J/AJ/169/145 Resolved binary stars in Pleiades (Chulkov+, 2025)
Resolving Pleiades binary stars with Gaia and speckle interferometric
observations.
Chulkov D., Strakhov I., Safonov B.
<Astron. J. 169, 145 (2025)>
=2025AJ....169..145C 2025AJ....169..145C (SIMBAD/NED BibCode)
ADC_Keywords: Interferometry; Stars, double and multiple; Clusters, open
Keywords: Open star clusters - Speckle interferometry - Visual binary stars
Abstract:
The Pleiades is the most prominent open star cluster visible from
Earth and an important benchmark for simple stellar populations
unified by common origin, age, and distance. Binary stars are its
essential ingredient, yet their contribution remains uncertain due to
heavy observational biases. A resolved multiplicity survey was
conducted for a magnitude-limited G<15mag sample of 423 potential
cluster members, including sources with poorly fitted astrometric
solutions in Gaia DR3. Speckle interferometric observations at the 2.5
meter telescope of the Sternberg Astronomical Institute, Moscow State
University observatory were combined with Gaia data, enabling the
identification of 61 resolved binary or multiple systems within the
0.04-10arcsec (5-1350au) separation range. With speckle observations,
we discovered 21 components in 20 systems. The existence of a Merope
(23 Tau) companion is confirmed after several previous unsuccessful
attempts. We show that the Gaia multipeak fraction is a strong
predictor of subarcsecond multiplicity, as all sources with
ipdfracmulti_peak > 4% are successfully resolved. We found that 10%
of Pleiades stars have a companion with a mass ratio q>0.5 within the
projected separation of 27<s<1350 u, and confirm a deficit of wide
binaries with s>300au. An observed dearth of wide pairs with a large
mass ratio (q>0.55) may imprint the transition from hard to soft
binaries regime at the early stages of cluster evolution. The total
binary fraction for q>0.5 systems is extrapolated to be around 25%.
Description:
The results of a resolved multiplicity survey in Pleiades. Systems
with at least one component having an apparent magnitude G<15 mag are
considered. The list of cluster members from Chulkov
(2024AJ....168..156C 2024AJ....168..156C, Cat. J/AJ/168/156) serves as the input sample.
Speckle observations were conducted with the 2.5-meter telescope of
the Sternberg Astronomical Institute, Moscow State University
observatory.
Table 2 contains Gaia-resolved pairs with angular separation within
10 arcsec.
Table 3 includes systems resolved with speckle interferometric
observations, with angular separation within 1.05 arcsec.
Table 5 includes a list of individual observations for
speckle-resolved binaries.
The detection limits for all entries are provided in Table 6.
Contrast curve and autocorrelation function plots for all observations
are stored at https://doi.org/10.5281/zenodo.14252721 .
Objects:
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RA (2000) DE Designation(s)
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03 46 24.24 +24 06 50.4 Pleiades = Cl Melotte 22
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 116 38 List of resolved Gaia DR3 systems in Pleiades
table3.dat 96 54 List of speckle-resolved systems in Pleiades
table5.dat 95 166 Observations of speckle-resolved Pleiades Stars
table6.dat 69 667 Detection limits for Pleiades sample stars
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/AJ/168/156 : Observational sample of Pleaides stars (Chulkov, 2024)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- WDS WDS Identification (J2000)
12- 28 I17 --- Gaia1 Gaia DR3 designation of primary source
30- 35 F6.3 mag Gmag1 Gaia DR3 G magnitude of primary source
37- 40 F4.2 Msun m1 Isochrone-estimated mass of primary star
42- 45 F4.2 Msun e_m1 Primary mass uncertainty
47- 63 I17 --- Gaia2 Gaia DR3 designation of secondary source
65- 70 F6.3 mag Gmag2 Gaia DR3 G magnitude of secondary source
72- 75 F4.2 Msun m2 Isochrone-estimated mass of secondary star
77- 80 F4.2 Msun e_m2 Secondary mass uncertainty
82- 85 F4.2 arcsec Sep Angular separation
87- 90 F4.2 mas/yr rel-PM ? Relative proper motion of components
92- 95 F4.2 --- Plxdev ? Parallax deviation (see Equation 2)
