Wednesday Colloquium


"Cyclic Conformal Cosmology"

Krzysztof Meissner (Institute of Theoretical Physics, Warsaw University)

The assumptions behind CCC will be discussed. With the help of Penrose diagrams the connection of our aeon with the previous one will be described. Possible observational traces of the previous aeon will be discussed.


"Simulation of the dynamics and geometry of broad line region in quasars"

Mohamad Naddaf (CAMK, Warsaw)

Broad emission lines are the most characteristic feature in the quasar’s spectra, known since 60 years, but we need a theoretical model for the localisation of the broad line region (BLR), the region that gives rise to production of those broad lines. The most successful non-ad-hoc physically-motivated model during the last decade which consistently explains the formation of broad emission lines in the spectra of quasars and provides the information on the location of BLR is the failed radiatively accelerated dusty outflow (FRADO). The model currently available in the 2.5D advanced version, which I developed, has taken very progressive concrete steps toward the goal. The model is on its way to ultimately pave the path for using quasars in cosmology.


"Evolution of massive stars with new hydrodynamic wind models"

Alex Gormaz-Matamala (CAMK, Warsaw)

We present evolutionary models for a set of massive stars, introducing a new prescription for the mass loss rate obtained from hydrodynamic calculations in which the wind velocity profile and the line-acceleration are obtained in a self consistently way. Evolutionary models with the new recipe for mass loss retain more stellar mass through their evolution, which is expressed in larger radii and consequently more luminous tracks over the Hertzsprung-Russell diagram. Also, models with self-consistent winds predict a weaker braking in the rotational velocity and a more marked drift redwards of the evolutionary tracks across the HRD, as a direct consequence of the differences in the stellar angular momentum loss and in the rotational mixing. Together with the prediction of higher masses at the end of main sequence, self-consistent tracks also predicts a distribution of rotational velocities for Galactic O-type stars more in agreement with the diagnostics of recent surveys. Other hypothetical implications, such as the masses of Ofpe stars at the Galactic Centre or the contribution of the isotope Al-26 to the ISM, are open to discussion.



Marek Szczepańczuk (LIGO-Virgo)



Anish Amarsi (Department of Physics and Astronomy, Uppsala University)


"Combining binary and asteroseismic information in stellar modelling"

Cole Johnston (Radboud University, Nijmegen, NL)

Large-scale high-precision space-based photometric missions have revealed that most stars are variable either through intrinsic (spots, pulsations) or external (eclipses) mechanisms. Fortunately, we can leverage the characteristics of this variability in order to learn something about stars. For instance, spots provide information on stellar rotation, pulsations reveal the interior structure of stars, and eclipses provide the opportunity to obtain highly precise estimates of the fundamental stellar parameters. Fortuitously, it is clear that many stars display multiple forms of variability. To this end, I will discuss my work in jointly modelling pulsating and eclipsing binary variables to cross-calibrate stellar evolutionary models at all masses across the Hertzsprung-Russell diagram.



Marcin Kuźniak (CAMK, AstroCent, Warsaw)



Alberto Martinez-Garcia (Instituto de Astrofísica de Canarias)