Eclipsing Binaries in the OGLE Variable Star Catalog.II. Light Curves of the W UMa-type Systems in Baade's Window

Abstract

Light curves of the contact systems visible in the direction of Baade's Window have been analyzed using the first coefficients of the Fourier representation. The results confirm that the geometric contact between components is usually weak. Systems showing significant differences in the depths of eclipses are very rare in the volume-limited sample to 3 kpc: only 2 among 98 contact systems show the difference larger than 0.065 mag; for most systems the difference is <0.04 mag. If this relative frequency of 1/50 is representative, then one among 12,500 - 15,000 Main Sequence F-K spectral-type stars is either a semi-detached or poor-thermal-contact system. Below the orbital period of 0.37 day, no systems with appreciable differences in the eclipse depths have been discovered. Since large depth differences are expected to be associated with the "broken-contact" phase of the Thermal Relaxation Oscillations, this phase must be very short for orbital periods above 0.37 day and possibly entirely absent for shorter periods. In the full sample, which is dominated by intrinsically bright, distant, long-period systems, larger eclipse-depth differences are more common with about 9% of binaries showing this effect. Sizes of these differences correlate with the sense of light-curve asymmetries (differing heights of maxima) for systems with orbital periods longer than 0.4 day suggesting an admixture of semi-detached systems with accretion hot spots on cooler components. The light-curve amplitudes in the full sample as well as in its volume-limited sub-sample are surprisingly small and strongly suggest a mass-ratio distribution steeply rising toward more dissimilar components. Many low mass-ratio systems remain to be discovered in the sky field.

latex 14 pages of text and 14 figures (aastex40 and psfig), submitted to AJ; the first paper astro-ph/9607009 will appear in AJ, Jan.1997

Cited by in corpus (25)

• Stellar Rotation in M35: Mass-Period Relations, Spin-Down Rates, and Gyrochronology
• Eclipsing binaries in ASAS catalog
• Radial Velocity Studies of Close Binary Stars.I
• Radial Velocity Studies of Close Binary Stars.IV
• Contact Binaries of the Galactic Disk: Comparison of the Baade's Window and Open Cluster Samples
• Physical parameters of 62 eclipsing binary stars using the ASAS-3 data$-$I
• The photometric-amplitude and mass-ratio distributions of contact binary stars
• A Comprehensive Catalogue of Variable Stars in the field of 47 Tucanae
• The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
• Time-Series Photometry of M67: W UMa Systems, Blue Stragglers, and Related Systems
• Automated classification of variable stars for ASAS 1-2 data
• Eclipsing binaries in the MACHO database: New periods and classifications for 3031 systems in the Large Magellanic Cloud
• 15000 Ellipsoidal Binary Candidates in TESS: Orbital Periods, Binary Fraction, and Tertiary Companions
• Eclipsing Binaries in the OGLE Variable Star Catalog.III. Long-Period Contact Systems
• Mass-ratio distribution of contact binary stars
• Photometric variability in the open cluster M67 I. Cluster members detected in X-rays
• W Crv: The shortest-period Algol with non-degenerate components?
• Case AD, AR, and AS binary evolution and their possible connections with W UMa binaries
• Long-term Photometric Analysis of the Active W UMa-type System TU Bootis
• Eclipsing Binaries in the OGLE Variable Star Catalog. IV. The Pre-Contact, Equal-Mass Systems
• Eclipsing Binaries in the OGLE Variable Star Catalogs.V. Long-Period Beta Lyrae-type Systems in the Small Magellanic Cloud and the PLC-beta Relation
• Zwicky Transient Facility and Globular Clusters: the Period-Luminosity and Period-Luminosity-Color Relations for Late-Type Contact Binaries
• Optical photometry and X-ray monitoring of the "Cool Algol" BD+05 706: Determination of the physical properties
• Contact Discontinuities in Models of Contact Binaries Undergoing Thermal Relaxation Oscillations
• Pipeline Reduction of Binary Light Curves from Large-Scale Surveys