Space weather effects are generally recognized as causes of degradation of satellite positioning, navigation and timing (PNT) services. We analyze GPS position estimation error during a geomagnetic ...storm, focusing on manifestations of geomagnetic processes. The position estimation error was analyzed in terms of GPS coordinates’ deviations (latitude, longitude and height) from their reference values. The storm’s impact was studied in the Northern Adriatic region where GPS observables from two Global Navigation Satellite System (GNSS) reference stations were analysed. Geomagnetic indices were elaborated, comprising readings from interplanetary, magnetospheric and geomagnetic observatories. Total Electron Content (TEC) on both stations was computed using dual frequency GPS pseudorange observables. The experiment was to reconstruct the movement of geomagnetic disturbances entering the geospace, reaching the earth’s surface. The aim was to correlate possible space weather manifestation on satellite positioning performance in terms of positioning error. Regularities in changes in positioning deviations were identified with relation to influential indices. The research offered a possibility of experimental positioning deviations assessment as well as forecasting. Evaluation of generated rudimentary Classification and Regression Trees (CART) models showed that the risk of satellite positioning errors could be assessed and predicted considering absolutes, as well as changes in values of geomagnetic indices. During the research process, several activities emerged as preferable continuation of the work, with the aim of further development of predictive models and the complement of space weather scenarios and their consequences on navigational systems. Along with summarized results, they are outlined in the conclusion section.
Abstract The Tarantula Nebula in the Large Magellanic Cloud is known for its high star formation activity. At its center lies the young massive star cluster R136, providing a significant amount of ...the energy that makes the nebula shine so brightly at many wavelengths. Recently, young massive star clusters have been suggested to also efficiently produce very high-energy cosmic rays, potentially beyond PeV energies. Here, we report the detection of very-high-energy γ -ray emission from the direction of R136 with the High Energy Stereoscopic System, achieved through a multicomponent, likelihood-based modeling of the data. This supports the hypothesis that R136 is indeed a very powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide an updated measurement of the γ -ray emission from 30 Dor C, the only superbubble detected at TeV energies presently. The γ -ray luminosity above 0.5 TeV of both sources is (2–3) × 10 35 erg s −1 . This exceeds by more than a factor of 2 the luminosity of HESS J1646−458, which is associated with the most massive young star cluster in the Milky Way, Westerlund 1. Furthermore, the γ -ray emission from each source is extended with a significance of >3 σ and a Gaussian width of about 30 pc. For 30 Dor C, a connection between the γ -ray emission and the nonthermal X-ray emission appears likely. Different interpretations of the γ -ray signal from R136 are discussed.
GRB221009A is the brightest gamma-ray burst ever detected. To probe the very-high-energy (VHE, $>$100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hours after ...the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection, after applying atmospheric corrections. The combined observations yield an integral energy flux upper limit of $\Phi_\mathrm{UL}^{95\%} = 9.7 \times 10^{-12}~\mathrm{erg\,cm^{-2}\,s^{-1}}$ above $E_\mathrm{thr} = 650$ GeV. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the SED occurring above the X-ray band. Compared to the VHE-bright GRB190829A, the upper limits for GRB221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB221009A, effectively ruling out an IC dominated scenario.
Automatic Vehicle Identification is an important subsystem of Intelligent Transport Systems. One of the most common methods is the application of the licence plate recognition which is conducted in ...the following steps: detecting and extracting vehicles in dynamic scene, image pre-processing, licence plate localization, extracting characters from the licence plate and recognition of the individual character. In this paper, the operation of the Automatic licence plate identification module and multifunctional system for automatic traffic monitoring is presented. The preview of the algorithm operation is achieved by using Matlab (MathWorks) software and the corresponding appropriate Tools. The system has shown satisfactory results in recognizing licence plates and usefulness in the planned scope.Original Abstract: Automatska identifikacija prijevoznih sredstava vazan je podsustav inteligentnih transportnih sustava. Jedna od zastupljenijih metoda je primjena raspoznavanja registarskih plocica koja se provodi u sljedecim radnjama: otkrivanje i izdvajanje vozila u dinamickoj sceni, predobrada slike, odredivanje pozicije registarske plocice, izdvajanje karaktera s registarske plocice i raspoznavanje pojedinih karaktera. U ovome je radu prikazano djelovanje modula za automatsko prepoznavanje registarskih plocica kao visenamjenskog sustava za automatsko nadziranje cestovnog prometa. Prikaz rada algoritama ostvaren je koristenjem programske podrske Matlab (MathWorks) i pripadajucih odgovarajucih alata (tools). Sustav je pokazao zadovoljavajuce rezultate u prepoznavanju registarskih plocica vozila i mogucnosti upotrebe u predvidenom podrucju primjene.
