The MAGIC Cerenkov telescope has observed very high energy (VHE) g-ray emission from the active galactic nucleus 1ES 1959+650 during 6 hr in 2004 September and October. The observations were carried ...out alternating with observations of the Crab Nebula, whose data were used as a reference source for optimizing g -ray/hadron separation and for flux comparison. The data analysis shows VHE g-ray emission of 1ES 1959+650 with 68 s significance, at a time of low activity in both optical and X-ray wavelengths. An integral flux above 6180 GeV of about 20% that of the Crab Nebula was obtained. The light curve, sampled over 7 days, shows no significant variations. The differential energy spectrum between 180 GeV and 2 TeV can be fitted with a power-law of index -2.72 c 0.14. The spectrum is consistent with the slightly steeper spectrum seen by HEGRA at higher energies, also during periods of low X-ray activity.
Commissioning and first tests of the MAGIC telescope Baixeras, C.; Bastieri, D.; Bigongiari, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
Major Atmospheric Gamma Imaging Cherenkov telescope is starting its operations with a set of engineering runs to tune the telescope subsystem elements to be ready for the first physics campaign. Many ...technical improvements have been developed and implemented in several elements of the telescope to reach the lowest energy threshold ever obtained by an Imaging Atmospheric Cherenkov Telescope. A general description of the telescope is presented. The commissioning of the telescope's elements is described and the expected performances are reviewed with the final detector set-up.
The long-duration g-ray burst GRB 050713a was observed by the MAGIC Telescope 40 s after the burst onset and followed up for 37 minutes, until twilight. The observation, triggered by a Swift alert, ...covered energies above -175 GeV. Using standard MAGIC analysis, no evidence of a g-ray signal was found. As the redshift of the GRB was not measured directly, the flux upper limit estimated by MAGIC is still compatible with the assumption of an unbroken power-law spectrum extending from a few hundred keV to our energy range.
Abstract Introduction Treatment of displaced heel fractures is controversial; however, ORIF is widely described in the literature to be the gold-standard. Percutaneous reduction and monolateral ...external fixation is gaining increasing attention because it provides a good and stable reduction, and minimises soft tissue complications due to open surgery, such as deep infections and delays in wound healing. The aim of this study was to show that the new Orthofix Calcaneal Minifixator (six pins) provides a greater stability than the four-pin version to enable a better and more stable reduction, an earlier weight-bearing (30 days) and improved functional outcomes. Methods A series of 69 consecutive closed heel intraarticular displaced fractures treated with the new Orthofix Calcaneal Minifixator were evaluated. Patients were assessed clinically with the Maryland Foot Score and radiologically with standard radiographs. Results The clinical results at follow-up were excellent in 37 cases (53.6%), good in 27 (39.2%), fair in two (2.9%) and poor in three (4.3%). The mean preoperative Böhler's angle was 5.2˚ (range 0–18˚) and the mean postoperative value was 28.5˚ (range 16–38˚). Conclusion The excellent functional outcomes were despite some radiological images of imperfect posterior facet anatomical reduction and seemed to correlate with the use of a good and stable minimally-invasive surgical technique. This technique enabled early weight-bearing, minimised complications, respected the delicate biology of this anatomical site and restored the good heel volume and Böhler angle.
Reactive oxygen species are critical mediators of the early phase of ischemic (IR) injury. The contribution of antioxidants, such as N-acetyl-cysteine (NAC), in ameliorating the parenchymal lesions, ...inflammatory parameters, and functional variables in renal IR is still controversial. We studied the effect of NAC administration on renal injury induced by IR. Mice were subjected to renal pedicle occlusion and subsequent reperfusion for 24 or 120 hours. NAC was administered prior to surgery at two concentrations (40 or 300 mg/kg, IP). Renal function and acute tubular necrosis were assessed, as well as immune phenotyping of infiltrating cells, by flow cytometry. At 40 mg/dL of NAC, we did not observe any significant improvement in renal function (1.85 ± 0.43 md/dL,
P = .367) or tissue architecture (% of ATN: 2.51 ± 0.27 mm,
P = .852) compared to the controls (1.87 ± 0.43 mg/dL and 3.12 ± 0.34 mm, respectively). However, animals that received 300 mg/dL of NAC showed lower serum creatinine values (24 hours: 1.25 ± 0.54 mg/dL) compared to controls (
P = .009) and less extensive acute tubular necrosis (1.54 ± 0.12 vs,
P < .05). Treatment with 300 mg/dL of NAC decreased renal dendritic cell infiltration. The protective effect of NAC was better observed at high concentrations and early times.
All but three (M87, BL Lac, and 3C 279) extragalactic sources detected so far at very high energy -rays belong to the class of high-frequency-peaked BL Lac objects. This suggested to us a systematic ...scan of candidate sources with the MAGIC telescope, based on the Donato et al. compilation of X-ray blazars. The observations took place from 2004 December to 2006 March and cover northern sky sources visible under small zenith distances image at culmination, constraining the declination to -2 degree to +58 degree . The sensitivity of the search was planned for detecting X-ray-bright image sources emitting at least the same energy flux at 200 GeV as at 1 keV. To avoid strong -ray attenuation close to the energy threshold, source redshift was constrained to image. Of the 14 sources observed, 1ES 1218+304 (for the first time at VHE) and 1ES 2344+514 (strong detection in a low flux state) were detected in addition to the known bright TeV blazars Mrk 421 and Mrk 501. A marginal excess of 3.5 capital sigma from the position of 1ES 1011+496 was observed and then confirmed as a VHE -ray source by a second MAGIC observation triggered by a high optical state. For the remaining sources, we present 99% c.l. upper limits on the integral flux image200 GeV. We characterize the HBL sample (including all HBLs detected at VHE so far) by looking for correlations between their multifrequency spectral indices determined from simultaneous optical, archival X-ray, and radio luminosities, finding that VHE-emitting HBLs do not seem to constitute a unique subclass. The HBLs' absorption-corrected -ray luminosities at 200 GeV are generally not higher than their X-ray luminosities at 1 keV.
Swift discovered GRB 050713A and slewed promptly to begin observing with its narrow-field instruments 72.6 s after the burst onset, while the prompt gamma-ray emission was still detectable in the ...BAT. Simultaneous emission from two flares is detected in the BAT and XRT. This burst marks just the second time that the BAT and XRT have simultaneously detected emission from a burst and the first time that both instruments have produced a well-sampled, simultaneous data set covering multiple X-ray flares. The temporal rise and decay parameters of the flares are consistent with the internal-shock mechanism. In addition to the Swift coverage of GRB 050713A, we report on the Konus-Wind (K-W) detection of the prompt emission, an upper limiting GeV measurement of the prompt emission made by the MAGIC imaging atmospheric Cerenkov telescope, and XMM-Newton observations of the afterglow. Simultaneous observations with Swift XRT and XMM-Newton produce consistent results, showing a break in the light curve at T sub(0)+6 15 ks. Together, these four observatories provide unusually broad spectral coverage of the prompt emission and detailed X-ray follow-up of the afterglow for 2 weeks after the burst trigger. Simultaneous spectral fits of K-W with BAT and BAT with XRT data indicate that an absorbed broken power law is often a better fit to GRB flares than a simple absorbed power law. These spectral results together with the rapid temporal rise and decay of the flares suggest that flares are produced in internal shocks due to late-time central-engine activity.
Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the ...detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.
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