RR
Lyrae from the PSF catalogs available from both the ZTF Public Data
Release 7 (including both public and Caltech data) and the partner
surveys until 2021 September 30.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 73 54 List of globular clusters and the number of
RR Lyrae in the sample
table3.dat 123 1209 Periods, mean magnitudes, amplitudes and reddenings
for our sample of RR Lyrae
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See also:
II/371 : The Dark Energy Survey (DES): Data Release 2 (Abbott+, 2021)
V/150 : Updated catalog of variable stars in globular clusters (Clement+ 2017)
J/AJ/108/1786 : Blue stragglers and variable stars in M3 (Guhathakurta+, 1994)
J/ApJ/463/26 : VI photometry of 29 Cepheids in M101. (Kelson+ 1996)
J/AJ/130/2140 : Abundances and velocities in globular clusters (Pritzl+, 2005)
J/MNRAS/372/1657 : BVI(c) light curves of variables in M3 (Benko+, 2006)
J/MNRAS/371/1503 : Synthetic photometry of RR Lyr (Marconi+, 2006)
J/A+A/474/121 : Galac. globular cluster 2MASS GC02 JKs phot. (Borissova+, 2007)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/AcA/63/91 : V-band light curves of variables in M80 (Kopacki, 2013)
J/MNRAS/439/3765 : RR Lyrae in 15 Galactic globular clusters (Dambis+, 2014)
J/ApJ/814/71 : Carina project IX: UBVI data Carina variables (Coppola+, 2015)
J/A+A/573/A13 : Metal abundances in 6 globular cluster (Dias+, 2015)
J/AJ/151/88 : LMC NIR Synoptic Surv. II. Wesenheit relations (Bhardwaj+, 2016)
J/AJ/152/170 : RRLs in globulars. IV. UBVRI phot. in Omega Cen (Braga+, 2016)
J/A+A/590/A9 : RGB stars in Galactic GC stellar parameters (Dias+, 2016)
J/ApJ/841/84 : Theoretical framework for RR Lyrae. II. MIR data (Neeley+, 2017)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/AJ/154/85 : CTIO/DECam photometry of RR Lyrae stars in M5 (Vivas+, 2017)
J/AJ/156/241 : A first cat. of variable stars measured by ATLAS (Heinze+, 2018)
J/ApJ/861/23 : RR Lyrae variables in the Crater II dwarf galaxy (Joo+, 2018)
J/MNRAS/481/1195 : Gaia DR2 RR Lyrae as standard candles (Muraveva+, 2018)
J/A+A/619/A13 : 28 distant globular clusters CaT metallicities (Vasquez+, 2018)
J/ApJ/883/11 : Magellan/IMACS spectra of Crater II & Hercules (Fu+, 2019)
J/MNRAS/490/4121 : DECam colour-magnitude diagram of Crater II (Walker+, 2019)
J/AJ/160/220 : NIR light curve of 234 RR Lyrae in Messier 3 (Bhardwaj+, 2020)
J/ApJ/896/L43 : Cepheids HST amplitudes in V- and H-band (Riess+, 2020)
J/ApJ/900/L10 : X-band data of GOTHAM Large Project for TMC-1 (McGuire+, 2020)
J/MNRAS/492/1061 : A DECam view of Crater II - Variable stars (Vivas+, 2020)
J/ApJ/922/20 : CFHT optical & NIR obs. of RR Lyrae in M15 (Bhardwaj+, 2021)
J/AJ/162/63 : ZTF LCs of 51 stars in 12 globular clusters (Ngeow+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- NameCl Globular cluster identifier
12- 21 A10 --- NameC17 Name of the globular cluster in Clement+2017
(V/150/clusters); Column added by CDS
23- 27 F5.2 [Sun] [Fe/H] [-2.36/-0.43] Metallicity in dex (1)
29- 32 F4.2 [Sun] e_[Fe/H] [0.01/0.73] Uncertainty in [Fe/H]
34- 36 I3 --- ngRR0 [0/101] Number of RR0 Lyrae in the cluster
based on g-band observations
38- 40 I3 --- nrRR0 [0/132] Number of RR0 Lyrae in the cluster
based on r-band observations
42- 43 I2 --- niRR0 [0/88] Number of RR0 Lyrae in the cluster
based on i-band observations
45- 46 I2 --- ngRR1 [0/53] Number of RR1 Lyrae in the cluster
based on g-band observations
48- 49 I2 --- nrRR1 [0/48] Number of RR1 Lyrae in the cluster
based on r-band observations
51- 52 I2 --- niRR1 [0/39] Number of RR1 Lyrae in the cluster
based on i-band observations
54- 56 I3 --- ntot [1/167] Total number of RR Lyrae in the
cluster (2)
58- 62 F5.2 kpc Dist [1.85/94.84] Distance to the cluster (1)
64- 67 F4.2 kpc e_Dist [0.02/3.23] Uncertainty in Dist
69- 73 F5.3 mag E [0/2.029] Averaged reddening (3)
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Note (1): Homogeneous metallicities and distances for each globular cluster were
adopted from the GOTHAM survey and
Baumgardt & Vasiliev (2021MNRAS.505.5957B 2021MNRAS.505.5957B), respectively;
see Section 2.2 for more details.
