Collinder 261

(VDBH 136; Harvard 6; MWSC 2055; OCL 889; vdBergh-Hagen 136; ESO 065 02; FSR 1627; FoF 45)

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1.0 UTI
1.0
CN
1.0
Cdens
1.0
CC3
1.0
Clit
1.0
Cdup
N50 (P>50% members) 4192
Stellar density (N50/rad) 167.0 [N/pc2]
C3 classification AA
  • CN 1.0 Very rich
  • Cdens 1.0 Very dense
  • CC3 1.0 Very high quality
  • Clit 1.0 Very well-studied
  • Cdup 1.0 Unique
πŸ“₯ Members πŸ“Š Colab πŸ”¬ Bayestar19 MOCAMOCA πŸ” CDS πŸ” Simbad πŸ” CDS (Ξ±, Ξ΄) πŸ” Simbad (Ξ±, Ξ΄)

Overview
ℹ️
Collinder 261 is a very rich, very dense object of very high C3 quality. Its parallax locates it at a moderate distance, below the mid-plane, affected by low extinction. It is catalogued as an extremely massive, near-solar metallicity, very old cluster, but with a large variance across recent sources for the age, metallicity, and mass parameters (see Parameters). It is very well-studied in the literature.

Note: This object contains blue stragglers according to at least one source.

Note: This object shares a very small percentage of members with a later reported entry. See table with shared members information.

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

Cavallo et al. (2024)
Gold sample.

Hunt & Reffert (2024)
Classified as open cluster. CMD class: 0.81 (50th percentile).

Rain et al. (2024)
The cluster hosts a rich BSS population forming a nearly continuous sequence overlapping the ZAMS and binary tracks. A few objects lie below the turnoff and may be sub-subdwarfs or misidentifications. One bright candidate resembles a YSS but does not meet standard CMD criteria.

Hunt & Reffert (2023)
Classified as open cluster. CMD class: 0.81 (50th percentile).

Rain et al. (2021)
There are several stragglers candidates with a radius larger than the apparent radius of the cluster (r=9.0 arcmin (Dias et al., 2002A&A...389..871D, Cat. B/ocl). This object probably suffers from differential reddening. We suggest exploring this effect in future works.

Ahumada & Lapasset (2007)
The red limit of the blue straggler area above the turnoff is (B-V)=0.86. In (1995MNRAS.273...59M) 10 short-period eclipsing variables are found among the 178 straggler candidates identified by the authors from their VI CCD photometry. Among our candidates, the variables are: star 772 (EW), star 1030 (EA/EB), star 1327 (EW), star 2287 (EB/EW), star 2290 (EA/EB).

Data
πŸ” Search references for Collinder 261 in: SciX Simbad
ℹ️
Reference Year RA [deg] DEC [deg] Plx [mas] pmRA [mas/yr] pmDE [mas/yr] Rv [km/s]
UCC 99999– 189.519 -68.379 0.343 -6.364 -2.676 -25.0
Otto et al. 2026 189.527 -68.381 – -6.35 -2.71 -25.2
Li et al. 2025 189.519 -68.377 0.315 -6.351 -2.705 –
Guerco et al. 2025 190.0 -68.4 0.35 -6.42 -2.63 -25.2
Hu & Soubiran 2025 189.512 -68.378 – – – –
Carrasco-Varela et al. 2025 189.802 -68.492 – – – –
Almeida et al. 2025 189.512 -68.378 – – – –
Hunt & Reffert 2024 189.527 -68.381 0.345 -6.367 -2.678 -25.508
Cavallo et al. 2024 189.512 -68.378 0.345 – – –
Rain et al. 2024 189.518 -68.377 0.346 -6.365 -2.686 –
Hunt & Reffert 2023 189.527 -68.381 0.345 -6.367 -2.678 -25.508
Angelo et al. 2023 189.512 -68.378 – -6.37 -2.68 –
Just et al. 2023 189.513 -68.364 – – – –
Jadhav & Subramaniam 2021 189.519 -68.377 – – – –
Jaehnig et al. 2021 189.525 -68.376 0.346 -6.344 -2.714 –
Netopil et al. 2022 189.52 -68.377 – – – -24.43
Rain et al. 2021 189.519 -68.377 0.315 -6.351 -2.705 –
Dias et al. 2021 189.512 -68.378 0.314 -6.344 -2.702 -24.654
Spina et al. 2021 189.522 -68.376 0.316 -6.342 -2.71 –
Cantat-Gaudin et al. 2020 189.519 -68.377 0.315 -6.351 -2.705 –
SΓ‘nchez et al. 2020 189.488 -68.367 – -6.32 -2.721 –
Cantat-Gaudin & Anders 2020 189.519 -68.377 0.315 -6.351 -2.705 –
Liu & Pang 2019 189.513 -68.383 0.331 -6.344 -2.694 –
Soubiran et al. 2018 189.519 -68.377 – – – -24.67
Bica et al. 2019 189.477 -68.369 – – – –
Cantat-Gaudin et al. 2018 189.519 -68.377 0.315 -6.351 -2.705 –
Dias et al. 2018 – – – -6.4 -1.95 –
Sampedro et al. 2017 189.488 -68.367 -0.97 -0.51 – –
Kharchenko et al. 2016 189.513 -68.364 – – – –
Netopil et al. 2016 189.488 -68.367 – – – –
Dias et al. 2014 189.487 -68.367 – -0.65 -0.51 –
Kharchenko et al. 2013 189.525 -68.367 – -10.27 3.32 -30.0
Gozha et al. 2012 189.488 -68.367 – – – –
Bukowiecki et al. 2011 189.521 -68.372 – – – –
Kharchenko et al. 2007 189.48 -68.37 – 0.08 – –
Ahumada & Lapasset 2007 189.475 -68.367 – – – –
van den Bergh 2006 189.475 -68.467 – – – –
Chen et al. 2003 189.479 -68.359 – – – –
Dias et al. 2002 189.488 -68.367 – -0.77 -0.55 -30.0
Lynga 1987 189.489 -68.479 – – – –
van den Bergh & Hagen 1975 188.725 -68.2 – – – –

