J/AJ/102/137 NGC 2004 (Bencivenni+, 1991)
The young Magellanic cluster NGC 2004
BENCIVENNI D., BROCATO E., BUONANNO R., CASTELLANI V.
<Astron. J. 102, 137 (1991)>
=1991AJ....102..137B 1991AJ....102..137B (SIMBAD/NED Reference)
ADC_Keywords: Magellanic Clouds; Clusters, open; Photometry, CCD;
Positional data
Abstract:
The results of a new CCD photometric investigation of stars in the field
of the LMC cluster NGC 2004 are reported and discussed. B, V photometry
is given for more than 1500 objects, the large majority to be ascribed
to the cluster. A new color-magnitude diagram is presented. It shows a
well-defined blue sequence (BS) of H-burning stars, running from
V~=21mag up to V~=13mag, together with a group of cluster He-burning red
supergiants with V~=13mag and a clump of field red giants at about
V~=19 mag. Theoretical evolutionary computations are reported covering
the range of massive stars evolving in the cluster. These evolutionary
tracks can match the observed CM diagram provided that a low efficiency
of the surface convection (a low value of the mixing length) is adopted.
Comparison of the theoretical luminosity function with the upper portion
of the observed BS distribution suggests a cluster age of about
8 million years, in agreement with previous evaluations. The completeness
of the sample and the contribution of field stars have been estimated.
The CM distribution of cluster stars has been compared with the results
of synthetic clusters based on the adopted evolutionary scenario. We find
that the observed distribution of cluster stars in the different
evolutionary phases appears in good agreement with prediction
based on theoretical evolutionary lifetimes. Moreover, the distribution
of H-burning stars agrees with a Salpeter distribution in the whole
range 2≤M/M☉≤20. After a short review of the current theoretical
scenario concerning massive stars, the CM diagram of field stars is
discussed, reaching the conclusion that the observed clump of red giants
is the natural consequence of the peculiar large lifetimes in the central
He burning phase of stars with M~=3M☉.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 27 1531 Program stars magnitudes, colors and positions
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 4 I4 --- No Star identification number
7- 11 F5.2 mag Vmag V magnitude
13- 17 F5.2 mag B-V B-V colour
20- 22 I3 pix X X position
24- 27 I4 pix Y Y position
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Historical note: Keypunched at CDS
(End) Patricia Bauer [CDS] 09-Dec-1994