Wednesday Colloquium


"Jets in microquasars"

Andrzej Zdziarski (CAMK, Warsaw)

I will review our current knowledge about three well-studied jets in X-ray binaries, MAXI J1820+070, Cyg X-1, and Cyg X-3. The first two accrete from their donors onto black holes, while this is likely but not certain in Cyg X-3. Thanks to an extensive multiwavelength campaign during the recent outburst of MAXI J1820+070, the structure of its compact jet emitting in radio to optical frequencies is now very well understood. The relatively long time lags measured between various radio and sub-mm frequencies prove that emission is formed at distances several orders of magnitude higher than the gravitational radius. We determine the jet opening angle, the location of the onset of the emission, the magnetic field strength and the electron distribution, and put constraints on the bulk Lorentz factor, the content of electron-positron pairs and the jet power. Then, I will compare those jet parameters with those in Cyg X-1 and Cyg X-3, both of which emit also high-energy gamma rays.


"Glitches: The restless life of a dead star"

Marco Antonelli (CAMK, Warsaw)

Gamers may think to have witnessed some hilarious and weird glitches, but this is nothing compared to what a pulsar can do. Pulsars are famous for being "natural clocks", but some of them display a "restless" behaviour: their rotational evolution is punctuated by sudden hiccups, known as glitches. The origin of glitches is debated, but there is an elegant analogy with the noisy motion of flux-tubes in superconductors: glitches can be explained by transitions in the rate with which vorticity is expelled from the internal layers of a neutron star. Spin in peace, little pulsar.


"Gravitational wave pulsars: the path from theory to observations"

Bryn Haskell (CAMK, Warsaw)


"Physics without experiment and cosmology with no observations?"

Stanisław Mrówczyński (Uniwersytet im. Jana Kochanowskiego and National Ceter of Nuclear Research)

In contemporary physics there emerged theories which cannot be tested experimentally due to either technological or truly fundamental limitations. The quantum gravity belongs to the first category while the theory of multiverse to the second one. One asks about a status of such theories, whether experimental verification can be replaced by another criteria. The whole problem is presented and discussed.