J/A+A/706/A62 Gaia open cluster stars properties and masses (Malhotra+, 2026)
Stellar masses and mass ratios for Gaia open cluster members.
Malhotra S., Castro-Ginard A., Anders F., Jordi C., Donada J., Luri X.,
Balaguer-Nunez L., Qin S., Jiang Y., Zupic A.
<Astron. Astrophys. 706, A62 (2026)>
=2026A&A...706A..62M 2026A&A...706A..62M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Photometry ;
Optical ; Infrared ; Stars, ages ; Stars, distances ;
Abundances, [Fe/H] ; Stars, masses ; Extinction ;
Parallaxes, trigonometric
Keywords: methods: data analysis - methods: statistical - binaries general -
open clusters and associations: general - solar neighbourhood
Abstract:
Unresolved binaries in star clusters can bias stellar and cluster mass
estimates, making their proper treatment essential for studying
cluster dynamics and evolution.
We aim to develop a fast and robust framework for jointly deriving
stellar masses and multiplicity statistics of member stars, together
with optimal cluster parameters.
We use Gaia DR3 parallaxes together with multi-band photometry of open
cluster (OC) members to infer stellar masses and binary mass-ratios
through simulation-based inference (SBI), while iteratively fitting
the cluster parameters. The validation of our SBI framework on
simulated clusters demonstrates that the inclusion of infrared
photometry significantly improves the detection of low mass-ratio
binaries. The minimum mass-ratio threshold for reliably identifying
unresolved binaries depends on cluster properties and the available
photometry, but typically lies below q=0.5.
Applying our method to 42 well-populated OCs, we derive a catalogue of
stellar masses and mass-ratios for 27201 stars, achieving typical
uncertainties of 0.08 in q and 0.01M☉ in the primary stellar
mass. We analyse the archetype OCs M67 and NGC 2360 in detail,
including mass segregation and mass-ratio distribution among other
characteristics, while deriving multiplicity fractions for the rest of
the sample. We find evidence that the high mass-ratio (q=>0.6) binary
fraction shows a strong correlation with the age and a weak
anti-correlation with the cluster metallicity. Furthermore, the
variation of the binary fraction with stellar mass in OCs shows strong
accordance with the observed dependence for field stars heavier than
~>0.6M☉.
Our work paves a path for future
population-level investigations of multiplicity statistics and
precision stellar masses in extended samples of OCs.
Description:
We provide two tables, clus_sum is a table providing a summary of the
estimated cluster parameters and the number of detected binaries for
each mass-ratio threshold and masses_q which is a catalogue of stellar
masses and mass-ratios of cluster members.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablef1.dat 78 42 Cluster parameters and physical properties
tablef2.dat 679 28073 Masses, mass ratios, posteriors and weighted
modes parameters of cluster star members
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See also:
J/A+A/690/A16 : Nearby open clusters empirical isochrone
(Rottensteiner+, 2024)
J/A+A/686/A42 : Improving the open cluster census. III. (Hunt+, 2024)
J/A+A/675/A89 : Multiplicity fractions in Gaia open clusters (Donada+, 2023)
J/A+A/673/A155 : StarHorse data for 8 spectroscopic surveys (Queiroz+, 2023)
J/A+A/673/A114 : Improving the open cluster census. II. (Hunt+, 2023)
J/A+A/672/A29 : 78 Galactic Open cluster structural parameters
(Cordoni+, 2023)
J/A+A/649/A178 : NGC6791 V604 Lyr disentangled component spectra
(Brogaard+, 2021)
