J/A+A/689/A108 Terzan 5 variables light curves (Figuera Jaimes+, 2024)
Digging deeper into the dense Galactic globular cluster Terzan 5 with
Electron-Multiplying CCDs. Variable star detection and new discoveries.
Figuera Jaimes R., Catelan M., Horne K., Skottfelt J., Snodgrass C.,
Dominik M., Jorgensen U.G., Southworth J., Hundertmark M., Longa-Pena P.,
Sajadian S., Tregolan-Reed J., Hinse T.C., Andersen M.I., Bonavita M.,
Bozza V., Burgdorf M.J., Haikala L., Khalouei E., Korhonen H., Peixinho N.,
Rabus M., Rahvar S.
<Astron. Astrophys. 689, A108 (2024)>
=2024A&A...689A.108F 2024A&A...689A.108F (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry ; Optical
Keywords: instrumentation: detectors - techniques: high angular resolution -
techniques: image processing - stars: variables: RR Lyrae -
globular clusters: individual: Terzan 5
Abstract:
High frame-rate imaging was employed to mitigate the effects of
atmospheric turbulence (seeing) in observations of globular
cluster Terzan 5.
High-precision time-series photometry has been obtained with the
highest angular resolution so far taken in the crowded central region
of Terzan 5, with ground-based telescopes, and ways to avoid
saturation of the brightest stars in the field observed.
The Electron-Multiplying Charge Coupled Device (EMCCD) camera
installed at the Danish 1.54-m telescope at the ESO La Silla
Observatory was employed to produce thousands of short-exposure time
images (ten images per second) that were stacked to produce the
normal-exposure-time images (minutes). We employed difference image
analysis in the stacked images to produce high-precision photometry
using the DanDIA pipeline.
Light curves of 1670 stars with 242 epochs were analyzed in the
crowded central region of Terzan 5 to statistically detect variable
stars in the field observed. We present a possible visual counterpart
outburst at the position of the pulsar J1748-2446N, and the visual
counterpart light curve of the low-mass X-ray binary CX 3.
Additionally, we present the discovery of 4 semiregular variables. We
also present updated ephemerides and properties of the only RR Lyrae
star previously known in the field covered by our observations in
Terzan 5. Finally, we report a significant displacement of two sources
by ∼0.62 and 0.59 arcseconds with respect to their positions in
previous images available in the literature.
Description:
To carry out observations, the Danish 1.54 m telescope was employed.
The MINDSTEp consortium program aimed to explore the Milky Way bulge
for exoplanet detection and characterization, with observations
occurring annually from April to September. However, in cases where
observations of the Galactic bulge were not possible, globular
clusters were utilized as alternatives. Terzan 5 was one of the chosen
globular clusters for these observations. A histogram in Fig. 1
displays the distribution of science images obtained between 2014 and
2021, showing that a total of 242 science images were obtained within
the field of Terzan 5.
I light curves of 45 Terzan 5 variables.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 107 45 Ephemerides and main properties of variable
stars studied in this work
table1.dat 93 10602 Time-series photometry for all known and new
variables in the field of view covered in
Terzan 5
table2.dat 64 3298 Information used to build the CMD for Terzan 5
with data listed in Ortolani et al.
(1996A&A...308..733O 1996A&A...308..733O, Cat. J/A+A/308/733)
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See also:
J/A+A/308/733 : NTT VI photometry in Terzan 5 (Ortolani+ 1996)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- VID Variable ID
5- 6 I2 h RAh Right ascension (J2000)
8- 9 I2 min RAm Right ascension (J2000)
11- 16 F6.3 s RAs Right ascension (J2000)
18 A1 --- DE- Declination sign (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 29 F5.2 arcsec DEs Declination (J2000)
31- 42 F12.4 d Epoch ?=- Epoch used in the phased light curves (HJD)
44- 53 F10.6 d Per ?=- Period estimation obtained in this work
55- 62 F8.6 d e_Per ? Period error
64- 66 A3 --- n_Per Note on Per (1)
68- 73 F6.3 mag Imag ?=- Median I magnitude
75- 78 F4.2 mag Amp ?=- Peak-to-peak amplitude
80- 82 I3 --- N Number of epochs
84- 87 A4 --- Type Classification of the variable
89-107 I19 --- GaiaDR3 ? Gaia DR3 identifier (from table 6)
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Note (1): Periods found using techniques as follows:
a = string length
b = fast chi2
c = least squares
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster [Terzan5] Cluster name
9- 11 A3 --- VID Variable ID
13 A1 --- Filter [I] Filter
15- 27 F13.5 d HJD Heliocentric Julian date of of mid-exposure (UTC)
29- 34 F6.3 mag Imagstd Standard I magnitude
36- 41 F6.3 mag Imaginst Instrumental I magnitude
43- 47 F5.3 mag e_Imaginst I magnitude error
49- 57 F9.3 --- Fref Reference flux of each star detected in the
reference frame (in ADU/s)
59- 65 F7.3 --- e_Fref Fref error (in ADU/s)
67- 76 F10.3 --- Fdiff Difference flux measured in the difference images
at the position of each star detected in the
reference frame (in ADU/s)
78- 85 F8.3 --- e_Fdiff Fdiff error (in ADU/s)
87- 93 F7.4 --- p Photometric scale factor used to scale the
reference frame to each image
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Star ID
6- 12 F7.2 pix Xpos X position
14- 20 F7.2 pix Ypos Y position
22- 27 F6.3 mag Vmag V magnitude
29- 34 F6.3 mag Imag I magnitude
36- 40 F5.3 mag V-I V-I colour index
42- 43 I2 h RAh Right ascension (J2000)
45- 46 I2 min RAm Right ascension (J2000)
48- 52 F5.2 s RAs [0/60] Right ascension (J2000)
54 A1 --- DE- Declination sign (J2000)
55- 56 I2 deg DEd Declination (J2000)
58- 59 I2 arcmin DEm Declination (J2000)
61- 64 F4.1 arcsec DEs [0/60] Declination (J2000)
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Acknowledgements:
Roberto Figuera Jaimes, robertofiguera(at)gmail.com
(End) Patricia Vannier [CDS] 27-Aug-2024