Search Results (85)

Dark matter dominates the matter content of the Universe, yet its particle nature remains elusive. Among the promising multi-messenger astronomy dark matter candidates are weakly interacting massive particles and superheavy dark matter, both of which may manifest themselves in cosmic ray, $\gamma$-ray, and neutrino signatures through annihilation or decay. Here, we explore potential multi-messenger signals from these candidates in galaxy clusters of the Shapley Supercluster—one of the most massive known structures in the local Universe (located at a distance of ∼200 Mpc and containing over ${10}^{16}{M}_{\odot }$ of dark matter). Using the CLUMPY code, we model $\gamma$-ray and neutrino fluxes for weakly interacting massive particle masses between 0.1 and 100 TeV across various final states, comparing the predictions with the sensitivities of current and forthcoming observatories, including CTAO, IceCube, and KM3NeT. For superheavy dark matter scenarios with masses from ${10}^{19}$ to ${10}^{28}$ eV, we employ HDMSpectra code to compute ultra-high-energy cosmic ray proton and neutrino fluxes in the ranges available for observations using present (Pierre Auger Observatory, IceCube, KM3NeT) and future (GRAND, GCOS, etc.) instruments. Full article

The subject of boosted fluxes of dark matter or cosmic relic neutrinos via scattering on cosmic rays has received considerable attention recently. This article investigates the boosted neutrino flux from the scattering of cosmic rays and the so-far undetected diffuse supernova neutrino background, taking into account both galactic and extragalactic cosmic rays. The calculated flux is many orders of magnitude smaller than either the galactic diffuse neutrino emission, the extragalactic astrophysical flux measured by IceCube, or the cosmogenic neutrino flux expected at the highest energies. Full article

Active galactic nuclei (AGNs) often exhibit broad-line regions (BLRs), populated by high-velocity clouds in approximately Keplerian orbits around the central supermassive black hole (SMBH) at subparsec scales. During episodes of intense accretion at super-Eddington rates, the accretion disk can launch a powerful, radiation-driven wind. This wind may overtake the BLR clouds, forming bowshocks around them. Two strong shocks arise: one propagating into the wind, and the other into the cloud. If the shocks are adiabatic, electrons and protons can be efficiently accelerated via a Fermi-type mechanism to relativistic energies. In sufficiently dense winds, the resulting high-energy photons are absorbed and reprocessed within the photosphere, while neutrinos produced in inelastic $pp$ collisions escape. In this paper, we explore the potential of super-accreting AGNs as neutrino sources. We propose a new class of neutrino emitter: an AGN lacking jets and gamma-ray counterparts, but hosting a strong, opaque, disk-driven wind. As a case study, we consider a supermassive black hole with $M_{\mathrm{BH}}={10}^6{M}_{\odot }$ and accretion rates consistent with tidal disruption events (TDEs). We compute the relevant cooling processes for the relativistic particles under such conditions and show that super-Eddington accreting SMBHs can produce detectable neutrino fluxes with only weak electromagnetic counterparts. The neutrino flux may be observable by the next-generation IceCube Observatory (IceCube-Gen2) in nearby galaxies with a high BLR cloud filling factor. For galaxies hosting more massive black holes, detection is also possible with moderate filling factors if the source is sufficiently close, or at larger distances if the filling factor is high. Our model thus provides a new and plausible scenario for high-energy extragalactic neutrino sources, where both the flux and timescale of the emission are determined by the number of clouds orbiting the black hole and the duration of the super-accreting phase. Full article

