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J/AJ/99/1831        M 68 BVRI photometry (Alcaino+ 1990)

BVRI CCD photometry of the metal-poor globular cluster M68 (NGC 4590) Alcaino G., Liller W., Alvarado F., Wenderoth E. <Astron. J. 99, 1831 (1990)> =1990AJ.....99.1831A
ADC_Keywords: Clusters, globular ; Photometry, CCD Abstract: We present BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) observed with a CCD camera and the 2.2m telescope at ESO/La Silla, and have compared our BV color-magnitude diagrams with the observational results of a previous research. At magnitudes V<22, our BV results, obtained using the INVENTORY code, are in very close agreement with those of the other authors who used DAOPHOT in their reductions. At fainter levels, selection effects appear to affect INVENTORY more than DAOPHOT. We find that VTO-HB=3.42±0.10, in accord with values found for other clusters. The comparison between our four-color observations and the theoretical isochrones consistently yield a cluster age of 13Gyr with a likely external uncertainty of 2 or 3Gyr. Our derived values for the interstellar reddening at longer wavelengths are generally in agreement (±0.02mag) with what would be expected assuming E(B-V)=0.07mag and (m-M)V=15.25. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 12 39 27.9 -26 44 35 M 68 = NGC 4590 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table6.dat 52 685 CCD magnitudes and colors for 685 stars in NGC 4590
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
1- 3 I3 -- Star Star number 5- 6 A2 --- Saw Sawyer Hogg name (1973PDDO....3....6S) 8- 10 I3 pix Xpos X position (2) 12- 14 I3 pix Ypos Y position (2) 16- 21 F6.3 mag Vmag V magnitude 23- 27 F5.3 mag B-V ? B-V colour index 29- 33 F5.3 mag V-R ? V-R colour index 35- 39 F5.3 mag R-I ? R-I colour index 41- 45 F5.3 mag V-I ? V-I colour index 47- 51 F5.3 mag B-I ? B-I colour index
Note (2): 1 pix = 0.36 arcsec. The origin of (X, Y) coordinates is located at the bottom right.
History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 16-May-1997
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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