πŸ’‘ 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] Bfrac BSS
UCC 99999– 2.78 1.0 1.27 6310 0.000 13424 0.37 54
Otto et al. 2026 – – – 6310 0.000(15) – – –
Li et al. 2025 2.74 0.94 – 6646 0.042 – – –
Guerco et al. 2025 – – – 6310 -0.010 – – –
Hu & Soubiran 2025 – – – – -0.190(5) – – –
Carrasco-Varela et al. 2025 2.71 1.00 – 7907 0.100 – – 64(1)
Almeida et al. 2025 2.81 1.00 – 7907 – 17516 – –
Hunt & Reffert 2024 – – – – – 9333(1) – –
Cavallo et al. 2024 2.36 1.24 – 5754 -0.250 – – –
Rain et al. 2024 2.57 1.02 – 8104 – 36941 0.37 –
Hunt & Reffert 2023 2.74 1.21 1.27 1995 – – – –
Angelo et al. 2023 2.61 1.14 – 5623 -0.060 76(1) – –
Just et al. 2023 – – – 5012 – 2254 – –
Spina et al. 2022 – – – – 0.044 – – –
Jadhav & Subramaniam 2021 2.84 0.81 – 6310 – 35172 – 32(1)
Jaehnig et al. 2021 2.88(1) – – – – – – –
Netopil et al. 2022 2.75(1) – – 6026 0.020(1) – – –
Rain et al. 2021 2.90 0.85 – 8913 – – – 53
Dias et al. 2021 2.81 1.00 – 7907 0.019 – – –
Spina et al. 2021 3.12 – – 6310 0.040(20) – – –
Cantat-Gaudin et al. 2020 2.84 0.81 – 6310 – – – –
Kounkel et al. 2020 2.89 1.07 – 1905 – – – –
Cantat-Gaudin & Anders 2020 2.90 – – – – – – –
Liu & Pang 2019 – – – 2630 0.500 – – –
Soubiran et al. 2018 2.90 – – – – – – –
Cantat-Gaudin et al. 2018 2.90 – – – – – – –
Kharchenko et al. 2016 2.68 1.05 – 5012 – – – –
Netopil et al. 2016 7.01 – – 7180 0.000(2) – – –
Heiter et al. 2014 – – – – 0.000 – – –
Kharchenko et al. 2013 2.68 1.05 – 5012 -0.030 – – –
Gozha et al. 2012 2.19 – – 8913 -0.030 – – –
Bukowiecki et al. 2011 3.73(1) 0.88 – 2818 – – – –
Ahumada & Lapasset 2007 – 0.85 – 8913 – – – 54
van den Bergh 2006 2.19 0.85 – 8913 – – – –
Chen et al. 2003 2.19 0.85 – 8900 -0.140(1) – – –
Dias et al. 2002 2.19 0.85 – 8913 -0.030 – – –

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

Cluster % RA DEC Plx pmRA pmDE Rv UTI
OC 0584 0.6 189.55 -68.37 0.42 -6.42 -2.65 – 0.0

πŸ’‘ Note: The % column shows the percentage of members that Collinder 261 shares with each listed object.

Visualization
ℹ️
Collinder 261 UCC
Collinder 261 HUNT23
Collinder 261 CANTAT20
Galactocentric position diagram