Large Distances Research Articles

Wideband FMCW radar for long-distance target detection based on photonic chirp pulse stitching.

Current wideband frequency-modulated continuous-wave (FMCW) radar fails in detecting long-distance target, since only the target whose echo is temporally close to the reference linear frequency modulation (LFM) chirp can be detected. We propose a long-distance target detection method for the wideband FMCW radar based on photonic chirp pulse stitching. The stitching photonic chirp pulse that is generated through optical up- and downconversion of the LFM is employed as local signal for the de-chirping process instead of the LFM itself, as currently used. By adjusting the transmitting signal period, a theoretically arbitrarily large detection distance can be obtained with the proposed method. Experiments obtain high-resolution range profiles for two targets located at 1.44 km and 14.5 km, respectively, proving the feasibility of the proposed scheme.

Influence of curing mode and aging on the bonding performance of universal adhesives in coronal and root dentin

BackgroundThis study aims to evaluate the microtensile bond strength (µTBS) of different resin composite restorations bonded to mid-coronal dentin and proximal root dentin using light-cured, chemical-cured, and dual-cured adhesives immediately and after aging. Nanoleakage and degree of cure were also assessed.MethodsEighty-four molars were divided into mid-coronal dentin and proximal root dentin. Each group was further subdivided into three subgroups based on the restorative systems used, which involved the utilization of light-cured, chemical-cured, and dual-cured adhesives. Half of the specimens underwent µTBS testing after 24 h, while the other half after aging. Representative specimens were analyzed for nanoleakage. The degree of cure of the tested adhesive systems was also assessed.ResultsAging showed a significant negative effect on µTBS results and led to increased nanoleakage (p < 0.001). Furthermore, in all subgroups, the µTBS values of proximal root dentin were lower compared to mid-coronal dentin, except in the aged subgroup for the system utilizing the dual-cured adhesive. The restorative systems with chemical and dual-cured adhesives demonstrated comparable bonding properties. However, the system with the light-cured adhesive exhibited the worst bonding properties after aging when bonded to proximal root dentin and cured at a large distance (p < 0.05).ConclusionsAll tested restorative systems were negatively affected by aging, and the regional dentin had variable effects on the bonding properties. Clinicians should exercise caution when using the tested light-cured adhesive in areas where the curing distance exceeds 3 mm.

Deep learning methods for modeling infrasound transmission loss in the middle atmosphere

Accurate modeling of infrasound transmission losses (TLs) is essential to assess the performance of the global International Monitoring System (IMS) infrasound network. Among existing propagation modeling tools, parabolic equation method (PE) enables TLs to be finely modeled, but its computational cost does not allow exploration of a large parameter space for operational monitoring applications. To reduce computation times, Brissaud et al. (2022) explored the potential of convolutional neural networks (CNNs) trained on a large set of regionally simulated wavefields (&gt;1000 km from the source) to predict TLs with negligible computation times compared to PE simulations. However, this new method shows difficulties in upwind conditions, especially at low frequencies, and causal issues with winds at large distances from the source affecting ground TLs close to the source. In this study, we have developed an optimized CNN network designed to minimize prediction errors while predicting TLs from globally simulated combined temperature and wind fields spanning over propagation ranges of 4000 km. Our approach enhances the previously proposed one by implementing key optimizations that improve the overall architecture performances. The implemented model predicts TLs with an average error of 20 dB in the whole frequency band (0.1-4 Hz) and explored realistic atmospheric scenarios.

