Pierre Colin

Measurement of the cosmic electron plus positron spectrum with the MAGIC telescopes

Cosmic electrons with energies in the TeV range lose their energy rapidly through synchrotron radiation and inverse Compton processes, resulting in a relatively short lifetime (� 10 5 years). They are only visible from compara- tively nearby sources (< 1 kpc). Unexpected features in their spectrum at a few hundreds GeV, as measured by several experiments (ATIC, Fermi and H.E.S.S. among others), might be caused by local sources such as pulsars or by dark mat- ter annihilation/decay. In order to investigate these poss ibilities, new measurements in the TeV energy region are needed. Since the completion of the stereo system, the MAGIC Cherenkov experiment is sensitive enough to measure the cosmic electron flux between a few hundred GeV and few TeV. The electr on signal has to be extracted from the overwhelming background of hadronic cosmic rays estimated through Monte Carlo simulations. Here we present the first results of the cosmic electron spectrum measured with the MAGIC telescopes.

Probing the CR positron/electron ratio at few hundreds GeV through Moon shadow observation with the MAGIC telescopes

The antimatter components measured in the Cosmic Ray (CR) flux are thought as secondary particles induced by the propagation of galactic CRs within the galaxy. Recent results from the PAMELA experiment show an unexpected increase of the positron electron ratio above 10 GeV. There could be different interpretations to explain that result, the most discussed ones being the signature of nearby compact astrophysical source(s) or of dark matter annihilation/decay. Probing the positron-fraction rise above 100 GeV would help to disentangle among different scenarios. Imaging Atmo- spheric Cherenkov Telescopes (IACT) can extract the cosmic lepton signal from the hadronic CR background between a few hundred GeV and a few TeV and reconstruct energy and incident direction with a very good resolution. In ad- dition, by using the natural spectrometer formed by the Moon and the geomagnetic field, it is possible to measure the positron/electron ratio at the TeV regime through the observation of the CR Moon shadow. Despite the technique is particularly challenging because of the high background light induced by the Moon and the treatment of data, the MAG- IC collaboration has performed for the first time such observations in 2010 and 2011. Here we present the observation strategy and the performance achieved during this campaign.

MAGIC measurement of the Crab Nebula spectrum over three decades in energy

The Crab Pulsar Wind Nebula is the best studied source of γ-ray astrophysics. The contribution of the various soft radiation fields to the Inverse Compton component of its high energy emission, the strenght of the internal magnetic field and the maximum energies reached by primary electrons are however still matter of study. The MAGIC stereoscopic system recorded almost 50 hours of Crab Nebula data in the last two years, between October 2009 and April 2011. Analysis of this data sample using the latest improvements in the MAGIC stereo software provided an unprecedented differential energy spectrum spanning three decades in energy, from 50 GeV up to 45 TeV. At low ener- gies, the MAGIC results, combined with the Fermi/LAT data, yield a precise measurement of the Inverse Compton peak. In addition, we present light curves of the Crab Nebula at different time scales, including a measurement simultaneous to one of the Crab Nebula flares recently detected by both Fermi/LAT and AGILE. Using the MAGIC spectrum together with multiwavelength data, we discuss the implications for the modeling of the Crab Nebula.

Constraining the Dark Matter decay lifetime with very deep observations of the Perseus cluster with the MAGIC telescopes

M. Doroa,b, M. Vazquez Acostac,d , P. Colina, C. Maggiob,e, J. Rico f , F. Zandanelg on behalf of the MAGIC Collaboration a Max Planck Institute for Physics (Munich, Germany), b INFN-Padova (Padova, Italy), c Instituto de Astrofisica de Canarias (E-38205 La Laguna, Tenerife, Spain), d Universidad de La Laguna, Dpto. Astrofisica (E-38206 La Laguna, Tenerife, Spain), e University of Padova (Padova, Italy), f Institut de Fisica d’Altes Energies, (E-08193 Barcelona, Spain), g GRAPPA Institute, University of Amsterdam, (1098 XH Amsterdam, The Netherlands)

Constraints on the cosmic ray cluster physics from a very deep observation of the Perseus cluster with MAGIC

Galaxy clusters are the largest and most massive gravitationally bound structures known in the Universe. Cosmic-Ray (CR) hadrons accelerated at structure formation shocks and injected by galaxies, are confined in galaxy clusters where they accumulate for cosmological times. The presence of diffuse synchrotron radio emission in several clusters proves the existence of high-energy electrons, and magnetic fields. However, a direct proof of CR proton acceleration is missing. The presence of CR protons can be probe through the diffuse gamma-ray emission induced by their hadronic interaction with the Intra-Cluster Medium (ICM). The Perseus cluster, a nearby cool-core cluster, has been identified to be among the best candidates to detect such emission. We present here the results of a very deep observation of the Perseus cluster with the MAGIC telescopes, accumulating about 250 hours of data from 2009 to 2014. No evidence of large-scale very-high-energy gamma-ray emission from CR-ICM interactions has been detected. The derived flux upper limits in the TeV regime allow us to put stringent constraints on the physics of cluster CRs, in particular on the CR-to-thermal pressure, the CR acceleration efficiency at formation shocks and the magnetic field of the central cluster region.

