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Weekly Seminars for November 2022 Print E-mail
Friday, November 25, 2022 at 4:00 PM (Italian time)
  ICRANet Pescara (Meeting room, 1st Floor)
 
ICRANet Seminar
 
 
 
Speaker: Prof. Gennady S. Bisnovatyi-Kogan

Institution: Space Research Institute of the Russian Academy of Sciences (SRI RAS)

Title: About the Observational Check of the Mechanism of Gamma Radiation in Soft Gamma Repeaters (SGR)‚Äč
 
Abstract:  
Soft gamma repeaters (SGR) are identified as single neutron stars (NS) inside the Galaxy, or nearby galaxies, with sporadic transient gamma radiation. A total number of discovered SGR, including relative Anomalous X-ray pulsars (AXP), is a few tens of objects. Many of them show periodic radiation, connected with NS rotation, with periods 2–12 s. The slow rotation is accompanied by small rate of loss of rotational energy, which is considerably smaller than the observed sporadic gamma ray luminosity, and is many orders less than the luminosity during giant bursts, observed in 4 SGR. Therefore the energy source is usually connected with annihilation of a very strong NS magnetic field. Another model is based on the release of nuclear energy stored in the NS non-equilibrium layer. We suggest here an observational test which could distinguish between these two models.
 
 
 
 
 
Friday, November 25, 2022 at 5:00 PM (Italian time)
  ICRANet Pescara (Meeting room, 1st Floor)
 
ICRANet Seminar
 
 
 
Speaker: Prof. Marco Merafina

Institution: University of Rome La Sapienza

Title: Multimass King models with Kroupa mass function
 
Abstract:  
Statistical analysis on Milky Way globular clusters distribution is developed in order to extract the best fit function and carry out the critical value of the onset of gravothermal catastrophe, connected with the maximum of the distribution function. Results show that gravothermal collapse for globular clusters onsets earlier than commonly believed and in accordance with theoretical results obtained by considering the presence of the effective potential which describes the effects of the tidal forces induced by the hosting galaxy. N-body simulations confirm the presence of the effective potential with the predicted form.
Theoretical model is generalized to multimass one by using Kroupa mass function. A detailed description of the projected densities at different W0 indicates similar luminosity profiles in complete accordance with observations. We also consider the effects of the mass segregation on the distribution of stars and the consequences on the equipartition process. N-body simulations in connection with mass distribution and segregation as well the computational development applied to multimass model are also shown at the present state of the art.
 
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