J/AJ/96/1632 CCD BV photometry in M55 (Schade+ 1988)
A color-magnitude diagram for the halo globular cluster M 55
Schade D., Vandenberg D.A., Hartwick F.D.A.
<Astron. J. 96, 1632 (1988)>
=1988AJ.....96.1632S 1988AJ.....96.1632S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, CCD
Abstract:
We present new CCD photometry for the globular cluster M55 that
extends well below the main-sequence turnoff. Combining these new data
with previously published photographic photometry of cluster giants
and horizontal-branch stars yields a high-quality composite
color-magnitude diagram (CMD). A comparison of the latter with recent
CMDs for M68 and NGC 6752-two clusters whose metallicities bracket
that of M55-suggests (1) that the reddening to M55 may be as high as
E(B-V)=0.14mag, and (2) that all three systems have similar ages. In
particular, if the apparent distance modulus to M55 is
(m-M)V=14.10mag, then isochrones for Y=0.24 and high [O/Fe] would
suggest an age of ∼14Gyr. Very encouraging agreement of the
observations with theoretical predictions is found.
Objects:
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RA (2000) DE Designation(s)
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19 39 59.3 -30 57 44 M 55 = NGC 6809
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 30 617 CCD photometry in M 55
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Byte-by-byte Description of file: table1
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Bytes Format Units Label Explanations
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1- 3 I3 --- Star [1/617]+ Star number
5- 9 F5.1 pix Xpos X position (1)
11- 15 F5.1 pix Ypos Y position (1)
17- 22 F6.3 mag Vmag V magnitude
24- 29 F6.3 mag B-V B-V colour index
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Note (1): 1 pix = 0.44"; X positive from West to East, Y from South to North.
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History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 18-Apr-1997