We report on the first detection of very high-energy gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. This result has been ...achieved by means of the 4 m ASTRI-Horn telescope, operated on Mt. Etna, Italy, and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, which allows us to implement large cameras with a large field of view, with small-size pixel sensors and a high level of compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers, managed by an unconventional front-end electronic system that is based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. These observations of the Crab Nebula were carried out in December 2018 during the telescope verification phase for a total observation time (after data selection) of 24.4 h, equally divided between on- and off-axis source exposure. The camera system was still under commission and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4
σ
above an energy threshold of ∼3 TeV. This result provides an important step toward the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine ASTRI-like telescopes with a large field-of-view is in the course of implementation.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
The origin of the gamma-ray emission from M 87 is currently a matter of debate. This work aims to localize the very high-energy (VHE; 100 GeV – 100 TeV) gamma-ray emission from M 87 and probe a ...potential extended hadronic emission component in the inner Virgo Cluster. The search for a steady and extended gamma-ray signal around M 87 can constrain the cosmic-ray energy density and the pressure exerted by the cosmic rays onto the intracluster medium and allow us to investigate the role of cosmic rays in the active galactic nucleus feedback as a heating mechanism in the Virgo Cluster. The High Energy Stereoscopic System (H.E.S.S.) telescopes are sensitive to VHE gamma rays and have been used to observe M 87 since 2004. We utilized a Bayesian block analysis to identify M 87 emission states with H.E.S.S. observations from 2004 to 2021, dividing them into low, intermediate, and high states. Because of the causality argument, an extended (≳1 kpc) signal is allowed only in steady emission states. Hence, we fitted the morphology of the 120 h low-state data and find no significant gamma-ray extension. Therefore, we derive for the low state an upper limit of 58″(corresponding to ≈4.6 kpc) in the extension of a single-component morphological model described by a rotationally symmetric 2D Gaussian model at the 99.7% confidence level. Our results exclude the radio lobes (≈30 kpc) as the principal component of the VHE gamma-ray emission from the low state of M 87. The gamma-ray emission is compatible with a single emission region at the radio core of M 87. These results, with the help of two multiple-component models, constrain the maximum cosmic-ray to thermal pressure ratio to
X
CR, max.
≲ 0.32 and the total energy in cosmic-ray protons to
U
CR
≲ 5 × 10
58
erg in the inner 20 kpc of the Virgo Cluster for an assumed cosmic-ray proton power-law distribution in momentum with spectral index
α
p
= 2.1.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
Context. We present the results of a multi-year monitoring campaign of the Galactic center (GC) with the MAGIC telescopes. These observations were primarily motivated by reports that a putative gas ...cloud (G2) would be passing in close proximity to the super-massive black hole (SMBH), associated with Sagittarius A*, located at the center of our galaxy. This event was expected to give astronomers a unique chance to study the effect of in-falling matter on the broad-band emission of a SMBH. Aims. We search for potential flaring emission of very-high-energy (VHE; ≥100 GeV) gamma rays from the direction of the SMBH at the GC due to the passage of the G2 object. Using these data we also study the morphology of this complex region. Methods. We observed the GC region with the MAGIC Imaging Atmospheric Cherenkov Telescopes during the period 2012–2015, collecting 67 h of good-quality data. In addition to a search for variability in the flux and spectral shape of the GC gamma-ray source, we use a point-source subtraction technique to remove the known gamma-ray emitters located around the GC in order to reveal the TeV morphology of the extended emission inside that region. Results. No effect of the G2 object on the VHE gamma-ray emission from the GC was detected during the 4 yr observation campaign. We confirm previous measurements of the VHE spectrum of Sagittarius A*, and do not detect any significant variability of the emission from the source. Furthermore, the known VHE gamma-ray emitter at the location of the supernova remnant G0.9+0.1 was detected, as well as the recently discovered VHE source close to the GG radio arc.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
Sleep and deprivation of it are known methods to increase the yield of epileptic abnormalities. Whereas neurophysiological mechanisms underlying discharges increase were suggested, less is known of ...the topographical distribution patterns in wake and sleep. We compared interictal epileptic discharges (IEDs) scalp distribution using 256-channels EEG recordings in wake and sleep in people with pharmaco-resistant temporal lobe epilepsy (TLE). 14 adults with Right TLE, identified through clinical data, 3T-MRI, PET and electrical source imaging, recorded during a daytime-nap were included. IEDs were identified in wake and S2. A mean of 21 IEDs in wake and 39 in sleep were selected ( p = 0.024) and processed to obtain the averaged spike. Digital signals from the averaged wake traces were then subtracted to the sleep ones (Geodesic-EGI, Oregon, USA) and a t -test between the two conditions run. Single subjects traces localized IEDs over the right temporal regions (rare zygomatic projection), topographically more circumscribed in sleep. EEG digital subtraction showed higher amplitude IEDs limited to the temporal mesio-posterior right areas, with a dipole inversion over the contralateral zygomatic leads. Student t -test confirmed a statistically significant signal increase over the same topographic region, with a slight posterior shift on temporal leads ( p = 0.039). This is the first report of a progressive breaking up of cortical modularity during sleep, even S2 stage, in a pathologically hyperactive brain. A similar phenomenon has been previously described (Massimini et al., 2005) using TMS during sleep in healthy subjects. Our data exploit naturally occurring interfering stimuli (IEDs) in a naturally sleeping epileptic brain, demonstrating how they reverberate differently in sleep and in wake, with a sleep related amplitude increase. Interestingly, such phenomenon tends to be constrained to a cortical area partially overlapping with the waking one, as to point to the progressive disconnection of integrated areas.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent ...detection of the system in the high energy (HE; E ≳ 60 MeV) gamma-ray range with Fermi-LAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E ≳ 100 GeV) regime during this X-ray state. We analyse ∼97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Γ = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 × 10−12 photons cm−2 s−1 and 1.0 × 10−11 photons cm−2 s−1, respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of the MAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.
