J/A+A/390/961 VI photometry in NGC 188 (Andreuzzi+, 2002)
The white dwarf cooling sequence in the old open cluster NGC 188.
Andreuzzi G., Richer H.B., Limongi M., Bolte M.
<Astron. Astrophys. 390, 961 (2002)>
=2002A&A...390..961A 2002A&A...390..961A
ADC_Keywords: Clusters, open ; Photometry, UBVRI
Keywords: open clusters and associations: individual: NGC 188 -
stars: white dwarfs - stars: luminosity function
Abstract:
We used HST-WFPC2 to study the white dwarf luminosity function of the
old open cluster NGC 188 in order to determine a lower limit to the
age of the cluster (∼5Gyr) by looking at the faint end of the
cooling sequence (down to V∼26.5).
Description:
HST-WFCs photometry in the F555W-F814W filters, is presented for 223
objects belonging to 4 different fields located on the center of the
cluster. By applying selection criteria to the catalog (stellarity
index, c≥0.8), we identified 157 candidate stars of which 28 white
dwarfs.
Objects:
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RA (2000) DE Designation(s)
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00 48 26 +85 15 21 NGC 188 cluster center
00 48 00 +85 13 30 Field f1
00 48 00 +85 16 00 Field f2
00 46 00 +85 16 00 Field f3
00 46 00 +85 13 30 Field f4
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 70 223 V, V-I photometry for stars in NGC 188
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See also:
J/AJ/124/601 : Absolute positions & proper motions in NGC 188 (Platais+, 2002)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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3- 9 F7.3 pix xpos x coordinate (1)
12- 18 F7.3 pix ypos y coordinate (1)
22- 27 F6.3 mag Imag Johnson I magnitude (from F814W filter)
32- 36 F5.3 mag e_Imag I photometric error
40- 45 F6.3 mag Vmag Johnson V magnitude (from F555W filter)
50- 54 F5.3 mag e_Vmag V photometric error
59- 63 F5.3 --- c Stellarity index (2)
65- 70 I6 --- ID Identification number (3)
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Note (1): The observations consisted of four fields, f1, f2, f3 and f4,
in such a way that WF4 of the field f4 overlaps WF2 of the field f1
and WF4 of the field f3 overlaps WF2 of the field f2.
1 pix = 0.1arcsec (HST-WFC).
The coordinates in the catalogue are computed respect to different
median images, obtained considering the single field and camera:
4 x WF2
4 x WF3
4 x WF4
Note (2): The catalog includes only the objects for which stellarity
index c is ≥0.2
Note (3): IDs in the catalog have been created to indicates the camera
and the field in which each object has been identified: the first
number in the ID indicate the field (f1, f2, f3, f4); the second one
indicate the camera:
WF2: ID<f30000; WF3: f30000≤ID<f40000; WF4: f40000≤ID<f50000
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Acknowledgements: Gloria Andreuzzi
History:
* 14-Apr-2004: the original catalog contained a decimal fraction ".000"
attached to each ID number (last column of catalog), which has been
removed.
(End) Patricia Bauer [CDS] 30-Aug-2002