J/A+A/548/A92 VrI light curves of NGC1904 variables (Kains+, 2012)
Constraining the parameters of globular cluster NGC 1904 from its variable star
population.
Kains N., Bramich D.M., Figuera Jaimes R., Arellano Ferro A., Giridhar S.,
Kuppuswamy K.
<Astron. Astrophys. 548, A92 (2012)>
=2012A&A...548A..92K 2012A&A...548A..92K
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry, CCD
Keywords: stars: variable: RR Lyrae - globular clusters: individual: NGC 1904
Abstract:
We present the analysis of 11 nights of V and I time-series
observations of the globular cluster NGC 1904 (M 79). Using this we
searched for variable stars in this cluster and attempted to refine
the periods of known variables, making use of a time baseline spanning
almost 8 years. We use our data to derive the metallicity and distance
of NGC 1904.
We used difference imaging to reduce our data to obtain high-precision
light curves of variable stars. We then estimated the cluster
parameters by performing a Fourier decomposition of the light curves
of RR Lyrae stars for which a good period estimate was possible. We
also derive an estimate for the age of the cluster by fitting
theoretical isochrones to our colour-magnitude diagram (CMD).
Out of 13 stars previously classified as variables, we confirm that 10
are bona fide variables. We cannot detect variability in one other
within the precision of our data, while there are two which are
saturated in our data frames, but we do not find sufficient evidence
in the literature to confirm their variability. We also detect a new
RR Lyrae variable, giving a total number of confirmed variable stars
in NGC 1904 of 11. Using the Fourier parameters, we find a cluster
metallicity [Fe/H]ZW=-1.63±0.14, or [Fe/H]UVES=-1.57±0.18,
and a distance of 13.3±0.4kpc (using RR0 variables) or 12.9kpc
(using the one RR1 variable in our sample for which Fourier
decomposition was possible).
Description:
V, I and r time-series photometry and difference imaging parameters
for all confirmed variables in NGC 1904.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table43.dat 101 11 Data for all confirmed variable stars in NGC1904
table2.dat 81 2511 *V, I and r lightcurves
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Note on table2.dat: r light curves were not used in the paper but are
supplied as they might be of use for future work.
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See also:
J/MNRAS/413/1275 : VrI light curves of NGC6981 variables (Bramich+, 2011)
Byte-by-byte Description of file: table43.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- VName Variable ID (VNN)
5- 6 I2 h RAh Right ascension (J2000) (1)
8- 9 I2 min RAm Right ascension (J2000) (1)
11- 15 F5.2 s RAs Right ascension (J2000) (1)
17 A1 --- DE- Declination sign (J2000) (1)
18- 19 I2 deg DEd Declination (J2000) (1)
21- 22 I2 arcmin DEm Declination (J2000) (1)
24- 27 F4.1 arcsec DEs Declination (J2000) (1)
29- 37 F9.4 d Ep ? Epoch (HJD-2450000)
39- 46 F8.6 d Per ? Period (2)
48- 56 F9.7 d Per1 ? Amigo et al. (2011, in RR Lyrae stars,
Metal-poor stars and the Galaxy, ed. A.
McWilliam, 127) period
58- 65 F8.6 d Per2 ? Rosino (1952MmSAI..23..101R 1952MmSAI..23..101R) period
66- 70 F5.2 mag <Vmag> Intensity-weighted mean V magnitude
71 A1 --- n_<Vmag> [b] Note on <Vmag> (3)
73- 77 F5.2 mag <Imag> ? Intensity-weighted mean I magnitude
78 A1 --- n_<Imag> [b] Note on <Imag> (3)
80 A1 --- l_Vamp [~] Limit flag on Vamp
81- 84 F4.2 mag Vamp Amplitude in V band
86 A1 --- l_Iamp [~] Limit flag on Iamp
87- 90 F4.2 mag Iamp Amplitude in I band
92-100 A9 --- VType Variable type
101 A1 --- n_VType [a] Note on VType (1)
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Note (1): Coordinates derived from our astrometric fit to the V-band reference
image.
Note (2): Periods are determined using phase dispersion minimisation (PDM)
and the string length method (see text)
Note (3): Notes as follows:
a = potentially RRd, see text
b = error-weighted mean magnitudes, rather than intensity-weighted magnitudes
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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- 3 A3 --- VName Variable ID (VNN), as in table4
5 A1 --- Filter [VIr] Observation filter
7- 19 F13.5 d HJD Heliocentric Julian date
21- 26 F6.3 mag mag.s Standard magnitude
28- 33 F6.3 mag mag.i Instrumental magnitude
35- 39 F5.3 mag e_mag.i Error on the magnitude
41- 49 F9.3 s-1 Fref Reference flux (in ADU/s)
51- 56 F6.3 s-1 e_Fref Error on the reference flux (in ADU/s)
58- 67 F10.3 s-1 DFlux Differential flux (in ADU/s)
69- 74 F6.3 s-1 e_DFlux Error on the differential flux (in ADU/s)
76- 81 F6.4 --- p Photometric scale factor
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Acknowledgements:
Noe Kains, nkains(at)eso.org
(End) Patricia Vannier [CDS] 16-Nov-2012