The accretion of matter by compact objects can be inhibited by radiationpressure if the luminosity exceeds the critical value, known as the Eddingtonlimit. Discovery of ultraluminous X-ray sources has shown that accretion canproceed even when the apparent luminosity significantly exceeds this limit.High apparent luminosity might be produced thanks to geometric beaming of theradiation by an outflow. The outflow half-opening angle, which determines theamplification due to beaming, has never been robustly constrained. Using theImaging X-ray Polarimetry Explorer, we made the measurement of X-raypolarization in the Galactic X-ray binary Cyg X-3. We find high, over 20%,nearly energy-independent linear polarization, orthogonal to the direction ofthe radio ejections. These properties unambiguously indicate the presence of acollimating outflow in the X-ray binary Cyg~X-3 and constrain its half-openingangle, <15 degrees. Thus, the source can be used as a laboratory for studyingthe super-critical accretion regime. This finding underscores the importance ofX-ray polarimetry in advancing our understanding of accreting sources.
The approach by Ettore Majorana for non-adiabatic transitions between twoquasi-crossing levels is revisited. We rederive the transition probability,known as the Landau-Zener-St\"{u}ckelberg-Majorana formula, and introduceMajorana's approach to modern readers. This result typically referred as theLandau-Zener formula, was published by Majorana before Landau, Zener,St\"{u}ckelberg. Moreover, we obtain the full wave function, including itsphase, which is important nowadays for quantum control and quantum information.The asymptotic wave function correctly describes dynamics far from theavoided-level crossing, while it has limited accuracy in that region.