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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
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: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 06 30.4 -64 19 NGC 2257 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
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 71 9 Derived properties of the field variables
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
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
Note (1): Alcaino I in Alcaino & Alvarado, 1988AJ.....95.1724A.
Byte-by-byte Description of file: table9.dat table11.dat
Bytes Format Units Label Explanations
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 <B>-<V> ? <Bmag> minus <Vmag> 41 A1 --- u_<B>-<V> 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
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) 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.
History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 29-Apr-1997
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