J/AJ/149/99 VVV globulars. I. 2MASS-GC 02, Terzan 10 (Alonso-Garcia+, 2015)
Variable stars in the VVV globular clusters. I. 2MASS-GC 02 and Terzan 10.
Alonso-Garcia J., Dekany I., Catelan M., Ramos R.C., Gran F., Amigo P.,
Leyton P., Minniti D.
<Astron. J., 149, 99 (2015)>
=2015AJ....149...99A 2015AJ....149...99A
ADC_Keywords: Clusters, globular ; Stars, variable ; Stars, distances ;
Photometry, infrared
Keywords: globular clusters: general -
globular clusters: individual (2MASS-GC 02, Terzan 10) -
stars: variables: general - stars: variables: RR Lyrae
Abstract:
The VISTA Variables in the Via Lactea (VVV) ESO Public Survey is
opening a new window to study inner Galactic globular clusters (GCs)
using their variable stars. These GCs have been neglected in the past
due to the difficulties caused by the presence of elevated extinction
and high field stellar densities in their lines of sight. However, the
discovery and study of any present variables in these clusters,
especially RR Lyrae stars, can help to greatly improve the accuracy of
their physical parameters. It can also help to shed some light on the
questions raised by the intriguing Oosterhoff dichotomy in the
Galactic GC system. In a series of papers we plan to explore variable
stars in the GCs falling inside the field of the VVV survey. In this
first paper, we search for and study the variables present in two
highly reddened, moderately metal-poor, faint, inner Galactic GCs:
2MASS-GC 02 and Terzan 10. We report the discovery of sizable
populations of RR Lyrae stars in both GCs. We use near-infrared
period-luminosity relations to determine the color excess of each RR
Lyrae star, from which we obtain both accurate distances to the GCs
and the ratios of the selective-to-total extinction in their
directions. We find the extinction toward both clusters to be
elevated, non-standard, and highly differential. We also find both
clusters to be closer to the Galactic center than previously thought,
with Terzan 10 being on the far side of the Galactic bulge. Finally,
we discuss their Oosterhoff properties, and conclude that both
clusters stand out from the dichotomy followed by most Galactic GCs.
Description:
In this series of papers, we will explore the near-infrared time
domain of the inner Galactic globular clusters in the framework of the
VISTA Variables in the Via Lactea (VVV) ESO Public Survey. In this
paper, the first of this series, we have chosen to study two
metal-intermediate, low-surface brightness globular clusters that show
some of the highest reddening in the VVV sample of globular clusters,
2MASS-GC 02 and Terzan 10.
Our observations are part of the VVV survey, which has been conducted
since early 2010 with the 4.1m VISTA Telescope in Cerro Paranal
Observatory, in Chile. The VIRCAM camera on the telescope consists of
16 detectors, each of them providing near-infrared images of
11.6'*11.6' with a pixel size of 0.34''. We used the stacks of two
slightly dithered (∼20'' in each direction) individual exposures of
the VVV fields that contain our targets globular clusters, 2MASS-GC 02
(VVV field b326) and Terzan 10 (VVV field b308).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 95 102 Properties of the variable candidates in
2MASS-GC 02 and immediate surroundings
table6.dat 95 160 Properties of the variable candidates in
Terzan 10 and immediate surroundings
figure2.dat 35 8627 Light curves of the variable candidates in
2MASS-GC02 and surroundings
figure7.dat 35 30829 Light curves of the variable candidates in Terzan 10
--------------------------------------------------------------------------------
See also:
