J/ApJ/336/780 gr photometry of NGC 5053 blue stragglers (Nemec+ 1989)
Blue straggler stars in the globular cluster NGC 5053
Nemec J.M., Cohen J.G.
<Astrophys. J. 336, 780 (1989)>
=1989ApJ...336..780N 1989ApJ...336..780N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, blue ; Photometry
Keywords: clusters: globular - stars: binaries - stars: evolution -
stars: stellar dynamics
Abstract:
Twenty-four blue straggler stars have been identified in the low
central concentration globular cluster NGC 5053. New deep
color-magnitude (C-M) diagrams to 23mag, constructed from photometry
of over 6000 stars on 4-shooter CCD frames, show that they form a
well-defined sequence in the C-M diagram, extending up to ∼2.2mag
brighter than the main-sequence turnoff point. The 12 most luminous
blue stragglers are found to be significantly more centrally
concentrated than the cluster subgiants with magnitudes in the same
interval (a similar result is known for the blue stragglers in the
globular cluster NGC 5466). Furthermore, they are also found to be
more centrally concentrated than the 12 lower luminosity blue
stragglers. Comparisons of the projected radial distributions of the
bright and faint blue stragglers, with the radial distributions that
are expected for stars of mass 0.8, 1.6, and 2.4M☉, (calculated
using multimass King models) suggests that the brightest blue
stragglers have an average mass of =1.3+/0.3M☉, which is less
than or comparable to twice the mean mass of a main-sequence turnoff
star, and the lower luminosity blue stragglers have a mean mass
similar to that of the main-sequence turnoff stars (i.e.,
M∼0.8M☉). By fitting theoretical isochrones computed by Bell and
VandenBerg to the observed main-sequence turnoff and subgiant branch
regions of NGC 5053, a distance modulus of (m-M)0=16.05±0.14mag,
and an age of 18±3Gyr are derived for NGC 5053. The main-sequence
luminosity function shows no sign of "turning over" for stars brighter
than Mg∼5mag.
For a description of the uvgr photometric system, see e.g. GCPD/38
Objects:
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RA (2000) DE Designation(s)
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13 16 26.9 +17 41 52 NGC 5053
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3 28 796 Photometry of the brightest stars in
fields 1, 2, 3 and 4
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Byte-by-byte Description of file: table3
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Bytes Format Units Label Explanations
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1 A1 --- Field [ABCD] Field designation (1)
2- 4 I3 --- Seq Sequential number in the field
6- 10 F5.1 pix Xpos X position (2)
12- 16 F5.1 pix Ypos Y position (2)
18- 22 F5.2 mag gmag g magnitude
24- 28 F5.2 mag g-r g-r colour index
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Note (1): A = Field 1, B = Field 2, C = Field 3, D = Field 4
Note (2): 1 pix = 0.33", X increasing to the North, Y increasing to the West.
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History: Prepared via OCR at CDS.
(End) Marie-Jose Wagner, Patricia Bauer [CDS] 29-Apr-1997