Circumstellar planets in binary star systems provide unique constraints on the formation and dynamical evolution of planets. We present an empirical formula for the stability boundary of coplanar retrograde orbits, similar to the classic one for coplanar prograde orbits. We discuss two of the tightest binaries with circumstellar planets: HD 59686 and ν Octantis. For HD 59686, dynamical fitting of the radial velocity data and stability analysis show that the planet must be either on a nearly coplanar retrograde orbit or in one of the narrow regions of prograde orbits stabilized by secular apsidal alignment. For ν Octantis, a nearly coplanar retrograde planetary orbit is the only option for dynamical stability. We also discuss the mysterious case of ε Cygni. It shows short-period radial velocity variations that closely resemble the signal of a Jupiter-mass planet, but the period and amplitude change over time and dynamical stability analysis rules out a planet.

In discussing open question in the field of massive stars, I consider their evolution from birth to death. After touching upon massive star formation, which may be bi-modal and not lead to a zero-age main sequence at the highest masses, I consider the consequences of massive stars being close to their Eddington limit. Then, when discussing the effects of a binary companion, I highlight the importance of massive Algols and contact binaries for understanding the consequences of mass transfer, and the role of binaries in forming Wolf-Rayet stars. Finally, a discussion on pair instability supernovae and of superluminous supernovae is provided.

In this poster, using the POSYDON code, we present results on binary progenitors of stripped-envelope SNe and their companions. We find that most progenitors are expected to explode, according to typical SN prescriptions (in contrast to single star progenitors). We also show the expected masses and position in the HR diagram of the companions of these SNe at the moment of explosion, allowing us to do a first statistical comparison with the compiled sample of observational detections (or upper limits) on these companions.

We present a sample of nearly 650 widely separated double white dwarf binaries found using Gaia DR2 astrometry. We derive preliminary total ages for each white dwarf in our sample using Gaia photometry and compare the total ages of both components of each binary in our sample. We find agreement within 3 sigma between the two ages ∼85% of the time with median age uncertainties of ∼3.5 Gyr depending on which initial-final mass relation is used. When a subsample with the most precise ages is used, the agreement within 3 sigma drops to ∼70% with median age uncertainties of 300-600 Myr.

Basic questions about black holes, some of which are fairly old, include (1) What is a black hole? (2) Do black holes exist? And the answer to this depends a good deal on the answer to (1), (3) Where, when, why, and how have they formed? and (4) What are they good for? Here I attempt some elaboration of the questions and partial answers, noting that general relativity is required to described some of the phenomena, while dear old Isaac Newton is OK for others.

Binary stars possibly exists in most galaxies and star clusters. Their evolution can lead to significant change in stellar population studies. Binary star to fit group (BS2fit: ∞) has built up a binary star stellar population synthesis model and used it in a few works. This page is to introduce the model and its possible applications.

Statistical information on 8280 individual radio observations of binary stars, predominantly at 8·4 GHz using the Parkes 64 m antenna, is presented. Three main groups are distinguished: (i) RS CVn stars, (ii) classical Algol binaries (EA2s), and (iii) detached pairs of generally early type (ETBs).

The RS CVn stars more frequently gave rise to detectable fluxes, while the ETBs, in these data, are a small and rather heterogeneous class. The Algols' emission appears to increase near conjunction phases, though we cannot clearly distinguish any special property of the Algols' phase-dependent behaviour that is not also shared by the RS CVn binaries. Both these categories' data show a bimodal, phase-dependent pattern to the distribution of detections, suggesting that these binary types share similar underlying physical properties, though there could also be other factors at play. The sample sizes of the Algols and particularly the ETB detections are too small for effective, discriminatory statistics, however.

The method of spectral disentangling has now created the opportunity for studying the chemical composition in previously inaccessible components of binary and multiple stars. This in turn makes it possible to trace their chemical evolution, a vital aspect in understanding the evolution of stellar systems. We review different ways to reconstruct individual spectra from eclipsing and non-eclipsing systems, and then concentrate on some recent applications to detached binaries with high-mass and intermediate-mass stars, and Algol-type mass-transfer systems.