The Shapley Supercluster, one of the largest and most massive structures in the nearby (redshift $z\le 0.1$) Universe, located approximately 200 Mpc away, is a unique laboratory for high-energy astrophysics. Galaxy clusters that comprise it are promising targets for multimessenger study due to the presence in the intracluster medium of the necessary conditions for the acceleration of cosmic rays up to ultra-high energies and the generation by them of non-thermal electromagnetic and neutrino emission. Using the Shapley Supercluster’s observational data from the recent eROSITA-DE Data Release, we recover the physical parameters of 45 X-ray luminous galaxy clusters and calculate the expected multiwavelength—from radio to very-high-energy γ-ray as well as neutrino emission, with a particular focus on hadronic interactions of accelerated cosmic ray nuclei with the nuclei of the intracluster medium. The results obtained allow verification of cluster models based on multimessenger observations of clusters, especially in $\gamma$-ray (Fermi-LAT, H.E.S.S., CTAO-South for the Shapley Supercluster case), and neutrino (Ice Cube, KM3NeT). We also estimate the ability of the Shapley Supercluster to manifest as cosmic Zevatrons and show that it can contribute to the PAO Hot Spot in the Cen A region at UHECR energies over 50 EeV. Full article

ComPair, a prototype of the All-sky Medium Energy Gamma-ray Observatory (AMEGO), completed a short-duration high-altitude balloon campaign on 27 August 2023 from Fort Sumner, New Mexico, USA. The goal of the balloon flight was to demonstrate ComPair as both a Compton and Pair telescope in flight, reject the charged particle background, and measure the background $\gamma$-ray spectrum. This analysis compares measurements from the balloon flight with Monte Carlo simulations to benchmark the instrument. The comparison finds good agreement between the measurements and simulations and supports the conclusion that ComPair accomplished its goals for the balloon campaign. Additionally, two charged particle background rejection schemes are discussed: a soft ACD veto that records a higher charged particle event rate but with less risk of event loss, and a hard ACD veto that limits the charged particle event rate on board. There was little difference in the measured spectra from the soft and hard ACD veto schemes, indicating that the hard ACD veto could be used for future flights. The successes of ComPair’s engineering flight will inform the development of the next generation of ComPair with upgraded detector technology and larger active area. Full article

The Pierre Auger Observatory, the world’s largest ultra-high-energy (UHE) cosmic ray (CR) detector, plays a crucial role in multi-messenger astroparticle physics with its high sensitivity to UHE photons and neutrinos. Recent Auger Observatory studies have set stringent limits on the diffuse and point-like fluxes of these particles, enhancing constraints on dark-matter models and UHECR sources. Although no temporal coincidences of neutrinos or photons with LIGO/Virgo gravitational wave events have been observed, competitive limits on the energy radiated in these particles have been established, particularly from the GW170817 binary neutron star merger. Additionally, correlations between the arrival directions of UHECRs and high-energy neutrinos have been explored using data from the IceCube Neutrino Observatory, ANTARES, and the Auger Observatory, providing additional neutrino flux constraints. Efforts to correlate UHE neutron fluxes with gamma-ray sources within our galaxy continue, although no significant excesses have been found. These collaborative and multi-faceted efforts underscore the pivotal role of the Auger Observatory in advancing multi-messenger astrophysics and probing the most extreme environments of the Universe. Full article

In recent years, the global demand for food ice cubes has increased. The aim of the study was to evaluate the hygienic quality of both ice and water used for its production. During January–October 2023, 108 ice and water samples were collected in catering locations in Apulia Region and examined for Escherichia coli, Enterococci, total bacterial count (TBC) and fungi. Median counts of E. coli, Coliforms and Enterococci were 0 CFU/100 mL both for ice and water samples, collected in bars (n = 78) and restaurants (n = 30). The median TBCs in ice and water samples were 175 and 43 CFU/mL (p < 0.0001) at 22 °C, and 80 and 30 CFU/mL (p < 0.0001) at 36 °C. Total fungi counts were 4 and 0 CFU/mL for ice and water (p < 0.0001). In restaurants, differences were found between ice and water only for fungal contamination, whereas for bars, a difference was found between ice and water for Coliforms, Enterococci, TBC at 22 °C and fungi. The only statistically significant difference between bars and restaurants was observed for the TBCs at 22 °C (p = 0.017) and 36 °C (p = 0.036). Ice contamination does not appear to be directly related to the hygienic quality of water, but likely linked to the production, storage and maintenance of ice machines. Full article

