Search for contact systems among EB-type binaries: I. TT Herculis.

In a search of contact systems among EB-type binaries, the existing photometric observations of TT Her have been analyzed. We find an unambiguous solution, contrary to previous analyses which resented several possibilities. The system is semi-detached, with the primary fillin the lobe. There is evidence that the primary is evolved off the main sequence, and that mass transfer is taking place from the primary to the secondary, which is therefore enlarged by accretion. The temperature of the primary component is found to be about 7240 K, thus solving one of the problems for this system. We conclude that TT Her is the progenitor of an evolved contact binary

The RS CVn eclipsing binary RT And revisited

All available photometric and spectroscopic data of the short-period RS CVn-like binary RT And have been reanalyzed in a homogeneous way. The long-term orbital period change is explained by two period jumps, a continuous period decrease combined with the light-time orbit or two light-time orbits. UBVRIJK light curves without maculation effects together with the radial velocities of both components were analysed with the Wilson-Devinney program to compute the photometric and spectroscopic elements and derive the masses of the components: [FORMULA] = 1.10[FORMULA]0.02 [FORMULA] and [FORMULA] = 0.83[FORMULA]0.02 [FORMULA]. The high orbital inclination [FORMULA] was confirmed by photoelectric observations of the secondary minimum. The mean observed U light curve shows additional light during the secondary minimum. The small eccentricity found by several authors from the light-curve analysis cannot be ruled out. The face-to-face position of the spots on the surface of both components in 1971 indicates the possibility of a mass transfer from the primary to the secondary component through a magnetic bridge connecting both active regions. Analysis of all available light curves suggests a random position of starspots and does not confirm the idea of active longitude belts. The absolute parameters of the binary together with maximal apparent V brightness set the distance of RT And to 83[FORMULA]2 pc, close to the Hipparcos value of 75[FORMULA]6 pc

The RS CVn binary XY UMa as a member of a triple system

New minima of the short period RS CVn binary system XY UMa taken in 1997-98 follow the light-time orbit with a 30.5 years period. An inferior conjunction of the third body with mass 0.23 [FORMULA] 0.03 [FORMULA] occurred in 1979. It is suggested that the light-curves of XY UMa taken in 1978-79 were affected by the eclipse of the binary system by a dusty envelope of the protostellar object responsible also for the observed infrared excess. There is no correlation between the long-term brightness variations of the system and the minima times in the O-C diagram, so its explanation by the Applegate mechanism proposed recently by Erdem & Güdür (1998) is brought into question

Multifrequency monitoring of RU Lupi: I. observations

Astronomy and Astrophysics Suppl., in pressConsiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Multifrequency monitoring of RU Lupi: II. the model

To appear in Astronomy and AstrophysicsConsiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Study Of Backward Produced Protons In Pi- Nucleus Interactions At 40-gev/c.

The backward production of protons in the reaction \u3c0-A \u2192 p\u2193X is studied at 40 GeV incident energy with the different nuclear targets : C, Cu, Pb. The structure function shows a slope independent of the target atomic weight A and slightly dependent on the proton production angle. The invariant cross-section, normalized to the nucleon, increases with A up to a plateau which varies with the incident energy. Finally the ratios R = (F A/A)/(FC/AC) and n = ln(F A/FC)/ln(A/AC), where F = (E/p 2)(d2\u3c3/(d p d\u3a9)), show a flat dependence on the momentum of the proton backward produced. These results are in favour of few-nucleon correlation models