J/MNRAS/424/2722 Variable stars in NGC 5024 (M53) (Bramich+, 2012)
Investigation of variable star candidates in the globular cluster
NGC 5024 (M53).
Bramich D.M., Arellano Ferro A., Figuera Jaimes R., Giridhar S.
<Mon. Not. R. Astron. Soc., 424, 2722-2732 (2012)>
=2012MNRAS.424.2722B 2012MNRAS.424.2722B
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry
Keywords: stars: variables: general, globular clusters: individual: NGC 5024
Abstract:
We have performed a careful investigation of the 74 candidate variable
stars presented by Safonova & Stalin (2011AJ....142..179S 2011AJ....142..179S) . For this
purpose we used our data base of imaging and light curves from
Arellano Ferro et al. (J/MNRAS/416/2265 and J/MNRAS/420/1333). We find
that two candidates are known variable stars, eight candidates were
discovered first by Arellano Ferro et al. (J/MNRAS/416/2265), but
would not have been known to Safonova & Stalin (2011AJ....142..179S 2011AJ....142..179S)
at the time of their paper submission, while four candidates are new
variables. Three of the new variables are SX Phe type and one is a
semiregular (SR) type red giant variable. We also tentatively confirm
the presence of true variability in two other candidates, and we are
unable to investigate another four candidates because they are not in
our data base. However, we find that the remaining 54 candidate
variable stars are spurious detections where systematic trends in the
light curves have been mistaken for true variability. We believe that
the erroneous detections are caused by the adoption of a very low
detection threshold used to identify these candidates.
Description:
Time-series V and I photometry for all the SX Phe and long-period
variables in NGC 5024 from the works of Arellano Ferro et al. (2011,
Cat. J/MNRAS/416/2265), Arellano Ferro et al. (2012, Cat.
J/MNRAS/420/1333) and this work. We list standard and instrumental
magnitudes and their uncertainties corresponding to the variable star
identification, filter, and epoch of mid-exposure. For completeness,
we also list the reference flux, difference flux, and photometric
scale factor, along with the uncertainties on the reference and
difference fluxes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 41 33 List of studied stars
table2.dat 81 19580 Time series V and I photometry for all the
SX Phe and long-period variables in NGC 5024
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See also:
J/AJ/116/1775 : BV photometry of M53 (Rey+, 1998)
J/PAZh/23/454 : Identification and coordinates in M 53 (Evstigneeva+, 1997)
J/A+A/358/547 : M53 variable stars V light curves (Kopacki, 2000)
J/A+A/507/803 : VI photometry of new M53 variables (Dekany+, 2009)
J/MNRAS/416/2265 : Variable stars in NGC 5024 (M53) (Arellano Ferro+, 2011)
J/MNRAS/420/1333 : Variable stars in NGC 5024 (M53) (Arellano Ferro+, 2012)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Variable star Name
6- 7 I2 h RAh Simbad Right ascension (J2000)
9- 10 I2 min RAm Simbad Right ascension (J2000)
12- 16 F5.2 s RAs Simbad Right ascension (J2000)
18 A1 --- DE- Simbad Declination sign (J2000)
19- 20 I2 deg DEd Simbad Declination (J2000)
22- 23 I2 arcmin DEm Simbad Declination (J2000)
25- 28 F4.1 arcsec DEs Simbad Declination (J2000)
30- 39 F10.7 d Per Period
41 A1 --- n_Per [abc*] Reference for period (1)
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Note (1): References for period as follows:
a = Arellano Ferro et al., 2011, Cat. J/MNRAS/416/2265
b = Period in "Mode 1", Arellano Perro et al., 2011, Cat. J/MNRAS/416/2265
* = Dekany & Kovacs, 2009 Cat. J/A+A/507/803
c = this paper
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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 A4 --- VName Variable star ID
6 A1 --- Filter [VI] Observation filter
8- 20 F13.5 d HJD Heliocentric Julian date at mid-exposure
22- 27 F6.3 mag magst Standard magnitude
29- 34 F6.3 mag maginst Instrumental magnitude
36- 40 F5.3 mag e_maginst Magnitude uncertainty (standard or instrumental)
42- 50 F9.3 s-1 Fref Reference flux (in ADU/s unit) (1)
52- 56 F5.3 s-1 e_Fref Reference flux uncertainty (in ADU/s unit)
58- 66 F9.3 s-1 DFlux Difference flux (in ADU/s unit) (1)
68- 74 F7.3 s-1 e_DFlux Difference flux uncertainty (in ADU/s unit)
76- 81 F6.4 --- p Photometric scale factor (1)
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Note (1): Light curves for each star were constructed by calculating the total
flux ftot(t) in adu/s at each epoch t from
ftot(t)=fref+fdiff(t)/p(t)
where fref is the reference flux (adu/s), fdiff(t) is the
differential flux (adu/s) and p(t) is the photometric scalefactor (the
integral of the kernel solution)
Conversion to instrumental magnitudes was achieved using
mins(t)=25.0-2.5log(ftot(t))
where mins(t) is the instrumental magnitude of the star at time t.
Uncertainties were propagated in the correct analytical fashion.
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Acknowledgements:
Daniel Bramich, dbramich(at)eso.org
(End) Daniel Bramich [ESO, Germany], Patricia Vannier [CDS] 31-Jan-2013