J/A+A/710/A49 New sample of low mass ratio contact binary systems (Poro+, 2026) ================================================================================ Multivariate statistical analysis of contact binaries with a low mass ratio: Definition, dynamical stability, and parameter relations. Poro A., Poggiani R., Foroutanfar A., Harzandjadidi R., Kahali Poor N., Alicavus F. =2026A&A...710A..49P (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Binaries, eclipsing ; Stars, masses ; Stars, diameters ; Optical Keywords: methods: data analysis - binaries: eclipsing - stars: fundamental parameters Abstract: This study explores multiple aspects of W Ursae Majoris (W UMa) contact binary systems with low mass ratios. We provide empirical insights into their definition, structure, rotational stability, and parameter relations. We first examined the range of mass ratios that characterize these systems, and based on an analysis of 818 contact binaries, we established an empirical threshold of q~0.27 to identify systems with a low mass ratio. To investigate the rotational stability, we conducted a Monte Carlo analysis of the squared gyration radii (k1^2^ and k2^2^) and assessed the resulting spin-to-orbital angular momentum ratio (Jspin/Jorb). While k1 remains nearly constant, k2 and Jspin/Jorb decrease slightly with increasing mass ratio. This emphasizes the role of the secondary star's internal structure. Moreover, we compiled a dedicated sample of 115 contact binaries with a low mass ratio and estimated their absolute parameters using Gaia DR3 parallaxes. From this dataset, we derived empirical parameter relations for systems with a low mass ratio that provide a useful reference for future observational and theoretical studies. The resulting datasets and statistical summaries offer benchmarks for modeling, stability evaluation, and evolutionary studies of W UMa-type binaries with low mass ratios. Description: This table contains the new sample of contact binary systems with a low mass ratio used in the paper. It lists literature identifiers and classifications, light-curve parameters, and absolute physical parameters derived or adopted in the analysis. Some systems may appear more than once if multiple literature solutions or classifications were retained for comparison. Blank entries denote unavailable values in the source data. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 319 115 New sample of low mass ratio contact binary systems -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 28 A28 --- System System name 30- 48 A19 --- Bibcode ADS bibliographic code of the reference source 50 A1 --- Subtype Contact-binary subtype (A or W) 52- 58 A7 --- EclType Eclipse type (Total or Partial) 60- 67 F8.6 d Period Orbital period 69- 70 A2 --- Method Source/method flag: SP or PH 72- 75 I4 K T1 Effective temperature of the primary component 77- 80 I4 K T2 Effective temperature of the secondary component 82- 86 F5.3 --- q Mass ratio used in the literature source 88- 92 F5.3 --- invq ? Inverse mass ratio, when applicable 94- 98 F5.2 deg i Orbital inclination 100-104 F5.3 --- f Fillout factor 106-110 F5.3 --- l1 Luminosity contribution/fraction of the primary component 112-116 F5.3 --- l2 Luminosity contribution/fraction of the secondary component 118-122 F5.3 --- r1 Fractional radius of the primary component 124-128 F5.3 --- r2 Fractional radius of the secondary component 130-132 A3 --- l3 Third-light flag or contribution 134-136 A3 --- Spot Spot flag 138-142 F5.3 Msun M1 Mass of the primary component 144-148 F5.3 Msun e_M1 Uncertainty in M1 150-154 F5.3 Msun M2 Mass of the secondary component 156-160 F5.3 Msun e_M2 Uncertainty in M2 162-166 F5.3 Rsun R1 Radius of the primary component 168-172 F5.3 Rsun e_R1 Uncertainty in R1 174-178 F5.3 Rsun R2 Radius of the secondary component 180-184 F5.3 Rsun e_R2 Uncertainty in R2 186-190 F5.3 Lsun L1 Luminosity of the primary component 192-196 F5.3 Lsun e_L1 Uncertainty in L1 198-202 F5.3 Lsun L2 Luminosity of the secondary component 204-208 F5.3 Lsun e_L2 Uncertainty in L2 210-214 F5.3 mag Mbol1 Bolometric magnitude of the primary component 216-220 F5.3 mag e_Mbol1 Uncertainty in Mbol1 222-226 F5.3 mag Mbol2 Bolometric magnitude of the secondary component 228-232 F5.3 mag e_Mbol2 Uncertainty in Mbol2 234-238 F5.3 [cm/s2] logg1 Surface gravity of the primary component 240-244 F5.3 [cm/s2] e_logg1 Uncertainty in logg1 246-250 F5.3 [cm/s2] logg2 Surface gravity of the secondary component 252-256 F5.3 [cm/s2] e_logg2 Uncertainty in logg2 258-262 F5.3 Rsun a Semimajor axis 264-268 F5.3 Rsun e_a Uncertainty in a 270-275 F6.3 --- logJ0 Logarithm of the orbital angular momentum 277-281 F5.3 --- e_logJ0 Uncertainty in logJ0 283-287 F5.3 mag Av Interstellar extinction in the V band 289-293 F5.3 mag e_Av Uncertainty in Av 295-300 F6.3 mag BC1 Bolometric correction of the primary component 302-306 F5.3 mag e_BC1 Uncertainty in BC1 308-313 F6.3 mag BC2 Bolometric correction of the secondary component 315-319 F5.3 mag e_BC2 Uncertainty in BC2 -------------------------------------------------------------------------------- Acknowledgements: Fahri Alicavus, fahrialicavus(at)comu.edu.tr License: CC-BY-4.0 ================================================================================ (End) Patricia Vannier [CDS] 04-May-2026