A multimessenger campaign has associated a high-energy cosmic neutrino with a distant gamma-ray blazar, TXS 0506+056. IceCube archival data subsequently revealed that the high-energy neutrino flux ...from the direction of this source, integrated over the last 10 yr, is dominated by a single bright neutrino flare in 2014, leaving the multimessenger flare as a subluminous second flare. The extraordinary brightness of the blazar despite its distance suggests that it may belong to a special class of sources that produce cosmic rays. We show that the diffuse IceCube flux discovered in 2013 can be accommodated by a subclass of blazars, on the order of 5%, that episodically produce neutrinos with the luminosity of the 2014 neutrino flare. Matching the cosmic-ray flux required to produce the neutrinos to the one observed implies highly efficient neutrino sources with large target photon densities that are not transparent to high-energy gamma-rays. The opacity of the source modifies the straightforward multimessenger connection in a way that is consistent with the gamma-ray observations coincident with the 2014 neutrino flare.
The intergalactic magnetic field (IGMF) in cosmic voids can be indirectly probed through its effect on electromagnetic cascades initiated by a source of teraelectronvolt (TeV) gamma-rays, such as ...active galactic nuclei (AGNs). AGNs that are sufficiently luminous at TeV energies, "extreme TeV blazars", can produce detectable levels of secondary radiation from inverse Compton scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature that utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars, 1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same framework. Through a recently developed, detailed, three-dimensional particle-tracking Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research the effects of major uncertainties, such as the spectral properties of the source, uncertainty in the ultraviolet and far-infrared extragalactic background light, undersampled very high energy (energy > or =, slanted 100 GeV) coverage, past history of gamma-ray emission, source versus observer geometry, and the jet AGN Doppler factor. The implications of these effects on the recently reported lower limits of the IGMF are thoroughly examined to conclude that the presently available data are compatible with a zero-IGMF hypothesis.
Highlights from the HAWC Observatory Weisgarber, Thomas
Nuclear and particle physics proceedings,
September-November 2019, 2019-09-00, Letnik:
306-308
Journal Article
Recenzirano
The High Altitude Water Cherenkov (HAWC) observatory is a wide-field survey instrument sensitive to gamma rays and cosmic rays in the energy range from ∼100 GeV to > 100 TeV. Located in the state of ...Puebla, Mexico at 4100 m above sea level, HAWC has been fully operational for over three years, since its inauguration in March 2015. This work highlights recent results from HAWC, including both Galactic and extragalactic gamma-ray sources as well as cosmic-ray observations. It also highlights HAWC's role in several multimessenger studies, focusing on what we can learn in conjunction with neutrinos observed by IceCube and HAWC observations of GRBs in the context of gravitational waves.
The selection of the specific electrical steel type is one of the most important decisions for electric motor design as it influences power density and efficiency of the machine strongly. Usually, ...the choice is limited to standard grades where a tradeoff between price, lowest losses and high induction is made. Additive manufacturing gives the opportunity to print sheets with lowest losses as thinner sheets as well as higher alloying contents can be fabricated. Processing into end geometry ensures maximum materials utilization. Electric motor design becomes more flexible and current limitations can be eliminated. Here, the results of additively manufactured Fe-6.5Si electrical steel sheets illustrate new paths opening a variety of possibilities as losses can be decreased and mechanical robustness is increased which is ultimately made for the application in higher frequency motors.
In this letter, the design and additive manufacturing (AM) of a groove gap waveguide (GGW) filter in the D-band is presented. For this kind of filter, the manufacturing of very small periodic pin ...structures is necessary. The conventional manufacturing of these structures by CNC milling is time-consuming, and high-precision milling machines are extremely expensive. Other manufacturing processes such as screen printing are, therefore, required for the cost-effective and efficient production of large quantities. The screen printing process is presented, and its suitability for the production of GGW components in the millimeter-wave area is validated by a third-order bandpass filter prototype in D-band, which was manufactured and electrically characterized.
The High Altitude Water Cherenkov (HAWC) Observatory is a wide-field-of-view gamma-ray observatory that is optimized to detect gamma rays between 300 GeV and several hundred TeV. The HAWC ...Collaboration recently released their third source catalog (3HWC), which contains 65 sources. One of these sources, the ultra-high-energy gamma-ray source 3HWC J1908+063, may exhibit a hardening of the spectral index at the highest energies (above 56 TeV). At least two populations of particles are needed to satisfactorily explain the highest energy emission. This second component could be leptonic or hadronic in origin. If it is hadronic in origin, it would imply the presence of protons with energies up to ~1 PeV near the source. We have searched other 3HWC sources for the presence of this spectral hardening feature. If observed, this would imply that the sources could make good PeVatron candidates.
