Examinando por Autor "Gansicke, B. T."

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    The White Dwarf Binary Pathways Survey – IV. Three close white dwarf binaries with G-type secondary stars
    (Royal Astronomical Society, 2021) Hernandez, M. S.; Schreiber, M. R.; Parsons , S. G.; Gansicke, B. T.; Lagos, F.; Raddi, R.; Toloza, O.; Tovmassian, G.; Zorotovic, M.; Irawati, P.; Pasten, E.; Rebassa-Mansergas, A.; Ren, J. J.; Rittipruk, P.; Tappert, C.
    Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.
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    WD 1856 b: a close giant planet around a white dwarf that could have survived a common envelope phase
    (Royal Astronomical Society, 2021) Lagos, F.; Schreiber, M. R.; Zorotovic, M.; Gansicke, B. T.; Ronco, M. P.; Hamers, Adrian S.
    The discovery of a giant planet candidate orbiting the white dwarf WD 1856+534 with an orbital period of 1.4 d poses the questions of how the planet reached its current position. We here reconstruct the evolutionary history of the system assuming common envelope evolution as the main mechanism that brought the planet to its current position. We find that common envelope evolution can explain the present configuration if it was initiated when the host star was on the asymptotic giant branch, the separation of the planet at the onset of mass transfer was in the range 1.69–2.35 au, and if in addition to the orbital energy of the surviving planet either recombination energy stored in the envelope or another source of additional energy contributed to expelling the envelope. We also discuss the evolution of the planet prior to and following common envelope evolution. Finally, we find that if the system formed through common envelope evolution, its total age is in agreement with its membership to the Galactic thin disc. We therefore conclude that common envelope evolution is at least as likely as alternative formation scenarios previously suggested such as planet–planet scattering or Kozai–Lidov oscillations.