Close Binary Stars in Planetary Nebulae through Gaia EDR3

The aim of this work is to search for evidence of close binary stars associated with planetary nebulae (ionized stellar envelopes in expansion) by mining the astronomical archive of Gaia EDR3. For this task, using big data techniques, we selected a sample of central stars of planetary nebulae from almost 2000 million sources in an EDR3 database. Then, we analysed some of their parameters, which could provide clues about the presence of close binary systems, and we ran a statistical test to verify the results. Using this method, we concluded that red stars tend to show more affinity with close binarity than blue ones.

Robo-AO and SOAR High-Resolution Surveys of Exoplanet Hosting Stars

In the past decade, space-based transit surveys have delivered thousands of potential planet-hosting systems. Each of these needs to be vetted and characterized using follow-up high-resolution imaging. We perform comprehensive imaging surveys of the candidate exoplanets detected by the Kepler and TESS missions using the fully autonomous Robo-AO system and the largely autonomous SOAR speckle imaging system. The surveys yielded hundreds of previously unknown close binary systems hosting exoplanets and resulted in verification of hundreds of exoplanet systems. Evidence of the interaction between binary stars and planetary systems was also detected, including a deep deficit of planets in close binary systems.

The evolution of massive binary systems

The evolution of massive stars in close binary systems is significantly different from single star evolution due to a series of interactions between the two stellar components. Such massive close binary systems are linked to various astrophysical phenomena, for example Wolf-Rayet stars, supernova type Ib and Ic, X-ray binaries and gamma-ray bursts. Also, the emission of gravitational waves, recently observed by the LIGO-Virgo detectors, is associated with mergers in binary systems containing compact objects, relics of massive stars - black holes and neutron stars. Evolutionary calculations of massive close binary systems were performed by various authors, but many aspects are not yet fully understood. In this paper, the main concepts of massive close binary evolution are reviewed, together with the most important parameters that can influence the final outcome of the binary system evolution, such as rotation, magnetic fields, stellar wind mass loss and mass accretion efficiency during interactions. An extensive literature overview of massive close binary models in the light of exciting observations connected with those systems is presented.

Internal magnetic fields, spin-orbit coupling, and orbital period modulation in close binary systems

We introduce a new model to explain the modulation of the orbital period observed in close stellar binary systems based on an angular momentum exchange between the spin of the active component and the orbital motion. This spin-orbit coupling is not due to tides, but is produced by a non-axisymmetric component of the gravitational quadrupole moment of the active star due to a persistent non-axisymmetric internal magnetic field. The proposed mechanism easily satisfies all the energy constraints having an energy budget ∼102 − 103 times smaller than those of previously proposed models and is supported by the observations of persistent active longitudes in the active components of close binary systems. We present preliminary applications to three well-studied binary systems to illustrate the model. The case of stars with hot Jupiters is also discussed showing that no significant orbital period modulation is generally expected on the basis of the proposed model.

What information can we derive from historical Far Eastern guest stars for modern research on novae and cataclysmic variables?

ABSTRACT Recently, there have been several studies on the evolution of binary systems using historical data that are treated as facts in the chain of argument. This paper discusses six case studies of modern dwarf novae with suggested historical counterparts from the historical point of view, as well as the derived consequences for the physics of close binary systems (the dwarf novae Z Cam and AT Cnc, the nebula in M22, and the possible Nova 101, Nova 483 and Nova 1437). I consider the historical Far Eastern reports and, after a careful re-reading of the text, map the given information on to the sky. In some cases, the positions given in modern lists of classical nova–guest star pairs turn out to be wrong, or they have to be considered highly approximate: the historical position should, in most cases, be transformed into areas of the celestial sphere and not into point coordinates. Based on the correct information, I consider the consequences concerning the evolution of close binary systems. The result is that none of the cases of cataclysmic variables suggested to have a historical counterpart can be (fully) supported. Because the identification of the historical record of observation with the cataclysmic variables known today turns out to be always uncertain, a potential historical observation alone cannot be relied on to draw conclusions on the evolution of binaries. Evolution scenarios should be derived from astrophysical observations and modelling only.