MAGIC detection of VHE Gamma-ray emission from NGC 1275 and IC 310

The MAGIC Cherenkov telescopes observed the Perseus cluste r sky region in stereo mode for nearly 90 hr from October 2009 to February 2011. This campaign led to the d iscovery of very high energy γ-ray emission from the central radio galaxy NGC 1275 and the head-tail radio galaxy IC 310. Here we report the results on the most recent discovery of NGC 1275 which was detected at low energies in th e 2010/2011 data. We also present latest results on IC 310, which had been detected in the 2009/2010 data.The MAGIC Cherenkov telescopes observed the Perseus cluster sky region in stereo mode for nearly 90 hr from October 2009 to February 2011. This campaign led to the discovery of very high energy Gamma-ray emission from the central radio galaxy NGC 1275 and the head-tail radio galaxy IC 310. Here we report the results on the most recent discovery of NGC 1275 which was detected at low energies in the 2010/2011 data. We also present latest results on IC 310, which had been detected in the 2009/2010 data.

Performance of the MAGIC telescopes after the major upgrade

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent a major upgrade. The main subsystems upgraded were the MAGIC-I camera and its trigger system and the readout system of both telescopes. We use observations of the Crab Nebula taken at low and medium zenith angles to assess the key performance parameters of the MAGIC stereo system. For low zenith angle observations, the standard trigger threshold of the MAGIC telescopes is about 50 GeV. The integral sensitivity for point-like sources with Crab Nebula-like spectra above 220 GeV is (0.66 +/- 0.03)% of Crab Nebula flux in 50 h of observations. The angular resolution, defined as the sigma of a 2-dimensional Gaussian distribution, at energies of a few hundred GeV is below 0.07degree, while the energy resolution is around 16%. We investigate the effect of the systematic uncertainty on the data taken with the MAGIC telescopes after the upgrade. We estimate that the systematic uncertainties can be divided in the following components: < 15% in energy scale, 11 - 18% in flux normalization and +/-0.15 for the slope of the energy spectrum.

THE 2010 M 87 VHE FLARE AND ITS ORIGIN: THE MULTI-WAVELENGTH PICTURE

The giant radio galaxy M 87, with its proximity (16 Mpc) and its very massive black hole ((3-6) × 109 M⊙), provides a unique laboratory to investigate very high energy (E>100 GeV; VHE) gamma-ray emission from active galactic nuclei and, thereby, probe particle acceleration to relativistic energies near supermassive black holes (SMBH) and in relativistic jets. M 87 has been established as a VHE γ-ray emitter since 2005. The VHE γ-ray emission displays strong variability on timescales as short as a day. In 2008, a rise in the 43 GHz Very Long Baseline Array (VLBA) radio emission of the innermost region (core; extension of < 100 Rs; Schwarzschild radii) was found to coincide with a flaring activity at VHE. This had been interpreted as a strong indication that the VHE emission is produced in the direct vicinity of the SMBH. In 2010 a flare at VHE was again detected triggering further multi-wavelength (MWL) observations with the VLBA, Chandra, and other instruments. At the same time, M 87 was also observed with the Fermi-LAT telescope at MeV/GeV energies, the European VLBI Network (EVN), and the Liverpool Telescope (LT). Here, preliminary results from the 2010 campaign will be reported.

Observation of the Perseus galaxy cluster with the MAGIC telescopes

The MAGIC ground-based Imaging Cherenkov experiment observed the Perseus galaxy cluster for a total of about 25 hr between November and December 2008 in single telescope mode and for nearly 90 hr between October 2009 and February 2011 in stereoscopic mode. This survey represents the deepest observation of a cluster of galaxies at very high energies ever. It resulted in the detection of the centr al radio galaxy NGC 1275 and the head-tail galaxy IC 310. It also permits for the first time to put constraints on emission models predicting -rays from cosmic ray acceleration in the cluster and to investigate dark matter scenarios. Here, we will report the latest MAGIC results on these studies.

Observation of the BL Lac objects 1ES 1215+303 and 1ES 1218+304 with the MAGIC telescopes

The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1215+303 was flaring also in VHE gamma-rays in 2011. In addition, the Swift ToO observations in X-rays showed that the flux was almost doubled respect to previous observations (December 2009). Instead, 1ES 1218+304 is a well known VHE gamma-ray emitter lying in the same field of view, which was then simultaneously observed with the MAGIC telescopes. The overall observation time of nearly 45 hours has permitted to measure the spectrum of this source with a much higher precision than previously reported by MAGIC. Here, we present the results of the MAGIC and the multi-wavelength observations of these two VHE gamma-ray emitting AGNs.