The question of at which energy the transition from galactic to extra-galactic cosmic rays takes place has been a long-standing conundrum in cosmic ray physics. The sun stands out as the closest and clearest astrophysical accelerator of cosmic rays, while other objects within and beyond the galaxy remain enigmatic. It is probable that the cosmic ray spectrum and mass components from these celestial sources share similarities, offering a novel approach to study their origin. In this study, we perform joint analysis of spectra and mass in the energy range from MeV to 10 EeV, and find the following: (1) $⟨\mathrm{lnA}⟩$ demonstrates three clear peaks, tagging component transition; (2) a critical variable $\Delta$ is adopted to define the location of the transition; (3) for protons, the knee is located at ∼1.8 PeV, and the boundary between the galaxy and extra-galaxy occurs at ∼60 PeV, marked by a spectral dip; and (4) the all-particle spectrum exhibits hardening at ∼60 PeV due to the contribution of nearby galaxies, and the extra-galaxy dominates ∼0.8 EeV. We hope the LHAASO experiment can perform spectral measurements of individual species to validate these specific observations. Full article

It has long been debated whether gamma-ray bursts (GRBs) could serve as potential sources of ultra-high-energy cosmic rays (UHECRs). In this study, we consider GRBs as sources of UHECR injection with an injection index of $\alpha =2$ and propagate them through the extragalactic magnetic field within the framework of CRPropa 3. The baryon loading factor $f_{CR}$ is taken into account to quantify the rate of UHECR energy injection. In the benchmark case with a jet opening angle of ${\theta }_j=1$ and $f_{CR}=1$, we find that both high- and low-luminosity populations contribute to less than 10% of the UHECR spectrum. The most constrained scenario suggests $f_{CR}\le 15$, indicating that GRBs are less efficient in producing the all-sky UHECR intensity. The high-energy diffuse neutrinos and gamma rays resulting from interactions between UHECRs from GRBs and extragalactic background photons do not dominate the observations of Fermi-LAT or IceCube. Full article

The rise of CubeSats has unlocked opportunities for cutting-edge space missions with reduced costs and accelerated development timelines. CubeSats necessitate a high-gain antenna that can fit within a tightly confined space. This paper is primarily concerned with designing a compact Ku-band offset cylindrical reflector antenna for a CubeSat-based Earth Observation mission, with the goal of monitoring Arctic snow and sea ice. The development of a Ku-band offset cylindrical reflector, with a compact aperture of 110 × 149 mm² (6.3λ × 8.5λ), is described alongside a patch array feed consisting of 2 × 8 elements. The patch array feed is designed using a lightweight Rogers substrate and is utilized to test the reflector. Adopting an offset configuration helped prevent gain loss due to feed blockage. Analyzing the reflector antenna, including the feed, thorough simulations and measurements indicates that achieving a gain of 25 dBi and an aperture efficiency of 52% at 17.2 GHz is attainable. The reflector’s cylindrical shape and compact size facilitate the design of a simple mechanism for reflector deployment, enabling the antenna to be stored within 1U. The array feed and reflector antenna have been fabricated and tested, demonstrating good consistency between the simulation and measurement outcomes. Full article

Ice slurry is a phase-changing material composed of liquid water, ice crystals, and a freezing point depressant. It is finer and more uniform compared to ice cubes or flake ices and is used in many industries, such as food preservation, comfortable cooling, medical protective cooling, sport cooling, instrument cooling, firefighting, and artificial snowmaking, due to its high energy storage density. Ice slurry with high concentration can be used for cleaning equipment as its friction is several times greater than that of water at the same flow rate. This paper describes in detail the developments of ice slurry, including production methods, concentration measurement approaches, flow and heat transfer characteristics, as well as its applications in various industries. Problems to be solved or improved are also discussed, providing suggestions for better developments and applications in industrial environments. Full article

