Ondřej Pejcha

Our group participated in a conference that was conveniently located in Prague. We contributed to the program by talks of Camille Landri, Jakub Cehula, and Ondřej Pejcha.

New paper by PhD student Camille Landri looks at how we can get asymmetric outflows from red supergiants such as VY CMa and other similar objects. The idea is that a companion coming in on a grazing excentric orbit will unbind a small amount of gas from the red supergiant. This gas is subject to rapid radiative cooling and forms dust, which gets pushed away from the supergiant by its radiative pressure. Radiative cooling and dust driving are necessary to form outflows that are anisotropic in the sense that the ejection happens only in a fraction of a solid angle near the pericenter. After many grazing orbits, the ejections form an asymmetric structure with imprinted spiral-like pattern. The paper (accepted to MNRAS) discusses origin, final fate, and observational implications of this scenario.

I had a great time giving colloquium at the historical library of Hamburg Observatory, talking to many interesting people and enjoying serene grounds and historic telescopes. Thanks Diego Calderón Espinoza for hosting me!

Our PhD student Milan Pešta is spending April at Australian National University in the group of Prof. Yuan-Sen Ting and working on various applications of machine learning in time-domain astronomy.

Our PhD students were successful in obtaining student grants from the Grant Agency of the Charles University. Camille Landri (with Anthony Kirilov as a co-I) won with a project title The impact of binary evolution on common envelope evolution, and Jakub Cehula will work on Baryon ejection in magnetar giant flares: implications for r-process nucleosynthesis and fast radio bursts. Congratulations!

Last week three of our PhD students travelled to New York to a Workshop on stable mass transfer in binaries held at Center for Computational Astrophysics. Milan and Jakub gave contributed talks on contact binaries and a new mass transfer model.

Congratulations to Michal Jireš who defended his Bachelor thesis entitled Simulation of rings surrounding the progenitor of SN1987A. Good luck with future endeavors!

We were again successful in the competition for time on national supercomputer IT4Innovations. PhD student Camille Landri won 20 000 node hours (4.32 million CPU hours) on Barbora cluster and postdoc Damien Gagnier secured 82 000 node hours (10.496 million CPU hours) on Karolina cluster. Both awards are intended for projects involving binary star interactions and common envelope evolution.

In the past two weeks we were visited by Łukasz Wyrzykowski from Warsaw University and Subo Dong and KIAA in Beijing. Both gave seminars and talked to students, postdocs, and staff.

PhD student Jakub Cehula submitted a paper on Dynamics of baryon ejection in magnetar giant flares: implications for radio afterglows, r-process nucleosynthesis, and fast radio bursts written together with Todd Thompson (Ohio State) and Brian Metzger (Columbia/Flatiron). The paper is a result of Jakub’s two month visit at Ohio State earlier this Spring.