2010AJ....140..954C


Query : 2010AJ....140..954C

2010AJ....140..954C - Astron. J., 140, 954-961 (2010/October-0)

Photometric characterization of the galactic star cluster Trumpler 20.

CARRARO G., COSTA E. and AHUMADA J.A.

Abstract (from CDS):

We present deep UBVI photometry for Trumpler 20, a rich, intermediate-age open cluster located at l = 301°.47, b = +2°.22 (α = 12h39m34s, δ = -60°37'00'', J2000.0) in the fourth Galactic quadrant. In spite of its interesting properties, this cluster has received little attention, probably because the line of sight to it crosses the Carina spiral arm twice (and possibly also the Scutum-Crux arm), which causes significant contamination of its color-magnitude diagram (CMD) by field stars, therefore seriously complicating its interpretation. In this paper, we provide more robust estimates of the fundamental parameters of Trumpler 20 and investigate the most prominent features of its CMD: a rich He-burning star clump, and a vertical sequence of stars above the turnoff, which can be either blue stragglers or field stars. Our precise photometry, in combination with previous investigations, has allowed us to derive updated values of the age and heliocentric distance of Trumpler 20, which we estimate to be 1.4±0.2 Gyr and 3.0±0.3 kpc, respectively. As predicted by models, at this age the clump has a tail toward fainter magnitudes and bluer colors, thus providing further confirmation of the evolutionary status of stars in this particular phase. The derived heliocentric distance places the cluster in the inter-arm region between the Carina and Scutum arms, which naturally explains the presence of the vertical sequence of stars (which was originally interpreted as the cluster itself) observed in the upper part of the CMD. Most of these stars would therefore belong to the general galactic field, while only a few of them would be bona fide cluster blue stragglers. Our data suggest that the cluster metallicity is solar and its reddening is E(B - V) = 0.35±0.04. Finally, we believe we have solved a previously reported inconsistency between the spectroscopic temperatures and colors of giant stars in the cluster.

Abstract Copyright:

Journal keyword(s): Galaxy: disk - Galaxy: structure - open clusters and associations: general - open clusters and associations: individual: Trumpler 20

Simbad objects: 15

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Number of rows : 15
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 2204 OpC 06 15 32 -18 40.2   9.35 8.6     ~ 140 0
2 SA 98- reg 06 52 04.1 -00 23 58           ~ 171 0
3 NGC 2660 OpC 08 42 40 -47 12.1   9.05 8.8     ~ 137 0
4 NAME Car Arm PoG 10 00 -60.0           ~ 415 1
5 V* UY Sex HS* 10 50 02.8265487864 -00 00 36.879009588 12.063 13.184 13.474 13.606 13.769 sdO9VIIHe6 154 0
6 NGC 4439 OpC 12 28 29 -60 05.8           ~ 43 0
7 NGC 4463 OpC 12 29 52 -64 48.0   7.62 7.2     ~ 56 0
8 NAME Crux-Scutum Spiral Arm reg 12 30 -60.0           ~ 297 0
9 NAME Coalsack Nebula DNe 12 31 19 -63 44.6           ~ 248 0
10 Cl Trumpler 20 OpC 12 39 32 -60 38.2           ~ 94 0
11 RCW 69 PN 12 44 27.4384824528 -62 31 18.880146408           ~ 20 1
12 HD 311999 * 12 50 22.6138415928 -61 35 00.794816232 11.14 11.40 10.77 10.76   OB 40 0
13 NGC 4755 OpC 12 53 40 -60 22.3           ~ 278 0
14 NGC 7789 OpC 23 57 20 +56 43.6   7.68 6.7     ~ 488 0
15 NAME Scutum Spiral Arm PoG ~ ~           ~ 320 0

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2022.09.26-07:20:54

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