Neutrino emission via proton-proton interaction and magnetic field screening in GRBs

Gamma-Ray Bursts (GRBs) are one of the most energetic astrophysical events of our Universe and a precise study of all the physical mechanisms occuring in these systems involves different branches of physics (from particles physics to General Relativity). The main subjects of this thesis concern the particles physics and the plasma physics fields. I study two different physical processes, operated by elementary particles as protons, electron/positron paris, photons and neutrinos, occuring in GRBs. In Ch. (1) I give a general introduction to GRBs, with some of their structural physical generalities and properties (as their different emission phases, spectral and temporal properties etc.). I introduce also the fireshell model, which has been developed during the years by Prof. Ruffini, R. and his group, in order to study and understand the several mechanisms behind the GRB emission. I will also highlight the principal differences between this model and the fireball model (which was the first model adopted in order to study the GRBs emission). The structure of the fireshell model considers a Reissner-Nordoström Black Hole, with a strong electric field that converts part of the BH total energy in e + e − plasma by the vacuum polarization process. These particles are accelerated and emit photons, and this leads to the formation of a relativistic optically thin fireshell of e + e − γ plasma (the “PEM–pulse”). This shell interacts with baryons, deposited in the ambient near the BH due to the collapse event, forming a new accelerated optically thick plasma of e + e − γ-baryons (PEMB–pulse). The transparency of this shell brings to the formation of the proper GRB emission (P-GRB emission). In Ch. (2) I introduce a classification of the GRBs in classes and subclasses. They differ from each other principally for their different progenitors, formation process, their isotropic energy E iso , their rest- frame spectral peak energy E p,i and local observed rate. In the Thesis, I have focused my attention principally on a particular type of long GRB class: the type I Binary-driven HyperNova (BdHN). The physical scenario and process, that leads to the formation of the BdHN class, is the Induced Gravitational Collapse (IGC), with the hypercritical accretion process paradigm. The two original studies of the Thesis, developed in Chs. (3) and (4), are based on the physical scenario of BdHN. In this chapter, I also show the connections between the several observations of a GRB event and the basic processes of the BdHN model. In Ch. (3), the first topic of the Thesis is presented, namely the neutrinos and photons production by proton-proton interaction, between accelerated protons and protons at rest. Keeping in mind the above discussed scenario for the dynamics of the e + e − γ-baryons plasma, recent numerical simulations have shown that the SN ejecta becomes highly asymmetric. Therefore, the electron-positron (e ± ) plasma created in the BH formation, during its isotropic and self-accelerating expansion, engulfs different amounts of ejecta baryons along different directions, leading to a direction-dependent Lorentz factor. In this configuration, I have studied the pp interaction occurring in two regions: an high density region and a low density region. In the conclusion of this chapter I also try to give an estimate of a possible, direct or indirect, detection of the neutrinos and photons created throught the above mechanism. From this analysis it came out that a possible detection of these neutrinos with currently operating detectors is plausible only for sources several order of magnitude more energetic than the ones considered in this work, and very-high energy ineracting protons (this subject is treated in App. (D) and will be better developed in future works). It also came out that an indirect detection of these neutrinos by means of the related photons emission is possible. The second subject of the Thesis is presented in Ch. (4) and concerns the study of the screening process of an electromagnetic field near a BH operated by electron-positron pairs. It has been shown that a rotating BH immersed in a test background magnetic field, of initial strength B 0 and aligned parallel to the BH rotation axis, generates an induced electric field, whose strength is proportional to the background magnetic field, E = 1/2 ΥB (where Υ is the BH spin parameter). In this analysis, I consider the configuration of crossed fields: B = Bẑ and E = E ŷ. In this system, an huge number of e + e − pairs can be emitted by vacuum polarization process, start to be accelerated to high energies by the induced electric field and emit synchrotron photons. These photons interact with the magnetic field via the magnetic pair production process (MPP): γ + B → e + + e − . The motion of all these particles around the magnetic field lines generates also an induced magnetic field oriented in the opposite direction to the background one, which implies a reduction of the background magnetic field. The principal results are that the combination of the processes described above can reduce the magnetic field in a small time scale, even if the production of pairs is not so efficient due to the low energy of the emitted photons, for the selected initial conditions of the field strengths and particles densities

Neutrino production from proton-proton interactions in binary-driven hypernovae

We estimate the neutrino emission from the decay chain of the $\pi$-meson and $\mu$-lepton, produced by proton-proton inelastic scattering in energetic ($E_{\rm iso}\gtrsim 10^{52}$~erg) long gamma-ray bursts (GRBs), within the type I binary-driven hypernova (BdHN) model. The BdHN I progenitor is \textcolor{red}{a} binary system composed of a carbon-oxygen star (CO$_{\rm core}$) and a neutron star (NS) companion. The CO$_{\rm core}$ explosion as supernova (SN) triggers a massive accretion process onto the NS. For short orbital periods of few minutes, the NS reaches the critical mass, hence forming a black hole (BH). Recent numerical simulations of the above scenario show that the SN ejecta becomes highly asymmetric, creating a \textit{cavity} around the newborn BH site, due to the NS accretion and gravitational collapse. Therefore, the electron-positron ($e^{\pm}$) plasma created in the BH formation, during its isotropic and self-accelerating expansion, engulfs different amounts of ejecta baryons along different directions, leading to a direction-dependent Lorentz factor. The protons engulfed inside the high-density ($\sim 10^{23}$~particle/cm$^3$) ejecta reach energies in the range $1.24\lesssim E_p\lesssim 6.14$ GeV and interact with the unshocked protons in the ejecta. The protons engulfed from the low density region around the BH reach energies $\sim 1$ TeV and interact with the low-density ($\sim1$~particle/cm$^3$) protons of the interstellar medium (ISM). The above interactions give rise, respectively, to neutrino energies $E_{\nu}\leq 2$ GeV and $10\leq E_{\nu}\leq 10^3$ GeV, and for both cases we calculate the spectra and luminosity.Comment: 19 pages, 22 figures, 2 tables, re-submitted to Physical Review Letters

