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Astrophysical Seminar (6 February 2020, 11:00)

Опубликовано: 03/02/2020

1) Speaker: M.S. Kirsanova (INASAN)

Title:  “Structure and kinematics of PDRs around S235A and S235C HII regions based on observations in the IR and radio bands”

Abstract: see Russian version

2) Speaker: S. Abbassi (Ferdowsi University of Mashhad, Iran)

Title:  “The Study of Magnetic Field and Self-gravity Effects on NDAFs’ Structure and its Evaluation as a Model for GRBs’ Central Engine”

Abstract: In the present work we study self-gravity effects on the vertical structure of a magnetized neutrino-dominated accretion disk as a central engine for gamma-ray bursts (GRBs). We are interested in investigating the possibility of the occurrence of X-ray flares, observed in late-time GRBs’ extended emission through the “magnetic barrier” and “fragmentation” processes in our model. The results lead us to interpret self-gravity as an amplifier for Blandford-Payne luminosity (BP power) and the generated magnetic field, but a suppressor for neutrino luminosity and magnetic barrier processes via highlighting the fragmentation mechanism in the outer disk, especially for the higher mass accretion rates. In the second part, to consider the magnetic barrier as a possible mechanism that might govern the accretion process of each magnetized clump, we construct a simple pattern in boundary conditions through which this mechanism might act. Regarding various model parameters, we probe for their influence and follow some key analogies between our model predictions and previous phenomenological estimates, for two different choices of boundary conditions (with and without a magnetic barrier). Our model is remarkably capable of matching the bolometric and X-ray light curves of flares, as well as reproducing their statistical properties, such as the ratios between rise and decay time, width parameter and peak time, and the power-law correlation between peak luminosity and peak time. Combining our results with the conclusions of previous studies, we are led to interpret a magnetic barrier as a less probable mechanism that might control the evolution of these clumps, especially those created later (or viciously evolved ones).

 

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