J/MNRAS/416/2265 Variable stars in NGC 5024 (M53) (Arellano Ferro+, 2011)
Exploring the variable stars in the globular cluster NGC 5024 (M53):
new RR Lyrae and SX Phoenicis stars.
Arellano Ferro A., Figuera Jaimes R., Giridhar S., Bramich D.M.,
Hernandez Santisteban J.V., Kuppuswamy K.
<Mon. Not. R. Astron. Soc., 416, 2265-2284 (2011)>
=2011MNRAS.416.2265A 2011MNRAS.416.2265A
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry
Keywords: stars: variables: RR Lyrae - globular clusters: individual: NGC 5024
Abstract:
We report CCD V and I time series photometry of the globular cluster
NGC 5024 (M53). The technique of difference image analysis has been
used which enables photometric precisions better than 10mmag for
stars brighter than V∼18.5mag even in the crowded central regions
of the cluster. The high photometric precision has resulted in the
discovery of two new RR1 stars and 13 SX Phe stars. A detailed
identification chart is given for all the variable stars in the field
of our images of the cluster. Periodicities were calculated for all RR
Lyrae and SX Phe stars and a critical comparison is made with previous
determinations.
Description:
The observations employed in the present work were performed using the
Johnson V and I filters on 2009 April 17, 18 and 19, on 2010 January
22 and 23, February 21 and 22, March 7 and 8, April 7 and 25, and May
6. A total of 177 epochs in the V filter and 184 in the I filter were
obtained. The 2.0-m telescope of the Indian Astronomical Observatory
(IAO), Hanle, India, located at 4500 m above sea level, was used. The
estimated seeing was ∼1arcsec. The detector was a Thompson CCD of
2048x2048pixels with a pixel scale of 0.296arcsec/pix and a
field of view of approximately 10.1x10.1arcmin2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 91 71 General data for confirmed variables in NGC 5024
table3.dat 87 28 Fourier coefficients Ak for k=0,1,2,3,4, and phases
φ(21, 31 and 41) for the 19 RR0-type and 9
RR1-type variables for which the Fourier
decomposition fit was successful
table6.dat 181 13 Frequencies and amplitudes of the newly found
SX Phe stars
table7.dat 42 5 Blue stragglers whose variability is to be confirmed
table1.dat 79 30907 Time series V and I photometry for all the
confirmed variables in our field of view
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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 name (V1-V92)
7- 13 A7 --- Type Bailey's type
15- 17 A3 --- OType Other type
19- 27 F9.6 d Per ? Period, this work
28 A1 --- n_Per [a] a: adopted from Dekany & Kovacs 2009
(Cat. J/A+A/507/803)
30- 38 F9.3 d Tmax ? Date of maximum light (HJD-2400000)
41- 46 F6.4 d Per2 ? Period from Jeon et al, 2003AJ....125.3165J 2003AJ....125.3165J
48- 56 F9.7 d Per3 ? Period from Kopacki, 2000 Cat. J/A+A/358/547
58- 67 F10.7 d Per4 ? Period from Dekany & Kovacs, 2009
Cat. J/A+A/507/803
69- 70 I2 h RAh Right ascension (J2000)
72- 73 I2 min RAm Right ascension (J2000)
75- 79 F5.2 s RAs Right ascension (J2000)
81 A1 --- DE- Declination sign (J2000)
82- 83 I2 deg DEd Declination (J2000)
85- 86 I2 arcmin DEm Declination (J2000)
88- 91 F4.1 arcsec DEs Declination (J2000)
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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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1- 3 A3 --- Type [RR0/RR1] Variability type
5- 8 A4 --- VName Variable star ID (V1-V92)
10- 15 F6.3 mag A0 Fourier coefficient A0 (V mag)
17 I1 mmag e_A0 rms uncertainty on A0
19- 23 F5.3 mag A1 Fourier coefficient A1 (V mag)
