The Galactic Cosmic Rays (GCRs, those Cosmic Rays with intermediate energy between 10s of GeV and 100s of TeV per unit of charge) are known from more than nine decades. Anyway, we still know very little about their origins. The Super Nova Remnants (SNRs) are the most popular GCRs candidate accelerators. But up to now we miss an unquestioned experimental proof of this theory. Therefore we investigated the SN 1006 remnant. This shell type remnant has been produced by the bright Super Nova, which has been visible during the year 1006. This is one of the few sources, from which TeV gamma rays have been detected. Here below I summarize the observations of the SN1006 with the HEGRA CT1 telescope. Very briefly the main steps of the data analysis and the main achievements are also listed. We observed SN 1006 for more than 220 hours from the 1999 to 2001 with the HEGRA CT1 telescope. CT1 is part of the HEGRA cosmic rays detector complex at La Palma (28.75$deg N, 17.9deg W, 2225 m asl). SN 1006 (RA 15:02:48.8, Dec -41:54:42) culminates at less than 20deg of elevation when observed from La Palma. therefore only large zenith (ZA) angle observations are possible. We collected in total more than 346000 so-called ON-source events, restricting observations to a narrow range between 71 and 73deg ZA, as well as a small set of OFF-source data at the same ZA. We recorded also a large background sample of muons passing through the telescope camera. Such muons leave narrow images, which might mimic gamma events. The data analysis of the SN 1006 data has been performed (as a part of my doctoral work), in order to search for the possible multi-TeV emission from this source. some innovations have been introduced to the standard analysis techniques. The main of them are : - The development and the validation of a novel background rejection method. The standard rejection is un-effective for the SN 1006 data, because of the large zenith angle (the present observation is the one at largest zenith angle ever successfully performed). - The implementation of a 2-dimensional analysis (False Source Method) and the scan of the CT1 field of view. The standard analysis is optimized for point-like objects, while SN 1006 remnant is an extended one. - A new treatment for the residual background (the so-called Ring method) which is used together with the CT1 standard one (the so-called Alpha fit). - The telescope calibration (i.e. calculation of the effective collection area, Impact parameter and Energy reconstruction). Also the calibration is affected by the large zenith angle, and therefore it is a new one. With the above mentioned analysis, the following main results have been achieved: - The detection of TeV gamma rays from the North-East cap of the SN1006 remnant. The TeV gamma rays emission is detected as an excess of events. The excess consists of 103+-17 events. The residual background consists of 225+-9 events. - the excess significance is 5.1 standard deviations, in accordance with the Lee and Ma theory, which is usually applied within the gamma ray astronomy field. The initial significance was 5.6 std. deviations , it has been reduced in order to account for the position indetermination (9 sky map bins). - The integral flux is: Phi_{gamma} (E > 18 +- 2 TeV) = (2.35 +- 0.4 _{stat} +-0.7 _{syst.} ) 10 ^{-13} cm ^{-2} s ^{-1} This flux is obtained under the assumption that: the source emits a differential energy spectrum in the form of a pure power-law, with spectral index Gamma = -2.0, which is the value favoured by the differential spectrum fit. The energy threshold (E_{th}) for the same photon index is 18+-2. - A systematic uncertainty delta_Phi_{syst.} = 30% has been considered for the fluxes calculations. With the inclusion of the systematic errors, the integral flux, for $\Gamma$ = -2.0, becomes: Phi_{gamma} (E > 18 +- 2 TeV) = (2.35 +- 0.4 _{stat} +-0.7 _{syst.} ) 10 ^{-13} cm ^{-2} s ^{-1}. \item The differential flux, in the form of a pure power law C_{scale}*E^{-Gamma}, is: dPhi/dE =(0.30 +- 0.36)* 10^{-11} *(E/TeV)^{-1.9+-0.4} TeV^{-1} \ cm^{-2} \ s^{-1} $$ The errors include the statistical ones, and those for the energy reconstruction. A 30% systematic error is not included. - No signal has been found at the South-West cap and at the central region location. It is therefore possible to set an upper-limit for the integral flux from the South-West cap: Phi (E > 18+-2TeV) _{gamma,SW} = 0.83 10 ^{-13} cm ^{-2} s ^{-1} at a confidence level of 95\%, under the assumption of a power law with photon index Gamma=-2. The upper limit for the SNR central region is: Phi (E > 18+-2TeV)_{gamma,center} = 0.66 10 ^{-13} cm ^{-2} s ^{-1} also this at a confidence level of 95\%, under the assumption of a power law with photon index Gamma=-2.
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The Galactic Cosmic Rays (GCRs, those Cosmic Rays with intermediate energy between 10s of GeV and 100s of TeV per unit of charge) are known from more than nine decades. Anyway, we still know very little about their origins. The Super Nova Remnants (SNRs) are the most popular GCRs candidate accelerators. But up to now we miss an unquestioned experimental proof of this theory. Therefore we investigated the SN 1006 remnant. This shell type remnant has been produced by the bright Super Nova, which h...
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