With increasing requirements for reliability, availability, efficiency, effectiveness, productivity, and security of the system, the importance of diagnostics and maintenance is also increasing. ...E-maintenance as a leading concept for maintenance management has so far primarily involved the use of domain-specific technical language processing (TLP) techniques on historical case data. Due to its popularity, generative AI (GAI) with large language models (LLMs) is starting to be used more and more in various technical areas, thus starting to take an increasingly important place in diagnostics and maintenance. Starting from the fact that the rapid development of information and communication technologies (ICT) was the main factor in the emergence and development of the concept of e-maintenance, the importance of the potential more serious application of all forms of generative AI in the context is clear. This is especially pronounced in cases of difficult or impossible access to the location of components or an uncertain situation related to the type of process (e.g., nuclear, aeronautical, space, offshore). Autonomous vehicles, vessels, and aircraft (as an indispensable part of today's intelligent transport systems) are certainly a leading example of these cases. Regardless of the level of autonomy, these systems are extremely complex and difficult to maintain and represent a clear challenge for the application of new approaches. Therefore, the authors of the paper propose the use of middleware that would enable the integration of various GAI tools, algorithms, and models to increase the effectiveness of diagnostics and maintenance as close as possible to real-time. However, the exact extent of the possibilities and limitations of this approach has yet to be determined.
PSR B1259-63 is a gamma-ray binary system that hosts a pulsar in an eccentric orbit, with a 3.4 year period, around an O9.5Ve star. At orbital phases close to periastron passages, the system radiates ...bright and variable non-thermal emission. We report on an extensive VHE observation campaign conducted with the High Energy Stereoscopic System, comprised of ~100 hours of data taken from \(t_p-24\) days to \(t_p+127\) days around the system's 2021 periastron passage. We also present the timing and spectral analyses of the source. The VHE light curve in 2021 is consistent with the stacked light curve of all previous observations. Within the light curve, we report a VHE maximum at times coincident with the third X-ray peak first detected in the 2021 X-ray light curve. In the light curve -- although sparsely sampled in this time period -- we see no VHE enhancement during the second disc crossing. In addition, we see no correspondence to the 2021 GeV flare in the VHE light curve. The VHE spectrum obtained from the analysis of the 2021 dataset is best described by a power law of spectral index \(\Gamma = 2.65 \pm 0.04_{\text{stat}}\) \(\pm 0.04_{\text{sys}}\), a value consistent with the previous H.E.S.S. observations of the source. We report spectral variability with a difference of \(\Delta \Gamma = 0.56 ~\pm~ 0.18_{\text{stat}}\) \(~\pm~0.10_{\text{sys}}\) at 95% c.l., between sub-periods of the 2021 dataset. We also find a linear correlation between contemporaneous flux values of X-ray and TeV datasets, detected mainly after \(t_p+25\) days, suggesting a change in the available energy for non-thermal radiation processes. We detect no significant correlation between GeV and TeV flux points, within the uncertainties of the measurements, from \(\sim t_p-23\) days to \(\sim t_p+126\) days. This suggests that the GeV and TeV emission originate from different electron populations.
Astrophysical Journal Letters 970, L21 (2024) The Tarantula Nebula in the Large Magellanic Cloud is known for its high star
formation activity. At its center lies the young massive star cluster R136,
...providing a significant amount of the energy that makes the nebula shine so
brightly at many wavelengths. Recently, young massive star clusters have been
suggested to also efficiently produce high-energy cosmic rays, potentially
beyond PeV energies. Here, we report the detection of very-high-energy
$\gamma$-ray emission from the direction of R136 with the High Energy
Stereoscopic System, achieved through a multicomponent, likelihood-based
modeling of the data. This supports the hypothesis that R136 is indeed a very
powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide
an updated measurement of the $\gamma$-ray emission from 30 Dor C, the only
superbubble detected at TeV energies presently. The $\gamma$-ray luminosity
above $0.5\,\mathrm{TeV}$ of both sources is $(2-3)\times
10^{35}\,\mathrm{erg}\,\mathrm{s}^{-1}$. This exceeds by more than a factor of
2 the luminosity of HESS J1646$-$458, which is associated with the most massive
young star cluster in the Milky Way, Westerlund 1. Furthermore, the
$\gamma$-ray emission from each source is extended with a significance of
$>3\sigma$ and a Gaussian width of about $30\,\mathrm{pc}$. For 30 Dor C, a
connection between the $\gamma$-ray emission and the nonthermal X-ray emission
appears likely. Different interpretations of the $\gamma$-ray signal from R136
are discussed.