Numerical modeling of infrasounds radiation and propagation in hurricanes

Infrasound can be useful for monitoring natural or human-induced energetic events in the atmosphere. For high-energy sources, the infrasonic signals can propagate over large distances around the globe, given the low rate of atmospheric absorption. This study focuses on the numerical simulation of infrasound propagation in realistic large-scale three-dimensional (3D) environments. More precisely, we are interested in the simulation of infrasound, called microbaroms, which are radiated from extreme weather conditions such as hurricanes. The simulation of hurricane-induced microbaroms relies on three main components: i) a hurricane model describing the atmospheric wind and pressure fields, ii) a microbarom source model, and iii) an infrasound propagation model. 3D simulations have been performed on a rectangular mesh. Azimuthal deviation caused by the hurricane and the stratified atmosphere can be seen in 3D. Further studies are needed to improve each model, and the correlation between them. The ultimate goal is to be able to simulate radiated infrasound propagation for any meteorological conditions.

AstroSat’s view of 4U 1735−44: spectral, temporal, and type I X-ray burst studies

ABSTRACT This study utilizes the simultaneous broad-band observations of 4U 1735−44 from AstroSat, offering enhanced spectral and temporal resolution, to investigate its spectral properties, temporal behaviour, and burst characteristics. Spectral, type I X-ray burst, and temporal analyses on 4U 1735−44 were performed using AstroSat/Soft X-ray Telescope and Large Area X-ray Proportional Counter (LAXPC) observations. The hardness–intensity diagram from LAXPC-20 showed a positive correlation between hardness and intensity, with a pattern resembling the banana branch typical of atoll sources. Spectral analysis carried out in the 0.7–20.0 keV energy range, using the model combination – $\tt {constant}$$\times$$\tt {tbabs}$ ($\tt {nthcomp}$$+$$\tt {diskbb}$$+$$\tt {bbodyrad}$), suggested a cool accretion disc truncated at a large distance from the neutron star in the system. Time-resolved spectral studies of two type I X-ray bursts detected from the source revealed evidence of photospheric radius expansion, allowing for an estimation of the source distance. Temporal analysis showed the presence of low-frequency quasi-periodic oscillation at $\sim$69 Hz (3.3$\sigma$ significance with more than 99 per cent confidence) and prominent noise features below 30 Hz.

Limitations of effective medium models for tissue phantoms in the THz frequency range

The absorption of terahertz (THz) radiation by water molecules facilitates its application to several biomedical applications such as cancer detection. Therefore, it is critical for the THz technologies to be characterised with water content in a sample. In this paper, we analyse gelatine phantoms in the THz frequency range, with continuously varying hydration levels as they dry over time. Water molecules in close proximity to the protein molecule, termed ‘bound water’, feature properties different from the ‘free water’ molecules at larger distances. We find that a common model for predicting electromagnetic properties of phantoms and tissue samples, which assumes that only the free water varies with hydration while the bound water remains constant, does not agree well with measured results. To gain insight into this behaviour, we simultaneously measured the phantom in Raman spectroscopy, which shows a continuously varying concentration of bound water with hydration level. It follows from this investigation, that the permittivity contributions of neither the biomolecules nor water are expected to be linear with water density. This means that the often used, simple effective medium model will not be accurate for many biological tissues or phantoms.

Genomic variation of European beech reveals signals of local adaptation despite high levels of phenotypic plasticity

Local adaptation is key for ecotypic differentiation and species evolution. Understanding underlying genomic patterns can allow the prediction of future maladaptation and ecosystem stability. Here, we report the whole-genome resequencing of 874 individuals from 100 range-wide populations of European beech (Fagus sylvatica L.), an important forest tree species in Europe. We show that genetic variation closely mirrors geography with a clear pattern of isolation-by-distance. Genome-wide analyses for genotype-environment associations (GEAs) identify relatively few potentially adaptive variants after correcting for an overwhelming signal of statistically significant but non-causal GEAs. We characterize the single high confidence genomic region and pinpoint a candidate gene possibly involved in winter temperature adaptation via modulation of spring phenology. Surprisingly, allelic variation at this locus does not result in any apparent fitness differences in a common garden. More generally, reciprocal transplant experiments across large climate distances suggest extensive phenotypic plasticity. Nevertheless, we find indications of polygenic adaptation which may be essential in natural ecosystems. This polygenic signal exhibits broad- and fine-scale variation across the landscape, highlighting the relevance of spatial resolution. In summary, our results emphasize the importance, but also exemplify the complexity, of employing natural genetic variation for forest conservation under climate change.

