J/A+A/706/A251 M-type variables in young nearby open clusters (Minniti+, 2026)
Gaia-VVVX search for M-type variable stars in young nearby open clusters.
Minniti D., Lopez M., Alonso-Garcia J., Cortes-Contreras M., Cruz P.,
Fernandez-Trincado J.G., Saito R.K., Fermiano V., Borissova J., Caceres C.,
Gomez M., Gramajo L.V., Guo Z., Ivanov V.D., Kurtev R., Lucas P.W.,
Majaess D., Obasi C., Palma T., Pullen J.B., Ramirez K.P., Sanders J.,
Smith L.C., Solano E.
<Astron. Astrophys. 706, A251 (2026)>
=2026A&A...706A.251M 2026A&A...706A.251M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Stars, M-type ; Proper motions ;
Photometry, infrared ; Abundances
Keywords: stars: low-mass - stars: variables: general -
open clusters and associations: individual: NGC 6405 -
open clusters and associations: individual: Trumpler 10 -
open clusters and associations: individual: NGC 2422 - infrared: stars
Abstract:
While large samples of nearby M dwarfs are becoming available, it is
usually difficult to estimate some intrinsic physical parameters for
isolated field M dwarfs, especially their ages, radii, and masses.
These parameters can be estimated through a comparison with model
stellar isochrones and/or by studying eclipsing binary systems.
Our goal is to gather and analyze a large sample of variable M dwarfs
that are members of nearby young open clusters and have known
reddenings, distances, ages, and metallicities. This distilled sample
would be useful for the comparison with theoretical models and also
for the identification of eclipsing binaries with substellar
companions (brown dwarfs or giant planets) for future follow-up.
We selected two dozen benchmark young and nearby open clusters (mostly
with 40<age<132Myr and 400<D<700pc, respectively). We then combined
the optical data from Gaia Data Release 3 (DR3) with near-IR JHKs
-band photometry from the VISTA Variables in the Via Lactea eXtended
survey (VVVX) for these target clusters using the proper motions in
order to select members within the cluster radii. Gaia and VVVX both
provide a wide areal coverage that is ideally suited for mapping these
nearby clusters, which are extended on the sky. We then produced
optical and near-IR color-magnitude and color-color diagrams and
applied appropriate color cuts to choose the M-type dwarfs at the end
of the main sequence. The reddening and extinction for all clusters
were estimated using the J-Ks color distributions of the cluster M
dwarfs. We also compared them with the PARSEC theoretical isochrones
adjusted to the respective cluster metallicities, ages, extinctions,
and distances.
Finally, we selected variable M stars according to Gaia DR3 (using
photvariableflag=VARIABLE) and present a catalog of 318 variable
M-dwarf star members of two dozen young nearby Galactic open clusters.
The cross-validation with the Gaia DR3 parallaxes supports the cluster
membership for all these sources. We also present a few examples to
validate the sample of variable cluster M dwarfs.
This well-characterized catalog of M-dwarf members of benchmark open
clusters not only constitutes a prime sample to search for transiting
substellar companions, but also offers a training dataset for
machine-learning applications aimed at selecting future similar
targets.
Description:
This catalogue contains astrometric and photometric parameters for 318
variable M-dwarf stars associated with 24 nearby (D<1kpc) open
clusters. Stellar data include Gaia DR3 coordinates, parallaxes,
proper motions, and optical photometry, as well as near-infrared JHKs
magnitudes from VVVX. Cluster properties such as Galactic coordinates,
distance, age, size, and metallicity are also provided.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
clusters.dat 70 24 *Physical parameters of the open clusters
variable.dat 110 318 Astrometric and photometric data for variable
M-dwarf stars
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Note on clusters.dat: One cluster (NGC 3228) was excluded from the catalogue
due to the absence of detected variable stars.
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Byte-by-byte Description of file: clusters.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Open cluster name
18- 25 F8.4 deg GLON Galactic longitude of the cluster center
27- 33 F7.4 deg GLAT Galactic latitude of the cluster center
35- 39 F5.1 mas/yr pmRA Mean proper motion in right ascension
41- 45 F5.1 mas/yr pmDE Mean proper motion in declination
47- 50 I4 pc Dist Heliocentric distance to the cluster
52- 56 F5.3 mas/yr plx Mean parallax of the cluster
58- 60 I3 Myr Age Cluster age
62- 64 I3 arcmin Size Angular radius of the cluster
66- 70 F5.3 --- [Fe/H] ?=- Mean cluster metallicity
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Byte-by-byte Description of file: variable.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [Gaia DR3]
10- 28 I19 --- GaiaDR3 Variable star Gaia ID
30- 37 F8.4 deg RAdeg Right ascension (J2000.0)
39- 46 F8.4 deg DEdeg Declination (J2000.0)
48- 52 F5.2 mas plx Parallax
54- 59 F6.2 mas/yr pmRA Proper motion in RA
61- 66 F6.2 mas/yr pmDE Proper motion in DEC
68- 72 F5.2 mag Gmag G magnitude
74- 77 F4.2 mag BP-RP Gaia BP-RP color
79- 83 F5.2 mag Jmag J magnitude
85- 88 F4.2 mag e_Jmag ?=- Error on J magnitude
90- 94 F5.2 mag Hmag ?=- H magnitude
96- 99 F4.2 mag e_Hmag ?=- Error on H magnitude
101-105 F5.2 mag Ksmag Ks magnitude
107-110 F4.2 mag e_Ksmag ?=- Error in Ks magnitude
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Acknowledgements:
Dante Minniti, vvvdante(at)gmail.com
Marcela Lopez, m.lpezulloa(at)uandresbello.edu
(End) Patricia Vannier [CDS] 31-Dec-2025