Ondrej Pejcha

Accepted to ApJL, this work marks the end of my @ERC_Research StG that finished in the summer but I hope it is also just a beginning on the path of making LRNe useful probes of binary evolution! arxiv.org/abs/2508.09257

Amazing to see how the shock feeds the energy to the rest of the ejecta for reprocessing, while remaining hidden inside. But the photosphere is not spherical and can dramatically change shape if the shock encounters a well-defined outer edge of the CSM.

We have good reasons to think that Luminous Red Novae (LRNe) signal the merger of two stars. But what powers the light curves of the brightest extragalactic events? Using radiation transport module developed by Diego Calderón for moving-mesh code JET by Paul Duffell...

Filantropům hledajícím jak pomoci české vědě doporučuji podpořit české držitele ERC grantů po konci grantu. Výhody: 1 evaluace žadatelů delegovaná mimo ČR. 2 zvýšená stabilita financování dobré vědy. Krátkodobé financování je velký neduh CZ vědy. 3 zvýšená motivace žádat o ERC.

simonsfoundation.org/2025/04/29/fla… Direct evidence magnetar giant flares eject neutron star crust material capable of heavy element nucleosynthesis and associated kilonova-like signals . As the gamma-ray signal came from the 2004 giant flare, in some since this was the "first" kilonova.

How was Czechoslovakia dismantled on the eve of WWII to appease Hitler. Similarity to current events is purely coincidental. Or not. Appeasement and sacrifice of Czechoslovakia did not stop Hitler. It made him bolder and better prepared for the war. en.wikipedia.org/wiki/Occupatio…

@PetrakovaVladka Congratulations! Really looks like stars! Do you care about more than detection: total flux, width, asymmetry,...? Do they move between images? What about fluxes at different wavelengths ("colors" in astronomy) or polarization?

Inspired by radars and astronomy, we used signal detection theory to design an optimal filter for microscopy and implement probabilistic thresholding that allows to control the level of false positive detections.

Our first paper is out! 🎉We present a method to detect molecules in microscopy images using probabilistic thresholding. With only one parameter to set conditions and describe error levels, it simplifies the process for users and enables reproducibility. rdcu.be/d5XQE

⭐️⭐️Už druhý ERC grant získal astrofyzik @pejco3am @matfyz @UniKarlova. To je neobyčejný úspěch dokazující pestrost jeho vědeckých nápadů. Do světa dvojhvězd vás Ondřej Pejcha zavede v rozhovoru pro @ukforumcz. @ERC_Research #ERCCoG 👉 link.cuni.cz/OndrejPejchaERC

A long thread on the war and the current situation. Although the worst-case scenarios didn’t materialize in 2024, it was the most difficult period since spring 2022. There were positive developments, and bright spots, but the current trajectory is negative. 1/

“Russian ambitions may not stop at Ukraine, and in the absence of Western action today, the costs of resisting Russian aggression will only rise,” write @AKendallTaylor and @KofmanMichael. foreignaffairs.com/russia/putins-…

All positions are financed by grants from European Research Council and Czech Science Foundation with internationally competitive salaries ad funds for travel. Our dedicated computing cluster will soon be expanded with new GPU nodes. For more details see utf.mff.cuni.cz/~pejcha/

We seek up to 3 PhD students working on various aspects of binary stars ranging from analysis of populations observed in time-domain surveys to developing new methods for computer simulations. Deadline is Jan 15 2025, for details see: mff.cuni.cz/.../physi.../f…

We are hiring postdocs and PhD students! We have openings for two postdocs (up to 5 yrs) to develop new methods for computer simulations of fluid dynamics in binary systems. Deadline is Jan 26 2025. For more details and application instructions see cuni.cz/UKEN-1573.html…

Conratulations to Milan Pešta, who defended PhD couple months ago, for winning postdoc fellowship from Czech Science Foundation to work the next two years on machine learning with @TingAstro at Department of Astronomy at OSU. The photo is from Milan's commencement today.

I am already looking for PhD students to start in Fall 2025: mff.cuni.cz/en/physicsphd/… The ad for two postdoc-level positions is coming as soon as the hiring is officially approved.

I am very happy and honoured to be awarded one of ERC Consolidator grants to construct new simulations of all sorts of binary stars. Thanks to all who have helped, especially students and postdocs, as well as my family for patience and support. Looking forward to what's coming!

But I don't completely understand bashing of Ukraine for delays in mobilization in this podcast. Given the demographic curve, there is a clear preferred alternative to getting all males killed while still losing: give up, flee West, and hope for returning in better times.

Yet, I interpret the signals as giving a slight of hope that the incoming US administration will do the right thing at least on this one issue. This includes forcing the European governments to do more. The current trajectory would clearly end up very badly eventually.

It makes me very sad to listen to the negative trajectory of events in the east, and that the negative trends have been accelerating. I don't know what to do both personally and on a bigger scale.