Host diversity of Aedes albopictus in relation to invasion history: a meta-analysis of blood-feeding studies

BackgroundThe invasive mosquito Aedes albopictus is a major concern for human and animal health given its high potential to spread over large geographical distances, adapt to various habitats and food sources, and act as a vector for pathogens. It is crucial to understand how this species establishes ecological relationships at different locations, as it determines its role in transmission of diseases.MethodsBased on published blood meal surveys, a meta-analysis was performed to investigate how host diversity changes along the process of invasion at a large scale. For 48 independent localities, the Shannon diversity index was calculated and was then assessed against several moderator variables describing invasion status, habitat type, methodology, survey year and the year of introduction for invasive populations.ResultsDiet diversity was higher in the invasive than in the native populations when the strong habitat effects were held constant. Furthermore, the year of introduction also had a significant role, as invasive populations that had been established earlier had wider diet diversity than more recent populations.ConclusionsInvasive Ae. albopictus has considerable ecological flexibility. The species’ ability to adapt to various food sources goes hand in hand with its successful worldwide dispersion, which has strong implications for its role in pathogen transmission.Graphical

Wildlife as Reservoirs of Encephalitozoon Cuniculi and Encephalitozoon Hellem and Molecular Genotyping of Encephalitozoon spp. in Small Mammals in the Czech Republic.

Parasites of genus Encephalitozoon are well known pathogens of domestic animals however less attention was paid to its spread among wildlife that can play an important role of reservoir of infection. The aim of the study was to conduct molecular detection and genotype characterization of Encephalitozoon spp. in wild small mammals trapped in localities both near to and at a large distance from residential areas. In total, 300 wild small mammals (274 Rodentia and 26 Eulipotyphla) were trapped in 41 localities of the Czech Republic and tested by nested PCR for Encephalitozoon spp. The DNA of Encephalitozoon spp. was proved in tissues (brain or liver) of 11% (32/300) of animals. There was a statistically significant difference (p < 0.001) in positivity among animal species with the most infected species Micromys minutus (50%, 4/8) and Myodes glareolus (17%, 9/53). There was also statistically significant difference (p < 0.001) between localities with the higher positivity (29%, 12/42) in localities near to residential areas, compared to localities with a large distance from residential areas (8%, 20/258). Sex and age of wild small mammals did not have effect on their positivity. Genotyping analysis revealed E. cuniculi genotype II in 22 samples and E. hellem genotype 1A in one sample. This study brings new information on the molecular characterization of Encephalitozoon spp. isolated from wild small mammals trapped in two different areas (localities in near to residential areas and localities with a large distance from residential areas).

Younger and rural children are more likely to be hospitalized for SARS-CoV-2 infections.

To identify characteristics of SARS-CoV-2 infection that are associated with hospitalization in children initially evaluated in a Pediatric Emergency Department (ED). We identified cases of SARS-CoV-2 positive patients seen in the Arkansas Children's Hospital (ACH) ED or hospitalized between May 27, 2020, and April 28, 2022, using ICD-10 codes within the Pediatric Hospital Information System (PHIS) Database. We compared infection waves for differences in patient characteristics and used logistic regressions to examine which features led to a higher chance of hospitalization. We included 681 pre-Delta cases, 673 Delta cases, and 970 Omicron cases. Almost 17% of patients were admitted to the hospital. Compared to Omicron-infected children, pre-Delta and Delta-infected children were twice as likely hospitalized (OR = 2.2 and 2.0, respectively; p<0.0001). Infants under one year were >3 times as likely to be hospitalized than children ages 5-14 years regardless of wave (OR = 3.42; 95%CI = 2.36-4.94). Rural children were almost three times as likely than urban children to be hospitalized across all waves (OR = 2.73; 95%CI = 1.97-3.78). Finally, those with a complex condition had nearly a 15-fold increase in odds of admission (OR = 14.6; 95%CI = 10.6-20.0). Children diagnosed during the pre-Delta or Delta waves were more likely to be hospitalized than those diagnosed during the Omicron wave. Younger and rural patients were more likely to be hospitalized regardless of the wave. We suspect lower vaccination rates and larger distances from medical care influenced higher hospitalization rates.

