Context.
The BL Lac object 1ES 0647+250 is one of the few distant
γ
-ray emitting blazars detected at very high energies (VHEs; ≳100 GeV) during a non-flaring state. It was detected with the MAGIC ...telescopes during a period of low activity in the years 2009−2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years.
Aims.
We aim to characterise the long-term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions.
Methods.
We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Z-transformed discrete correlation function, as well as its spectral evolution in X-rays and
γ
rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with
Fermi
-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data.
Results.
We find significant long-term variability, especially in X-rays and VHE
γ
rays. Furthermore, significant (3−4
σ
) correlations were found between the radio, optical, and high-energy (HE)
γ
-ray fluxes, with the radio emission delayed by about ∼400 days with respect to the optical and
γ
-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV <
E
< 100 GeV) and VHE
γ
-ray emission of the source. The indirect estimation of the redshift yielded a value of
z
= 0.45 ± 0.05, which is compatible with some of the values reported in the literature. The SEDs related to the low-activity state and the three flaring states of 1ES 0647+250 can be described reasonably well with the both one-component and two-component leptonic scenarios. However, the long-term correlations indicate the need for an additional radio-producing region located about 3.6 pc downstream from the gamma-ray producing region.
We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope ...resolve extended emission overlapping the elongated radio SNR. The 7.3sigma (pre-trials) detection has a full angular extent of roughly 0.{sup 0}6 by 0.{sup 0}4. Most notably, the centroid of the VHE emission is centered near the peak of the coincident {sup 12}CO (J = 1-0) emission, 0.{sup 0}4 away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. The VHE energy spectrum measured with VERITAS is well characterized by a power law dN/dE = N {sub 0}(E/3 TeV){sup -G}AMMA with a differential index of GAMMA = 2.29 +- 0.33{sub stat} +- 0.30{sub sys} and a flux of N{sub 0} = (1.15 +- 0.27{sub stat} +- 0.35{sub sys}) x 10{sup -13} cm{sup -2} s{sup -1} TeV{sup -1}. The integral flux above 1 TeV corresponds to {approx}5 percent of the steady Crab Nebula emission above the same energy. We describe the observations and analysis of the object and briefly discuss the implications of the detection in a multiwavelength context.
ABSTRACT
We report multiwavelength observations of the gravitationally lensed blazar QSO B0218+357 in 2016–2020. Optical, X-ray, and GeV flares were detected. The contemporaneous MAGIC observations ...do not show significant very high energy (VHE; ≳100 GeV) gamma-ray emission. The lack of enhancement in radio emission measured by The Owens Valley Radio Observatory indicates the multizone nature of the emission from this object. We constrain the VHE duty cycle of the source to be <16 2014-like flares per year (95 per cent confidence). For the first time for this source, a broad-band low-state spectral energy distribution is constructed with a deep exposure up to the VHE range. A flux upper limit on the low-state VHE gamma-ray emission of an order of magnitude below that of the 2014 flare is determined. The X-ray data are used to fit the column density of (8.10 ± 0.93stat) × 1021 cm−2 of the dust in the lensing galaxy. VLBI observations show a clear radio core and jet components in both lensed images, yet no significant movement of the components is seen. The radio measurements are used to model the source-lens-observer geometry and determine the magnifications and time delays for both components. The quiescent emission is modelled with the high-energy bump explained as a combination of synchrotron-self-Compton and external Compton emission from a region located outside of the broad-line region. The bulk of the low-energy emission is explained as originating from a tens-of-parsecs scale jet.
ABSTRACT
In recent years, a new generation of optical intensity interferometers has emerged, leveraging the existing infrastructure of Imaging Atmospheric Cherenkov Telescopes (IACTs). The MAGIC ...telescopes host the MAGIC-SII system (Stellar Intensity Interferometer), implemented to investigate the feasibility and potential of this technique on IACTs. After the first successful measurements in 2019, the system was upgraded and now features a real-time, dead-time-free, 4-channel, GPU-based correlator. These hardware modifications allow seamless transitions between MAGIC’s standard very-high-energy gamma-ray observations and optical interferometry measurements within seconds. We establish the feasibility and potential of employing IACTs as competitive optical Intensity Interferometers with minimal hardware adjustments. The measurement of a total of 22 stellar diameters are reported, 9 corresponding to reference stars with previous comparable measurements, and 13 with no prior measurements. A prospective implementation involving telescopes from the forthcoming Cherenkov Telescope Array Observatory’s Northern hemisphere array, such as the first prototype of its Large-Sized Telescopes, LST-1, is technically viable. This integration would significantly enhance the sensitivity of the current system and broaden the UV-plane coverage. This advancement would enable the system to achieve competitive sensitivity with the current generation of long-baseline optical interferometers over blue wavelengths.
