Conveners
Monday morning
- Debora Lančová
Monday morning
- Debora Lančová
Relativistic jets are ubiquitous on many different systems. From stellar-size objects such as X-ray binaries (XRBs) and gamma-ray bursts (GRBs) to billion times larger such as in active galactic nuclei (AGNs). Similarly, the inferred Lorentz factors of the jets range from mildly relativistic to ultra-relativistic with Gamma ~1000 in some GRBs. Despite decades of research, the structure,...
Shock waves are abundant in astrophysical sources, and are responsible for much of the electromagnetic emission that we observe from many sources. Therefore, the shock dynamics can significantly affect the observable signatures, and are important to account for when interpreting the observations. I will first discuss a planar collision between two cold shells, which may be relevant either for...
Gamma-ray bursts (GRBs) eject relativistic jets that are initially optically thick. The trapped radiation is released at the photosphere and could be responsible for the GRB prompt emission. For this to be feasible, subphotospheric dissipation should occur before the photons decouple from the plasma, with shocks being a likely dissipation mechanism. Due to the high radiation pressure, shocks...
I will present cuHARM, a general relativistic radiation magnetohydrodynamic solver optimized to exploit exascale computing facililties. After describing the core numerical strategy for multi-node and multi-GPU setups, I will detail how radiation and its feedback on the dynamics are modeled. In cuHARM, the specific intensity is discretized in space and momentum, and is evolved through the...
Recent observations indicate that stripped-envelope core-collapse supernovae are often surrounded by dense circumstellar material (CSM). Motivated by this, we develop an analytic model to systematically study the dynamics of long gamma-ray burst (LGRB) jet propagation in various CSM environments. We derive a general expression for the jet head velocity ($\beta_{\rm h}$) and breakout time...
Recent observations of peculiar gamma-ray bursts (GRBs), such as GRB 211211A and GRB 230307A, challenge the traditional view that hyper-accreting black holes power these events. Instead, key signatures—temporal, spectral, and kilonova features—suggest millisecond magnetars as central engines, formed in compact star mergers. This talk highlights recent progress in understanding magnetar-driven...
In this work, I will presentthe t-distributed stochastic neighbour embedding (t-SNE), a machine-learning technique, to classify GRBs. We present the results for GRBs observed until 2022 July by the Swift/ BAT (Burst Alert Telescope)instrument in all its energy bands. We show the effects of varying the learning rate and perplexity parameters, as well as the benefit of preprocessing the data...