Genetic Diversity of Local Chili (Capsicum annum L.) from West Sumatra Indonesia Based on Inter Simple Sequences Repeat (ISSR) Markers

Capsicum annum L. is the most widely cultivated species due to its economic importance and health benefits. West Sumatra is one of the largest chili pepper producers in Indonesia, so it has a lot of local chili genetic resources. There is inadequate information on the genetic diversity of local chilies in West Sumatra. The purpose of this research was to analyze the genetic diversity of 23 genotypes of chili pepper from West Sumatra amplified with 10 markers of ISSR. The material used was leaves from 23 genotypes of West Sumatra’s local chili which are collections of the Agriculture Faculty, Andalas University, Padang, West Sumatra. The results showed that ISSR markers (ISSR primer 12, ISSR UBC, and ISSR 3M) had produced 84 polymorphic DNA bands with a total polymorphic percentage of 61.45%. The dendrogram based on 10 ISSR markers showed that the 23 chili genotypes were retrieved into three main groups (I, II, III, IV) with genetic similarity coefficient values ranging from 0.67 to 0.97 or a diversity of features of 0.03–0.33 (30%). Group I consisted of 1 genotype, group II consisted of 3 genotypes, and group III consisted of 14 genotypes. Kopay chili (G20) has a large genetic distance compared to the other genotypes, while Lolai and Gero chilies have a very high similarity. This genetic diversity information can be used as a basis for generating crosses between genotypes in a breeding program. The farther the genetic distance will produce a high population diversity, the greater the chance of getting superior hybrids. Keywords: Capsicum annum, ISSR, local chili, West Sumatra

Scrutinizing black hole stability in cubic vector Galileon theories

In a subclass of generalized Proca theories where a cubic vector Galileon term breaks the U(1) gauge invariance, it is known that there are static and spherically symmetric black hole (BH) solutions endowed with nonvanishing temporal and longitudinal vector components. Such hairy BHs are present for a vanishing vector-field mass (m=0) with a non-zero cubic Galileon coupling β 3. We study the linear stability of those hairy BHs by considering even-parity perturbations in the eikonal limit. In the angular direction, we show that one of the three dynamical perturbations has a nontrivial squared propagation speed c Ω,1 2, while the other two dynamical modes are luminal.We could detect two different unstable behaviors of perturbations in all the parameter spaces of hairy asymptotically flat BH solutions we searched for. In the first case, an angular Laplacian instability on the horizon is induced by negative c Ω,1 2. For the second case, it is possible to avoid this horizon instability, but in such cases, the positivity of c Ω,1 2 is violated at large distances. Hence these hairy BHs are generally prone to Laplacian instabilities along the angular direction in some regions outside the horizon. Moreover, we also encounter a pathological behavior of the radial propagation speeds c r possessing two different values of c r 2 for one of the dynamical perturbations. Introducing the vector-field mass m to cubic vector Galileons, however, we show that the resulting no-hair Schwarzschild BH solution satisfies all the linear stability conditions in the small-scale limit, with luminal propagation speeds of three dynamical even-parity perturbations.

