Surface flux patterns on planets in circumbinary systems and potential for photosynthesis

Recently, the Kepler Space Telescope has detected several planets in orbit around a close binary star system. These so-called circumbinary planets will experience non-trivial spatial and temporal distributions of radiative flux on their surfaces, with features not seen in their single-star orbiting counterparts. Earth-like circumbinary planets inhabited by photosynthetic organisms will be forced to adapt to these unusual flux patterns. We map the flux received by putative Earth-like planets (as a function of surface latitude/longitude and time) orbiting the binary star systems Kepler-16 and Kepler-47, two star systems which already boast circumbinary exoplanet detections. The longitudinal and latitudinal distribution of flux is sensitive to the centre-of-mass motion of the binary, and the relative orbital phases of the binary and planet. Total eclipses of the secondary by the primary, as well as partial eclipses of the primary by the secondary add an extra forcing term to the system. We also find that the patterns of darkness on the surface are equally unique. Beyond the planet's polar circles, the surface spends a significantly longer time in darkness than latitudes around the equator, due to the stars’ motions delaying the first sunrise of spring (or hastening the last sunset of autumn). In the case of Kepler-47, we also find a weak longitudinal dependence for darkness, but this effect tends to average out if considered over many orbits. In the light of these flux and darkness patterns, we consider and discuss the prospects and challenges for photosynthetic organisms, using terrestrial analogues as a guide.

Magnetic field generation in an accretion disk of close binary star

Using results of 3D MHD numerical simulations we investigate the generation of the magnetic field in an accretion disk of a close binary star. Analysis of the numerical simulations shows that the magnetic field, which is mainly toroidal, is intensively generated in the accretion disk. In the disk, we can distinguish three regions: inner region of the intensive toroidal field generation due to the differential rotation; region of the current sheets; and outer region of the magnetic field dissipation. In the outer regions of the accretion disk of a magnetic close binary system two types of the dynamo may exist. One of them is the laminar dynamo that occurs as a result of the nonaxisymmetric motions. The other type is the turbulent αω-dynamo. Numerical simulations show that during the disk lifetime the dynamo effect in the outer region of the disk can be significant.

Identification of phase-independent spectral lines in close binary V455 CYG: I. Telluric lines

Spectroscopic observations of close binary star V455 Cygni reveal many lines that originate in interstellar and circumstellar medium and the atmo?sphere of the Earth; we found over two hundred such spectral features, and in this paper we present the list of telluric lines we identified through comparison with HITRAN database of molecular lines. The lines that remain unidentified or show peculiar behavior will be discussed in the second part of the paper. .