J/A+A/651/A47 Variable stars in VVV globulars. II. (Alonso-Garcia+, 2021)
Variable stars in the VVV globular clusters. II. NGC 6441,
NGC 6569, NGC 6626 (M 28), NGC 6656 (M 22), 2MASS-GC 02, and Terzan 10.
Alonso-Garcia J., Smith L.C., Catelan M., Minniti D., Navarrete C.,
Borissova J., Carballo-Bello J.A., Contreras Ramos R.,
Fernandez-Trincado J.G., Ferreira Lopes C.E., Gran F., Garro E.R.,
Geisler D., Guo Z., Hempel M., Kerins E., Lucas P.W., Palma T.,
Pena Ramirez K., Ramirez-Alegria S., Saito R.K.
<Astron. Astrophys. 651, A47 (2021)>
=2021A&A...651A..47A 2021A&A...651A..47A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Stars, distances ;
Photometry, infrared
Keywords: globular clusters: general - stars: variables: general -
stars: variables: RR Lyrae
Abstract:
The Galactic globular clusters (GGCs) located in the inner regions of
the Milky Way suffer from high extinction that makes their observation
challenging. High densities of field stars in their surroundings
complicate their study even more. The VISTA Variables in the Via
Lactea (VVV) survey provides a way to explore these GGCs in the
near-infrared where extinction effects are highly diminished.
We conduct a search for variable stars in several inner GGCs, taking
advantage of the unique multi-epoch, wide-field, near-infrared
photometry provided by the VVV survey. We are especially interested in
detecting classical pulsators that will help us constrain the physical
parameters of these GGCs. In this paper, the second of a series, we
focus on NGC 6656 (M 22), NGC 6626 (M 28), NGC 6569, and NGC 6441;
these four massive GGCs have known variable sources, but quite
different metallicities. We also revisit 2MASS-GC 02 and Terzan 10,
the two GGCs studied in the first paper of this series.
We present an improved method and a new parameter that efficiently
identify variable candidates in the GGCs. We also use the proper
motions of those detected variable candidates and their positions in
the sky and in the color-magnitude diagrams to assign membership to
the GGCs.
We identify and parametrize in the near-infrared numerous variable
sources in the studied GGCs, cataloging tens of previously undetected
variable stars. We recover many known classical pulsators in these
clusters, including the vast majority of their fundamental mode RR
Lyrae. We use these pulsators to obtain distances and extinctions
toward these objects. Recalibrated period-luminosity-metallicity
relations for the RR Lyrae bring the distances to these GGCs to a
closer agreement with those reported by Gaia, except for NGC 6441,
which is an uncommon Oosterhoff III GGC. Recovered proper motions for
these GGCs also agree with those reported by Gaia, except for 2MASS-GC
02, the most reddened GGC in our sample, where the VVV near-infrared
measurements provide a more accurate determination of its proper
motions.
Description:
In this second paper of the series, we focus on several well-known
GGCs located in the VVV footprint: NGC 6441, NGC 6569, NGC 6626 (M
28), and NGC 6656 (M 22). These GGCs show a significant range in their
metallicities and in their Oosterhoff classification. By drawing a
comparison with previous literature, we aim to examine the reliability
of our methods to detect variable stars and to infer the physical
parameters (distance, extinction, and proper motion) for their GGCs.
While achieving this, we also provide a look at the variable stars of
these GGCs from their innermost regions to their outskirts at
near-infrared wavelengths for the first time. Additionally, we also
revisit 2MASS-GC 02 and Terzan 10 to check the advantages and
drawbacks of our updated approach to detect variable sources.
