J/AJ/112/1061 BV photometry of NGC 7099 (Bergbusch 1996)
Luminosity functions for post-turnoff stars in globular clusters. II. NGC 7099
Bergbusch P.A.
<Astron. J. 112, 1061 (1996)>
=1996AJ....112.1061B 1996AJ....112.1061B
ADC_Keywords: Clusters, globular ; Stars, bright ; Photometry, CCD
Abstract:
New BV CCD photometry for the bright stars in cluster fields centered
on the core of NGC 7099 is presented. The morphology of the LF though
the turnoff region is similar to that found in other metal-poor
clusters in that the relative number of turnoff to giant stars is
lower than predicted by canonical models. Comparisons with
evolutionary sequences of horizontal branch stars suggest a reddening
E(B-V)=0.06 and a distance modulus (m-M)_V=14.83. Isochrone fits to
[Fe/H]=-2.03, [O/Fe]=+0.70 models are consistent with an age of at
least 14 Gyr. The model LF for this age accurately predicts the
brightness of the tip of the red giant branch (RGB) as well as the
location of the break which signals the transition from the base of
the RGB to the main sequence. There is an indication that the
evolutionary pause on the RGB, which manifests itself as a bump in the
LF, occurs one magnitude fainter than the models predict. The excess
of HB stars with respect to giants is confirmed and implies a helium
abundance Y=0.28, which is higher than that found in other metal-poor
globular clusters from the R method. From a comparison with the
metal-rich, blue horizontal branch cluster NGC 288, it is argued that
age cannot by itself be the solution to the second parameter problem.
Objects:
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RA (2000) DE Designation(s)
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21 40.3 -23 11 NGC 7099
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 51 852 Photometry for stars brighter than V=18.0
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Star Star number
8-15 F8.2 pix Xpos X pixel coordinate
17-24 F8.2 pix Ypos Y pixel coordinate
28-33 F6.3 mag Vmag V magnitude
37-42 F6.3 mag B-V B-V color index
47-51 F5.3 --- Chi Mean profile fitting statistic, chi
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Origin: AAS CD-ROM series, Volume 7, 1996 Lee Brotzman [ADS] 25-Sep-1996
(End) [CDS] 30-Jan-1997