Slowly positively drifting bursts generated by large-scale magnetic reconnection

Context. The slowly positively drifting bursts (SPDBs) are rarely observed in radio emission of solar flares. Aims. To understand how the SPDBs are generated, we studied the radio observations at 600–5000 MHz together with the imaging observations made in ultraviolet (UV) and extreme ultraviolet (EUV) during the SPDB-rich C8.7 flare of 2014 May 10 (SOL2014-05-10T0702). Methods. Because the SPDBs propagate towards locations of higher plasma density, we studied their associations with individual flare kernels, located either within the flare core itself, or distributed at longer distances, but connected to the flaring region by large-scale hot loops. For each kernel we constructed light curves using 1600 Å and 304 Å observations and compared these light curves with the temporal evolution of radio flux at 1190 MHz, representing all observed groups of SPDBs. We also analysed the UV/EUV observations to understand the evolution of magnetic connectivity during the flare. Results. The flare starts with a growing hot sigmoid observed in 131 Å. As the sigmoid evolves, it extends to and interacts with a half dome present within the active region. The evolving sigmoid reconnects at the respective hyperbolic flux tube, producing large-scale magnetic connections and an EUV swirl. Three groups of SPDBs are observed during this large-scale magnetic reconnection, along with a group of narrow-band type III bursts. The light curves of a kernel corresponding to the footpoint of spine line analogue show good agreement with the radio flux at 1190 MHz, indicating that the SPDBs are produced by the large-scale magnetic reconnection at the half dome. In addition, one of the kernels appeared in the neighbouring active region and also showed a similar evolution to the radio flux, implying that beams of accelerated particles can synchronize radio and UV/EUV light curves across relatively large distances.

An exceptional phytoplankton bloom in the southeast Madagascar Sea driven by African dust deposition

Abstract Rising surface temperatures are projected to cause more frequent and intense droughts in the world's drylands. This can lead to land degradation, mobilization of soil particles, and an increase in dust aerosol emissions from arid and semi-arid regions. Dust aerosols are a key source of bio-essential nutrients, can be transported in the atmosphere over large distances, and ultimately deposited onto the ocean's surface, alleviating nutrient limitation and increasing oceanic primary productivity. Currently, the linkages between desertification, dust emissions and ocean fertilization remain poorly understood. Here, we show that dust emitted from Southern Africa was transported and deposited into the nutrient-limited surface waters southeast of Madagascar, which stimulated the strongest phytoplankton bloom of the last two decades during a period of the year when blooms are not expected. The conditions required for triggering blooms of this magnitude are anomalous, but current trends in air temperatures, aridity, and dust emissions in Southern Africa suggest that such events could become more probable in the future. Together with the recent findings on ocean fertilization by drought-induced megafires in Australia, our results point toward a potential link between global warming, drought, aerosol emissions, and ocean blooms.

On the Origin of the Ancient, Large-scale Cold Front in the Perseus Cluster of Galaxies

The intracluster medium of the Perseus Cluster exhibits spiral-shaped X-ray surface brightness discontinuities known as “cold fronts,” which simulations indicate are caused by the sloshing motion of the gas after the passage of a subcluster. Recent observations of Perseus have shown that these fronts extend to large radii. In this work, we present simulations of the formation of sloshing cold fronts in Perseus using the AREPO magnetohydrodynamics code, to produce a plausible scenario for the formation of the large front at a radius of 700 kpc. Our simulations explore a range of subcluster masses and impact parameters. We find that low-mass subclusters cannot generate a cold front that can propagate to such a large radius, and that small impact parameters create too much turbulence, which leads to the disruption of the cold front before it reaches such a large distance. Subclusters that make only one core passage produce a stable initial front that expands to large radii, but without a second core passage of the subcluster, other fronts are not created at a later time in the core region. We find a small range of simulations with subclusters with mass ratios of R ∼ 1:5 and an initial impact parameter of θ ∼ 20°–25° that not only produce the large cold front but a second set in the core region at later times. These simulations indicate that the “ancient” cold front is ∼6–8.5 Gyr old. For the simulations providing the closest match with observations, the subcluster has completely merged into the main cluster.