In our analysis, we used observations from VVV, one of the six
original ESO public surveys conducted with the 4.1 m VISTA telescope
in the Cerro Paranal Observatory. The camera installed in the
telescope provides wide-field images of 1.6 square degrees of the sky,
with gaps due to the separation of the 16 chips in the camera. The VVV
survey uses five near-infrared filters (Z, Y, J, H, and K_s). Our
analysis is based on the VVV photometry and astrometry provided by
VIRAC2, an updated version of the VVV Infrared Astrometric Catalogue.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
17 50 13.06 -37 03 05.2 NGC6 441 = Cl VDBH 248
18 02 57.40 -26 04 00.0 Terzan 10 = ESO 521-16
18 09 36.5 -20 46 44 2MASS-GC 02 = NAME 2MASS-GC02
18 13 38.88 -31 49 35.2 NGC 6569 = Cl VDBH 260
18 24 32.89 -24 52 11.4 NGC 6626 = M 28
18 36 23.94 -23 54 17.1 NGC 6656 = M 22
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 140 439 Properties of the variable candidates in
NGC 6656 (M 22)
table5.dat 130 88 Properties of the variable candidates in
NGC 6626 (M 28)
table6.dat 130 27 Properties of the variable candidates in
NGC 6569
table7.dat 130 59 Properties of the variable candidates in
NGC 6441
table8.dat 105 45 Properties of the variable candidates in
2MASS-GC 02
table9.dat 130 65 Properties of the variable candidates in
Terzan 10
figure4.dat 36 32359 Light curves of the variable candidates in
NGC 6656 (M 22)
figure7.dat 36 6596 Light curves of the variable candidates in
NGC 6626 (M 28)
figure8.dat 36 1995 Light curves of the variable candidates in
NGC 6569
figure9.dat 36 5103 Light curves of the variable candidates in
NGC 6441
figure12.dat 36 4081 Light curves of the variable candidates in
2MASS-GC 02
figure13.dat 36 21598 Light curves of the variable candidates in
Terzan 10
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See also:
V/150 : Updated catalog of variable stars in globular clusters
(Clement+ 2017)
J/AJ/149/99 : VVV globulars. I. 2MASS-GC 02, Terzan 10 (Alonso-Garcia+, 2015)
J/AcA/66/405 : Galactic bulge eclipsing + ellipsoidal binaries
(Soszynski+, 2016)
J/AcA/67/297 : OGLE Galactic center Cepheids and RR Lyrae (Soszynski+, 2017)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Identifier of variable candidate
6- 10 A5 --- IDClement Identifier according to the Clement catalog
(2001AJ....122.2587C 2001AJ....122.2587C, Cat. V/150)
12- 31 A20 --- IDOGLE Identifier according to the OGLE catalog (G1)
33- 37 A5 --- IDRos17 Identifier according to Rozyczka et al.
(2017AcA....67..203R 2017AcA....67..203R)
39- 40 I2 h RAh Right Ascension (J2000)
42- 43 I2 min RAm Right Ascension (J2000)
45- 49 F5.2 s RAs Right Ascension (J2000)
51 A1 --- DE- Declination (J2000)
52- 53 I2 deg DEd Declination (J2000)
55- 56 I2 arcmin DEm Declination (J2000)
58- 61 F4.1 arcsec DEs Declination (J2000)
63- 67 F5.2 arcmin Dist Projected distance to the cluster center
69- 77 F9.6 d Period Period of variation
79- 83 F5.3 mag Ksamp Amplitude of variation in the Ks band
85- 90 F6.3 mag <Ksmag> Mean Ks band magnitude
92- 96 F5.3 mag Z-Ks ? (Z-Ks) color index
98-103 F6.3 mag Y-Ks ? (Y-Ks) color index
105-110 F6.3 mag J-Ks ? (J-Ks) color index
112-117 F6.3 mag H-Ks ? (H-Ks) color index
119-125 F7.3 mas/yr pmRA Proper motion in Right Ascension
127-133 F7.3 mas/yr pmDE Proper motion in Declination
135 I1 --- MemberFlag [0/1] Globular cluster membership (G2)