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Minniti+, 2014)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/571/A36 : M dwarfs in b201 tile of VVV survey (Rojas-Ayala+, 2014)
J/A+A/564/L9 : Near-IR photometry in VVV CL08 (Ramirez Alegria+, 2014)
J/A+A/562/A115 : VVV: star formation and embedded clusters (Solin+, 2014)
J/A+A/554/A123 : Near-IR catalog of novae in VVV survey area (Saito+, 2013)
J/MNRAS/429/385 : Short-period variables near Galactic Centre
(Matsunaga+, 2013)
J/A+A/552/A74 : NIR photometry of Galactic PNe with VVV Survey
(Weidmann+, 2013)
J/AJ/144/127 : 204 galaxy candidates from VVV infrared photometry
(Amores+, 2012)
J/AJ/143/70 : Differential reddening in MW globulars (Alonso-Garcia+, 2012)
J/A+A/532/A131 : New Galactic star clusters in VVV survey (Borissova+, 2011)
J/A+A/474/121 : Galactic globular cluster 2MASS GC02 JKs photometry
(Borissova+, 2007)
J/A+AS/126/319 : Terzan 10, ESO456-SC38, UKS 1 VIz photometry (Ortolani+ 1997)
Byte-by-byte Description of file: table[36].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [NV]
3- 5 I3 --- NV [1/160] Number of the New Variable candidate
7 A1 --- f_NV [*] Parameters light curve not well defined (1)
9- 10 I2 h RAh Hour of Right Ascension (J2000)
12- 13 I2 min RAm Minute of Right Ascension (J2000)
15- 19 F5.2 s RAs Second of Right Ascension (J2000)
21 A1 --- DE- Sign of the Declination (J2000)
22- 23 I2 deg DEd Degree of Declination (J2000)
25- 26 I2 arcmin DEm Arcminute of Declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of Declination (J2000)
33- 36 F4.2 arcmin Dist Distance to the cluster center
38 A1 --- l_Per [>] Limit flag on Per
40- 49 F10.6 d Per [0.1/500] Period
51 A1 --- f_Kamp [~] Approximate flag on Kamp
53- 57 F5.3 mag Kamp Amplitude of variation in the Ks band
59 A1 --- f_<Ksmag> [~] Approximate flag on <Ksmag>
61- 66 F6.3 mag <Ksmag> Mean Ks band magnitude
68- 72 F5.3 mag Z-Ks ? The (Z-Ks) color index (2)
74- 78 F5.3 mag Y-Ks ? The (Y-Ks) color index (2)
80- 84 F5.3 mag J-Ks ? The (J-Ks) color index (2)
86- 90 F5.3 mag H-Ks ? The (H-Ks) color index (2)
92- 95 A4 --- Type Variable type (Ceph, Ecl, LPV, or RRab) (3)
--------------------------------------------------------------------------------
Note (1): * = The physical parameters of the star should be considered with
caution, since the light curve is not well defined yet.
Note (2): Colors measured from single-epoch measurements in Z, Y, J, and H bands
(see Section 4.3 and Section 5.3 for further explanation about 2MASS-GC 02
and Terzan 10 color indices, respectively).
Note (3): Type of variable:
Ceph = Cepheid;
Ecl = Eclipsing binary;
LPV = Long-Period Variable;
RRab = RR Lyrae star.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: figure[27].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [NV]
3- 5 I3 --- NV Number of the New Variable candidate (1)
7- 20 F14.8 d HJD Heliocentric Julian Date (HJD-2400000.5)
22- 27 F6.3 mag Ksmag The Ks band magnitude
29- 33 F5.3 mag e_Ksmag Uncertainty in Ksmag
35 I1 --- f_Ksmag [0/1] Observation flag on Ksmag
(0=measure considered, 1=measure rejected) (2)
--------------------------------------------------------------------------------
Note (1): Note that the variable stars in Figure 2 and 7 (see the paper) have
been phase-folded, and batches of successive exposures taken within a few
minutes for every epoch has been weighted averaged, while in the table
they have not.
Note (2): Flag on Ksmag:
1 = The measure has been identified as an outlier when performing a
threshold rejection around the Fourier fit to the light curve
(see Section 3), and rejected from the phase-folded light curve figure;
0 = The value have been considered to build the phase-folded light curve
figure.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 17-Mar-2015