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J/AJ/122/2569       VI photometry of NGC 288, 362 and 1851   (Bellazzini+, 2001)

Age as the second parameter in NGC 288/NGC 362? I. Turnoff ages: a purely differential comparison. Bellazzini M., Pecci F.F., Ferraro F.R., Galleti S., Catelan M., Landsman W.B. <Astron. J. 122, 2569 (2001)> =2001AJ....122.2569B
ADC_Keywords: Clusters, globular ; Photometry, CCD Keywords: color-magnitude diagrams - globular clusters: general - globular clusters: individual (NGC 288, NGC 362, NGC 1851) - stars: horizontal-branch - stars: Population II Abstract: We present deep V, I photometry of the globular clusters NGC 288, 362, and 1851 obtained during a single observational run under strictly homogeneous conditions. We use the bimodal horizontal branch (HB) of NGC 1851 as a "bridge" to obtain the optimum relative match between the HBs of NGC 288 and NGC 362. In this way we can effectively remove the uncertainties associated with distance, reddening, and inhomogeneities in the absolute calibration, thus obtaining a very robust, purely differential estimate of the age difference between these two clusters. According to the bridge test, NGC 288 is found to be older than NGC 362 by 2±1Gyr. The observations were carried out during the nights of 1997 January 2 and 3 at the 2.2 m ESO/MPI telescope at La Silla (Chile), with the EFOSC2 camera equipped with a Loral/Lesser 2048x2048 pixel CCD. The pixel scale is 0.26"/pix, and the effective field of view is 8x8arcmin2. The gain is 1.63 e-ADU-, and the readout noise is 6.3 e-rms. The seeing conditions were average during the January 2 night (∼1.3") when the NGC 1851 and NGC 288 observations were carried out, and they worsened (∼2") during the second night when we observed NGC 362. Objects: ----------------------------------------- RA (2000) DE Designation(s) ----------------------------------------- 00 52 45.3 -26 34 43 NGC 288 01 03 14.3 -70 50 54 NGC 362 05 14 06.3 -40 02 50 NGC 1851 ----------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 65 10990 Photometry of NGC 288 table2.dat 65 9118 Photometry of NGC 1851 table3.dat 65 7492 Photometry of NGC 362
Byte-by-byte Description of file: table1.dat table2.dat table3.dat
Bytes Format Units Label Explanations
1- 5 I5 --- BPF Object identification (1) 8- 13 F6.3 mag Vmag The V band magnitude 16- 20 F5.3 mag e_Vmag Error in Vmag 23- 28 F6.3 mag Imag The I band magnitude 31- 35 F5.3 mag e_Imag Error in Imag 39- 45 F7.2 pix Xpix The X pixel position (2) 48- 55 F8.2 pix Ypix The Y pixel position (2) 58- 65 A8 --- Name Other object identification (3)
Note (1): In Simbad, the designations are: Cl* NGC 288 BPF NNNNN in table1.dat Cl* NGC 1851 BPF NNNN in table2.dat Cl* NGC 362 BPF NNNN in table3.dat Note (2): 1 pix = 0.26" Note (3): Other object identification: V# = Cl* NGC AAAA SAW VNN in Simbad e.g. Cl* NGC 288 Saw VN, RR Lyrae variables found by Kaluzny (1996A&AS..120...83K) in table1.dat, Cl* NGC 1851 SAW VNN, RR Lyrae variables in common with Walker (1998AJ....116..220W) in table2.dat Cl* NGC 362 SAW VNNN, RR Lyrae variables identified in the Sawyer-Hogg (1973, updated by C. Clement, 1997, Cat. V/97), in table3.dat Guo 4110 = A non member star identified in the proper motions database by Guo (1995, Ph.D. thesis, Yale Univ.); EHB1 = The extreme HB star identified by Bellazzini & Messineo (1999, in The Chemical Evolution of the Milky Way: Stars versus Clusters, ed. F. Matteucci & F. Giovannelli (Dordrecht: Kluwer), 213). UIT-# = UV sources identified by the UIT satellite (see Cat. VI/104) PNM = probable non member (only for stars near the HB) according to Tucholke (1992, Cat. J/A+AS/93/311). MJ #### = Cl* NGC 362 MJ NNNNN, BHB star that is a confirmed member of the cluster according to Moehler et al. (2000A&A...361..937M).
History: From electronic version of the journal Comments: Modifications made from the original: in "Other object identification" column for Cl* NGC 1851 BPF 617, No 8 identified to Cl* NGC 1851 SAW V8 for Cl* NGC 362 BPF 1898, No 3 identified to Cl* NGC 362 SAW V3 for Cl* NGC 362 BPF 134, No 5 identified to Cl* NGC 362 SAW V5 References: Catelan, 2000ApJ...531..826C Catelan et al., 2001ApJ...560..970C Catelan et al., paper II 2001AJ....122.3171C
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 18-Jan-2002
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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