137-140 A4 --- Type Variable type (Cep, Ecl, RRab, or RRc) (G3)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat table6.dat table7.dat table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ID Identifier of variable candidate
5- 8 A4 --- IDClement Identifier according to the Clement catalog
(2001AJ....122.2587C 2001AJ....122.2587C, Cat. V/150)
10- 29 A20 --- IDOGLE Identifier according to the OGLE catalog (G1)
31- 32 I2 h RAh Right Ascension (J2000)
34- 35 I2 min RAm Right Ascension (J2000)
37- 41 F5.2 s RAs Right Ascension (J2000)
43 A1 --- DE- Declination (J2000)
44- 45 I2 deg DEd Declination (J2000)
47- 48 I2 arcmin DEm Declination (J2000)
50- 53 F4.1 arcsec DEs Declination (J2000)
55- 59 F5.2 arcmin Dist Projected distance to the cluster center
61- 69 F9.6 d Period Period of variation
71- 75 F5.3 mag Ksamp Amplitude of variation in the Ks band
77- 82 F6.3 mag <Ksmag> Mean Ks band magnitude
84- 88 F5.3 mag Z-Ks ? (Z-Ks) color index
90- 94 F5.3 mag Y-Ks ? (Y-Ks) color index
96-100 F5.3 mag J-Ks ? (J-Ks) color index
102-107 F6.3 mag H-Ks ? (H-Ks) color index
109-115 F7.3 mas/yr pmRA Proper motion in Right Ascension
117-123 F7.3 mas/yr pmDE Proper motion in Declination
125 I1 --- MemberFlag [0,1] Globular cluster membership flag (G2)
127-130 A4 --- Type Variable type (Cep, Ecl, RRab, or RRc) (G3)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- ID Identifier of variable candidate
5- 8 A4 --- IDPaperI Identifier according to Alonso-Garcia et al.
(2015, Cat. J/AJ/149/99)
10- 11 I2 h RAh Right Ascension (J2000)
13- 14 I2 min RAm Right Ascension (J2000)
16- 20 F5.2 s RAs Right Ascension (J2000)
22 A1 --- DE- Declination (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 32 F4.1 arcsec DEs Declination (J2000)
34- 37 F4.2 arcmin Dist Projected distance to the cluster center
39- 47 F9.6 d Period Period of variation
49- 53 F5.3 mag Ksamp Amplitude of variation in the Ks band
55- 60 F6.3 mag <Ksmag> Mean Ks band magnitude
62- 66 F5.3 mag Z-Ks ? (Z-Ks) color index
68- 72 F5.3 mag Y-Ks ? (Y-Ks) color index
74- 78 F5.3 mag J-Ks ? (J-Ks) color index
80- 84 F5.3 mag H-Ks ? (H-Ks) color index
86- 91 F6.3 mas/yr pmRA Proper motion in Right Ascension
93- 98 F6.3 mas/yr pmDE Proper motion in Declination
100 I1 --- MemberFlag [0/1] Globular cluster membership flag (G2)
102-105 A4 --- Type Variable type (Cep, Ecl, RRab, or RRc) (G3)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: fig*.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Identifier of variable candidate in the cluster
6- 17 F12.6 d MJD Modified Julian Day
19- 23 F5.3 --- Phase Phase
25- 30 F6.3 mag Ksmag Magnitude in the Ks band
32- 36 F5.3 mag e_Ksmag Uncertainty in Ksmag
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Global notes:
Note (G1): OGLE catalogs, Soszynski et al. (2016, Cat. J/AcA/66/405;
2017 Cat. J/AcA/67/297; 2019AcA....69..321S 2019AcA....69..321S)
Note (G2): Membership code as follows:
0 = non-member
1 = member
Note (G3): Type of variable as follows:
Cep = Cepheid
Ecl = Eclipsing binary
RRab = Fundamental-mode RR Lyrae star
RRc = First-overtone RR Lyrae star
--------------------------------------------------------------------------------
Acknowledgements:
Javier Alonso-Garcia, javier.alonso(at)uantof.cl
References:
Alonso-Garcia et al., Paper I, 2015AJ....149...99A 2015AJ....149...99A, Cat. J/AJ/149/99
(End) Patricia Vannier [CDS] 16-May-2021