2000AJ....120.1384V

Query : 2000AJ....120.1384V

2000AJ....120.1384V - Astron. J., 120, 1384-1395 (2000/September-0)

The white dwarf cooling age of the open cluster NGC 2420.

VON HIPPEL T. and GILMORE G.

Abstract (from CDS):

We have used deep HST WFPC2 observations of two fields in NGC 2420 to produce a cluster color-magnitude diagram down to V~27. After imposing morphological selection criteria we find eight candidate white dwarfs in NGC 2420. Our completeness estimates indicate that we have found the terminus of the WD cooling sequence. We argue that the cluster distance modulus is likely to be close to 12.10 with E(B-V)=0.04. With these parameters we find a white dwarf cooling age for NGC 2420 of 2.0±0.20 (1 σ) Gyr. The 0.20 Gyr uncertainty includes errors in the photometry, sequence fitting, precursor timescales, and theoretical white dwarf cooling timescales. Comparing the cluster white dwarf cooling age to ages derived from stellar isochrone fitting we find a preference for ages derived from models incorporating convective overshoot.

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Journal keyword(s): Galaxy: Stellar Content - open clusters and associations: individual (NGC 2420) - Stars: Evolution - Stars: White Dwarfs

Nomenclature: Table 2: Cl* NGC 2420 VGWD N (Nos 1-8). Table 5: Cl* NGC 2420 VGMS N (Nos 1-3).

Simbad objects: 19

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Number of rows : 19
N Identifier Otype ICRS (2000)
RA 		ICRS (2000)
DEC 		Proper motions Parallaxes Redshift Rad. vel. cz Mag U Mag B Mag V Mag R Mag I Sp type Morph. type Angular size #ref
1983 - 2024
1 NGC 188 OpenCluster 00 47 11.5 +85 14 38 -2.3087 -0.9565 0.5053 -0.000140 -42.03 -42.03           ~ ~ 32.6 32.6 0 846
2 Cl Melotte 22 OpenCluster 03 46 24.2 +24 06 50 19.997 -45.548 7.364 0.000020 5.88 5.88           ~ ~ 76.86 76.86 ~ 3300
3 Cl* NGC 2420 VGWD 2 Star 07 38 08.07 +21 33 08.8 ~ ~ ~     22.52     ~ ~ ~ ~ ~ 1
4 Cl* NGC 2420 VGWD 1 Star 07 38 10.62 +21 32 33.5 ~ ~ ~     21.43     ~ ~ ~ ~ ~ 1
5 Cl* NGC 2420 VGWD 4 Star 07 38 10.85 +21 31 56.6 ~ ~ ~     24.15     ~ ~ ~ ~ ~ 1
6 Cl* NGC 2420 VGMS 3 Star 07 38 23.74 +21 35 30.4 ~ ~ ~           ~ ~ ~ ~ ~ 1
7 NGC 2420 OpenCluster 07 38 24.5 +21 34 30 -1.190 -2.125 0.363 0.000248 74.26 74.27   9.0 8.3     ~ ~ 6.4 6.4 0 440
8 Cl* NGC 2420 VGWD 3 Star 07 38 26.54 +21 35 13.1 ~ ~ ~     23.66     ~ ~ ~ ~ ~ 1
9 Cl* NGC 2420 VGWD 6 Star 07 38 29.68 +21 36 45.4 ~ ~ ~     25.64     ~ ~ ~ ~ ~ 1
10 Cl* NGC 2420 VGWD 8 Star 07 38 30.12 +21 36 34.0 ~ ~ ~     25.69     ~ ~ ~ ~ ~ 1
11 Cl* NGC 2420 VGWD 7 Star 07 38 30.50 +21 34 31.3 ~ ~ ~     25.68     ~ ~ ~ ~ ~ 1
12 Cl* NGC 2420 VGMS 1 Star 07 38 30.94 +21 34 44.9 ~ ~ ~     26.9     ~ ~ ~ ~ ~ 1
13 Cl* NGC 2420 VGWD 5 Star 07 38 31.26 +21 35 56.6 ~ ~ ~     25.45     ~ ~ ~ ~ ~ 1
14 Cl* NGC 2420 VGMS 2 Star 07 38 31.62 +21 36 37.3 ~ ~ ~     27.5     ~ ~ ~ ~ ~ 1
15 NGC 2451 Cluster* 07 45.4 -37 58 -21.063 15.378 5.163 0.000076 22.85 22.85           ~ ~ ~ ~ ~ 139
16 NGC 2477 OpenCluster 07 52 11.0 -38 32 13 -2.449 0.870 0.665 0.000024 7.3 7.30   6.64 5.8     ~ ~ 18.0 18.0 0 262
17 NGC 2632 OpenCluster 08 40 13.0 +19 37 16 -36.047 -12.917 5.371 0.000117 34.94 34.94           ~ ~ 118.2 118.2 0 1500
18 NGC 2682 OpenCluster 08 51 23.0 +11 48 50 -10.9737 -2.9396 1.1325 0.000113 33.92 33.92           ~ ~ 25.0 25.0 0 2235
19 M 4 GlobCluster 16 23 35.22 -26 31 32.7 -12.48 -18.99 0.556 0.000237 71.0 71.01           ~ ~ 26.3 26.3 90 1806

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