Abstract
Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the ...very high-energy (VHE,
E
> 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated
Swift
observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine–layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.
Context. PKS 1510−089 is one of only a few flat spectrum radio quasars detected in the very-high-energy (VHE, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties ...of the PKS 1510−089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510−089 with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes during a long, high gamma-ray state in May 2015. In order to perform broadband modeling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray, and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510−089 was detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, owing to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to those obtained during previous measurements of the source. The observed flux variability sets constraints for the first time on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models.
MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent a series of upgrades, involving the ...exchange of the MAGIC-I camera and its trigger system, as well as the upgrade of the readout system of both telescopes. We use observations of the Crab Nebula taken at low and medium zenith angles to assess the key performance parameters of the MAGIC stereo system. For low zenith angle observations, the standard trigger threshold of the MAGIC telescopes is ∼ 50GeV. The integral sensitivity for point-like sources with Crab Nebula-like spectrum above 220GeV is (0.66 ± 0.03)% of Crab Nebula flux in 50h of observations. The angular resolution, defined as the σ of a 2-dimensional Gaussian distribution, at those energies is ≲ 0.07°, while the energy resolution is 16%. We also re-evaluate the effect of the systematic uncertainty on the data taken with the MAGIC telescopes after the upgrade. We estimate that the systematic uncertainties can be divided in the following components: < 15% in energy scale, 11%–18% in flux normalization and ± 0.15 for the energy spectrum power-law slope.
The fishery biology of the goldfish Carassius auratus was studied in Lake Trasimeno by analysing the selectivity of the equipment that can be used to control this invasive species. Sampling was ...conducted monthly from February 2003 to January 2004 by means of electrofishing, fyke-nets and gill-nets of different-sized mesh (22, 25, 28, 35, 40, 50, 70 and 80 mm). The average value of the CPUEs of goldfish caught was 10175.48 g·10−2·m−2 for gill-nets, 246.97 g·h−1 for fyke-nets and 606.50 g·min−1 for electrofishing. The efficiency of electrofishing was not uniform in all periods of the year, the mean CPUEs being highest in spring, when specimens of reproductive age were preferentially caught. Gill-nets yielded abundant catches of goldfish in all seasons, and displayed good sampling efficiency even in winter. With regard to the selectivity of gill-nets, estimated optimum selection lengths for each mesh size were: 11.92 cm, 13.55 cm, 15.18 cm, 18.97 cm, 21.68 cm, 27.10 cm, 37.94 cm and 43.36 cm. The results of this research demonstrate that the various fishing techniques can be effectively combined with the aim of controlling the goldfish population in Lake Trasimeno.
La biologie halieutique du carassin Carassius auratus a été étudiée dans le lac Trasimeno par analyse de sélectivité des équipements utilisables pour contrôler cette espèce invasive. L’échantillonnage a été conduit mensuellement de février 2003 à janvier 2004 par pêche électrique, verveux et filets maillants de différentes tailles de maille (22, 25, 28, 35, 40, 50, 70 and 80 mm). La valeur moyenne des CPUE de carassin était de 10175,48 g·10−2·m−2 pour les filets maillants, de 246,97 g·h−1 pour les verveux et de 606,50 g·min−1 pour la pêche électrique. L’efficacité de la pêche électrique n’est pas uniforme suivant les périodes de l’année, les CPUE moyennes sont plus fortes au printemps, quand les individus en âge de se reproduire sont principalement pêchés. Les captures de carassin par filet maillant sont abondantes en toute saison et montrent même une bonne efficacité en hiver. Compte tenu de la sélectivité des filets, les longueurs modales sélectionnées par chaque taille de maille sont : 11,92 cm, 13,55 cm, 15,18 cm, 18,97 cm, 21,68 cm, 27,10 cm, 37,94 cm et 43,36 cm. Les résultats de ces recherches montrent que les différentes techniques de pêche peuvent être efficaces en étant combinées pour contrôler la population de carassins du lac Trasimeno.
This study investigated the reproductive properties of the population of chub Squalius squalus (Linnaeus, 1758) in the Assino creek, one of the largest tributaries of the upper course of the River ...Tiber. A total of 547 specimens were caught monthly from March 2008 to May 2009. The age composition of the sample ranged between 0+ and 11+. The sample was made up of 64.54% males and 35.46% females; sexual maturity was attained in both sexes in the second year of life. Analysis of the gonado-somatic index (GSI) and of the stage of gonad maturation throughout the year suggests that the reproductive period of the population extends over a long time (April–July). The relationship between total length and fecundity was F = 5.466TL2.312. The mean number (±SE) of eggs produced by each female was 15 351 ± 1705 and increased with the size and age of the specimens; with regard to relative fecundity, an average value (±SE) of 53 553 ± 4098 eggs·kg-1 was observed. The mean diameter (±SE) of ripe eggs was 0.117 ± 0.004 cm. This study sheds light on some important characteristics of the reproductive biology of the chub that have not been fully investigated in Italian populations.
