Wednesday Colloquium


"Astrophysics in Horava's quantum gravity"

Ronaldo Vieira (Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, Brazil)

Abstract: Horava gravity has received much attention in the recent years. The Kehagias-Sfetsos (KS) solution, a Schwarzschild-like solution to a modified version of the theory, was used to constrain the Horava parameter in many Solar-system tests. In this talk we discuss some qualitative properties of this solution such as the near-Schwarzschild and naked singularity cases, as well as the stability of circular geodesics.


"Emission of compact jets powered by internal shocks"

Julien Malzac (University of Cambridge )

I will present an internal shock model for the variable radio to infrared emission of the jets of X-ray binaries in the hard state.


"General relativistic magnetohydrodynamical (GR MHD) simulations of accretion disk around Sgr A*"

Bhupendra Prakash Mishra (NCAC, Warsaw)

The talk will cover current status of General Relativistic MagnetoHydroDynamical (GR MHD) simulations. I shall also give a short introduction of the GRMHD code COSMOS++, and its abilities for a wide range of research problems. Since we know that Sgr A* is the best laboratory in space to test our knowledge of general relativity, my main interest in this talk will be to present GR effects in MHD accretion flows around rotating Sgr A*. The results for accretion disk around Sgr A* will be presented for different magnetic field configurations, poloidal as well as toroidal in the torus and also for different spin parameters of the Sgr A*, by this way we can see the very strong effects of magnetic field configuration in the accretion flows in GR regime. The theoretical model to setup the numerical code is based on classical polish doughnut model to which we slightly modified by including an essential parameter in the accretion flows which is magnetic field in the torus. I shall also talk about whether the cooling processes are important in GRMHD accretion flows or not.


"Three players in the interstellar clouds: dust grains, free radicals and diffuse band carriers"

Jacek Krełowski (Astronomy Center, Toruń)

Translucent interstellar clouds produce typically three kinds of absorptions: continuous extinction, believed to be caused by interstellar dust particles, identified bands of simple radicals (OH, OH+, CH, CH+, NH, CN, C2 and C3) and more than 400 unidentified diffuse interstellar bands. The latter are commonly believed to be carried by some complex molecular species but none of them was until now identified beyond a doubt. The talk will present the above mentioned absorptions in different interstellar clouds. It seems important that that any change of the extinction law is accompanied by changes in molecular and diffuse spectra. This demonstrates a complex chemistry of translucent interstellar clouds. The observed molecular species are likely building bricks for prebiotic molecules.