38. Meeting of Polish Astronomical Society

On September 11-14, in Zielona Góra the Polish Astronomical Society held their 38th bi-annual meeting. Our group presented there in the session devoted to High Energy Astrophysics. Mikołaj Grzędzielski gave a talk on the “modified viscosity in accretion disks”, and Katarzyna Wojczuk prepared a poster on the “Nucleosynthesis of heavy elements in the plasma around the gamma-ray burst central engine”. The figure below, taken from this poster, shows the distribution of Nickel isotope synthesized in the accretion disk wind in GRB.

ni60_a


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X-ray conference in Warsaw

On September 6-8, the conference on the topic of “The power of X-ray spectroscopy” was held in Warsaw. The main organizers were scientists from the Copernicus Astronomical Center in Warsaw, profs. Andrzej Zdziarski and Agata Różańska. Workshop was devoted to selected aspects of both theoretical and observational X-ray spectroscopy, and, in particular, to the upcoming mission Athena.

Agnieszka Janiuk presented there a talk about “Stability of radiation pressure dominated accretion disks”, in which several of our recent papers were discussed.

The website of the meeting, with programme and list of participants, is here.


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Shocks in the relativistic transonic accretion

Our article “Shocks in the relativistic transonic accretion with low angular momentum”, by Petra Sukova, Szymon Charzyński, and Agnieszka Janiuk, has been accepted by the Monthly Notices of RAS, and now is available on-line.

In the extensive numerical study, which is the firs of this kind (former works were based on analytical approaches), we study different directional distributions of angular momentum of falling matter and varying values of key parameters such as spin of central black hole, energy and angular momentum of matter. In some of the scenarios the shock front is formed. We identify ranges of parameters for which the shock after formation moves towards or outwards the central black hole or the long lasting oscillating shock is observed.

The results are scalable with mass of central black hole and can be compared to the quasi-periodic oscillations of selected microquasars (such as GRS 1915+105, XTE J1550-564 or IGR J17091-3624), as well as to the supermassive black holes in the centres of weakly active galaxies, such as Sgr A*.

Figure below shows the distribution of the Mach number, as well as the density and specific angular momentum for one of the simulations.

Link to the article is here.

K500_NMRAS_122


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