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 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.
Aims. We investigate the extension of the very high-energy spectral tail of the Crab Pulsar at energies above 400 GeV. Methods. We analyzed ~320 h of good-quality Crab data obtained with the MAGIC ...telescope from February 2007 to April 2014. Results. We report the most energetic pulsed emission ever detected from the Crab Pulsar reaching up to 1.5 TeV. The pulse profile shows two narrow peaks synchronized with those measured in the GeV energy range. The spectra of the two peaks follow two different power-law functions from 70 GeV up to 1.5 TeV and connect smoothly with the spectra measured above 10 GeV by the Large Area Telescope (LAT) on board the Fermi satellite. When making a joint fit of the LAT and MAGIC data above 10 GeV the photon indices of the spectra differ by 0.5 ± 0.1. Conclusions. Using data from the MAGIC telescopes we measured the most energetic pulsed photons from a pulsar to date. Such TeV pulsed photons require a parent population of electrons with a Lorentz factor of at least 5 × 106. These results strongly suggest IC scattering off low-energy photons as the emission mechanism and a gamma-ray production region in the vicinity of the light cylinder.
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.
Context. During February–March 2014, the MAGIC telescopes observed the high-frequency peaked BL Lac 1ES 1011+496 (z = 0.212) in flaring state at very-high energy (VHE, E> 100 GeV). The flux reached a ...level of more than ten times higher than any previously recorded flaring state of the source. Aims. To describe the characteristics of the flare presenting the light curve and the spectral parameters of the night-wise spectra and the average spectrum of the whole period. From these data we aim to detect the imprint of the extragalactic background light (EBL) in the VHE spectrum of the source, to constrain its intensity in the optical band. Methods. We analyzed the gamma-ray data from the MAGIC telescopes using the standard MAGIC software for the production of the light curve and the spectra. To constrain the EBL, we implement the method developed by the H.E.S.S. collaboration, in which the intrinsic energy spectrum of the source is modeled with a simple function (≤4 parameters), and the EBL-induced optical depth is calculated using a template EBL model. The likelihood of the observed spectrum is then maximized, including a normalization factor for the EBL opacity among the free parameters. Results. The collected data allowed us to describe the night-wise flux changes and also to produce differential energy spectra for all nights in the observed period. The estimated intrinsic spectra of all the nights could be fitted by power-law functions. Evaluating the changes in the fit parameters, we conclude that the spectral shape for most of the nights were compatible, regardless of the flux level, which enabled us to produce an average spectrum from which the EBL imprint could be constrained. The likelihood ratio test shows that the model with an EBL density 1.07 (–0.20, +0.24)stat+sys, relative to the one in the tested EBL template, is preferred at the 4.6σ level to the no-EBL hypothesis, with the assumption that the intrinsic source spectrum can be modeled as a log-parabola. This would translate into a constraint of the EBL density in the wavelength range 0.24 μm, 4.25 μm, with a peak value at 1.4 μm of λFλ = 12.27-2.29+2.75 nW m-2 sr-1, including systematics.
During a normal vaginal delivery, the muscle cells propagate electrical signals throughout the uterine wall, resulting in uterine contractions. However, uncoordinated uterine activity may disturb the ...uterine contractions pattern and negatively impact fetal and maternal health. Some of the abnormalities identified by the specialists are excessively short resting intervals and tachysystole. This work aims to investigate the influence of abnormal uterine activity in terms of maximum principal stress distribution and collagen fibers stretch in the uterine tissue during vaginal delivery with (i) excessively short resting intervals without changing the contraction time, and (ii) tachysystole (contraction and reduced resting times). These patterns are compared with a normal uterine contraction pattern. To achieve our aims, a biomechanical model was developed, including finite element models of the uterus and the fetus, and an electro-chemo-mechanical constitutive model. Generally, the excessively short resting intervals exhibit higher average maximum principal stresses during the contraction and resting stages, lower average fibers stretch values in the longitudinal direction and higher stretch in the circumferential direction. On the other hand, the tachysystole exhibit generally lower stress values during the uterine contraction and higher stress values during the resting stages, higher stretch in the longitudinal direction, and lower stretch in the circumferential direction.
Caesarean section is one of the most common surgeries worldwide, even though there is no evidence supporting maternal and perinatal long-term benefits. Furthermore, the mechanical behavior of a ...caesarean scar during a vaginal birth after caesarean (VBAC) is not well understood since there are several questions regarding the uterine wound healing process. The aim of this study is to investigate the biomechanical Maylard fiber reorientation and stiffness influence during a VBAC through computational methods. A biomechanical model comprising a fetus and a uterus was developed, and a chemical–mechanical constitutive model that triggers uterine contractions was used, where some of the parameters were adjusted to account for the matrix and fiber stiffness increase in the caesarean scar. Several mechanical simulations were performed to analyze different scar fibers arrangements, considering different values for the respective matrix and fibers stiffness. The results revealed that a random fiber arrangement in the Maylard scar has a much higher impact on its mechanical behavior during a VBAC than the common fibers arrangement present in the uninjured uterine tissue. An increase of the matrix scar stiffness exhibits a lower impact, while an increase of the fiber’s stiffness has no significant influence.
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.
This paper presents a finite element analysis to investigate the biomechanical changes caused by transforaminal (TLIF) and anterior lumbar interbody fusion (ALIF) at the L5-S1 level, applying two ...different implants: T_PAL (TLIF) and SynFix (ALIF). The main objective is to determine which one is more stable for patients. Numerical simulations of segmental motion show that, in the early postoperative phase, displacements and rotation angles obtained in ALIF are greater than the corresponding ones obtained in TLIF, as well as the principal stress values on the ligaments. So, TLIF performed with T_PAL is more stable than ALIF, especially during the recovery phase.
Abstract
We present the first detection of the nearby (z = 0.084) low-luminosity BL Lac object 1ES 1741+196 in the very high energy (E > 100 GeV) band. This object lies in a triplet of interacting ...galaxies. Early predictions had suggested 1ES 1741+196 to be, along with several other high-frequency BL Lac sources, within the reach of MAGIC detectability. Its detection by MAGIC, later confirmed by VERITAS, helps to expand the small population of known TeV BL Lacs. The source was observed with the MAGIC telescopes between 2010 April and 2011 May, collecting 46 h of good quality data. These observations led to the detection of the source at 6.0 σ confidence level, with a steady flux F(>100 GeV) = (6.4 ± 1.7stat ± 2.6syst) × 10−12 ph cm−2s−1 and a differential spectral photon index Γ = 2.4 ± 0.2stat ± 0.2syst in the range of ∼80 GeV–3 TeV. To study the broad-band spectral energy distribution (SED) simultaneous with MAGIC observations, we use KVA, Swift/UVOT and XRT and Fermi/LAT data. One-zone synchrotron-self-Compton (SSC) modelling of the SED of 1ES 1741+196 suggests values for the SSC parameters that are quite common among known TeV BL Lacs except for a relatively low Doppler factor and slope of electron energy distribution. A thermal feature seen in the SED is well matched by a giant elliptical's template. This appears to be the signature of thermal emission from the host galaxy, which is clearly resolved in optical observations.
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