Wednesday Colloquium



01.10.2025

"Jets in accreting black-hole binaries"

Andrzej Zdziarski (Copernicus Astronomical Center, Warsaw)

The most spectacular jets are observed from active galactic nuclei, in particular, from quasars. However, highly interesting jets are also launched by accretion flows in stellar binaries containing a normal star accreting onto a stellar-mass black hole. Such systems are analogs of quasars on a much smaller scale and are called microquasars. There are two distinctly different types of jets in microquasars. Jets of the first type are steady and are launched during accretion states characterized by hard X-ray emission. They are launched over weeks to months but are observed only up to maximum distances of about 1/1000 of a parsec. Those of the other type are launched on time scales of only a day during transitions of the accretion flow from the hard to soft spectral states but are observed as moving ejecta up to a parsec scale, i.e., up to ~1000 times larger distances. I will discuss possible causes of this difference, the jet emission mechanisms, collimation, the presence of electron-positron pairs, magnetic fields, bulk Lorentz factors, and the jet power.


08.10.2025

"Potential new applications of photon sources in astronomy, medicine and computation"

Jarosław Duda (Jagiellonian University, Cracow)

While naively laser only excites target, it can also cause its deexcitation – as stimulated emission, SASE (self-amplified spontaneous emission), synchrotron self-absorption, ASE (amplified spontaneous emission), or in Rabi cycle cyclically causing excitation and deexcitation. STED microscopy is a popular application of laser causing deexcitation - I would like to propose and discuss a few more, based on its properties suggested by CPT symmetry. For example, while CT scanner makes 3D maps of absorption coefficient, CPT symmetry suggests how to analogously measure/map emission coefficients, what should have much better transparency thanks to lower concentrations (N2 << N1). Related medical application could be causing deexcitation of autoluminescent molecules like NADH, e.g. to starve cancer tissue. It suggests also how to build new type of telescope - seeing synchrotron radiation, but not thermal. Finally, the original motivation was more symmetric and powerful two-way quantum computers (2WQC), for example with photonic chip between coupled laser resonators.


15.10.2025

"TBA"

Surajit Kalita (Warsaw University Observatory)


22.10.2025

"Toward Autonomous Observatories: Development of the Cerro Murphy Observatory Software System"

Mirosław Kicia (CAMK PAN, Warsaw)


29.10.2025

"tba"

Pratik Dabhade (National Center for Nuclear Research (NCBJ), Warsaw)