97-100 F4.2 --- Prob Chance alignment probability
102-106 F5.3 --- q Estimated mass ratio
108-112 F5.3 --- e_q Mass ratio uncertainty
114-116 A3 --- Notes [CFPRSW,] Notes (1)
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Note (1): Notes as follows:
C = multiplicity is suspected from color-magnitude diagram analysis
F = possible cluster nonmember
P = secondary magnitude is derived from isochrone
R = the system has speckle-resolved companion within 1 arcsec (Table 3)
S = spectroscopic binarity related to unresolved companion
W = WDS identifier is newly introduced
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- WDS WDS Identification (J2000)
12- 28 I17 --- Gaia Gaia DR3 designation of primary source
30- 35 F6.3 mag Gmag Gaia DR3 G magnitude of primary source
37- 44 F8.3 yr Date Observation date
46- 49 F4.2 arcsec Sep Angular separation
51 A1 --- Band [Iyz] Passband of the filter (1)
53- 55 F3.1 mag Delm Magnitude contrast
57- 60 F4.2 Msun m1 Isochrone-estimated mass of primary star
62- 65 F4.2 Msun e_m1 Primary mass uncertainty
67- 70 F4.2 Msun m2 Isochrone-estimated mass of primary star
72- 75 F4.2 Msun e_m2 Secondary mass uncertainty
77- 80 F4.2 --- b_q Lower bound of mass ratio m1/m2
82- 85 F4.2 --- q Mass ratio m1/m2
87- 90 F4.2 --- B_q Upper bound of mass ratio m1/m2
92- 96 A5 --- Notes [BDFGNSTW,] Notes (2)
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Note (1): Passband of the filter as follows:
I = Ic Johnson-Cousins passband
y = 550nm 50nm half-width passband
z = 880nm 70nm half-width passband
Note (2): Notes as follows
B = source is blended; G-band magnitude represents the total flux
D = a distant companion is present in Gaia (Table 2)
F = possibly a cluster nonmember
G = this pair is Gaia resolved (Table 2)
N = the companion is previously unreported
S = spectroscopic binarity related to unresolved companion
T = three resolved components within 1 arcsec.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 17 I17 -- Gaia Gaia DR3 designation
19- 28 A10 -- WDS Washington Double Star Catalog designation
30- 35 F6.3 mag Gmag Gaia DR3 G magnitude
37- 44 F8.3 yr Date Observation date
46 A1 -- Band [IRyz] Passband of the filter (1)
48- 51 F4.2 arcsec Seeing Seeing during observations
53 I1 -- Pair Pair number within multiple system
55- 60 F6.4 arcsec Sep Angular separation
62- 67 F6.4 arcsec e_Sep Angular separation uncertainty
69- 74 F6.2 deg PA Position angle
76- 79 F4.2 deg e_PA Position angle uncertainty
81- 84 F4.2 mag Delm Magnitude contrast
86- 89 F4.2 mag e_Delm Magnitude contrast intrinsic uncertainty
91- 95 A5 -- Notes [PRUWq,] Notes (2)
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Note (1): Passband of the filter as follows:
I = Ic Johnson-Cousins passband
R = Rc Johnson-Cousins passband
y = 550nm 50nm half-width passband
z = 880nm 70nm half-width passband
Note (2): Notes as follows:
P = 180 degree ambiguity in position angle
R = no reference star used; contrast estimation less accurate
U = unreliable contrast due to anisoplanatism
W = WDS designation newly introduced
q = observation used for q calculation
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 17 I17 -- Gaia Gaia DR3 designation
19- 24 F6.3 mag Gmag ? Gaia DR3 G magnitude
26- 33 F8.3 yr Date Observation date
35 A1 -- Band [IRyz] Passband of the filter (1)
37- 40 F4.2 arcsec Seeing Seeing during observations
42- 45 F4.2 mag Delm01 Detection limit at 0.1 arcsec
47- 50 F4.2 mag Delm02 Detection limit at 0.2 arcsec
52- 55 F4.2 mag Delm04 Detection limit at 0.4 arcsec
57- 60 F4.2 mag Delm06 Detection limit at 0.6 arcsec
62- 65 F4.2 mag Delm10 Detection limit at 1.0 arcsec
67- 69 A3 -- Notes [bd,] Notes (2)
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Note (1): Passband of the filter as follows:
I = Ic Johnson-Cousins passband
R = Rc Johnson-Cousins passband
y = 550nm 50nm half-width passband
z = 880nm 70nm half-width passband
Note (2): Notes as follows:
b = system is successfully resolved, see binarity parameters in Table 5
d = detection limits are affected (degraded) by the resolved component
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Acknowledgements:
Dmitry Chulkov, chulkovd(at)gmail.com
(End) Patricia Vannier [CDS] 27-Feb-2025