AT 21

(Alessi-Teutsch 21; Alessi 23; Alessi-Teutsch 1)

0.63 UTI

0.8

C_N

1.0

C_dens

0.75

C_C3

0.3

C_lit

1.0

C_dup

N₅₀ (P>50% members) 229

Stellar density (N₅₀/rad) 18.1 [N/pc²]

C3 classification AB

C_N 0.8 Rich
C_dens 1.0 Very dense
C_C3 0.75 High quality
C_lit 0.3 Poorly studied
C_dup 1.0 Unique

📥 Members 📊 Colab 🔬 Bayestar19

MOCA 🔍 CDS 🔍 Simbad 🔍 CDS (α, δ) 🔍 Simbad (α, δ)

Overview

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AT 21 is a rich, very dense object of high C3 quality. Its parallax locates it at a relatively close distance, below the mid-plane, affected by low extinction. It is catalogued as a near-solar metallicity, intermediate-age cluster (see Parameters). It is poorly studied in the literature.

Note: This object shares a large percentage of members with 3 later reported entries. See table with shared members information.

Relatively close Low extinction Near-solar metallicity Intermediate age

Cavallo et al. (2024)
Gold sample.

Data

🔍 Search references for AT 21 in: SciX Simbad

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Reference	Year	RA [deg]	DEC [deg]	Plx [mas]	pmRA [mas/yr]	pmDE [mas/yr]	Rv [km/s]
UCC	99999–	15.054	55.411	0.769	-4.431	-2.059	-32.589
Zhang et al.	2024	15.098	55.406	–	–	–	–
Hunt & Reffert	2024	15.098	55.406	0.76	-4.438	-2.065	-33.137
Cavallo et al.	2024	15.054	55.402	0.769	–	–	–
Hunt & Reffert	2023	15.098	55.406	0.76	-4.438	-2.065	-33.137
Bica et al.	2019	15.073	55.38	–	–	–	–

💡 Note: The UCC values are estimated from its identified members.

Reference	Year	Dist [kpc]	Av [mag]	DAv [mag]	Age [Myr]	[Fe/H] [dex]	Mass [Msun]	B_frac	BSS
UCC	99999–	1.25	0.885	0.67	362	0.134	519	–	–
Zhang et al.	2024	–	–	–	–	0.068⁽¹⁾	–	–	–
Hunt & Reffert	2024	–	–	–	–	–	519⁽¹⁾	–	–
Cavallo et al.	2024	1.28	0.96	–	355	0.200	–	–	–
Hunt & Reffert	2023	1.22	0.81	0.67	368	–	–	–	–

(N): Indicates that there are N extra values assigned to this parameter in the corresponding reference.

Cluster	%	RA	DEC	Plx	pmRA	pmDE	Rv	UTI
UBC 35	90.8	15.05	55.41	0.77	-4.44	-2.05	-32.45	0.01
COIN-Gaia 2	80.8	15.05	55.41	0.77	-4.44	-2.06	-32.25	0.0
CWWDL 3306	29.3	15.08	55.39	0.78	-4.44	-2.08	-32.19	0.0

💡 Note: The % column shows the percentage of members that AT 21 shares with each listed object.

Visualization

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