Wednesday Colloquium


"Accretion discs around magnetised Neutron Stars: distortion of magnetic field lines"

Luca Naso (SISSA, Trieste)

I will discuss a possible way of improving the old analytic models describing magnetic fields in accretion discs, with a semi-analytic approach. The results seem to show that the magnetic field profile can be very different from the suggested one for both the poloidal and the toroidal component. In particular the toroidal one is not governed only by the relative angular velocity between the disc and the star, as usually assumed.


"Thermal instability in accretion disks"

Włodzimierz Kluźniak (Copernicus Astronomical Centre, Warsaw)

Radiation pressure dominated alpha disks are thermally unstable. However, the resulting limit-cycle instability is not observed in binary X-ray sources. I will try to reconcile these two facts.


"Thick and luminous accretion disks in microquasars"

Aleksander Sądowski (Copernicus Astronomical Centre, Warsaw)

Microquasars' emission in the highśt state is dominated by the thermal disk component. At low luminosities it is well described by the classical Novikov and Thorne model of a radiatively efficient and thin accretion disk. The adopted assumptions, however, break down when the luminosity exceeds some critical value, e.g., 30 percent of the Eddington luminosity. In this talk I am going to present state-of-the-art hydrodynamical models of such luminous and geometrically thick accretion disks, discuss their applicability and describe the road-map for their development.


"On the structure of accretion disks with outflows"

Cheng-Liang Jiao (Department of Astronomy, School of Physics, Peking University, China)

We solve the set of hydrodynamic equations for accretion disks in the spherical coordinates to obtain the explicit structure along the theta direction. Our results indicate that the outflows should be common in various accretion disks and may be stronger in slim disks, where both advection and radiation pressure are dominant.