Source Geometry and Rupture Characteristics of the 20 February 2023 Mw 6.4 Hatay (Türkiye) Earthquake at Southwest Edge of the East Anatolian Fault

AbstractFollowing the catastrophic 6 February 2023 Mw 7.8 and Mw 7.6 Kahramanmaraş earthquakes in the East Anatolian Fault Zone (EAFZ; southeast Türkiye), numerous aftershocks occurred along the major branches of this left‐lateral shear zone. The spatio‐temporal distribution of the earthquakes implied the stress‐triggering effects of co‐seismic ruptures on closely connected fault segments over large distances. On the 20 February 2023 two earthquakes with Mw 6.4 and Mw 5.2 struck Hatay (Türkiye) located near the Samandağ‐Antakya segment of the EAFZ. To understand the rupture evolution of these earthquakes, we first re‐located the aftershock sequence that occurred over a 3‐month period in the Hatay‐Syria region. A normal faulting mechanism with a significant amount of left‐lateral strike‐slip component at a shallow focal depth of 12 km was estimated for the 2023 Mw 6.4 earthquake from the inversion of seismological data. Our slip models describe a relatively simple and unilateral rupture propagation along about 36 km‐long active segments of the EAFZ. The co‐seismic horizontal displacements inferred from the Global Navigation Satellite System data are compatible with the oblique slip kinematics. Furthermore, we suggest that this earthquake did not produce notable tsunami waves on the adjacent coasts since the rupture plane did not extend to the seafloor of the Eastern Mediterranean with substantial amount of vertical displacement. We reckon that a future large earthquake (Mw ≥ 7.0) in the Hatay‐Syria region where increased stress was transferred to the fault segments of the EAFZ and the Dead Sea Fault Zone (DSFZ) after the 2023 earthquakes will be a probable source of tsunami at the coastal plains of the Eastern Mediterranean Sea region.

Lopsided distribution of MATLAS and ELVES dwarf satellite systems around isolated host galaxies

The properties of satellite dwarf galaxies provide important empirical insights for verifying cosmological models on galaxy scales. Their phase-space correlations, in particular, offer interesting insights into a broad range of models, since they are dominated by gravity and are largely independent of the specific dark matter flavor or baryonic processes that are considered. Next to the much-debated planes-of-satellites phenomenon, the lopsided distribution of satellites relative to their host galaxy has been studied observationally and in cosmological simulations. The degree to which observed lopsidedness is consistent with expectations from simulations is still unclear. We quantified the level of lopsidedness in isolated observed satellite systems under six different metrics. We studied 47 systems from the MATLAS survey beyond the local volume (LV) as well as 21 LV satellite systems from the ELVES survey. The satellite systems are complete to an estimated absolute magnitude of M ∼ −9. We find that the so-called wedge metric, counting the number of dwarfs in wedges with varying opening angles, is best suited to capture a system’s overall lopsidedness. Under this metric, our analysis reveals that ∼16 percent of the tested satellite systems exhibit a statistically significant degree of lopsidedness when compared to systems with randomly generated satellite position angles. This presents a notable excess over the expected 5% (2σ level) of significantly lopsided systems in a sample with no overall inherent lopsidedness. To gain the most rounded picture, however, a combination of metrics that are sensitive to different features of lopsidedness should be used. Combining all tested metrics, the number of significantly lopsided systems increases to ∼21 percent. Contrary to recent results from the literature, we find more lopsided systems among the red early-type galaxies in the MATLAS survey compared to the mostly blue late-type hosts in ELVES. We further find that satellite galaxies at larger distances from the host, potentially recently accreted, are likely the primary contributors to the reported excess of lopsidedness. Our results set the groundwork that allows a comparison with similar systems in cosmological simulations to assess the consistency with the standard model.

