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 (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 NGC 188 OpC 00 47 11.5 +85 14 38           ~ 922 0
2 Cl Melotte 22 OpC 03 46 24.2 +24 06 50           ~ 3432 0
3 Cl* NGC 2420 VGWD 2 * 07 38 08.07 +21 33 08.8     22.52     ~ 1 0
4 Cl* NGC 2420 VGWD 1 * 07 38 10.62 +21 32 33.5     21.43     ~ 1 0
5 Cl* NGC 2420 VGWD 4 * 07 38 10.85 +21 31 56.6     24.15     ~ 1 0
6 Cl* NGC 2420 VGMS 3 * 07 38 23.74 +21 35 30.4           ~ 1 0
7 NGC 2420 OpC 07 38 24.5 +21 34 30   9.0 8.3     ~ 476 0
8 Cl* NGC 2420 VGWD 3 * 07 38 26.54 +21 35 13.1     23.66     ~ 1 0
9 Cl* NGC 2420 VGWD 6 * 07 38 29.68 +21 36 45.4     25.64     ~ 1 0
10 Cl* NGC 2420 VGWD 8 * 07 38 30.12 +21 36 34.0     25.69     ~ 1 0
11 Cl* NGC 2420 VGWD 7 * 07 38 30.50 +21 34 31.3     25.68     ~ 1 0
12 Cl* NGC 2420 VGMS 1 * 07 38 30.94 +21 34 44.9     26.9     ~ 1 0
13 Cl* NGC 2420 VGWD 5 * 07 38 31.26 +21 35 56.6     25.45     ~ 1 0
14 Cl* NGC 2420 VGMS 2 * 07 38 31.62 +21 36 37.3     27.5     ~ 1 0
15 NGC 2451 Cl* 07 45.4 -37 58           ~ 158 1
16 NGC 2477 OpC 07 52 11.0 -38 32 13   6.64 5.8     ~ 290 0
17 NGC 2632 OpC 08 40 13.0 +19 37 16           ~ 1564 0
18 NGC 2682 OpC 08 51 23.0 +11 48 50           ~ 2342 0
19 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1847 0

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