Computing time at IT4I


Our postdocs were again successful in obtaining supercomputer time on the Czech supercomputer infrastructure IT4Innovations. Diego Calderón won 2.2 million CPU hours to perform radiation hydrodynamics simulations of transients. Damien Gagnier won 12.3 million CPU hours on the brand new Karolina cluster to perform 3D hydrodynamic simulations of common envelope.

Mass-ratio distribution of contact binary stars

First paper by PhD student Milan Pešta developing a method to estimate mass-ratio distribution of contact binaries simply from the distribution of their light curve amplitudes. This was originally proposed by Rucinski (2001), but in this paper we reach sufficient sensitivity to determine the minimum mass ratio, when contact binaries merge due to the Darwin instability. This is possible thanks to a new Bayesian method to filter contaminants and Kepler data. The method can be easily extended to much bigger samples from TESS or Gaia. The paper is submitted to A&A and the preprint can be accessed at https://arxiv.org/abs/2212.02553.

Trip to Valašské Meziříčí

Just like last year, this September we travelled to Observatory at Valašské Meziříčí to gain hands-on experience with telescopes and photometry. Unfortunately, the weather was extremely bad and it rained almost the whole time. But we still toured the observatory, learned about telescopes and detectors, and enjoyed sights and events nearby.

The complex dynamical past and future of double eclipsing binary CzeV343: misaligned orbits and period resonance

New paper on double eclipsing binary (2+2 quadruple) CzeV343 discovered and meticulously followed by Pavel Cagaš over the last 11 years (99 nights). Combining his data with TESS, including 2-min data from our GI proposal, and spectroscopy, we find a bunch of interesting things.

Continue reading “The complex dynamical past and future of double eclipsing binary CzeV343: misaligned orbits and period resonance”

Computing time at IT4I

Our postdocs were successful in obtaining supercomputer time on the Czech supercomputer infrastructure IT4Innovations. Diego Calderón won 26 000 node hours (approx. 900 000 CPU hours) on Barbora cluster to perform radiation hydrodynamics simulations of transients. Damien Gagnier won 36 000 node hours (approx. 4 600 000 CPU hours) on the brand new Karolina cluster to develop 3D hydrodynamic simulations of common envelope.

Supernovae in colliding-wind binaries: observational signatures in the first year

When a core-collapse supernova explodes in a binary star system, the ejecta might encounter an overdense shell, where the stellar winds of the two stars previously collided. It is worth looking more closely at this colliding-wind shell, because it’s structure can be relatively well predicted based on the properties of the binary. Together with Diego and Petr, we investigated what observable effect for light curves and flash ionization arises from supernova hitting the colliding wind shell. In the process, we developed a semi-analytic model of CSM distribution in colliding-wind binaries calibrated by Diego’s 3D AMR simulations. We combined this model with a thin shell model for supernova shock interaction that is angularly dependent. The conclusion is that observable signatures still require relatively high wind mass-loss rates, which might not be completely realistic, and nearly equal-mass companions at large separations, which might be rare. Preprint available here.

Observing trip to Valašské Meziříčí

We are a primarily theoretical group, but close connection to observations is essential to keep us grounded in the reality. We spent three nights in Valašské Meziříčí with the aim of using 20cm telescope with CCD camera at the local Observatory. Although only one night was clear, we learned how to use the telescope, got familiar with basic deep sky objects, and tried processing time-series photometry on archival data. Media coverage of our visit.