J/PASP/122/288 UBVIKC photometry in NGC 2309 (Piatti+, 2010)
NGC 2309: a relatively young open cluster projected onto a random stellar
concentration.
Piatti A.E., Claria J.J., Ahumada A.V.
<Publ. Astron. Soc. Pac., 122, 288-298 (2010)>
=2010PASP..122..288P 2010PASP..122..288P
ADC_Keywords: Clusters, open ; Photometry, CCD ; Photometry, UBVRI
Abstract:
We have obtained CCD UBVIKC photometry down to V∼22.0 for the open
cluster NGC 2309 and its surrounding field. Twenty three probable
cluster members have been identified for the first time on the basis
of sound photometric criteria. Because NGC 2309 is a relatively poor
cluster projected onto a rich star field showing density fluctuations,
the frequently used membership criteria based on stellar density
profiles or proper motion measurements would not be enough to assess
the star membership status if employed independently. We estimated a
cluster radius of 7.9' and a radius at half the maximum of the
cluster density profile of 1.7'. Based on the best fits of
isochrones computed by the Geneva group to the cluster
color-magnitude and color-color diagrams, previously shifted by
the cluster reddening (E(B-V)=0.32) and distance (d=2.5kpc), we
derived the cluster age (250Myr) and metallicity ([Fe/H]∼0.0). If an
8.5kpc distance from the Sun to the center of the Galaxy is assumed,
then NGC 2309 is found to be located just in front of the Perseus
spiral arm.
Description:
We obtained images for NGC 2309 on the night of 2000 December 25 with
the UBVIKC filters and a 2048x2048 pixel Tektronix CCD attached to
the Cerro Tololo Inter-American Observatory (CTIO, Chile) 0.9m
telescope.
Objects:
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RA (2000) DE Designation(s)
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06 56.2 -07 12 NGC 2309 = Cl Collinder 122
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 80 2275 UBVI data of stars in the field of NGC 2309
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq [1/2275] Sequential number
6- 13 F8.3 pix Xpos X position (1)
15- 22 F8.3 pix Ypos Y position (1)
24- 29 F6.3 mag Vmag Johnson V magnitude
31- 35 F5.3 mag e_Vmag rms uncertainty on Vmag
37 I1 --- o_Vmag Number of observation for Vmag
39- 44 F6.3 mag U-B ?=99.999 Johnson U-B colour index
46- 50 F5.3 mag e_U-B ?=9.999 rms uncertainty on U-B (2)
52 I1 --- n_U-B Number of observation for U-B
54- 59 F6.3 mag B-V ?=99.999 Johnson B-V colour index
61- 65 F5.3 mag e_B-V ?=9.999 rms uncertainty on B-V (2)
67 I1 --- n_B-V Number of observation for B-V
69- 74 F6.3 mag V-Ic ?=99.999 Johnson-Cousins V-I colour index
76- 80 F5.3 mag e_V-Ic ?=9.999 rms uncertainty on V-Ic (2)
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Note (1): (x,y) coordinates correspond to the reference system of Figure 1.
North is up, and east is to the left.
Note (2): Magnitude and color errors are the standard deviations of the
mean or the observed photometric errors for stars with only one
measurement.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 06-Apr-2010