J. Zapatero

Universitat Autònoma de Barcelona

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M. Doro

University of Padua

R. Mirzoyan

Max Planck Institute for Physics

F. Dazzi

National Institute for Astrophysics

D. Bastieri

Guangzhou University

M. Garczarczyk

Deutsches Elektronen-Synchrotron DESY

M. Mariotti

University of Padua

E. Lindfors

University of Turku

S. Commichau

ETH Zurich

A. Stamerra

National Institute for Astrophysics

M. Errando

Washington University in St. Louis

Cooperative Institutions

Centre National de la Recherche Scientifique

141

National Institute for Astrophysics

139

University of Würzburg

126

Max Planck Institute for Physics

115

Institute for High Energy Physics

110

Universidad Complutense de Madrid

109

ETH Zurich

109

University of Turku

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Universitat de Barcelona

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THE JUNE 2008 FLARE OF MARKARIAN 421 FROM OPTICAL TO TeV ENERGIES

The Astrophysical Journal (2008)

I. Donnarumma V. Vittorini S. Vercellone E. Del Monte M. Feroci

We present optical, X-ray, high energy ($\lessapprox 30$ GeV) and very high energy ($\gtrapprox 100$ GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high energy $\gamma$-ray signal was detected by AGILE with \sqrt{TS}=4.5 on June 9--15, with $F(E>100 \mathrm{MeV})= 42^{+14}_{-12}\times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. This flaring state is brighter than the average flux observed by EGRET by a factor of $\sim$3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a 5-day flare (June 9-15) peaking at $\sim$ 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A Swift/XRT observation near the flaring maximum revealed the highest 2-10 keV flux ever observed from this source, of 2.6 $\times 10^{-9}$ erg cm$^{-2}$ s$^{-1}$ (i.e. > 100 mCrab). A peak synchrotron energy of $\sim$3 keV was derived, higher than typical values of $\sim$0.5-1 keV. VHE observations with MAGIC and VERITAS on June 6-8 show the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a twelve-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The $\gamma$-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet.

Flare

Spectral energy distribution

10.1088/0004-637x/691/1/l13

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Citations (100)

DISCOVERY OF VERY HIGH ENERGY γ-RAYS FROM THE BLAZAR S5 0716+714

The Astrophysical Journal (2009)

H. Anderhub L. A. Antonelli P. Antoranz Michael Backes C. Baixeras

The MAGIC collaboration reports the detection of the blazar S5 0716+714 z=0.31+-0.08 in very high energy gamma-rays. The observations were performed in November 2007 and in April 2008, and were triggered by the KVA telescope due to the high optical state of the object. An overall significance of the signal accounts to S =5.8sigma for 13.1 hours of data. Most of the signal S = 6.9sigma comes from the April 2008 data sample during a higher optical state of the object suggesting a possible correlation between the VHE gamma-ray and optical emissions. The differential energy spectrum of the 2008 data sample follows a power law with a photon index of Gamma = 3.45+-0.54_(stat)+-0.2_(syst), and the integral flux above 400GeV is at the level of 7.5+-2.2_(stat)+-2.3_(syst)*10^-12 cm^-2 s^-1 corresponding to a 9% Crab Nebula flux. Modeling of the broad band spectral energy distribution indicates that a structured jet model appears to be more promising in describing the available data than a simple one zone synchrotron self-Compton model.

BL Lac object

Crab Nebula

Spectral energy distribution

10.1088/0004-637x/704/2/l129

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Citations (83)

Discovery of Very High Energy Gamma Radiation from IC 443 with the MAGIC Telescope

The Astrophysical Journal (2007)

J. Albert E. Aliu H. Anderhub P. Antoranz A. Armada

We report the detection of a new source of very high energy (VHE; Eγ ≥ 100 GeV) γ-ray emission located close to the Galactic plane, MAGIC J0616+225, which is spatially coincident with supernova remnant IC 443. The observations were carried out with the MAGIC telescope in the periods 2005 December-2006 January and 2006 December-2007 January. Here we present results from this source, leading to a VHE γ-ray signal with a statistical significance of 5.7 σ in the 2006/2007 data and a measured differential γ-ray flux consistent with a power law, described as dNγ/(dA dt dE) = (1.0 ± 0.2) × 10-11(E/0.4 TeV)-3.1±0.3 cm-2 s-1 TeV-1. We briefly discuss the observational technique used and the procedure implemented for the data analysis. The results are placed in the context of the multiwavelength emission and the molecular environment found in the region of IC 443.

Galactic plane

High energy

10.1086/520957

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Observation of Pulsed γ-Rays Above 25 GeV from the Crab Pulsar with MAGIC

Science (2008)

E. Aliu H. Anderhub L. A. Antonelli P. Antoranz Michael Backes

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 GeV. In this configuration, we detected pulsed gamma-rays from the Crab pulsar that were greater than 25 GeV, 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.

Crab Pulsar

Cut-off

10.1126/science.1164718

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Citations (196)

Discovery of Very High Energy Gamma Rays from 1ES 1218+30.4

The Astrophysical Journal (2006)

J. Albert E. Aliu H. Anderhub P. Antoranz A. Armada

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 σ significance. The differential energy spectrum for an energy threshold of 120 GeV can be fitted by a simple power law, yielding FE(E) = (8.1 ± 2.1) × 10-7[E/(250 GeV)]-3.0±0.4 TeV-1 m-2 s-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.

