Semináře v letošním roce

Constraining the Rapid Neutron-Capture Process with Meteoritic I-129 and Cm-247
Přednášející: Andrés Yagüe López
Afiliace:Konkoly Observatory, Budapest
Datum a čas: 5. 11. 2020, 13:00
Místo: Zoom meeting (ID: 895 7440 5459)
Abstrakt: Among all radioactive isotopes produced in the Galaxy, a small number of them have relatively short mean lives between 0.1 and 100 Myr. Early Solar System abundances of these radioisotopes can be determined through meteoritic analysis and, due to their short half lives, give us insight into the sites and processes that produced them. In this talk, I discuss the ratio of two of these short-lived radioisotopes, I-129 and Cm-247. I also show how, due to their remarkably similar half lives, they give us a unique opportunity to constrain the physical conditions of the last rapid neutron-capture process event that contributed to the enrichment of the pre-solar nebula.

Background for gravitational wave signal at LISA from refractive index of solar wind plasma
Přednášející: Adam Smetana
Datum a čas: 24.09.2020, 13:00
Místo: Zoom meeting

Future images of black holes
Přednášející: Włodzimierz Kluźniak
Datum a čas: 9.3.2020, 15:45
Místo: Seminární místnost Fyzikálního ústavu

Radio bimodality of Swift/BAT AGNs
Přednášející: Katarzyna Rusinek
Datum a čas: 5.3.2020, 13:45
Místo: Seminární místnost Fyzikálního ústavu

Radiative GRMHD simulations of accreting ULXs
Přednášející: David Abarca
Datum a čas: 5.3.2020, 13:00
Místo: Seminární místnost Fyzikálního ústavu

Modeling 2009–2013 observations of M87* with an asymmetric ring
Přednášející: Maciek Wielgus
Afiliace: Black Hole Initiative, Harvard University, USA
Datum a čas: 27.2.2020, 13:00
Místo: Seminární místnost Fyzikálního ústavu
Abstrakt: The Event Horizon Telescope (EHT) has delivered first resolved images of M87*, a supermassive black hole in the center of the M87 galaxy. These results are based on the 230 GHz observations performed in April 2017. Dedicated tools were developed to facilitate the modeling and analysis of the EHT 2017 data set in the Markov chain Monte Carlo (MCMC) framework, demonstrating that the source morphology can be very well represented by a crescent. More data, from different time epochs, are required to investigate the long term stability of the source parameters, such as its diameter and orientation. To address that need, we analyze archival data from proto-EHT 230 GHz observations of M87* in the framework utilized for the 2017 data analysis. We fit geometric models to the observations taken in 2009, 2012 (published in the past) and 2011, 2013 (not published previously), exploring the parameter space with a MCMC algorithm. We validate the procedure using synthetic data and M87* source models derived from the 2017 data. While the archival data sets are far less constraining than the 2017 observations, we obtain measurements of the source diameter and orientation. Variations of the M87* morphology in the 2009–2017 period are found to be roughly consistent with the predictions of general relativistic magnetohydrodynamic simulations of a turbulent accretion flow.

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