AGN feedback can produce metal enrichment on galaxy scales

Context. Giant (&gt; 100 kpc) nebulae associated with active galaxies provide rich information about the circumgalactic medium around galaxies, its link with the interstellar medium of the hosts, and the mechanisms involved in their evolution. Aims. We have studied the giant nebula associated with the Teacup (z = 0.085) quasar based on VLT MUSE integral field spectroscopy to investigate whether the well-known giant (∼10 kpc) active galactic nucleus (AGN) -induced outflow has an impact on the distribution of heavy elements in and outside the host galaxy. Methods. We have mapped the oxygen and nitrogen gas relative abundances (O/H and N/O) in two spatial dimensions across the giant nebula and within the galaxy by means of comparing emission line ratios with photoionisation model predictions. Results. The widely studied AGN-driven outflow responsible for the ∼10 kpc ionised bubble is enhancing the gas metal abundance up to ∼10 kpc from the AGN. O/H is solar or slightly higher at the edges of the bubble, in comparison with the subsolar abundances across the rest of the nebula median (O/H ∼0.63 (O/H)⊙). Conclusions. AGN feedback can produce metal enrichment at large extranuclear distances in galaxies (≥10 kpc).

Resonant effects of long-period ship-induced waves near shallow coasts

This work analyzes the propagation properties of long-period ship-induced waves of vessels in confined waterways that are surrounded by wide and shallow water bodies using numerical simulations. Previous measurements indicated that, in the presence of shallow water surroundings, the drawdown being part of the long-period wave system can travel in the form of depression waves over several ship lengths distance [Parnell et al., “Ship-induced solitary Riemann waves of depression in Venice Lagoon,” Phys. Lett. A 379, 555–559 (2015); Scarpa et al., “The effects of ship wakes in the Venice Lagoon and implications for the sustainability of shipping in coastal waters,” Sci. Rep. 9, 19014 (2019)]. The exact conditions leading to these unexpectedly large propagation distances could to date not be clarified [Parnell et al., “Depression Waves Generated by Large Ships in the Venice Lagoon,” J. Coastal Res. 75, 907–911 (2016)]. In this work, evidence from numerical simulations is presented, indicating that the far-field propagation properties are governed by the wave speed of the shallow water surroundings. In case the ship speed is larger than the surrounding wave speed (supercritical conditions), a free wave is continuously generated traveling over the shallow water with only minimal height decay. In the simulations, depression waves can travel over a distance of three ship-lengths with a height reduction below 10% in the supercritical regime, as compared to 80% height reduction in the sub-critical regime. In a one-dimensional environment, this agreement of free and forced wave speed is known as Proudman resonance.

A Gamma-Ray Flare from TXS 1508+572: Characterizing the Jet of a z = 4.31 Blazar in the Early Universe

Blazars can be detected from very large distances due to their high luminosity. However, the detection of γ-ray emission of blazars beyond z = 3 has only been confirmed for a small number of sources. Such observations probe the growth of supermassive black holes close to the peak of star formation in the history of galaxy evolution. As a result from a continuous monitoring of a sample of 80 z > 3 blazars with the Fermi Large Area Telescope (Fermi-LAT), we present the first detection of a γ-ray flare from the z = 4.31 blazar TXS 1508+572. This source showed high γ-ray activity from 2022 February to August, reaching a peak luminosity comparable to the most luminous flares ever detected with Fermi-LAT. We conducted a multiwavelength observing campaign involving XMM-Newton, the Neil Gehrels Swift Observatory, the Effelsberg 100 m radio telescope, and the Very Long Baseline Array. In addition, we make use of the monitoring programs by the Zwicky Transient Facility and the Near-Earth Object Wide-field Infrared Survey Explorer at optical and infrared wavelengths, respectively. We find that the source is particularly variable in the infrared band on daily timescales. The spectral energy distribution collected during our campaign is well described by a one-zone leptonic model, with the γ-ray flare originating from an increase of external Compton emission as a result of a fresh injection of accelerated electrons.