HESS J1813\(-\)178 is a very-high-energy \(\gamma\)-ray source spatially coincident with the young and energetic pulsar PSR J1813\(-\)1749 and thought to be associated with its pulsar wind nebula ...(PWN). Recently, evidence for extended high-energy emission in the vicinity of the pulsar has been revealed in the Fermi Large Area Telescope (LAT) data. This motivates revisiting the HESS J1813\(-\)178 region, taking advantage of improved analysis methods and an extended data set. Using data taken by the High Energy Stereoscopic System (H.E.S.S.) experiment and the Fermi-LAT, we aim to describe the \(\gamma\)-ray emission in the region with a consistent model, to provide insights into its origin. We performed a likelihood-based analysis on 32 hours of H.E.S.S. data and 12 years of Fermi-LAT data and fit a spectro-morphological model to the combined datasets. These results allowed us to develop a physical model for the origin of the observed \(\gamma\)-ray emission in the region. In addition to the compact very-high-energy \(\gamma\)-ray emission centered on the pulsar, we find a significant yet previously undetected component along the Galactic plane. With Fermi-LAT data, we confirm extended high-energy emission consistent with the position and elongation of the extended emission observed with H.E.S.S. These results establish a consistent description of the emission in the region from GeV energies to several tens of TeV. This study suggests that HESS J1813\(-\)178 is associated with a \(\gamma\)-ray PWN powered by PSR J1813\(-\)1749. A possible origin of the extended emission component is inverse Compton emission from electrons and positrons that have escaped the confines of the pulsar and form a halo around the PWN.
The radio galaxy M87 is a variable very-high energy (VHE) gamma-ray source, exhibiting three major flares reported in 2005, 2008, and 2010. Despite extensive studies, the origin of the VHE gamma-ray ...emission is yet to be understood. In this study, we investigate the VHE gamma-ray spectrum of M87 during states of high gamma-ray activity, utilizing 20.2\(\,\) hours the H.E.S.S. observations. Our findings indicate a preference for a curved spectrum, characterized by a log-parabola model with extra-galactic background light (EBL) model above 0.3\(\,\)TeV at the 4\(\sigma\) level, compared to a power-law spectrum with EBL. We investigate the degeneracy between the absorption feature and the EBL normalization and derive upper limits on EBL models mainly sensitive in the wavelength range 12.4$\,$$\mu\(m - 40\)\,$$\mu$m.
The Crab Nebula is a unique laboratory for studying the acceleration of electrons and positrons through their non-thermal radiation. Observations of very-high-energy \(\gamma\) rays from the Crab ...Nebula have provided important constraints for modelling its broadband emission. We present the first fully self-consistent analysis of the Crab Nebula's \(\gamma\)-ray emission between 1 GeV and \(\sim\)100 TeV, that is, over five orders of magnitude in energy. Using the open-source software package Gammapy, we combined 11.4 yr of data from the Fermi Large Area Telescope and 80 h of High Energy Stereoscopic System (H.E.S.S.) data at the event level and provide a measurement of the spatial extension of the nebula and its energy spectrum. We find evidence for a shrinking of the nebula with increasing \(\gamma\)-ray energy. Furthermore, we fitted several phenomenological models to the measured data, finding that none of them can fully describe the spatial extension and the spectral energy distribution at the same time. Especially the extension measured at TeV energies appears too large when compared to the X-ray emission. Our measurements probe the structure of the magnetic field between the pulsar wind termination shock and the dust torus, and we conclude that the magnetic field strength decreases with increasing distance from the pulsar. We complement our study with a careful assessment of systematic uncertainties.
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