We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum ...gravity (QG), which predict a vacuum refractive index ≃1+(E/MQGn)n, n=1,2. Parametrizing the delay between γ-rays of different energies as Δt=±τlE or Δt=±τqE2, we find τl=(0.030±0.012) s/GeV at the 2.5-σ level, and τq=(3.71±2.57)×10−6 s/GeV2, respectively. We use these results to establish lower limits MQG1>0.21×1018 GeV and MQG2>0.26×1011 GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report on the results from the observations in the very high energy band (VHE; unk greater than or equal to 100 GeV) of the black hole X-ray binary (BHXB) Cygnus X-1. The observations were ...performed with the MAGIC telescope, for a total of 40 hr during 26 nights, spanning the period between 2006 June and November. Searches for steady Y-ray signals yielded no positive result, and upper limits to the integral flux ranging between 1% and 2% of the Crab Nebula flux, depending on the energy, have been established. We also analyzed each observation night independently, obtaining evidence of Y-ray signals at the 4.0 sigma significance level (3.2 sigma after trial correction) for 154 minutes of effective on-time (EOT) on September 24 between 20:58 and 23:41 UTC, coinciding with an X-ray flare seen by RXTE, Swift, and INTEGRAL. A search for faster-varying signals within a night resulted in an excess with a significance of 4.9 sigma (4.1 sigma after trial correction) for 79 minutes EOT between 22:17 and 23:41 UTC. The measured excess is compatible with a pointlike source at the position of Cygnus X-1 and excludes the nearby radio nebula powered by its relativistic jet. The differential energy spectrum is well fitted by an unbroken power law described as dN/(dA dt dE) = (2.3 plus or minus 0.6) x 10- super(12)(E/1TeV) super(-3.2 plus or minus 0.6). This is the first experimental evidence of VHE emission from a stellar mass black hole and therefore from a confirmed accreting X-ray binary.
The paper describes an application of the tree classification method Random Forest (RF), as used in the analysis of data from the ground-based gamma telescope MAGIC. In such telescopes, cosmic ...gamma-rays are observed and have to be discriminated against a dominating background of hadronic cosmic-ray particles. We describe the application of RF for this gamma/hadron separation. The RF method often shows superior performance in comparison with traditional semi-empirical techniques. Critical issues of the method and its implementation are discussed. An application of the RF method for estimation of a continuous parameter from related variables, rather than discrete classes, is also discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Cherenkov light flashes produced by extensive air showers are very short in time. A high bandwidth and fast digitizing readout, therefore, can minimize the influence of the background from the ...light of the night sky, and improve the performance in Cherenkov telescopes. The time structure of the Cherenkov image can further be used in single-dish Cherenkov telescopes as an additional parameter to reduce the background from unwanted hadronic showers. A description of an analysis method which makes use of the time information and the subsequent improvement on the performance of the MAGIC telescope (especially after the upgrade with an ultra fast 2 GSamples/s digitization system in February 2007) will be presented. The use of timing information in the analysis of the new MAGIC data reduces the background by a factor two, which in turn results in an enhancement of about a factor 1.4 of the flux sensitivity to point-like sources, as tested on observations of the Crab Nebula.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The MAGIC collaboration has studied the high-frequency-peaked BL Lac object 1ES 1218+30.4, at a redshift z = 0.182, using the MAGIC imaging air Cerenkov telescope located on the Canary Island of La ...Palma. A gamma-ray signal was observed with 6.4 s significance. The differential energy spectrum for an energy threshold of 120 GeV can be fitted by a simple power law, yielding F sub(E)(E) = (8.1 c 2.1) x 10 super(-7) E/(250 GeV) super(-3.0c0.4) TeV super(-1) m super(-2) s super(-1). During the 6 days of observation in 2005 January, no time variability on timescales of days was found within the statistical errors. The observed integral flux above 350 GeV is nearly a factor of 2 below the upper limit reported by the Whipple collaboration in 2003.
Unfolding of differential energy spectra in the MAGIC experiment Albert, J.; Antoranz, P.; Armada, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2007, Volume:
583, Issue:
2
Journal Article
Peer reviewed
Open access
The paper describes the different methods, used in the MAGIC experiment, to unfold experimental energy distributions of cosmic ray particles (
γ
-rays). Questions and problems related to the ...unfolding are discussed. Various procedures are proposed which can help to make the unfolding robust and reliable. The different methods and procedures are implemented in the MAGIC software and are used in most of the analyses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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.
Zusammenfassung
Hintergrund
Notaufnahmen in Deutschland werden mit steigenden Patientenzahlen konfrontiert. Um den wachsenden Bedarf an medizinischer Versorgung zu managen, wurden flächendeckend ...standardisierte Triagesysteme eingeführt und gesetzlich vorgeschrieben.
Ziel der Arbeit
Nach der Implementation des Manchester Triage System in der chirurgischen Notaufnahme eines überregionalen Traumazentrums gab es Hinweise auf relevante Fehltriagierung. Diese Arbeit untersucht die Prävalenz und die Ursachen der Fehltriagierung und zeigt mögliche Gegenmaßnahmen.
Material und Methoden
Eine Querschnittstudie mit 2 Studienzweigen einer prospektiven Prozessbeobachtung und einer retrospektiven Fallanalyse von Triageepisoden.
Ergebnisse
Von 14.156 im Beobachtungszeitraum behandelten Patienten wurden 497 Triageepisoden prospektiv beobachtet und 720 Triageepisoden retrospektiv untersucht. Es wurden 51,6 % der Dringlichkeitsstufe „Rot“ bzw. 37,1 % „Blau“ fehltriagiert. Mögliche Ursachen fanden sich in den Bereichen der Anwender („Rot“: 88,9 %, „Blau“: 85,7 %), der Prozessgestaltung („Rot“: 91,9 %, „Blau“: 12,8 %) und des Triagesystems („Rot“: 8,1 %, „Blau“: 15,8 %).
Diskussion
Die Studie zeigt das Vorliegen einer relevanten Fehltriagierung und impliziert, dass auch ein standardisiertes Triagesystem nach Implementation einer Überprüfung und Integration in bestehende Strukturen bedarf. Wie sich zeigte, ist die Fehltriage ein multifaktorielles Geschehen, verschiedene mögliche Fehlerquellen bedingen sich gegenseitig und führen zu fehlerhaften Einschätzungen. Dem sollte nicht mit Einzelmaßnahmen, sondern mit einem Maßnahmenpaket begegnet werden, um die Triage sicher und effizient zu gestalten.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
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