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.
The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in ...short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.
HPD imaging properties in Cherenkov telescopes Piccioli, A; Pegna, R; Fedorko, I ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2004, Volume:
525, Issue:
1
Journal Article
Peer reviewed
We discuss the imaging properties of Hybrid Photon Detectors (HPDs) in the framework of an Imaging Air Cherenkov Telescope experiment. We present also some preliminary results on Night Sky Background ...measurements, made with an HPD located in the focal plane of a single CLUE telescope.
We present the results from a multiwavelength campaign on the TeV blazar 1ES 1959+650, performed in 2006 May. Data from the optical, UV, soft- and hard-X-ray, and very high energy (VHE) gamma-ray ...(image GeV) bands were obtained with the Suzaku and Swift satellites, the MAGIC telescope, and other ground-based facilities. The source spectral energy distribution (SED), derived from Suzaku and MAGIC observations at the end of 2006 May, shows the usual double hump shape, with the synchrotron peak at a higher flux level than the Compton peak. With respect to historical values, during our campaign the source exhibited a relatively high state in X-rays and optical, while in the VHE band it was at one of the lowest level so far recorded. We also monitored the source for flux spectral variability on a time window of 10 days in the optical-UV and X-ray bands and 7 days in the VHE band. The source varies more in the X-ray than in the optical band, with the 2-10 keV X-ray flux varying by a factor of image2. The synchrotron peak is located in the X-ray band and moves to higher energies as the source gets brighter, with the X-ray fluxes above it varying more rapidly than the X-ray fluxes at lower energies. The variability behavior observed in the X-ray band cannot be produced by emitting regions varying independently and suggests instead some sort of 'standing shock' scenario. The overall SED is well represented by a homogeneous one-zone synchrotron inverse Compton emission model, from which we derive physical parameters that are typical of high-energy peaked blazars.
In 2005 and 2006, the MAGIC telescope observed very high energy gamma-ray emission from the distant BL Lac object PG 1553+113. The overall significance of the signal was 8.8 s for 18.8 hr of ...observation time. The light curve shows no significant flux variations on a daily timescale; the flux level during 2005 was, however, significantly higher compared to 2006. The differential energy spectrum between 690 and 500 GeV is well described by a power law with photon index = 4.2 c 0.3. The combined 2005 and 2006 energy spectrum provides an upper limit of z = 0.74 on the redshift of the object.
HPD: new UV detector for Imaging Air Cherenkov Telescopes Piccioli, A.; Pegna, R.; Giunta, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2003, Volume:
504, Issue:
1-3
Journal Article
Peer reviewed
We propose to use a new large photocathodic area UV Rb2Te HPD developed at CERN (TOM collaboration) as a detector well suited for IACT experiments. Some aspects of UV atmospheric transmission are ...presented.
The MAGIC collaboration has observed very high energy gamma-ray emission from the AGN 1ES 2344+514. A gamma-ray signal corresponding to an 11 sigma excess and an integral flux of (2.38 unk 0.30 unk ...plus or minus 0.70 unk) x 10 super(-11) cm super(-2) s super(-1) above 200 GeV has been obtained from 23.1 hr of data taking between 2005 August 3 and 2006 January 1. The data confirm the previously detected gamma-ray emission from this object during a flare seen by the Whipple collaboration in 1995 and the evidence (below 5 sigma significance level) from long-term observations conducted by the Whipple and HEGRA groups. The MAGIC observations show a relatively steep differential photon spectrum that can be described by a power law with a photon index of unk = -2.95 plus or minus 0.12 unk plus or minus 0.2 unk between 140 GeV and 5.4 TeV. The observations reveal a low-flux state, about 6 times below the 1995 flare seen by Whipple and comparable with the previous Whipple and HEGRA long-term measurements. During the MAGIC observations no significant time variability was observed.
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.
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