TeV emission from Gamma Ray Bursts, checking the hadronic model

Gamma-Ray Bursts (GRBs) are the most luminous explosions in the Universe. Their luminous prompt emission makes them detectable from cosmological distances. Most GRBs have been detected below a few MeV, however at least a hundred GRBs have been detected at high (0.1 GeV) energies and observed up to tens of GeV with the Fermi Large Area Telescope (LAT). Some GRBs have been observed at (0.1–1) TeV by ground-based imaging atmospheric Cherenkov telescopes. To date, the high energy emission mechanism is not understood. In this paper we review the possible leptonic and hadronic mechanisms capable of producing the ∼ TeV emission detected in GRBs. In paricular we concentrate on the hadronic origin of this radiation component and discuss in detail the numerical simulation elaborated to reproduce the observed sub-TeV observations of GRB190114C

Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

The high activity of 3C 454.3 in autumn 2007: Monitoring by the WEBT during the AGILE detection

The quasar-type blazar 3C 454.3 underwent a phase of high activity in summer and autumn 2007, which was intensively monitored in the radio-to-optical bands by the Whole Earth Blazar Telescope (WEBT). The gamma-ray satellite AGILE detected this source first in late July, and then in November-December 2007. In this letter we present the multifrequency data collected by the WEBT and collaborators during the second AGILE observing period, complemented by a few contemporaneous data from UVOT onboard the Swift satellite. The aim is to trace in detail the behaviour of the synchrotron emission from the blazar jet, and to investigate the contribution from the thermal emission component. Optical data from about twenty telescopes have been homogeneously calibrated and carefully assembled to construct an R-band light curve containing about 1340 data points in 42 days. This extremely well-sampled optical light curve allows us to follow the dramatic flux variability of the source in detail. In addition, we show radio-to-UV spectral energy distributions (SEDs) at different epochs, which represent different brightness levels. In the considered period, the source varied by 2.6 mag in a couple of weeks in the R band. Many episodes of fast (i.e. intranight) variability were observed, most notably on December 12, when a flux increase of about 1.1 mag in 1.5 hours was detected, followed by a steep decrease of about 1.2 mag in 1 hour. The contribution by the thermal component is difficult to assess, due to the uncertainties in the Galactic, and possibly also intrinsic, extinction in the UV band. However, polynomial fitting of radio-to-UV SEDs reveals an increasing spectral bending going towards fainter states, suggesting a UV excess likely due to the thermal emission from the accretion disc

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

TeV emission from Gamma Ray Bursts, checking the hadronic model

Gamma-Ray Bursts (GRBs) are the most luminous explosions in the Universe. Their luminous prompt emission makes them detectable from cosmological distances. Most GRBs have been detected below a few MeV, however at least a hundred GRBs have been detected at high (0.1 GeV) energies and observed up to tens of GeV with the Fermi Large Area Telescope (LAT). Some GRBs have been observed at (0.1–1) TeV by ground-based imaging atmospheric Cherenkov telescopes. To date, the high energy emission mechanism is not understood. In this paper we review the possible leptonic and hadronic mechanisms capable of producing the ∼ TeV emission detected in GRBs. In paricular we concentrate on the hadronic origin of this radiation component and discuss in detail the numerical simulation elaborated to reproduce the observed sub-TeV observations of GRB190114C

Volcanic SO2 fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS

Sulphur dioxide (SO2) fluxes of active degassing volcanoes are routinely measured with ground-based equipment to characterize and monitor volcanic activity. SO2 of unmonitored volcanoes or from explosive volcanic eruptions, can be measured with satellites. However, remote-sensing methods based on absorption spectroscopy generally provide integrated amounts of already dispersed plumes of SO2 and satellite derived flux estimates are rarely reported. Here we review a number of different techniques to derive volcanic SO2 fluxes using satellite measurements of plumes of SO 2 and investigate the temporal evolution of the total emissions of SO2 for three very different volcanic events in 2011: Puyehue-Cordón Caulle (Chile), Nyamulagira (DR Congo) and Nabro (Eritrea). High spectral resolution satellite instruments operating both in the ultraviolet-visible (OMI/Aura and GOME-2/MetOp-A) and thermal infrared (IASI/MetOp-A) spectral ranges, and multispectral satellite instruments operating in the thermal infrared (MODIS/Terra-Aqua) are used. We show that satellite data can provide fluxes with a sampling of a day or less (few hours in the best case). Generally the flux results from the different methods are consistent, and we discuss the advantages and weaknesses of each technique. Although the primary objective of this study is the calculation of SO 2 fluxes, it also enables us to assess the consistency of the SO 2 products from the different sensors used. © 2013 Author(s).SCOPUS: ar.jinfo:eu-repo/semantics/publishe