J/AJ/98/2086 CCD photometry of NGC 2257 RR Lyrae (Walker 1989)
CCD photometry of the RR Lyrae variables in the LMC cluster NGC 2257
and the adjacent field
Walker A.R.
<Astron. J. 98, 2086 (1989)>
=1989AJ.....98.2086W 1989AJ.....98.2086W
ADC_Keywords: Stars, variable ; Photometry, CCD
Abstract:
B and V band CCD photometry is used to study 33 cluster and nine field
RR Lyrae variables near the LMC cluster, NGC 2257. It is found that
the mean magnitudes for the two groups differ by 0.17 mag. The cluster
and field variables both have an Fe/H abundance ratio of -1.8±0.1.
The results are compared used to compare NGC 2257 with galactic
globular clusters, showing that NGC 2257 is indistinguishable from its
local counterparts.
Objects:
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RA (2000) DE Designation(s)
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06 30.4 -64 19 NGC 2257
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 27 462 Photometry for the NGC 2257 non-variables
table9.dat 71 33 Derived properties of the NGC 2257 variables
table11.dat 65 9 Derived properties of the field variables
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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- 3 I3 --- Seq Star sequential number
5- 9 F5.1 arcsec Xoff X offset from star 78 (Alcaino I) (+=West) (1)
11- 15 F5.1 arcsec Yoff Y offset from star 78 (Alcaino I) (+=North) (1)
17- 21 F5.2 mag Vmag V magnitude
23- 27 F5.2 mag B-V B-V colour index
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Note (1): Alcaino I in Alcaino & Alvarado, 1988AJ.....95.1724A 1988AJ.....95.1724A.
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Byte-by-byte Description of file: table9.dat table11.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Star Star number (1)
7- 15 F9.7 d Per Period (1)
17- 18 A2 --- Type Variable type
20- 25 F6.3 mag <Vmag> ? Intensity mean V magnitude
26 A1 --- u_<Vmag> Uncertainty flag on <Vmag>
28- 33 F6.3 mag <Bmag> ? Intensity mean B magnitude
34 A1 --- u_<Bmag> Uncertainty flag on <Bmag>
36- 40 F5.3 mag - ? <Bmag> minus <Vmag>
41 A1 --- u_- Uncertainty flag on <Bmag>-<Vmag>
43- 47 F5.3 mag <B-V> ? B-V magnitude mean
48 A1 --- u_<B-V> Uncertainty flag on <B-V>
50- 53 F4.2 mag AV ? V amplitude
54 A1 --- u_AV Uncertainty flag on AV
56- 59 F4.2 mag AB ? B amplitude
60 A1 --- u_AB Uncertainty flag on AB
62- 65 F4.2 --- Rise ? Rise time to maximum (in phase units)
66 A1 --- u_Rise Uncertainty flag on Rise
68- 71 F4.2 --- Phase ? Phase at the maximum light
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Note (1): Star number and period come from NHH (Nemec et al.
1985ApJS...57..329) for V1 to V44 (cluster stars), and from NHU
(Nemec et al. 1985ApJS...57..287N 1985ApJS...57..287N) for 4-digit numbers (field stars).
For NHH stars, the period given here is that adopted by NHH, and
corresponds to the epoch given by these authors (Tables V, VI of NHH).
The phase at maximum light in February 1988 (column Phase) corresponds
to this ephemeris. See text for revised periods and period change
rates for many of these stars.
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History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 29-Apr-1997