J/AJ/109/1112 NGC 6584 (Sarajedini + 1995)
CCD Photometry for the Galactic Globular Cluster NGC 6584
Sarajedini A., Forrester W.L.
<Astron. J. 109, 1112 (1995)>
=1995AJ....109.1112S 1995AJ....109.1112S
ADC_Keywords: Clusters, globular ; Photometry, CCD
Abstract:
We present CCD photometry in the B and V passbands for the Galactic
globular cluster NGC 6584. The color-magnitude diagram reveals a
horizontal branch (HB) populated on both the red and blue sides of the
RR Lyrae instability strip. The cluster contains 42 confirmed RR Lyrae
variables, and we find an additional 56 stars which are possible RR
Lyraes. The mean magnitude of the RR Lyraes on our CCD frames is
combined with that of the nonvariable stars to yield <V(HB)> = 16.53
± 0.03. Using a polynomial fit to the cluster giant stars, we derive
the color of the giant branch at the level of the HB to be (B-V)g =
0.89 ± 0.02. Our photometry has also been used to isolate the red
giant branch "clump," which forms when stars pause and sometimes
reverse their course as they evolve up the giant branch. Its
luminosity is primarily dependent upon the cluster metallicity, and we
have used this fact to derive a metallicity of [Fe/H] = -1.44 ± 0.16
for NGC 6584. Coupled with the color of the giant branch given above,
this yields a cluster reddening of E(B-V) = 0.07 ± 0.04. To the
extent that our photometry can be used to study the age of NGC 6584,
we find it to be comparable to M3, which is not surprising given their
similar HB morphologies. The color-magnitude diagram also exhibits a
significant population of blue straggler stars. From a comparison of
the blue straggler radial distribution to that of the subgiant stars
with similar V magnitudes, we find that the blue stragglers are more
centrally concentrated than the subgiants, indicative of a higher mass
for the blue stragglers.
Objects:
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RA (2000) DE Name
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18 18.6 -52 13 NGC 6584
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 2901 CCD photometry for NGC 6584
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Star Star number
7-15 F9.2 pix Xpos X pixel position
16-24 F9.2 pix Ypos Y pixel position
25-33 F9.2 mag Vmag V magnitude
34-42 F9.3 mag e_Vmag V magnitude error
43-51 F9.2 mag B-V B-V color
52-60 F9.3 mag e_B-V B-V color error
61-63 I3 --- Det Number of detections
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Origin: AAS CD-ROM series, Volume 5, 1995 Lee Brotzman [ADS] 17-Jul-1995
(End) [CDS] 09-Jan-1996