This study shows that, among the contact binary systems studied, some have an extremely low mass ratio (q < 0.1) or an ultra-short orbital period (Porb < 0.25 d), which are expected to show evidence of mass transfer progress. It was found that mass, radius and luminosity of the components follow certain relations along the MS and new empirical power relations are extracted.We found that 30 per cent of the systems in the current sample show extreme values in their parameters, expressed in their mass ratio or fill-out factor. Together with 51 already covered by the project and an additional 67 in the existing literature, these systems bring the total number of contact binaries with known combined spectroscopic and photometric solutions to 138. This paper presents the results of a combined spectroscopic and photometric study of 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT Cnc, EE Cet, RWCom, KR Com, V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 Oph, V2612 Oph, V1363 Ori, V351 Peg, V357 Peg, Y Sex, V1123 Tau and W UMa, which was conducted in the frame of the W UMa Project. In this work we describe the scientific rationale, the observing facilities to be used and the methods that will be followed to achieve the goals of CoBiToM Project and we present the first results as an example of the current research on evolution of contact binary systems. The innovation of CoBiToM Project is based on a multi-method approach and a detailed investigation, that will shed light for the first time on the origin of stellar mergers and rapidly rotating stars. A comprehensive analysis will be conducted, in order to investigate the possibility of contact binaries to host planets, as well as the link between inflated hot Jupiters and stellar mergers.
Gravitational phenomena in multiple-star environments will be linked with stellar evolution.
the orbital period modulation, spot activity etc. Obtaining observational data of approximately 100 eclipsing binaries and multiple systems and more than 400 archival systems, the programme aspires to give insights for their physical and orbital parameters and their temporal variations, e.g. The goal is to investigate stellar coalescence and merging processes, as the final state of stellar evolution of low-mass contact binary systems. The Contact Binaries Towards Merging (CoBiToM) Project is a programme that focuses on contact binaries and multiple stellar systems, as a key for understanding stellar nature. Independently of details of the evolution in contact and a relation betweenĪ- and W-type systems, the ultimate fate of contact binaries involves the coalescence of both components into a single fastīinary and multiple stellar systems are numerous in our solar neighborhood with 80 per cent of the solar-type stars being members of systems with high order multiplicity. Is seen between the tracks and the observed graphs. Wind, accompanied by mass transfer from an advanced evolutionary secondary to the main-sequence primary. Theoretical tracks are computed assuming angular momentum loss from a system via stellar It results from the observed correlations among contact binary An alternative scenario of evolution in contact is presented and discussed, based on the observationalĭata of over one hundred low-temperature contact binaries. The mass/energy transfer rate is different, leading to quiteĭifferent evolutionary results. In a similar way but under slightly different circumstances. As the components of close detached binaries approach each other and contact binariesĪre formed, following evolutionary paths transforms them into systems of two categories: A-type and W-type. Sequences connecting A- and W-type systems. Various scenarios of contact binary evolution have been proposed in the past, giving hints of (sometimes contradictory) evolutionary
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