Possible gamma-ray burst radio detections by the Square Kilometre Array. New perspectives

The next generation interferometric radio telescope, the Square Kilometre Array (SKA), which will be the most sensitive and largest radio telescope ever constructed, could greatly contribute to the detection, survey and characterization of Gamma Ray Bursts (GRBs). By the SKA, it will be possible to perform the follow up of GRBs even for several months. This approach would be extremely useful to extend the Spectrum Energetic Distribution (SED) from the gamma to the to radio band and would increase the number of radio detectable GRBs. In principle, the SKA could help to understand the physics of GRBs by setting constraints on theoretical models. This goal could be achieved by taking into account multiple observations at different wavelengths in order to obtain a deeper insight of the sources. Here, we present an estimation of GRB radio detections, showing that the GRBs can really be observed by the SKA. The approach that we present consists in determining blind detection rates derived by a very large sample consisting of merging several GRB catalogues observed by current missions as Swift, Fermi, Agile and INTEGRAL and by previous missions as BeppoSAX, CGRO, GRANAT, HETE-2, Ulysses and Wind. The final catalogue counts 7516 distinct sources. We compute the fraction of GRBs that could be observed by the SKA at high and low frequencies, above its observable sky. Considering the planned SKA sensitivity and through an extrapolation based on previous works and observations, we deduce the minimum fluence in the range 15-150 keV. This is the energy interval where a GRB should emit to be detectable in the radio band by the SKA. Results seem consistent with observational capabilities

The SKA contribution to GRB cosmology

Although they are not standard candles, the use of Gamma–Ray Bursts (GRBs) as a tool formeasuring the geometry and expansion rate of the Universe is strongly motivated by their uniquecombination of huge luminosities, up to more than 1053erg/s, with a redshift distribution ex-tending up to more thanz= 9. Several attempts to exploit the correlation between the photonenergy at which the spectral energy distribution peaks (peak energy) and the radiated energy (orluminosity) for standardizing GRBs and to use them to estimate cosmological parameters havebeen made. These studies show that with the present data–set, GRBs can provide a significantand independent confirmation ofΩM∼0.3 for a flatΛCDM. The SKA, through its unprecedentedcapabilities of characterizing the radio afterglow light-curve from the peak emission up to thetransition to non–relativistic regime for a significant fraction of GRBs, and in combination withmeasurements from next generation GRB experimens, will provide unique clues on the collima-tion angles and energy budget of these events, thus reducing significantly the dispersion of thepeak energy–radiated energycorrelation and improving its reliability and accuracy in investigat-ing dark energy properties and evolutio

Design and CFD Analysis of the Fluid Dynamic Sampling System of the “MicroMED” Optical Particle Counter

MicroMED is an optical particle counter that will be part of the ExoMars 2020 mission. Its goal is to provide the first ever in situ measurements of both size distribution and concentration of airborne Martian dust. The instrument samples Martian air, and it is based on an optical system that illuminates the sucked fluid by means of a collimated laser beam and detects embedded dust particles through their scattered light. By analyzing the scattered light profile, it is possible to obtain information about the dust grain size and speed. To do that, MicroMED’s fluid dynamic design should allow dust grains to cross the laser-illuminated sensing volume. The instrument’s Elegant Breadboard was previously developed and tested, and Computational Fluid Dynamic (CFD) analysis enabled determining its criticalities. The present work describes how the design criticalities were solved by means of a CFD simulation campaign. At the same time, it was possible to experimentally validate the results of the analysis. The updated design was then implemented to MicroMED’s Flight Model