J/A+A/649/A3 : Gaia Early Data Release 3 photometric passbands
(Riello+, 2021)
J/A+A/640/A1 : Portrait Galactic disc (Cantat-Gaudin+, 2020)
J/A+A/632/A3 : MUSE binaries in NGC 3201 (Giesers+, 2019)
J/A+A/623/A108 : Age of 269 GDR2 open clusters (Bossini+, 2019)
J/A+A/622/A110 : Spectroscopic membership for NGC 3532 (Fritzewski+, 2019)
J/A+A/619/A155 : Open cluster kinematics with Gaia DR2 (Soubiran+, 2018)
J/A+A/616/A10 : 46 open clusters GaiaDR2 HR diagrams
(Gaia Collaboration, 2018)
J/A+A/437/457 : NGC 2548 uvbyHβ and proper motions
(Balaguer-Nunez+, 2005)
J/A+A/323/139 : K magnitude of Pleiades low-mass binaries (Bouvier+ 1997)
J/MNRAS/504/356 : Updated parameters of 1743 open clusters (Dias+, 2021)
J/MNRAS/501/4329 : [Fe/H] dependence of the wide-binary fraction (Hwang+, 2021)
J/ApJ/921/117 : 43yr spectrosc. monitoring of the Pleiades region
(Torres+, 2021)
J/ApJ/901/91 : Sp. obs. of rapidly rotating stars in the Pleiades
(Torres, 2020)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/AJ/169/116 : Gaia & 2MASS fitting for Pleiades members (Liu+, 2025)
J/AJ/167/12 : Open cluster parameters with ANN (Cavallo+, 2024)
J/AJ/165/108 : Properties of 600 bona fide stars in the Hyades
(Brandner+, 2023)
J/AJ/165/45 : (H-W2)-W1 vs W2-(BP-K) for 4 open cluster members
(Malofeeva+, 2023)
J/AJ/162/285 : Parameters of 37 binaries in NGC2516 and NGC2422
(Lipartito+, 2021)
J/AJ/161/190 : Radial Velocities of binary population in M67 (Geller+,2021)
J/AJ/161/160 : BINOCS: NEWFIRM & IRAC IR photometry of clusters
(Thompson+, 2021)
J/AJ/157/216 : Stellar multiplicity rate of M dwarfs within 25 pc
(Winters+, 2019)
J/AJ/151/66 : Velocities of WOCS 24009 and WOCS 40007 in NGC 6819
(Brewer+, 2016)
J/AJ/123/1570 : alpha Persei and Praesepe Clusters (Patience+, 2002)
V/160 : SHBoost 2024 (Khalatyan+, 2024)
VII/233 : 2MASS All-Sky Extended Source Catalog (XSC)
(IPAC-UMass, 2003-2006)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/354 : StarHorse2, Gaia EDR3 photo-astrometric distances
(Anders+, 2022)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: tablef1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Cluster name (Cluster)
15- 19 F5.3 [yr] logAge Mean estimated log(Age) of the cluster
(mean_logage)
21- 28 F8.3 pc D Mean estimated distance of the cluster
(mean_dist)
30- 35 F6.3 [Sun] [Fe/H] Value adopted from Joshi et al.
(2024FrASS..1148321J) (mean_feh)
37- 41 F5.3 mag AV Mean estimated extinction in V band (mean_Av)
43- 47 F5.3 --- MR1 Mass-ratio threshold when infrared photometry
is available (qthreshgaia_plus)
49- 53 F5.3 --- MR2 Mass-ratio threshold when only Gaia photometry
is available (qthreshgaia)
55- 58 I4 --- N1 Total number of detected unresolved binaries
above qthreshgaia_plus (nstarsbinaries)
60- 63 I4 --- N2 Total number of detected unresolved binaries
above qthreshgaia (nstarsbinaries_gaia)
65- 68 I4 --- N Number of stars in the MS and have G≤19 mag
(nstarsMS)
70- 73 F4.2 Msun M*low Lowest stellar mass in the catalogue with a
mass-ratio estimate (MSlowermass)
75- 78 F4.2 Msun M*hi Highest stellar mass in the catalogue with a
mass-ratio estimate (MSuppermass)
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Byte-by-byte Description of file: tablef2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name Cluster name (Cluster)
15- 33 I19 --- GaiaDR3 Gaia DR3 source ID (source_id)
35- 44 F10.7 mag Gmag Mean G-band magnitude from GaiaDR3 (app_G)
46- 55 F10.7 mag BPmag Mean BP-band magnitude from GaiaDR3 (app_BP)
57- 66 F10.7 mag RPmag Mean RP-band magnitude from GaiaDR3 (app_RP)
68- 86 F19.16 mas Plx Mean parallax from GaiaDR3 (parallax)