BL Lac object

Energy spectrum

10.1086/504845

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Citations (97)

SEARCH FOR VHE γ-RAY EMISSION FROM THE GLOBULAR CLUSTER M13 WITH THE MAGIC TELESCOPE

The Astrophysical Journal (2009)

H. Anderhub L. A. Antonelli P. Antoranz Michael Backes C. Baixeras

Based on MAGIC observations from June and July 2007, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of $F(E>200 \textrm{GeV})<5.1\times10^{-12} \textrm{cm}^{-2} \textrm{s}^{-1}$, and differential upper limits for $E>140 \textrm{GeV}$. 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.

10.1088/0004-637x/702/1/266

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Discovery of Very High Energy γ-Rays from 1ES 1011+496 at z = 0.212

The Astrophysical Journal (2007)

J. Albert E. Aliu H. Anderhub P. Antoranz A. Armada

We report on the discovery of very high energy (VHE) γ-ray emission from the BL Lacertae object 1ES 1011+496. The observation was triggered by an optical outburst in 2007 March and the source was observed with the MAGIC telescope from 2007 March to May. Observing for 18.7 hr, we find an excess of 6.2 σ with an integrated flux above 200 GeV of (1.58 ± 0.32) × 10-11 photons cm-2 s-1. The VHE γ-ray flux is >40% higher than in 2006 March-April (reported elsewhere), indicating that the VHE emission state may be related to the optical emission state. We have also determined the redshift of 1ES 1011+496 based on an optical spectrum that reveals the absorption lines of the host galaxy. The redshift of z = 0.212 makes 1ES 1011+496 the most distant source observed to emit VHE γ-rays to date.

High energy

Photon flux

10.1086/521982

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Citations (86)

First Bounds on the High-Energy Emission from Isolated Wolf-Rayet Binary Systems

The Astrophysical Journal (2008)

E. Aliu H. Anderhub L. A. Antonelli P. Antoranz Michael Backes

High-energy gamma-ray emission is theoretically expected to arise in tight binary star systems (with high mass loss and high velocity winds), although the evidence of this relationship has proven to be elusive so far. Here we present the first bounds on this putative emission from isolated Wolf-Rayet (WR) star binaries, WR 147 and WR 146, obtained from observations with the MAGIC telescope.

Wolf–Rayet star

Star (game theory)

10.1086/592433

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Citations (13)

DISCOVERY OF A VERY HIGH ENERGY GAMMA-RAY SIGNAL FROM THE 3C 66A/B REGION

The Astrophysical Journal (2009)

E. Aliu H. Anderhub L. A. Antonelli P. Antoranz Michael Backes

The MAGIC telescope observed the region around the distant blazar 3C 66A for 54.2 hr in 2007 August–December. The observations resulted in the discovery of a γ-ray source centered at celestial coordinates R.A. = 2h23m12s and decl. = 43°07 (MAGIC J0223+430), coinciding with the nearby radio galaxy 3C 66B. A possible association of the excess with the blazar 3C 66A is discussed. The energy spectrum of MAGIC J0223+430 follows a power law with a normalization of (1.7 ± 0.3stat ± 0.6syst) × 10−11 TeV−1 cm−2 s−1 at 300 GeV and a photon index Γ = −3.10 ± 0.31stat ± 0.2syst.

10.1088/0004-637x/692/1/l29

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Citations (56)

MAGIC observation of the GRB 080430 afterglow

Astronomy and Astrophysics (2010)

J. Aleksić H. Anderhub L. A. Antonelli P. Antoranz Michael Backes

Context. Gamma-ray bursts are cosmological sources emitting radiation from the gamma-rays to the radio band. Substantial observational efforts have been devoted to the study of gamma-ray bursts during the prompt phase, i.e. the initial burst of high-energy radiation, and during the long-lasting afterglows. In spite of many successes in interpreting these phenomena, there are still several open key questions about the fundamental emission processes, their energetics and the environment.Aims. Independently of specific gamma-ray burst theoretical recipes, spectra in the GeV/TeV range are predicted to be remarkably simple, being satisfactorily modeled with power-laws, and therefore offer a very valuable tool to probe the extragalactic background light distribution. Furthermore, the simple detection of a component at very-high energies, i.e. at ~100 GeV, would solve the ambiguity about the importance of various possible emission processes, which provide barely distinguishable scenarios at lower energies.Methods. We used the results of the MAGIC telescope observation of the moderate resdhift (z ~ 0.76) GRB 080430 at energies above about 80 GeV, to evaluate the perspective for late-afterglow observations with ground based GeV/TeV telescopes.Results. We obtained an upper limit of F_{95% CL_{= 5.5 × 10^{-11^{erg cm^{-2^{s^{-1^{for the very-high energy emission of GRB 080430, which cannot set further constraints on the theoretical scenarios proposed for this object also due to the difficulties in modeling the low-energy afterglow. Nonetheless, our observations show that Cherenkov telescopes have already reached the required sensitivity to detect the GeV/TeV emission of GRBs at moderate redshift (z ≲ 0.8), provided the observations are carried out at early times, close to the onset of their afterglow phase.}}}}}}}}

10.1051/0004-6361/200913461

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Citations (18)