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J/AJ/113/669                         Stars in M13 core (Cohen+ 1997)

Globular Cluster Photometry with the Hubble Space Telescope. VI. WF/PC-I Observations of the Stellar Populations in the Core of M13 (NGC 6205) Cohen R.L., Guhathakurta P., Yanny B., Schneider D.P., Bahcall J.N. <Astron. J. 113, 669 (1997)> =1997AJ....113..669C
ADC_Keywords: Clusters, globular ; Photometry Mission_Name: HST Abstract: We study the dense core of the globular cluster Messier 13 (NGC 6205) using pre-refurbishment Planetary Camera-I images obtained with the Hubble Space Telescope. Short exposures (60s) through the F555W and F785LP filters (similar to Johnson V and I, respectively) have been used to obtain V and I photometry of 2877 stars brighter than V∼20 in a 1.25arcmin2 region of the cluster including its core and extending out to r∼66arcsec (2.3pc) from its center. The sample is complete to V~=18.3 (the main sequence turnoff) and the 1σ photometric error is about 0.1mag. We find 15 blue straggler star candidates and 10 other possible blue stragglers in this region of M13. Their specific frequency is in the range F_(BSS)=0.04-0.07, comparable to what is observed near the centers of other dense clusters. A comparison between M13's observed V band stellar luminosity function and a theoretical model (Bergbusch & Vandenberg, 1992ApJS...81..163B) for the luminosity function of an old, metal-poor cluster shows that the model predicts too few of the brightest red giants (V∼12.5-15) by a factor of two relative to subgiants/turnoff stars (>6σ effect). The radial distributions of red giants, blue stragglers, and subgiants are consistent with one another, and are well fit by a King profile of core radius r(core)=38±6arcsec (90% confidence limits) or 1.3pc. Stars in the blue horizontal branch of M13, however, appear to be centrally depleted relative to other stellar types. We combine data from three dense ``King model clusters,'' M13, M3, and 47 Tuc, and two post core collapse clusters, M30 and M15, and compare the distributions of various stellar types as a function of (r/r_(half light)_) and (r/r(core)). The horizontal branch stars in the combined sample appear to be centrally depleted relative to the giants (97% significance), this depletion is only a 1-2σ effect in each of the clusters taken individually. The blue stragglers in the combined sample are centrally concentrated relative to the giants. (Copyright) 1997 American Astronomical Society. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 55 6436 Stars in the core of M13
See also: J/AJ/107/1745 : HST UVI photometry of M15. II. (Yanny+, 1994) J/AJ/108/1786 : Blue stragglers + variable stars in M3 (Guhathakurta+, 1994) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 ---- ID Identification number 6- 11 F6.2 arcsec dRA *R.A. J2000 offset from star #5540 13- 18 F6.2 arcsec dDE *Dec. J2000 offset from star #5540 20 I1 --- CCD PC number of the CCD 22- 25 F4.1 arcsec r Angular distance from center of M13 27- 31 F5.2 mag F555W F555W magnitude 33- 37 F5.2 mag F785LP ? F785LP magnitude 39- 43 F5.2 mag Vmag ? V magnitude 45- 49 F5.2 mag Imag ? I magnitude 51- 55 F5.2 mag V-I ? V-I color
Note on dRA, dDE: All positions are on the equinox J2000 coordinate system, and are measured relative to the reference star U (#5540) whose coordinates are: RA = 16h 41m 41.61s, DE = +36d 27' 42.06", accurate to about 0.25 arcsec.
References: Guhathakurta et al., Paper I. 1992AJ....104.1790G Yanny et al., Paper II. 1994AJ....107.1745Y, cat. J/AJ/107/1745 Guhathakurta et al., Paper III. 1994AJ....108.1786G, Cat. J/AJ/108/1786 Guhathakurta et al., Paper V. 1996AJ....111..267G Origin: AAS CD-ROM series, Volume 8, 1997 Lee Brotzman [ADS] 09-Apr-1997
(End) [CDS] 03-Jul-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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