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 γ-ray Imaging Cherenkov (MAGIC) telescope to 25 giga--electron volts. In this configuration, we detected pulsed γ-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.
We report the detection of a new source of very high energy (VHE; unk greater than or equal to 100 Gev) Y-ray emission located close to the Galactic plane, MA J0616+225, which is spatially coincident ...with supernova remnant IC 443. The observations were carried out with the MAGIC telescope unk 2005 December-2006 January and 2006 December-2007 January. Here we present results from this source, leading to a VHE Y-ray unk statistical significance of 5.7 sigma in the 2006/2007 data and a measured differential Y-ray flux consistent with a power law, described as unk(dAdtdE) = (1.0 plus or minus 0.2) x 10 super(11)(E/0.4TeV)-3.1 plus or minus 0.3 cm super(-2) s super(-1) Tev super(-1). we briefly discuss the observational technique used and the unk implemented for the data analysis. The results are placed in the context of the multiwavelength emission and the molecular environment region of IC 443.
M87 is the only known nonblazar radio galaxy to emit very high energy (VHE) gamma rays. During a monitoring program of M87, a rapid flare in VHE gamma-rays was detected by the MAGIC telescope in ...early 2008. The flux was found to be variable above 350 GeV on a timescale as short as 1 day at a significance level of 5.6 capital sigma . The highest measured flux reached 15% of the Crab Nebula flux. We observed several substantial changes of the flux level during the 13 day observing period. The flux at lower energies (150-350 GeV), instead, is compatible with being constant. The energy spectrum can be described by a power law with a photon index of 2.30 +/- 0.11 sub(stat) +/- 0.20 sub(syst). The observed day-scale flux variability at VHE prefers the M87 core as source of the emission and implies that either the emission region is very compact (just a few Schwarzschild radii) or the Doppler factor of the emitting blob is rather large in the case of a nonexpanding emission region.
The MAGIC collaboration observed BL Lacertae for 22.2 hr during 2005 August to December and for 26 hr during 2006 July to September. The source is the historical prototype and eponym of a class of ...low-frequency-peaked BL Lacertae (LBL) objects. A very high energy (VHE) gamma -ray signal was discovered with a 5.1 a excess in the 2005 data. Above 200 GeV, an integral flux of (0.6 plus or minus 0.2) x 10 super(-11) cm super(-2)8 super(-1) was measured, corresponding to approximately 3% of the Crab flux. The differential spectrum between 150 and 900 GeV is rather steep with a photon index of -3.6 plus or minus 0.5. The light curve shows no significant variability during the observations in 2005. For the first time a clear detection of VHE gamma -ray emission from an LBL object was obtained with a signal below previous upper limits. The 2006 data show no significant excess. This drop in flux follows the observed trend in optical activity.
The MAGIC telescope took data of very high energy gamma -ray emission from the blazar Markarian 421 (Mrk 421) between 2004 November and 2005 April. We present a combined analysis of data samples ...recorded under different observational conditions, dowr to gamma -ray energies of 100 GeV. The flux was found to vary between 0.5 and 2 crab (integrated above 200 GeV), considered a low state when compared to known data. Although the flux varied day by day, no short-term variability was observed, although there is some indication that not all nights show an equally quiescent state. The results at higher energies were found to be consistent with previous observations. A clear correlation is observed between gamma -ray and X-ray fluxes, whereas no significant correlation between gamma -ray and optical data is seen. The spectral energy distribution between 100 GeV and 3 TeV shows a clear deviation from a power law, more clearly and at lower flux than previous observations at higher energies. The deviation persists after correcting for the effect of attenuation by the extragalactic background light, and most likely is source-inherent. There is a rather clear indication of an inverse Compton peak around 100 GeV. The spectral energy distribution of Mrk 421 can be fitted by a one-zone synchrotron self-Compton model, suggesting once again a leptonic origin of the very high energy gamma -ray emission from this blazar.
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