25 I1 mmag e_A1 rms uncertainty on A1
27- 31 F5.3 mag A2 Fourier coefficient A2 (V mag)
33 I1 mmag e_A2 rms uncertainty on A2
35- 39 F5.3 mag A3 ?=- Fourier coefficient A3 (V mag)
41 I1 mmag e_A3 ? rms uncertainty on A3
43- 47 F5.3 mag A4 ?=- Fourier coefficient A4 (V mag)
49 I1 mmag e_A4 ? rms uncertainty on A4
51- 55 F5.3 rad phi21 Phase φ21
57- 59 I3 mrad e_phi21 rms uncertainty on phi21
61- 65 F5.3 rad phi31 ?=- Phase φ31
67- 69 I3 mrad e_phi31 ? rms uncertainty on phi31
71- 75 F5.3 rad phi41 ?=- Phase φ41
77- 80 I4 mrad e_phi41 ? rms uncertainty on phi41
82- 83 I2 --- N Number of harmonics used to fit the light
curve of each variable
85- 87 F3.1 --- Dm ? Deviation parameter (see Section 4.3)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Variable name (V93-V105)
5 A1 --- n_VName [a] small amplitude (1)
7- 12 F6.3 mag Vmag V magnitude
14- 18 F5.3 mag V-I V-I colour index
20- 21 I2 h RAh Right ascension (J2000.0)
23- 24 I2 min RAm Right ascension (J2000.0)
26- 30 F5.2 s RAs Right ascension (J2000.0)
32 A1 --- DE- Declination sign (J2000.0)
33- 34 I2 deg DEd Declination (J2000.0)
36- 37 I2 arcmin DEm Declination (J2000.0)
39- 42 F4.1 arcsec DEs Declination (J2000.0)
44- 51 F8.5 d-1 Freq1 Frequency in mode "Mode1"
53- 54 I2 10-5d-1 e_Freq1 rms uncertainty on Freq1
56- 60 F5.3 mag A1 Amplitude in mode "Mode1"
62- 63 I2 mmag e_A1 rms uncertainty on A1
65- 71 F7.5 d Per1 Period in mode "Mode1"
73- 82 A10 --- Mode1 First mode identification (2)
84- 91 F8.5 d-1 Freq2 ? Frequency in mode "Mode2"
93- 94 I2 10-5d-1 e_Freq2 ? rms uncertainty on Freq2
96-100 F5.3 mag A2 ? Amplitude in mode "Mode2"
102-103 I2 mmag e_A2 ? rms uncertainty on A
105-111 F7.5 d Per2 ? Period in mode "Mode2"
113-131 A19 --- Mode2 Second mode identification (2)
133-140 F8.5 d-1 Freq3 ? Frequency in mode "Mode3"
142-143 I2 10-5d-1 e_Freq3 ? rms uncertainty on Freq
145-149 F5.3 mag A3 ? Amplitude in mode "Mode3"
151-152 I2 mmag e_A3 ? rms uncertainty on A
154-160 F7.5 d Per3 ? Period in mode "Mode3"
162-181 A20 --- Mode3 Third mode identification (2)
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Note (1): a: Although clear variations are seen and a distinctive peak is
seen in the frequency spectrum, the amplitude is very small.
Note (2): Mode is
F = Fundamental mode;
1O = First overtone;
2O = Second overtone.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- VName Variable name (S1-S5)
7- 12 F6.3 mag Vmag V magnitude
14- 19 F6.3 mag V-I V-I colour index
21- 22 I2 h RAh Right ascension (J2000.0)
24- 25 I2 min RAm Right ascension (J2000.0)
27- 30 F4.1 s RAs Right ascension (J2000.0)
32 A1 --- DE- Declination sign (J2000.0)
33- 34 I2 deg DEd Declination (J2000.0)
36- 37 I2 arcmin DEm Declination (J2000.0)
39- 42 F4.1 arcsec DEs Declination (J2000.0)
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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- 4 A4 --- VName Variable name (S1-S5, V1-V105)
6 A1 --- Band [VI] Observed band
8- 20 F13.5 d HJD Heliocentric Julian date
22- 27 F6.3 mag mag Standard magnitude, in Band
29- 34 F6.3 mag magi Instrumental magnitude, in Band
36- 40 F5.3 mag e_mag rms uncertainty on mag
42- 49 F8.3 s-1 fref Reference flux (in ADU/s) (1)
51- 55 F5.3 s-1 e_fref rms uncertainty on fref (in ADU/s)
57- 65 F9.3 s-1 fdiff Differential flux (in ADU/s) (1)
67- 72 F6.3 s-1 e_fdiff rms uncertainty on fdiff
74- 79 F6.4 --- p Photometric scalefactor (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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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Apr-2012