The Ultra-High-Energy Source MGRO J1908+06 Malone, Kelly; Abeysekara, Anushka Udara; Albert, Andrea ...
Pos : proceedings of science,
07/2021, Letnik:
395
Journal Article
Recenzirano
Odprti dostop
The TeV gamma-ray source MGRO J1908+06 is one of the highest-energy sources known, with observed emission by the High Altitude Water Cherenkov (HAWC) Observatory extending well past 100 TeV. The ...source exhibits both energy-dependent morphology and a spatially-dependent spectral index. The emission is likely to be dominantly leptonic, and associated with the radio-quiet PSR J1907+0602. However, one-population models do not describe the data well; a second particle population is needed to explain the shape of the spectral energy distribution at the highest energies. This component can be well-described by either leptonic or hadronic hypotheses. We discuss this feature and implications for detection by multi-wavelength and multi-messenger experiments.
Observations of the galaxies, clusters, and filaments of the large-scale structure (LSS) of the universe reveal that these objects possess magnetic fields exhibiting complicated structure with ...strengths on the order of a microGauss. Recent observations have also begun to shed light on the extragalactic magnetic field (EGMF), which is believed to exist in the voids that likely comprise the majority of the LSS. Such a field could have been generated primordially, for instance during phase transitions in the early universe. In this case, its detection and characterization could reveal information about conditions in the early universe. A primordially generated field is also physically compelling because many models of magnetic field formation in galaxies require an initial seed field, a role that can be readily filled by an EGMF existing prior to galaxy formation. Alternatively, astrophysical mechanisms have been proposed to generate the EGMF via bulk outflows of magnetized plasma from active and starburst galaxies. In this case, the detection of an EGMF would provide evidence for the unexpected efficiency in the transport of magnetic energy into the voids. Over the past few decades, the development of ground-based gamma-ray astronomy has opened many new opportunities to study the universe at high energies. One such opportunity involves a recently developed technique exploiting the observations of distant blazars to measure or constrain the EGMF. Because of the cosmological distances that they must cross to propagate to Earth, very-high-energy gamma rays from blazars are attenuated by their interactions with the extragalactic background light and cosmic microwave background radiation. Due to this attenuation, an electromagnetic cascade of electrons, positrons, and gamma rays arises in extragalactic space. The deflection of the electrons and positrons by the EGMF ultimately produces two effects on the secondary gamma rays in the cascades. These gamma rays are delayed in time with respect to a primary gamma ray that travels directly from the source to Earth, and they form an angular distribution, or "halo," around what would otherwise appear as a pointlike blazar. In this work, I develop a new method for accurately quantifying the extended gamma-ray halo that arises due to the influence of the EGMF on the extragalactic cascades. This method is sensitive to EGMF strengths between 3 × 10 –17 and 10–14 Gauss. I compare the predictions from a Monte Carlo simulation to combined data from ground-based imaging atmospheric Cherenkov telescopes and the Fermi Gamma-Ray Space Telescope in an attempt to measure or constrain the properties of the EGMF. Depending on certain assumptions about the source lifetime, I interpret the absence of any detectable gamma-ray halo around the blazars RGB J0710+591 and 1ES 0229+200 as evidence for an EGMF with a strength greater than 3 × 10 –15 Gauss. This represents the strongest firm lower limit on the EGMF strength at the present time.
The High Altitude Water Cherenkov (HAWC) Observatory recently began full-scale operations, surveying 2/3 of the entire sky at very high energy (VHE; E > 100 GeV). This new view of the sky offers the ...opportunity to detect flares from blazars, facilitating studies of the mechanisms powering their central engines and providing an avenue to constrain the properties of particles and fields in intergalactic space. The HAWC Collaboration has implemented an online flare monitor to search for rapid and extreme transient activity from a set of blazars either known or suspected to produce VHE emission. The goal of this project is to issue alerts sufficiently rapidly to form a complete multiwavelength picture of the flare. We describe the current status of the online flare monitor, demonstrating its ability to detect flares via a study of the blazars Markarian 421 and Markarian 501 in offline data.
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