Background
Studies checking antimicrobial resistance (AMR) of Listeria monocytogenes (Lm) are ongoing, coupled with disease surveillance. Lm resistant strains are reported and are increasing. The aim ...of the work was to investigate AMR of clinical strains of Lm collected from nine regions (mostly in Lombardy and Marche regions) from 2008 to 2020.
Methods
The dataset consisted of 233 Lm human strains collected from nine regions during the period 2008-2020. All the strains were tested using Sensititre™ Haemophilus Plate (Thermo Scientific, Milano, Italy). Results were expressed according to EUCAST breakpoints for Lm, S. pneumoniae and E. faecalis. Resistant strains were sequenced using Illumina platform, ABRicate was used to predict antimicrobial resistance genes and plasmids.
Results
Most of the strains were detected in Lombardy and Marche. The MIC results showed that 11 out of 233 strains were resistant, one to ampicillin, four to tetracycline and six to clarithromycin. Analysing the sequences, all the resistant strains showed to have a common antimicrobial resistant pattern (mprF, norB, FosX, (MLS)lin, lin and lmo0919). Genomic determinants for ampicillin and clarithromycin resistance were not detected. Indeed, only in 3 out of 4 resistant strains tetM was found. Meanwhile, plasmids were detected in 7 strains.
Conclusions
The distribution of the strains considered in this work did not reflect the real epidemiological situation in Italy, because their origin was mostly from two regions. The emergence of AMR also for Lm needs to be considered. Moreover, official breakpoints for Lm are not defined and to date limited to five antimicrobials excluding clarithromycin and tetracycline, where the pathogen showed resistance. Finally, the incongruence between phenotypic and genomic data suggests that the mechanisms involved in the resistance is not fully known especially for ampicillin. Further investigations are needed to improve the knowledge on Lm AMR.
Key messages
Monitoring AMR of Listeria monocytogenes is crucial, only effective drug in clinical cases should be used.
Further investigations are needed to explore the mechanisms involved in antimicrobial resistance of Listeria monocytogenes.
Aims. We have performed the first broadband study of Mrk 421 from radio to TeV gamma rays with simultaneous measurements of the X-ray polarization from IXPE. Methods. The data were collected as part ...of an extensive multiwavelength campaign carried out between May and June 2022 using MAGIC, Fermi -LAT, NuSTAR , XMM-Newton , Swift , and several optical and radio telescopes to complement IXPE data. Results. During the IXPE exposures, the measured 0.2–1 TeV flux was close to the quiescent state and ranged from 25% to 50% of the Crab Nebula without intra-night variability. Throughout the campaign, the very high-energy (VHE) and X-ray emission are positively correlated at a 4 σ significance level. The IXPE measurements reveal an X-ray polarization degree that is a factor of 2–5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the VHE photons are emitted co-spatially with the X-rays, in the vicinity of a shock front. The June 2022 observations exhibit a rotation of the X-ray polarization angle. Despite no simultaneous VHE coverage being available during a large fraction of the swing, the Swift -XRT monitoring reveals an X-ray flux increase with a clear spectral hardening. This suggests that flares in high synchrotron peaked blazars can be accompanied by a polarization angle rotation, as observed in some flat spectrum radio quasars. Finally, during the polarization angle rotation, NuSTAR data reveal two contiguous spectral hysteresis loops in opposite directions (clockwise and counterclockwise), implying important changes in the particle acceleration efficiency on approximately hour timescales.
Abstract
We report on a long-lasting, elevated gamma-ray flux state from VER J0521+211 observed by VERITAS, MAGIC, and Fermi-LAT in 2013 and 2014. The peak integral flux above 200 GeV measured with ...the nightly binned light curve is (8.8 ± 0.4) × 10
−7
photons m
−2
s
−1
, or ∼37% of the Crab Nebula flux. Multiwavelength observations from X-ray, UV, and optical instruments are also presented. A moderate correlation between the X-ray and TeV gamma-ray fluxes was observed, and the X-ray spectrum appeared harder when the flux was higher. Using the gamma-ray spectrum and four models of the extragalactic background light (EBL), a conservative 95% confidence upper limit on the redshift of the source was found to be
z
≤ 0.31. Unlike the gamma-ray and X-ray bands, the optical flux did not increase significantly during the studied period compared to the archival low-state flux. The spectral variability from optical to X-ray bands suggests that the synchrotron peak of the spectral energy distribution (SED) may become broader during flaring states, which can be adequately described with a one-zone synchrotron self-Compton model varying the high-energy end of the underlying particle spectrum. The synchrotron peak frequency of the SED and the radio morphology of the jet from the MOJAVE program are consistent with the source being an intermediate-frequency-peaked BL Lac object.
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