88-103 A16 --- 2MASS ? Source ID in 2MASS catalogue
(designation_2MASS)
105-107 F3.1 --- NN2MASS ? Number of neighbours in 2MASS catalogue
(numberofneighbours_2MASS)
109-111 F3.1 --- NM2MASS ? Number of mates of 2MASS source in Gaia
catalogue (numberofmates_2MASS)
113-115 A3 --- Q2MASS JHK photometric quality flag (phqual2MASS)
117-135 F19.16 mag Jmag ? Mean J-band magnitude (app_J)
137-155 F19.16 mag Hmag ? Mean H-band magnitude (app_H)
157-175 F19.16 mag Kmag ? Mean K-band magnitude (app_K)
177-195 A19 --- WISE Source ID in AllWISE catalogue
(designation_WISE)
197-199 F3.1 --- NNWISE ? Number of neighbours in AllWISE catalogue
(numberofneighbours_WISE)
201-203 F3.1 --- NMWISE ? Number of mates of AllWISE source in Gaia
catalogue (numberofmates_WISE)
205-208 A4 --- QWISE Photometric quality flag of WISE passbands
(phqualWISE)
210-215 F6.3 mag W1mag ? Mean W1-band magnitude (app_W1)
217-222 F6.3 mag W2mag ? Mean W2-band magnitude (app_W2)
224-229 F6.4 Msun MassA ? Mode of mass_A posterior (massAmode) (1)
231-236 F6.4 Msun MassA16 ? 16th percentile of mass_A posterior
(massA16)
238-243 F6.4 Msun MassA50 ? 50th percentile of mass_A posterior
(massA50)
245-250 F6.4 Msun MassA84 ? 84th percentile of mass_A posterior
(massA84)
252-258 F7.4 [Sun] [Fe/H] ? Mode of [Fe/H] posterior (feh_mode)
260-266 F7.4 [Sun] [Fe/H]16 ? 16th percentile of [Fe/H] posterior
(feh_16)
268-274 F7.4 [Sun] [Fe/H]50 ? 50th percentile of [Fe/H] posterior
(feh_50)
276-282 F7.4 [Sun] [Fe/H]84 ? 84th percentile of [Fe/H] posterior
(feh_84)
284-289 F6.4 [yr] logAge ? Mode of log(Age) posterior (logage_mode)
291-296 F6.4 [yr] logAge16 ? 16th percentile of log(Age) posterior
(logage_16)
298-303 F6.4 [yr] logAge50 ? 50th percentile of log(Age) posterior
(logage_50)
305-310 F6.4 [yr] logAge84 ? 84th percentile of log(Age) posterior
(logage_84)
312-317 F6.4 --- q ? Mode of mass-ratio posterior (q_mode) (2)
319-324 F6.4 --- q16 ? 16th percentile of mass-ratio posterior
(q_16)
326-331 F6.4 --- q50 ? 50th percentile of mass-ratio posterior
(q_50)
333-338 F6.4 --- q84 ? 84th percentile of mass-ratio posterior
(q_84)
340-348 F9.4 pc D ? Mode of distance posterior (dist_mode)
350-358 F9.4 pc D16 ? 16th percentile of distance posterior
(dist_16)
360-368 F9.4 pc D50 ? 50th percentile of distance posterior
(dist_50)
370-378 F9.4 pc D84 ? 84th percentile of distance posterior
(dist_84)
380-385 F6.4 mag AV ? Mode of extinction in V band posterior
(Av_mode)
387-392 F6.4 mag AV16 ? 16th percentile of extinction in V band
posterior (Av_16)
394-399 F6.4 mag AV50 ? 50th percentile of extinction in V band
posterior (Av_50)
401-406 F6.4 mag AV84 ? 84th percentile of extinction in V band
posterior (Av_84)
408-417 A10 --- Phot ? Observed photometry used to sample the SBI
posterior (Posterior_used) (3)
419-424 F6.4 Msun MassAw ? Mode of mass_A posterior weighted by
cluster parameters (massAweighted_mode)
426-431 F6.4 Msun MassAw16 ? 16th percentile of mass_A posterior
weighted by cluster parameters
(massAweighted_16)
433-438 F6.4 Msun MassAw50 ? 50th percentile of mass_A posterior
weighted by cluster parameters
(massAweighted_50)
440-445 F6.4 Msun MassAw84 ? 84th percentile of mass_A posterior
weighted by cluster parameters
(massAweighted_84)
447-453 F7.4 [Sun] [Fe/H]w ? Mode of [Fe/H] posterior weighted by
cluster parameters (fehweightedmode)
455-461 F7.4 [Sun] [Fe/H]w16 ? 16th percentile of [Fe/H] posterior
weighted by cluster parameters
(fehweighted16)
463-469 F7.4 [Sun] [Fe/H]w50 ? 50th percentile of [Fe/H] posterior
weighted by cluster parameters
