J/MNRAS/511/1285 M14 (NGC 6402). Variable stars VI light curves (Yepez+, 2022)
A new photometric study of M14 (NGC 6402):
an interpretation of the horizontal branch and beyond.
Yepez M.A., Arellano Ferro A., Deras D., Bustos Fierro I., Muneer S.,
Schroder K.-P.
<Mon. Not. R. Astron. Soc., 511, 1285-1302 (2022)>
=2022MNRAS.511.1285Y 2022MNRAS.511.1285Y (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, VRI ;
Keywords: stars: fundamental parameters - stars: horizontal branch -
stars: variables: RR Lyrae - globular clusters: individual: (M14)
Abstract:
We present a CCD VI photometric study of the globular cluster M14.
Particular attention is given to the variable stars. This allowed new
classifications and cluster membership considerations. New variables
are reported: 3 RRc, 18 SR, and 1 SX Phe. The Fourier decomposition of
RR Lyrae light curves lead to the mean cluster metallicity of
[Fe/H]zw≃1.3±0.2. Several independent methods yield a mean
distance of 9.36±0.16kpc. A colour-magnitude diagram outlined by
the cluster members enabled a matching with theoretical predictions of
isochrones and zero-age horizontal branches (HBs), whose fitting to
the observations is in good agreement with the above distance and
metallicity. The Oosterhoff type of M14 is confirmed as Oo-int, and
the pulsating mode distribution of RR Lyrae stars on the HB shows that
the bimodal region of the instability strip is shared by RRab and RRc
stars. By modelling the mass-loss at the red giant branch after the He
flash events, we were able to represent the blue tail of the HB, using
a core mass of 0.48M☉ and total masses of 0.52-0.55M☉.
A progenitor star on the main sequence (MS) of 0.84M☉ reaches
the HB in about 12.5Gyr, consonant with previous age determinations
of the cluster. Type II Cepheids of M14 may be interpreted as products
of post-HB evolution, driven by the complex processes involving the
burning of the very thin low mass hydrogen and helium shells of these
stars and their minuscule envelopes. No pieces of evidence were found
in favour of M14 being of extragalactic origin.
Description:
The CCD VI observations of M14 employed in this work were obtained
at two sites. The first set of observations were performed with the
0.84-m telescope at the San Pedro Martir observatory, in Baja
California, Mexico in two different seasons: between 2018 June and
August. The detector used was a Spectral Instruments CCD of
1024x1024-pixels with a scale of 0.444-arcsec/pixel, resulting in an
FoV of approximately 7.57x7.57-arcmin2, and between 2019 May and July,
when the detector was a Marconi5 CCD of 1024x1032-pixels with a scale
of 0.493-arcsec/pixel for an FoV of 8.41x8.48-arcmin2. The
second set of observations made between 2020 August and October
(hereafter Han20) come from 2.0-m telescope at the Indian Astronomical
Observatory (IAO), Hanle, India. The detector used was a Thompson
grade 0 ED2V 4482-0-E93 CCD of 2048x2048 pixels with a scale of
0.296-arcsec/pixel, translating into an FoV of approximately
10.1x10.1-arcmin2.
V and I time-series CCD photometry for known and newly reported
variables in the 10.1'x10.1' filed of view of NGC 6402 (M14).
Objects:
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RA (2000) DE Designation(s)
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17 37 36.15 -03 14 45.3 NGC 6402 = M 14
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 88 158 Variable stars in the field of NGC 6402 (M14)
table3.dat 50 211001 Time-series V and I photometry for variables
in the field of NGC 6402 (M14)
lc/* . 4 Light curve files in pdf
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See also:
J/AJ/146/57 : NGC 6402. I. BV photometry (Contreras Pena+, 2013)
J/AJ/155/116 : NGC 6402. II. Variable stars (Contreras Pena+, 2018)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- VName Variable name, VNNN (V1-V194)
5 A1 --- n_VName [ab] Note on VName (1)
7 A1 --- T3 [n] n when no light curve data in table3
9- 13 A5 --- VType Variable Type
15- 20 F6.3 mag Vmag ?=- Intensity weighted V magnitude
22- 27 F6.3 mag Imag ?=- Intensity weighted I magnitude
29- 33 F5.3 mag AV ?=- V amplitude
35- 39 F5.3 mag AI ?=- I amplitude
41- 50 F10.6 d Per ?=- Period this work
52- 60 F9.4 d Epoch ?=- Epoch
62- 63 I2 h RAh Right ascension (J2000.0)
65- 66 I2 min RAm Right ascension (J2000.0)
68- 72 F5.2 s RAs Right ascension (J2000.0)
74 A1 --- DE- Declination sign (J2000.0)
75- 76 I2 deg DEd Declination (J2000.0)
78- 79 I2 arcmin DEm Declination (J2000.0)
81- 84 F4.1 arcsec DEs Declination (J2000.0)
86- 88 A3 --- Memb [mf-?/] Membership, this work
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Note (1): Note as follows:
a = Out of the field of our images
b = Newly reported in this work.
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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2- 5 A4 --- VName Variable name
10 A1 --- Filter [VI] Observation filter
15- 27 F13.5 d HJD Epoch of mid-exposure (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 (1)
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Note (1): The uncertainty on maginst, which also corresponds to the
uncertainty on magst.
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Acknowledgements:
Armando Arellano Ferro, armando(at)astro.unam.mx
(End) A. Arelano Ferro [IA-UNAM, Mexico], P. Vannier [CDS] 29-Jul-2022