Note (2): Number of RR Lyrae in a given globular cluster after removing
RR Lyrae with N<10 in all gri-band ZTF light curves in our
two-iteration template light-curve fitting procedures (see
Section 2.4).
Note (3): Here E is the averaged reddening value returned from the
Bayerstar2019 3D reddening map (Green et al., 2019ApJ...887...93G 2019ApJ...887...93G)
for the RR Lyrae in a given globular cluster, where the number of
RR Lyrae used in calculating the averaged reddening value was listed
in the ntot column.
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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- 10 A10 --- NameCl Name of the globular cluster (1)
12- 21 A10 --- NameC17 Name of the globular cluster in Clement+2017
(V/150/clusters); Column added by CDS
23- 30 A8 --- NameRR Name of the RR Lyrae in globular cluster (1)
32- 34 A3 --- Type Either RR0 (for fundamental mode) or RR1
(for first-overtone mode)
36- 45 F10.8 d Per [0.21/0.96] Period in days
47- 53 F7.3 mag gmag [-100/20.8] Mean g band magnitude (2)
55- 60 F6.3 mag gAmp [-10/3.4] Amplitude in g band (2)
62- 65 I4 --- Ng [0/1385] Number of data points in g band (3)
67- 73 F7.3 mag rmag [-100/20.9] Mean r band magnitude (2)
75- 81 F7.3 mag rAmp [-10/102.6] Amplitude in r band (2)
83- 86 I4 --- Nr [0/1415] Number of data points in r band (3)
88- 94 F7.3 mag imag [-100/20.4] Mean i band magnitude (2)
96- 101 F6.3 mag iAmp [-10/1.1] Amplitude in i band (2)
103- 105 I3 --- Ni [0/428] Number of data points in i band (3)
107- 111 F5.3 mag E [0/2.1] Reddening from Bayestar19 map (4)
113- 117 F5.3 mag e_E [0/0.021] Error in reddening
119- 123 A5 --- Flag Flags (5)
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Note (1): The original format found in the paper for the names of the RR Lyrae
in globular clusters is [GC]_[RRL Name], where [RRL Name] is adopted
from Clement2017 (V/150). Note that the authors renamed 23 P1 in
NGC 6712 as 23_P1 in the article table.
Note (2): Values of -99.990 and -9.990 denote no data or rejected light curves.
The g,r,i-Amp is the amplitude based on the best-fit template light
curve.
Note (3): Ng,r,i is the number of data points in a given filter after the
two-steps template fitting processes as described in Section 2.3.
Note (4): E is the reddening value returned from the Bayerstar2019 3D reddening
map (Green et al., 2019ApJ...887...93G 2019ApJ...887...93G) using the globular cluster
distance listed in Table 2.
Note (5): Flags include "A", "C", and/or "R", for filtering the RR Lyrae using
amplitudes, colors, and PL/PW residuals. Flags as follows:
A = RR Lyrae in our sample that did not satisfy the selection criteria based
on either the amplitudes, amplitude ratios, or both. See Section 3.1.
C = RR Lyrae located outside the 3σ boundaries, adopted as cuts, of
either the three PC relations or the PQ relation. See Section 3.2.
R = RR Lyrae with residuals beyond the boundaries determined for the either
the PL or PW relations and adopted as cuts. See Section 3.3.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 13-Oct-2025