The central pixel of the MAGIC telescope for optical observations Lucarelli, F.; Barrio, J.A.; Antoranz, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2008, Letnik:
589, Številka:
3
Journal Article
Recenzirano
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The MAGIC telescope has been designed for the observation of Cherenkov light generated in Extensive Air Showers initiated by cosmic particles. However, its 17m diameter mirror and optical design ...makes the telescope suitable for direct optical observations as well. In this paper, we report about the development of a system based on the use of a dedicated photo-multiplier (PMT) for optical observations. This PMT is installed in the centre of the MAGIC camera (the so-called central pixel). An electro-to-optical system has been developed in order to transmit the PMT output signal by an optical fibre to the counting room, where it is digitized and stored for off-line analysis. The performance of the system using the optical pulsation of the Crab nebula as calibration source is presented. The time required for a 5σ detection of the Crab pulsar in the optical band is less than 20s. The central pixel will be mainly used to perform simultaneous observations of the Crab pulsar both in the optical and γ-ray regimes. It will also allow for periodic testing of the precision of the MAGIC timing system using the Crab rotational optical pulses as a very precise timing reference.
The binary system LS I +61 303 is one of four γ-ray binaries known. The system was studied intensively with the MAGIC telescope between September 2005 and December 2006. The total amount of 166 hours ...of data were taken during two observation campaigns of 6 and 4 month duration. We produced the most detailed light curve of the system in γ-rays with energy above 100 GeV. We found a clear variation of the flux level in different orbital phase bins and on timescales of about one day. The spectral energy distribution can be described well by a power law with spectral photon index of 2.6 ± 0.2. We found no significant change in the spectral index between different orbital phases or during the different observation campaigns.
MAGIC observations of the HMXB LS I +61 303 in VHE gamma rays Jogler, T.; Bosch-Ramon, V.; Cortina, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2008, Letnik:
588, Številka:
1-2
Journal Article
Recenzirano
The MAGIC collaboration discovered with their 17m diameter imaging atmospheric Cherenkov telescope, the High Mass X-ray Binary (HMXB) LS I +61 303 at VHE (VHE,E>50GeV)γ-rays. The emission from LS I ...+61 303 was found to be variable, and the source was visible at energies above 200GeV in different runs during some orbital phases only. These orbital phases do not coincide with the periastron passage. Here we report the results of the analysis of the LS I +61 303 MAGIC observations.
The MAGIC collaboration has recently reported the discovery of g-ray emission from the binary system LS I +61°303 in the TeV energy region. Here we present new observational results on this source in ...the energy range between 300 GeV and 3 TeV. In total, 112 hr of data were taken between 2006 September and December covering four orbital cycles of this object. This large amount of data allowed us to produce an integral flux light curve covering for the first time all orbital phases of LS I +61°303. In addition, we also obtained a differential energy spectrum for two orbital phase bins covering the phase range 0.5 < < 0.6 and 0.6 < < 0.7. The photon index in the two phase bins is consistent within the errors with an average index = 2.6 ± 0.2stat ± 0.2sys. LS I +61°303 was found to be variable at TeV energies on timescales of days. These new MAGIC measurements allowed us to search for intranight variability of the very high energy emission; however, no evidence for flux variability on timescales down to 30 min was found. To test for possible periodic structures in the light curve, we apply the formalism developed by Lomb and Scargle to the LS I +61°303 data taken in 2005 and 2006. We found the LS I +61°303 data set to be periodic with a period of (26.8 ± 0.2) days (with a post-trial chance probability of 10-7), close to the orbital period.
Based on MAGIC observations from 2007 June to July, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of F(E>200 GeV) < 5.1 X 10-12 cm-2 s-1, and ...differential upper limits for E > 140 GeV. Those limits allow us to constrain the population of millisecond pulsars within M13 and to test models for acceleration of leptons inside their magnetospheres and surrounding. We conclude that in M13 either millisecond pulsars are fewer than expected or they accelerate leptons less efficiently than predicted.
One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By ...developing a new electronic trigger, we lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts. In this configuration, we detected pulsed gamma-rays from the Crab pulsar that were greater than 25 giga-electron volts, revealing a relatively high cutoff energy in the phase-averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar-cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot-gap scenario. PUBLICATION ABSTRACT
The nearby dwarf spheroidal galaxy Draco, with its high mass to light ratio, is one of the most auspicious targets for indirect dark matter (DM) searches. Annihilation of hypothetical DM particles ...can result in high-energy -rays, e.g., from neutralino annihilation in the supersymmetric framework. A search for a possible DM signal originating from Draco was performed with the MAGIC telescope during 2007. Analysis of the data results in a flux upper limit (2 capital sigma ) of image photons cm super(-2) s super(-1) for photon energies above 140 GeV, assuming a pointlike source. A comparison with predictions from supersymmetric models is also given. While our results do not constrain the mSUGRA phase parameter space, a very high flux enhancement can be ruled out.
Aims. We searched for very high energy (VHE) \gamma-ray emission from the supernova remnant Cassiopeia A Methods. The shell-type supernova remnant Cassiopeia A was observed with the 17 m MAGIC ...telescope between July 2006 and January 2007 for a total time of 47 h. Results. The source was detected above an energy of 250 GeV with a significance of 5.2\sigma and a photon flux above 1 TeV of (7.3 \pm 0.7_{\rm stat} \pm 2.2_{\rm sys}) \times 10 super(-13) cm super(-2) s super(-1). The photon spectrum is compatible with a power law d N /d E \propto E-\Gamma} with a photon index \Gamma = 2.3 \pm 0.2_{\rm stat} \pm 0.2_{\rm sys}. The source is point-like within the angular resolution of the telescope.
Presently, the MAGIC telescope uses a 300 MHz FADC system to sample the
transmitted and shaped signals from the captured Cherenkov light of air
showers. We describe a method of Digital Filtering of ...the FADC samples to
extract the charge and the arrival time of the signal: Since the pulse shape is
dominated by the electronic pulse shaper, a numerical fit can be applied to the
FADC samples taking the noise autocorrelation into account. The achievable
performance of the digital filter is presented and compared to other signal
reconstruction algorithms.
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