(fehweighted50)
471-477 F7.4 [Sun] [Fe/H]w84 ? 84th percentile of [Fe/H] posterior
weighted by cluster parameters
(fehweighted84)
479-484 F6.4 [yr] logAgew ? Mode of log(Age) posterior weighted by
cluster parameters (logageweightedmode)
486-491 F6.4 [yr] logAgew16 ? 16th percentile of log(Age) posterior
weighted by cluster parameters
(logageweighted16)
493-498 F6.4 [yr] logAgew50 ? 50th percentile of log(Age) posterior
weighted by cluster parameters
(logageweighted50)
500-505 F6.4 [yr] logAgew84 ? 84th percentile of log(Age) posterior
weighted by cluster parameters
(logageweighted84)
507-512 F6.4 --- qw ? Mode of q posterior weighted by cluster
parameters (qweightedmode)
514-519 F6.4 --- qw16 ? 16th percentile of q posterior weighted by
cluster parameters (qweighted16)
521-526 F6.4 --- qw50 ? 50th percentile of q posterior weighted by
cluster parameters (qweighted50)
528-533 F6.4 --- qw84 ? 84th percentile of q posterior weighted by
cluster parameters (qweighted84)
535-543 F9.4 pc Dw ? Mode of dist posterior weighted by cluster
parameters (distweightedmode)
545-553 F9.4 pc Dw16 ? 16th percentile of dist posterior weighted
by cluster parameters (distweighted16)
555-563 F9.4 pc Dw50 ? 50th percentile of dist posterior weighted
by cluster parameters (distweighted50)
565-573 F9.4 pc Dw84 ? 84th percentile of dist posterior weighted
by cluster parameters (distweighted84)
575-580 F6.4 mag AVw ? Mode of extinction in V band posterior
weighted by cluster parameters
(Avweightedmode)
582-587 F6.4 mag AVw16 ? 16th percentile of extinction in V band
posterior weighted by cluster parameters
(Avweighted16)
589-594 F6.4 mag AVw50 ? 50th percentile of extinction in V band
posterior weighted by cluster parameters
(Avweighted50)
596-601 F6.4 mag AVw84 ? 84th percentile of extinction in V band
posterior weighted by cluster parameters
(Avweighted84)
603 I1 --- Outlier [0/1]? Flag if star is a photometric outlier
(outlier_flag)
605-628 A24 --- ClusParam Cluster parameters estimated using this star
(usedinestimating)
630-635 F6.4 --- Single ? Probability of being a single star
(singlestarprobability) (4)
637-657 F21.15 --- Nval ? Number of samples with non-zero weight
when posterior is weighted by cluster
parameters (nvalidsamples)
659 I1 --- inMS [0/1]? Flag if star is in the main-sequence
(MS) and has app_G ≤ 19 mag (in_MS)
661-665 F5.3 --- qthr Mass-ratio threshold above which a star is
considered an unresolved binary
(qthreshused)
667-672 F6.4 --- qadop ? Adopted mass-ratio value, Set to
qweightedmode if => 'qthreshused' for
stars with 'in_MS' = 1, otherwise 0 or NaN
(q_adopted)
674-679 F6.4 --- e_qadop ? Difference between 84th and 16th
percentiles of weighted q posterior
(qadoptederror)
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Note (1): Mass_A is the primary stellar mass i.e. the luminous source with the
larger mass.
Note (2): Mass-ratio (q) is defined as massA/massB, mass_A and mass_B are
primary and secondary respectively. q is always between 0 and 1.
Note (3): Posterior used are as follows:
All_Mags = If photometry from all passbands (Gaia, 2MASS and WISE)
is used, 12321 sources in our sample
Gaia_TMASS = If only Gaia and 2MASS photometry is used, 6370 sources
in our sample
Gaia = If only Gaia photometry is used, 9382 sources in our
sample
Note (4): singlestarprobability is estimated as the fraction of the weighted
posterior samples corresponding to the case of an unresolved binary.
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Acknowledgements:
Sagar Malhotra, sagar(at)fqa.ub.edu
(End) Luc Trabelsi [CDS] 15-Dec-2025