In the field of visual double stars, a long term follow-up is required, since their orbital periods may reach several centuries. Created in 1981 within the Société Astronomique de France (SAF) with the support of the late Paul Muller (1910-2000), the Commission des Etoiles Doubles provides the framework for the necessary collaboration between professional and amateur astronomers, through generations. The late Dr. Paul Baize (1901-1995) was a model for its members. Several professional astronomers became scientific advisors of the Commission and have guided many works made by amateurs.

We numerically investigate the conditions for planetesimal accretion in the circumprimary disk under the perturbing presence of a companion star, with focus on the γ Cephei system. Gas drag is included with a dissipating time scale of 105 years. We show at the beginning(within 103 ∼ 104 years), gas drag damps the ΔV between planetesimals of same sizes and increases ΔV between planetesimals of different sizes. However, after increasing to high values(300∼800m/s), we find the ΔV between bodies of different sizes decrease to very low values (below 10m/s) in a few 105yrs (depending on the gas-dissipating time scale Tdamp, radial size Rp and semi-major axis ap of planetesimals). Hence, the high ΔV is somewhat short-lived, and runaway accretion can be turned on later. We conclude that the conditions for planetary formation in binary systems (even close binary systems) are much better than what we expected before.

As of today more than 30 planetary systems have been discovered in binary stars. In all cases the configuration is circumstellar, where the planets orbit around one of the stars. The formation process of planets in binary stars is more difficult than around single stars due to the gravitational action of the companion. An overview of the research done in this field will be given. The dynamical influence that a secondary companion has on a circumstellar disk, and how this affects the planet formation process in this challenging environment will be summarized. Finally, new fully hydrodynamical simulations of protoplanets embedded in disks residing in a binary star will be presented. Applications with respect to the planet orbiting the primary in the system γ Cephei will be presented.

The presence of close (≲ 0.1 AU) stellar companions must greatly alter the circumstellar environment of classical T Tauri stars, including severe truncation if not elimination of circumstellar disks. It is thus remarkable how little impact the presence of a close companion has on our observable diagnostics for accretion and outflow. Emission line shapes, degrees of continuum veiling, and spectral energy distributions are all indistinguishable between single classical T Tauri stars and classical T Tauri close binaries. Some of the most classical T Tauri stars that laid the foundation for our single-star accretion-disk paradigm have turned out to have close companions. Periodicities in spectral signatures are suggestive of the presence of accretion flows from circumbinary disks to the circumstellar regions; the subsequent flow of material through the circumstellar region to the stellar surface in the presence of a stellar magnetosphere is unstudied. Observations of stellar rotation distributions in close binaries suggest that inner disk regions may act to regulate stellar angular momentum.

The winding up of a conference like this provides the opportunity to look (1) backwards at how we reached the present stage of understanding of binary star behavior and its relationship to the rest of astronomy, (2) around at the garden of unsolved problems, and (3) cautiously forward at what might come next.

Processing long-baseline interferometry data presents a unique set of complications: How does one derive relative astrometry from interferometric data? How can 1-D interferometric results be used to solve a 2-D orbit? How can baseline-only solutions be combined with historical data and how should interferometric data be published so that they can be combined with archived data? What new techniques for interferometers are coming on line? This paper contains a brief review of interferometric data analysis in the context of binary star astrometry.

Population synthesis of binary stars with relativistic component is presented.

Very massive stars (${\gtrsim} 20$ M$_{\odot}$) are rare but important components of galaxies. Products of core nucleosynthesis from these stars are distributed into the circumstellar environment via wind-driven mass loss. Explosive nucleosynthesis after core collapse further enriches the galactic medium. Clusters of such stars can produce galactic chimneys which can pierce the galactic disk and chemically enrich intergalactic space. Such processes are vitally important to the chemical evolution of the early Universe, when the stellar mass function was much more weighted to massive stars.

Very massive stars are difficult to study, since they are formed in distant clusters which yield problems of sensitivity and source crowding. A relatively new tool for studying these systems is via high spatial, spectral and temporal resolution observations in the X-ray band. In this note we describe some recent progress in studying mechanisms by which very massive stars produce X-ray emission.

V923 Aql is a well known Be star with strong shell spectrum. It was included in the list of shell stars of Merrill and Burwell (1949). A detailed study of the radial velocity variations in the spectrum of the star based on wide collection of spectral observations was presented in the work of Koubsky et al. (1988). In this work an orbital period of 214.756 days was suggested for the binary system consisting of a B5–7 primary and low mass (0.5 Msol).