On the properties of contact binary stars

Abstract

Abstract.We have compiled a catalogue of light curve solutions of contact binary stars. It contains the results of 159 light curve solutions. The properties of contact binary stars were studied using the catalogue data. As is well known since Lucy's (1968a,b) and Mochnacki's (1981) studies, primary components transfer their own energy to the secondary star via the common envelope around the two stars. This transfer was parameterized by a transfer parameter (ratio of the observed and intrinsic luminosities of the primary star). We prove that this transfer parameter is a simple function of the mass and luminosity ratios. We introduced a new type of contact binary stars: H subtype systems which have a large mass ratio (q > 0.72). These systems show behaviour in the luminosity ratio-transfer parameter diagram that is very different from that of other systems and according to our results the energy transfer rate is less efficient in them than in other types of contact binary stars. We also show that different types of contact binaries have well defined locations on the mass ratio -luminosity ratio diagram. Several contact binary systems do not follow Lucy's relation (L 2 /L 1 = (M 2 /M 1 ) 0.92 ). No strict mass ratio -luminosity ratio relation of contact binary stars exists.

A Variable Star Census in a Perseus Field

“…This high value of the third light squeezes the amplitude to the observed value and can explain the large difference in the observed amplitudes. Similarly high third light values are common in other EW binaries, e.g., with a record of (Lipari & Sistero 1985;Csizmadia & Klagyivik 2004). The results for NSVS 1913469 are shown in Table 2 and in Figure 4. …”

“…Among the modeled EW-type variables, we further distinguish between A-subtype and W-subtype systems following Binnendijk (1965) and Csizmadia & Klagyivik (2004). In an A-subtype system, the hotter star is the more massive component and it is vice versa for members of a W-subtype system.…”

TYC 2675-663-1: a newly discovered W UMa system in an active state

“…TYC 2675-663-1 displays eclipses with clearly different depths, which would imply non-thermal equilibrium. Nevertheless, the stars have spectral types of F5 and G7 in the typical range of W UMa class and appear to be in geometrical contact despite the temperatures being different by approximately 940 K. The high mass ratio we derive, q ≡ M 2 /M 1 = 0.81 ± 0.05, identifies the object as an H-type W UMa variable ("H" for high mass ratio), a subgroup first proposed by Csizmadia et al (2004). In these objects the energy transfer rate appears to be less efficient than in other types of contact binaries.…”

Modelling of W UMa-type variable stars

“…In the A-type systems the larger component has the higher temperature whereas in the W-type systems the smaller component has the higher temperature. Observationally it has been found 23 that the A-type systems tend to have low mass ratios (q < 0.3) and spectral type from A to F. W-type systems usually have mass ratios q > 0.3 and spectral types of G or K. In most cases, the orbital periods of W-type systems are smaller than those of the A-types. 24 The O'Connell effect is noted more in the light curves of the W-type systems, suggesting that they are more magnetically active than the A-type systems.…”