UPK 640

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0.90 UTI
1.0
CN
1.0
Cdens
1.0
CC3
0.75
Clit
1.0
Cdup
C3 classification AA
Number of members (P>50%) 755
Radius (P>50% members) 75.9 [arcmin]
  • CN 1.0 Very rich
  • Cdens 1.0 Very dense
  • CC3 1.0 Very high quality
  • Clit 0.75 Well-studied
  • Cdup 1.0 Unique
đŸ“Ĩ Members 📊 Colab đŸ”Ŧ Bayestar19 🔍 CDS 🔍 Simbad 🔍 CDS (Îą, δ) 🔍 Simbad (Îą, δ)

Overview
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UPK 640 is a very rich, very dense object of very high C3 quality. Its parallax locates it at a very close distance, near the mid-plane, affected by low extinction. It is catalogued as a near-solar metallicity, young cluster, but with a large variance across recent sources for the absorption parameter (see Parameters). It is well-studied in the literature.

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

Very close Low extinction Near-solar metallicity Young

Almeida et al. (2025)
Mass determination: good fit. Isochrone match: good fit. Gold sample.

Cavallo et al. (2024)
Gold sample.

Data
🔍 Search references for UPK 640 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 – 250.199 -39.526 5.68 -11.943 -21.349 0.538
Li et al. 2025 250.26 -39.494 5.673 -11.973 -21.25 –
Almeida et al. 2025 250.414 -39.574 – – – –
Alfonso et al. 2024 249.186 -39.497 5.701 -12.409 -21.491 –
Hunt & Reffert 2024 249.692 -39.507 5.706 -11.882 -21.391 1.831
Celli et al. 2024 250.26 -39.494 – – – –
Cavallo et al. 2024 250.389 -39.451 5.701 – – –
Hunt & Reffert 2023 249.692 -39.507 5.706 -11.882 -21.391 1.831
Almeida et al. 2023 250.321 -39.565 – – – –
He et al. 2022 250.048 -39.528 5.676 -11.914 -21.277 –
Dias et al. 2021 250.414 -39.574 5.666 -12.014 -21.35 1.174
Cantat-Gaudin et al. 2020 250.26 -39.494 5.673 -11.973 -21.25 –
Cantat-Gaudin & Anders 2020 250.26 -39.502 5.684 -11.845 -21.275 –
Sim et al. 2019 250.134 -39.528 – -11.89 -21.15 –

💡 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] Bfr BSS
Li et al. 2025 0.16 0.37 – 21 -0.148 – – –
Almeida et al. 2025 0.17 0.19 – 24 – 419 – –
Alfonso et al. 2024 0.17 0.39 – 17 0.148 – – –
Hunt & Reffert 2024 – – – – – 406* – –
Celli et al. 2024 – – – 25 – 414 – –
Cavallo et al. 2024 0.17 1.06 – 18 -0.050 – – –
Hunt & Reffert 2023 0.17 0.24 0.76 10 – – – –
Almeida et al. 2023 0.17 0.32 – 24 0.145 385* 0.31 –
He et al. 2022 – 0.05 – 14 – – – –
Dias et al. 2021 0.17 0.19 – 24 0.149 – – –
Cantat-Gaudin et al. 2020 0.17 0.40 – 25 – – – –
Cantat-Gaudin & Anders 2020 0.17 – – – – – – –
Sim et al. 2019 0.18 – – 32 – – – –

(*): Indicates that this parameter is assigned more than one value in the corresponding reference.

Cluster % RA DEC Plx pmRA pmDE Rv UTI
FoF 2442 77.7 250.22 -39.53 5.67 -11.92 -21.3 0.21 0.0
OCSN 212 75.9 250.14 -39.52 5.68 -11.94 -21.32 0.2 0.0
CWNU 1146 3.3 252.86 -38.13 6.03 -11.84 -22.52 -4.5 0.0

💡 Note: The % column shows the percentage of members that UPK 640 shares with each listed object.

Visualization
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UPK 640 UCC
UPK 640 HUNT23
UPK 640 CANTAT20
Galactocentric position diagram