Conveners
Monday afternoon
- Andrzej Niedzwiecki
Monday afternoon
- Andrzej Niedzwiecki
In this talk, I will overview the results of recent simulations of black holes that are hungry, yet picky: they end up ejecting most of the gas they have access to. I will discuss the factors that affect their picky-ness and make the connection to the production of relativistic collimated outflows, or jets.
"Classical" accretion disks are geometrically thin, radiatively efficient and mechanized by turbulent viscosity. Yet, many observational and theoretical issues challenge this paradigm. Realistic quasar disks may be fed from cold, highly magnetized gas complexes, which can result in magnetically dominated disks that accrete extremely quickly. I will present horizon-scale simulations of...
Observations of the 3C120 jet indicate that this jet is likely pair-dominated [Zdziarski, et al. 2022]. This result implies strong production of the electron-positron plasma in the system. The currently accepted model of pair production involves an electromagnetic cascade near the base of the jet. Numerically solving the model equations one shows that the cascade indeed forms and can populate...
The most spectacular jets are observed from active galactic nuclei, in particular from quasars. However, highly interesting jets are also launched by accretion flows in stellar binaries containing a normal star accreting onto a stellar-mass black hole. Such systems are analogs of quasars on a much smaller scale, and are called microquasars. There are two distinctly different types of jets in...
ULXs are non-nuclear extragalactic sources that emit X-rays at luminosities exceeding $10^{39}\, erg/s$. One of the most accepted models to explain the extraordinary luminosity of ULXs is the super-Eddington accretion onto stellar-mass compact objects. This model with the central object of a neutron star revived interest in 2014, after the discovery of the neutron star-like pulsation period in...
We apply machine learning techniques to model the multi-wavelength emission of the extremely bright GRB 210822A using the AFTERGLOWPY library. This approach allows us to estimate the observer angle $\theta_{obs}$, the initial energy $E_0$, the electron index $p$, the thermal energy fractions in electrons ($\epsilon_{e}$) and in the magnetic field ($\epsilon_{B}$), the efficiency $\chi$, and...
Accretion disks are essential for understanding the dynamics of gas around black holes. The magnetically arrested disk (MAD) state, where the magnetic flux near the event horizon becomes saturated, has garnered significant attention following observations of supermassive black holes in M87 and Sagittarius A* by the Event Horizon Telescope (EHT) collaboration, which suggest that this is the...
In this talk, I will present the wide range of multi-messenger signals expected from gravitational wave (GW) sources across the frequency bands of all current and future GW detectors. I will begin at high frequency, discussing compact object binary mergers and massive stellar death. I will present some novel results on signatures expected from these latter events, which call into question our...
Collapsars are known to be the origin of GRB jets, black hole populations, and even potentially important r-process production sites in the early universe. In this talk, I will demonstrate how we can study the central engines of collapsars and jets, and establish the natal properties of their black holes. In particular, I will discuss how collapsar black holes acquire the strong magnetic...
GRBs from collapsars have been studied by imposing jets at intermediate scales beyond the iron core region while exploring a wide range of parameters, such as luminosity and central engine duration. However, these conditions should be validated by studying jets launched directly from the central engine to show a global picture of the jet propagation inside and outside of the progenitor star....
In recent years, the Magnetically Arrested Disc (MAD) model of accretion flows onto spinning black holes has gained significant attention due to its consistency with several observations, including those of Sgr A∗ and M87∗ . Such discs support powerful relativistic jets and episodic magnetic flux eruptions powering high-energy flares, which were also found to impact the structure of the inner...
This study focuses on the analysis of relativistic jets in collapsars with a self-gravitating stellar envelope. In our simulations the initial mass of the black hole is three solar masses, while the stellar envelope mass is twenty-five solar masses. Therefore, self-gravity cannot be neglected in the analysis. We compare two models—with and without self-gravity—under identical initial...
