J/MNRAS/532/2159 Variable stars in the field of NGC 6558 (Arellano Ferro+, 2024)
The variable stars in the field of the bulge cluster NGC 6558
Arellano Ferro A., Zerpa Guillen L.J., Yepez M.A., Bustos Fierro I.H..,
Prudil Z., Perez Parra C.E.
<Mon. Not. R. Astron. Soc., 532, 2159-2173>
=2024MNRAS.532.2159A 2024MNRAS.532.2159A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry ; Optical
Keywords: star: horizontal branch - stars: variables: RR Lyrae -
stars: fundamental parameters -
globular clusters: individual (NGC 6558)
Abstract:
We made a survey of the variable stars in a 13.2x13.2 arcmin2
centred on the field of the Galactic bulge cluster NGC 6558. A total
of 78 variables were found in the field of the cluster. Many of these
variables are included in the catalogue of variable stars in Galactic
globular clusters (Clement et al. 2001), OGLE or Gaia DR3 data
releases. A membership analysis based on the proper motions of Gaia
DR3 revealed that many of these variables do not belong to the
cluster. We employed the data from the aforementioned surveys and our
own data in the VI photometric system to estimate the periods, which
along with the light-curves morphology and position in a deferentially
dereddened colour-magnitude diagram (CMD), help classifying the
variable types. Two new member variables were found; an eclipsing
binary (V18) and a semiregular SR/L (V19). In the end, we conclude
that only nine variables are likely cluster members. Member variables
were used to discuss the mean metallicity and distance of the parental
cluster and find the average values.
Description:
The data used in this work were obtained at the Bosque Alegre
Astronomical Station (EABA), of the National Observatory of Cordoba,
Argentina during August-September 2018 and between June and August
2019. Two different detectors were used; a CCD KAF-16803 (2018) and
CCD KAF-6303E (2019 covering a field of 16.9x16.9 arcmin2 and
12.6x8.4 arcmin2 respectively. The data reductions were carried out
with the DanDIA pipeline (Bramich, 2008MNRAS.386L..77B 2008MNRAS.386L..77B; Bramich et
al., 2013MNRAS.428.2275B 2013MNRAS.428.2275B). A membership analysis was performed using
the Gaia-DR3 proper motions and our V and I time-series CCD photometry
was employed to produce a clean color-magnitude diagram and to study
the variable stars in the cluster. Two new variables are announced.
Member variables were used to discuss the mean metallicity and
distance of the parental cluster and find the average values for
NGC 6558.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea.dat 125 78 *General data for variables in the field of the
cluster (table A2) and crossmatch between
OGLE and Gaia DR3 (table A1)
table3.dat 50 11553 VI photometry of 11 variables in the field
of NGC 6558
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Note on tablea.dat: The large majority are not cluster member stars.
All periods and epochs were estimated in this work.
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/AcA/69/321 : OGLE RR Lyrae stars in Galactic bulge & disk (Soszynski+, 2019)
Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- LC [LC] indicates available light curves
4- 6 A3 --- VName Variable name
8- 12 A5 --- AName Other identifier
14- 18 A5 --- Vtype Variable type
20- 25 F6.3 mag <Vmag> ?=- Mean V magnitude
27- 32 F6.3 mag <Imag> Mean I magnitude
34- 38 F5.3 mag AV ?=- Amplitude of variation in V
40- 44 F5.3 mag AI ?=- Amplitude of variation in I
46- 55 F10.6 d Per ?=- Period
57- 66 F10.5 d Epoch ?=- Epoch (JD-2450000)
68- 69 I2 h RAh Right ascension (J2000)
71- 72 I2 min RAm Right ascension (J2000)
74- 78 F5.2 s RAs Right ascension (J2000)
80 A1 --- DE- Declination sign (J2000)
81- 82 I2 deg DEd Declination (J2000)
84- 85 I2 arcmin DEm Declination (J2000)
87- 91 F5.2 arcsec DEs Declination (J2000)
93 A1 --- Flag [mfu-] Flag (1)
95-105 A11 --- OGLE OGLE name
107-125 I19 --- GaiaDR3 ? GaiaDR3 name
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Note (1): Flag as follows:
m = cluster member
f = field star
u = unknown due to lack of proper motion
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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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2- 4 A3 --- VName Variable name
10 A1 --- Filter [VI] Observation filter
15- 27 F13.5 d HJD Heliocentric Julian date
30- 35 F6.3 mag magst Standard magnitude
38- 43 F6.3 mag maginst Instrumental magnitude
46- 50 F5.3 mag e_maginst Error on the magnitude
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Acknowledgements:
Armando Arellano Ferro, armando(at)astro.unam.mx
(End) A. Arelano Ferro [IA-UNAM, Mexico], P. Vannier [CDS] 09-Aug-2024