Edible ice is often produced by special machines that can represent a source of significant chemical and microbiological contamination. In this work, the presence of phthalic acid esters (phthalates, PAEs) and heavy metals in ice cubes distributed by 77 vending machines installed in two different zones in southern Italy and fed by water from the public water supply was investigated. Solid-phase microextraction coupled to gas chromatography−mass spectrometry (SPME-GC/MS) was used to evaluate contamination with four PAEs, which were selected because they are commonly used in the production of food-contact plastics, while inductively coupled plasma mass spectrometry (ICP/MS) was used to quantify the heavy metals. It was found that ice samples, especially those from one of the two considered zones (zone 2), exceeded the dibutyl phthalate (DBP) threshold limit value; some ice cubes from the other zone (zone 1) instead showed levels of both lead (Pb) and nickel (Ni) up to one order of magnitude higher than those observed in samples collected in zone 2 and higher than the maximum permitted values (European Directive n. 2184/2020). Since the water source connected to the ice vending machines was found to be free from significant levels of all considered target compounds and metals, the high levels of DBP, Ni, and Pb in ice cubes could be attributed to the components and/or to the state of repair of the ice vending machines themselves. Full article

African scientific research faces formidable challenges, particularly with limited access to state-of-the-art measurement instruments. The high cost associated with these devices presents a significant barrier for regional research laboratories, impeding their ability to conduct sophisticated experiments and gather precise data. This predicament not only hampers the individual laboratories but also has broader implications for the African scientific community and the advancement of knowledge in developing nations—the financial cost barrier considerably impacts the research quality of these laboratories. Reflection on technical and economical solutions needs to be quickly found to help these countries advance their research. In civil engineering, the thermal conductivity property is the most important measurement for characterizing heat transfer in construction materials. Existing devices (i.e., conductometers) in a laboratory are expensive (approximately EUR 30,000) and unavailable for some African laboratories. This study proposes a new and affordable device to evaluate thermal conductivity in construction materials. The method involves establishing a thermal flux between a heat source (from the Joule effect provided by steel wool where a current is circulating) and a cold source (generated by ice cubes) under steady-state conditions. The development of the cylindrical prototype is based on the comparative flux-meter method outlined in the measuring protocol of the ASTM E1225 standard document. Experiments were conducted on four distinct materials (polystyrene, wood, agglomerated wood, and rigid foam). The results indicate a correct correlation between the experimental values obtained from the newly developed prototype and the reference values found in the literature. For example, concerning the experimental polystyrene study, the detailed case analysis reveals a good correlation, with a deviation of only 4.88%. The percent error found falls within the acceptable range indicated by the standard recommendations of the ASTM E1225 standard, i.e., within 5% acceptable error. Full article

Low fluxes of astrophysical neutrinos at TeV energies, and the overwhelming background of atmospheric neutrinos below that, render the current paradigm of neutrino astronomy a severely statistics-limited one. While many hints have emerged, all the evidence gathered by IceCube and ANTARES, over the course of almost a decade and a half of operation, has fallen short of providing any conclusive answer to the puzzle of the origin of high-energy cosmic rays and neutrinos. The advancement of the field is thus closely associated with not only the neutrino observatories coming online in the next few years, but also on the coordinated efforts of the EM, GW and cosmic ray communities to develop dedicated channels and infrastructure that allow for the swift and comprehensive multi-messenger follow-up of relevant events detected in any of these sectors. This paper highlights the strides that have been already taken in that direction and the fruits that they have borne, as well as the challenges that lie ahead. Full article

This study explores the potential for dark matter annihilation within brown dwarfs, investigating an unconventional mechanism for neutrino production. Motivated by the efficient accumulation of dark matter particles in brown dwarfs through scattering interactions, we focus on a mass range above 10 GeV, considering dark matter annihilation channels $\chi \chi \to \nu \overline{\nu }\nu \overline{\nu }$ through long-lived mediators. Using the projected sensitivity of IceCube Generation 2, we assess the detection capability of the local population of brown dwarfs within 20 pc and exclude dark matter-nucleon scattering with cross-sections as low as a few multiples of ${10}^{-36}{\mathrm{cm}}^2$. Full article