J/ApJ/783/56 UBVI photometry in NGC 6752 (Kravtsov+, 2014)
Galactic globular cluster NGC 6752 and its stellar population as inferred from
multicolor photometry.
Kravtsov V., Alcaino G., Marconi G., Alvarado F.
<Astrophys. J., 783, 56 (2014)>
=2014ApJ...783...56K 2014ApJ...783...56K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, UBVRI ; Photometry, CCD
Keywords: globular clusters: general - globular clusters: individual: NGC 6752
Abstract:
This paper is devoted to photometric study of the Galactic globular
cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its
stellar population. We emphasize that our U passband is (1) narrower
than the standard one due to its smaller extension blueward and (2)
redshifted by ∼300Å relative to its counterparts, such as the HST
F336W filter. Accordingly, both the spectral features encompassed by
it and photometric effects of the multiplicity revealed in our study
are somewhat different than in recent studies of NGC 6752. Main
sequence stars bluer in U-B are less centrally concentrated, as red
giants are. We find a statistically significant increasing luminosity
of the red giant branch (RGB) bump of ΔU~0.2mag toward
the cluster outskirts with no so obvious effect in V. The photometric
results are correlated with spectroscopic data: the bluer RGB stars in
U-B have lower nitrogen abundances. We draw attention to a larger
width of the RGB than the blue horizontal branch (BHB) in U-B. This
seems to agree with the effects predicted to be caused by molecular
bands produced by nitrogen-containing molecules. We find that brighter
BHB stars, especially the brightest ones, are more centrally
concentrated. This implies that red giants that are redder in U - B,
i.e., more nitrogen enriched and centrally concentrated, are the main
progenitors of the brighter BHB stars. However, such a
progenitor-progeny relationship disagrees with theoretical predictions
and with the results on the elemental abundances in horizontal branch
stars. We isolated the asymptotic giant branch clump and estimated the
parameter ΔVZAHBclump=0.98±0.12.
Description:
The observations were acquired on three nights (1999 October 13, 15,
and 17) with the 1.3m Warsaw telescope at Las Campanas Observatory
using a set of UBVI filters and a 2048*2048 CCD camera with a gain of
3.8 and a readout noise of 5.5e- rms. The scale was 0.417''/pixel,
giving a field of view of 14'*14'. The center of the measured field of
NGC6752 was approximately 30'' to the east and 30'' to the south of
the cluster center. The average seeing on each night (FWHM), estimated
from the observations, was in the range of slightly subarcsecond to
1.5'', 1.3''-1.9'', and 1.4''-2.7'' on the three consecutive nights,
respectively.
The instrumental magnitudes and colors (v, u-b, b-v, v-i) obtained for
the measured stars were then transformed to the standard system (V,
U-B, B-V, V-I) The obtained photometric data are given in Table2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 18246 Photometry of NGC 6752
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/573/A70 : UBVI photometry in 3 globular clusters (Nardiello+, 2015)
J/A+A/567/A72 : Stellar parameters and abundances in NGC6752 (Gruyters+, 2014)
J/A+A/557/A128 : Stellar [Fe/H] and [Na/H] in NGC6752 (Carretta, 2013)
J/MNRAS/423/2901 : NGC 6752 multiwavelength survey (Thomson+, 2012)
J/AcA/62/357 : Proper motions in 6 globular clusters (Zloczewski+, 2012)
J/ApJ/750/L14 : Abundances of red giants in NGC 6752 (Carretta+, 2012)
J/A+A/516/A23 : UBVI Photometry of NGC 1261 (Kravtsov+, 2010)
J/A+A/469/529 : UBVI photometry of NGC 6864 (Kravtsov+, 2007)
J/A+A/464/927 : Abundances of red giants in NGC 6752 (Carretta+, 2007)
J/A+A/440/901 : Reddening and metallicity of NGC 6752 (Gratton, 2005)
J/MNRAS/324/580 : Sources in NGC 4038-39 and 6752 direction (Daniels+, 2001)
J/AJ/116/2415 : CCD UBVRI Photometry of M80 (Alcaino+ 1998)
J/A+AS/121/95 : Giant stars abundances in 24 clusters (Carretta+ 1997)
J/ApJS/99/637 : Equivalent widths for 54 red giants (Norris+ 1995)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star [1/18246] Star running sequence number
7- 12 F6.3 mag Vmag [9.1/21.7] The V magnitude
14- 19 F6.3 mag U-B [-1.5/2.2]? The U-B color index
21- 26 F6.3 mag B-V [-0.6/1.8]? The B-V color index
28- 33 F6.3 mag V-I [-0.5/1.8]? The V-I color index
35- 39 F5.3 mag sigU [0/0.91]? Standard deviation for U band magnitude
σU
41 I1 --- NU [2/6]? Number of U band measurements
43- 47 F5.3 mag sigB [0/0.71]? Standard deviation for B band magnitude
σB
49 I1 --- NB [2/6]? Number of B band measurements
51- 55 F5.3 mag sigV [0/0.92]? Standard deviation for V band magnitude
σV
57 I1 --- NV [2/6]? Number of V band measurements
59- 63 F5.3 mag sigI [0/1.3]? Standard deviation for I band magnitude
σI
65 I1 --- NI [2/6]? Number of I band measurements
67- 73 F7.2 pix Xpos [0.1/2066] The X coordinate (1)
75- 81 F7.2 pix Ypos [6.8/2059] The Y coordinate (1)
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Note (1): The pixel size is 0.417x0.417arcsec of a 2048x2048 CCD camera; the
total field is 14x14arcmin. The center of the measured field of NGC 6752
was approximately 30'' to the east and 30'' to the south of the cluster
center (α2000=19h10m52.0s and δ2000=-59°59'05'').
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 14-Apr-2016