Gamma-Ray Burst observations by the Square Kilometre Array. New perspectives

Gamma-Ray Bursts (GRBs) are the most powerful astrophysical source in the universe and have been studied since the '70s. Nevertheless, these objects are still not completely understood and many hypotheses have not been confirmed yet. Past and current observations have been made mostly at gamma, X and optical frequencies. This thesis aims to promote radio GRB observations, in order to thin out a menagerie of different opinions about these sources. In fact, GRBs have been prevalently studied as single cases, more often highlighting their peculiar features than elucidating their common characteristics, and thus leading to fragment the problem. Here the general properties are discussed, so that the attention is moved from the exception to the general case. In other words, this work suggests viewing GRBs in a broad ensemble instead of searching out single cases to explain every peculiarity and as a result increasing the number of possible groups to categorize them. \par This work concerns astrophysics, Gamma-Ray Bursts (GRBs) sources, the \textit{Square Kilometre Array} (SKA) radio telescope, radio observations and cosmology. For this reason, it has been divided into three parts, with six chapters in total. Each chapter is a step that leads to the next one following a precise scheme. In the end, all this work highlights both the importance of GRB radio observations and their real feasibility. \\ The first part concerns the high energies and consists of two chapters. The first chapter contains an overview about GRB state of the art, showing how from the gamma range the GRB afterglow emission reaches the lower frequency range up to the radio band. The second chapter passes from the theory to the practice, where different GRB satellite missions are listed with their gamma payloads, having thus an idea about GRB detection. \par The second part is dedicated solely to the radio observations. Chapter 3 regards radio instrumentations and so the SKA is introduced here. This chapter may need some elucidation. My Ph.D. has been carried out between the University and the \textit{Societa' Aerospaziale Mediterranea S.c.r.l.} company, hence on one hand I have been able to conduct a study about GRBs, on the other hand I have had the opportunity to collaborate with a company in charge of designing the feed indexer of the SKA. This mechanical component will be assembled with the telescope antenna to select the receivers during the radio observations and details are contained in the chapter. \\ Since the SKA is a interferometer, chapter 4 regards the radio interferometry. This brief introduction to interferometry helps for the reading of the next chapter, where GRB radio observations are discussed. Chapter 5 concerns principally three works in radio astronomy. Firstly, the first radio observations ever for a very large GRB sample are presented. Secondly, the first considerations deduced from analyses of those first results. Finally, a work of mine currently submitted to the \textit{Monthly Notices of the Royal Astronomical Society} where it is discussed the GRB detection rate for the SKA. \par After discussions of observational techniques, detections and possible observational studies in the radio band about GRBs, the third part and its last chapter close the thesis by explaining what advantages a precise and complete study of GRBs can provide for cosmology. Indeed, these sources will be able to shine a light on the various cosmological models created to attempt to explain the expansion of the universe. This last point will be possible only when GRBs are studied proceeding with the precise method suggested here, considering GRBs as complex sources which must be observed and analyzed at all available wavelengths

Design and CFD Analysis of the Fluid Dynamic Sampling System of the “MicroMED” Optical Particle Counter

MicroMED is an optical particle counter that will be part of the ExoMars 2020 mission. Its goal is to provide the first ever in situ measurements of both size distribution and concentration of airborne Martian dust. The instrument samples Martian air, and it is based on an optical system that illuminates the sucked fluid by means of a collimated laser beam and detects embedded dust particles through their scattered light. By analyzing the scattered light profile, it is possible to obtain information about the dust grain size and speed. To do that, MicroMED’s fluid dynamic design should allow dust grains to cross the laser-illuminated sensing volume. The instrument’s Elegant Breadboard was previously developed and tested, and Computational Fluid Dynamic (CFD) analysis enabled determining its criticalities. The present work describes how the design criticalities were solved by means of a CFD simulation campaign. At the same time, it was possible to experimentally validate the results of the analysis. The updated design was then implemented to MicroMED’s Flight Model

High precision measurements of neutrino fluxes with ENUBET

Neutrino fluxes are currently affected by large normalization uncertainties (5-10%). Neutrino physics will require measurements of absolute neutrino cross sections at the GeV scale with exquisite (1%) precision in the near future. For this reason a reduction of the present uncertainties by one order of magnitude would be highly beneficial. This goal might be achieved by producing a sign and momentum selected narrow band beam and monitoring the production of $e^{+}$ in the decay tunnel from the decays of charged Kaons ($K_{e3}$ channel). This technique, which requires a special instrumented beam-line, would allow a 1% level measurement of the cross-sections of the neutrino species ($\nu_e$ and $\bar{\nu}_e$) which are the final states involved in the searches for CP violation with muon neutrino beams at long-baseline. The ENUBET Horizon-2020 ERC Consolidator Grant, approved by the European Research Council in 2015, is the framework within which such a non conventional beam-line will be developed. We present a progress report of the project (2016-2021) after about one year of work, the experimental results on ultra-compact calorimeters suited for the instrumenting the decay tunnel and the R&D in the design of the hadronic beamline