To describe the intraoperative appearance or improvement of lower extremity muscle motor evoked potentials (mMEPs) during tethered cord surgery for spinal dysraphisms. A 3-year old male child with ...dermal sinus and dorsal lipoma, and a 30-year old male with a sacral lipoma were operated on for untethering the cord under Intra-operative neurophysiological monitoring (IONM) surveillance. The IONM protocol included: Transcranially elicited mMEPs, Posterior Tibial Nerve Somatosensory Evoked Potentials (TPN-SSEPs), recording of the bulbo-cavernous reflex (BCR), and mapping of the cauda equina. Recording electrodes were inserted bilaterally in the Anterior Tibialis (AT), Gastrocnemius (GR), Abductor Hallucis Brevis (AHB), and the anal sphincter muscles (ASM). In the child, at baseline only the right AHB mMEP was elicitable at 200 mA. Following cord untethering a progressive reappareance of the left GR, AT and AHB mMEP was observed starting about 10 min. after the cord was completely untethered. In the adult case, all mMEPs were present at baselines but, in spite of unchanged stimulation intensity, after untethering the cord mMEP amplitude increased significantly in the left AHB and GR muscles. The anesthesiological regimen was stable throughout the procedures. IONM may detect acute improvement of mMEPs during cord untethering, possibly due to better oxidative metabolism in the conus.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Corticobulbar muscle motor evoked potentials (CBT-mMEPs) monitoring is usually reported for the VII cranial nerve (CN) but rarely for the IX/X and XII CN, and its application is anecdotal in young ...children. We present three cases of children younger than 2 years operated on for brainstem tumour, with continuous monitoring of lower CN CBT-mMEPs. CBT-mMEPs were elicited by transcranial electrical stimulation at C3/Cz and C4/Cz using a train of 4 stimuli (ISI 2 ms, duration 0.5 ms each, at 1 Hz and intensity up to 200 mA). Recording hook-wire electrodes were placed in pharyngeal and hypoglossal muscles for the IX/X and XII CN respectively. In all patients CBT-mMEPs were stable throughout the entire surgical procedure with no changes in threshold intensity. Post-operatively, none of the children experienced significant tongue palsy or dysphagia/dysphonia. Therefore three true negative cases were observed. CBT-mMEPs of the lower CN is not of widespread use; in particular, there is virtually no report on the use of this technique in very young children where the incomplete myelination of motor pathways may impair a successful monitoring under general anaesthesia. CBT-mMEPs for the IX/X and XII CN is feasible and reliable even in children younger than 2 years.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The ASTRI Mini-Array is a next-generation system of nine imaging atmospheric Cherenkov telescopes that is going to be built at the Observatorio del Teide site. After a first phase, in which the ...instrument will be operated as an experiment prioritizing a schedule of primary science cases, an observatory phase is foreseen in which other significant targets will be pointed. We focus on the observational feasibility of extragalactic sources and on astrophysical processes that best complement and expand the ASTRI Mini-Array core science, presenting the most relevant examples that are at reach of detection over long-term time scales and whose observation can provide breakthrough achievements in the very-high energy extragalactic science. Such examples cover a wide range of γ-ray emitters, including the study of AGN low states in the multi-TeV energy range, the possible detection of Seyfert galaxies with long exposures and the searches of dark matter lines above 10 TeV. Simulations of the presented objects show that the instrument performance will be competitive at multi-TeV energies with respect to current arrays of Cherenkov telescopes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
