In this contribution we present the analysis of GRB221009A, the brightest Gamma-Ray Burst (GRB) ever detected by the Fermi Large Area Telescope (LAT). The burst triggered the Gamma-Ray Burst Monitor (GBM), and the high-energy emission of the triggering pulse started in the LAT before the associated low-energy component detected by the GBM. During the prompt phase, we identified a Bad Time...
GRB 221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth on 2022 October 9th after traveling through the dust of the Milky Way. The Imaging X-ray Polarimetry Explorer (IXPE) pointed at GRB 221009A on October 11th and measured, for the first time, the 2-8 keV X-ray polarization of both a GRB afterglow and rings of dust-scattered photons which are echoes of the GRB prompt...
As the most energetic explosions in the Universe, long-duration Gamma-ray Bursts (GRBs) provide a unique opportunity to explore physics at extreme energy scales that are otherwise impossible to investigate in Earth-bound laboratories. The radiation produced by the interaction of their ejecta with the environment contains clues to their progenitors and to the mechanisms responsible for...
The brightest long gamma-ray burst (GRB) detected so far by the \textit{Swift}-BAT and \textit{Fermi}-GBM telescopes, GRB~221009A, provides an unprecedented opportunity for understanding the high-energy processes in extreme transient phenomena. We find that the conventional leptonic models for the afterglow emission from this source, synchrotron and synchrotron-self-Compton, have difficulties...
The duration distribution of gamma-ray bursts is bimodal, and the general consensus has been that the two groups stem from separate progenitors: binary compact object mergers and supernovae for short and long GRBs, respectively. A number of events discovered in the recent past has however proven this distinction to be imperfect. Kilonovae, the smoking-guns of mergers, were detected following...
The origin of gamma-ray bursts (GRBs) is still mysterious. We believe that binary neutron star (BNS) mergers produce short GRBs, while long GRBs are associated to the collapse of massive stars.
This GRB dichotomy, based on the duration of the prompt pulse, was recently challenged by the detection of the bright and relatively close (z=0.076) GRB 211211A. Despite its long duration (~30 s), the...
The merger rate density of binary compact objects and the properties of their host galaxies carry crucial information to understand the sources of gravitational waves. In this talk, I present galaxyRate, a new code that estimates the merger rate density of binary compact objects and the properties of their host galaxies, based on observational scaling relations. We generate synthetic...
Binary neutron stars (BNSs) wield a pivotal role in modern astrophysics. Merging BNSs not only can be loud sources of gravitational waves, but also trigger short gamma-ray bursts and kilonovae. A great example of such event is the renowned GW170817; the observation of its electromagnetic counterpart paved the way for new frontiers in multimessenger astrophysics.
Moreover, thanks to the timing...
Pulsars are the largest class of Galactic sources detected by NASA's Large Area Telescope (LAT) on the Fermi mission. Pulsars are generally acknowledged as very stable astrophysical rotators, and they gradually slow down by emitting radiation at the expense of their rotational energy. Occasionally, pulsars can undergo transient events called glitches, which consist in rapid changes in their...
W44 is a middle-aged Supernova Remnant (SNR) largely investigated to probe acceleration of Cosmic Rays (CRs). Previous studies already showed the presence of gamma-ray emission not only from the remnant, but also from its surroundings, thought to be due to high-energy CRs escaping from the forward shock of the remnant.
We present a detailed morphological and spectral analysis of Fermi-LAT...
GW170817 is an outstanding event as it paved the way for multi-messenger astrophysics. It is a binary neutron stars merger, that saw the detection of a gravitational wave (GW), a gamma ray burst (GRB) and an afterglow. Such events are interesting also from a cosmological point of view, as we can derive an Hubble constant ($H_0$) measurement (the current expansion rate of the Universe),...
GRB absorption spectra are powerful probes of the circumburst medium of their progenitor and the host galaxy's ISM. The column densities as derived from the X-ray and the optical spectra differ by up to an order of magnitude, suggesting the presence of a highly ionised region close to the GRB. This happens because the X-ray absorption probes the total column along the line of sight, including...
Prompt emission of GRB is believed to be produced from electrons accelerated up to non thermal energies in the internal shocks. This emission peaks in the keV-MeV energy band, but a high energy component is theoretically expected. While photons in the very high energy domain have been detected by Cherenkov Telescopes in recent years, prompt-related VHE photons have not been observed yet....
The rare multimessenger event GW170817 showed a new way of making cosmology with the potential to resolve the tension between different measurements of the expansion rate of the Universe given by the Hubble constant.
However, most of the detected gravitational wave signals from compact binaries up to date do not have a multi-messenger counterpart, earning them the designation of dark...
Molecular clouds in the Galactic Centre will glow in neutrinos and gamma-rays when bombarded by energetic hadrons. Gamma-ray imaging of the Galactic Centre has therefore been employed to study the cosmic-ray energy spectrum and density distribution around Sgr A*. While part of the gamma-rays may be contributed by leptons, leading to uncertainty that is challenging to estimate, neutrinos serve...