Ce travail a étudié les caractéristiques de la reproduction de la population du chevesne, Squalius squalus (Linnaeus, 1758), dans le ruisseau Assino, l’un des principaux affluents du cours supérieur du Tibre. Au total 547 spécimens ont été capturés du mois de mars 2008 à mai 2009. La composition par âge de l’échantillon variait entre 0+ et 11+. L’échantillon était composé de 64,54 % de mâles et 35,46 % de femelles; la maturité sexuelle est atteinte chez les deux sexes dans la deuxième année de vie. L’analyse de l’indice gonado-somatique (GSI) et du stade de maturation des gonades au cours de l’année suggère que la période de reproduction de la population s’étend sur une longue période (avril–juillet). La relation entre la longueur totale et la fécondité était F = 5.466TL2.312. Le nombre moyen (±SE) des œufs produits par femelle était 15 351 ± 1705 et a augmenté avec la taille et l’âge des spécimens; pour la fécondité relative, une valeur moyenne (±SE) de 53 553 ± 4098 d’œufs·kg -1 a été observée. Le diamètre moyen (±SE) des œufs mûrs était 0 117 ± 0 004 cm. Cette étude met en lumière quelques caractéristiques importantes de la biologie reproductive du chevesne qui n’ont pas été entièrement étudiées dans les populations italiennes.
Spontaneous breaking of Lorentz symmetry at energies on the order of the Planck energy or lower is predicted by many quantum gravity theories, implying non-trivial dispersion relations for the photon ...in vacuum. Consequently, gamma-rays of different energies, emitted simultaneously from astrophysical sources, could accumulate measurable differences in their time of flight until they reach the Earth. Such tests have been carried out in the past using fast variations of gamma-ray flux from pulsars, and more recently from active galactic nuclei and gamma-ray bursts. We present new constraints studying the gamma-ray emission of the galactic Crab Pulsar, recently observed up to TeV energies by the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) collaboration. A profile likelihood analysis of pulsar events reconstructed for energies above 400 GeV finds no significant variation in arrival time as their energy increases. Ninety-five percent CL limits are obtained on the effective Lorentz invariance violating energy scale at the level of ( ) for a linear, and ( ) for a quadratic scenario, for the subluminal and the superluminal cases, respectively. A substantial part of this study is dedicated to calibration of the test statistic, with respect to bias and coverage properties. Moreover, the limits take into account systematic uncertainties, which are found to worsen the statistical limits by about 36%-42%. Our constraints would have been much more stringent if the intrinsic pulse shape of the pulsar between 200 GeV and 400 GeV was understood in sufficient detail and allowed inclusion of events well below 400 GeV.
MAGIC, a system of two imaging atmospheric Cherenkov telescopes, achieves its best performance under dark conditions, i.e. in absence of moonlight or twilight. Since operating the telescopes only ...during dark time would severely limit the duty cycle, observations are also performed when the Moon is present in the sky. Here we develop a dedicated Moon-adapted analysis to characterize the performance of MAGIC under moonlight. We evaluate energy threshold, angular resolution and sensitivity of MAGIC under different background light levels, based on Crab Nebula observations and tuned Monte Carlo simulations. This study includes observations taken under non-standard hardware configurations, such as reducing the camera photomultiplier tubes gain by a factor ∼ 1.7 (reduced HV settings) with respect to standard settings (nominal HV) or using UV-pass filters to strongly reduce the amount of moonlight reaching the cameras of the telescopes. The Crab Nebula spectrum is correctly reconstructed in all the studied illumination levels, that reach up to 30 times brighter than under dark conditions. The main effect of moonlight is an increase in the analysis energy threshold and in the systematic uncertainties on the flux normalization. The sensitivity degradation is constrained to be below 10%, within 15–30% and between 60 and 80% for nominal HV, reduced HV and UV-pass filter observations, respectively. No worsening of the angular resolution was found. Thanks to observations during moonlight, the maximal duty cycle of MAGIC can be increased from ∼ 18%, under dark nights only, to up to ∼ 40% in total with only moderate performance degradation.
ABSTRACT Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different ...wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three "target-of-opportunity" observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering the X-ray and optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray band), along with contemporaneous observations from other gamma-ray facilities (MAGIC and Fermi-Large Area Telescope) and a number of radio and optical facilities. Although neither rapid flares nor significant X-ray/TeV correlation are detected, these observations reveal subtle changes in the X-ray spectrum of the source over the course of a few days. We search the simultaneous X-ray and TeV data for spectral hysteresis patterns and time delays, which could provide insight into the emission mechanisms and the source properties (e.g., the radius of the emitting region, the strength of the magnetic field, and related timescales). The observed broadband spectra are consistent with a one-zone synchrotron self-Compton model. We find that the power spectral density distribution at 4 × 10−4 Hz from the X-ray data can be described by a power-law model with an index value between 1.2 and 1.8, and do not find evidence for a steepening of the power spectral index (often associated with a characteristic length scale) compared to the previously reported values at lower frequencies.
The MAGIC telescopes are two Imaging Atmospheric Cherenkov Telescopes (IACTs) located on the Canary island of La Palma. The telescopes are designed to measure Cherenkov light from air showers ...initiated by gamma rays in the energy regime from around 50GeV to more than 50TeV. The two telescopes were built in 2004 and 2009, respectively, with different cameras, triggers and readout systems. In the years 2011–2012 the MAGIC collaboration undertook a major upgrade to make the stereoscopic system uniform, improving its overall performance and easing its maintenance. In particular, the camera, the receivers and the trigger of the first telescope were replaced and the readout of the two telescopes was upgraded. This paper (Part I) describes the details of the upgrade as well as the basic performance parameters of MAGIC such as raw data treatment, linearity in the electronic chain and sources of noise. In Part II, we describe the physics performance of the upgraded system.
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