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18 results on '"BL Lacertae object"'

1. Multi-Band Intra-Night Optical Variability of BL Lacertae.

Author

Gaur, Haritma, Gupta, Alok C., Bachev, Rumen, Strigachev, Anton, Semkov, Evgeni, Wiita, Paul J., Minfeng Gu, and Ibryamov, Sunay

Subjects
BL Lacertae objects, ASTRONOMICAL observations, OPTICAL spectroscopy, ACTIVE galaxies, RADIO jets (Astrophysics)
Abstract

We monitored BL Lacertae frequently during 2014–2016 when it was generally in a high state. We searched for intra-day variability for 43 nights using quasi-simultaneous measurements in the B, V, R, and I bands (totaling 143 light curves); the typical sampling interval was about eight minutes. On hour-like timescales, BL Lac exhibited significant variations during 13 nights in various optical bands. Significant spectral variations are seen during most of these nights such that the optical spectrum becomes bluer when brighter. The amplitude of variability is usually greater for longer observations but is lower when BL Lac is brighter. No evidence for periodicities or characteristic variability time-scales in the light curves was found. The color variations are mildly chromatic on long timescales. [ABSTRACT FROM AUTHOR]

Published
2017
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2. Spektrale Merkmale elektromagnetischer Kaskaden in Jets von Blazaren

Author

Wendel, Christoph, Mannheim, Karl, and Wilms, Jörn

Subjects
Pair production, Broad-line region, Non-thermal radiation, Paarbildung, Markarian 501, msc:00A79, Blazar, 520 Astronomie und zugeordnete Wissenschaften, BL Lacertae object, Vacuum gap, Inverse Compton scattering, 3C 279, Electromagnetic cascades, Relativistic jet, Active galactic nucleus, Radiative processes, Compton-Streuung, BL Lacertae objects, ddc:520, Flat-spectrum radio quasar
Abstract

The extragalactic gamma-ray sky is dominated by blazars, active galactic nuclei (AGN) with a relativistic jet that is closely aligned with the line of sight. Galaxies develop an active nucleus if the central supermassive black hole (BH) accretes large amounts of ambient matter and magnetic flux. The inflowing mass accumulates around the plane perpendicular to the accretion flow's angular momentum. The flow is heated through viscous friction and part of the released energy is radiated as blackbody or non-thermal radiation, with luminosities that can dominate the accumulated stellar luminosity of the host galaxy. A fraction of the accretion flow luminosity is reprocessed in a surrounding field of ionised gas clouds. These clouds, revolving around the central BH, emit Doppler-broadened atomic emission lines. The region where these broad-line-emitting clouds are located is called broad-line region (BLR). About one in ten AGN forms an outflow of radiation and relativistic particles, called a relativistic jet. According to the Blandford-Znajek mechanism, this is facilitated through electromagnetic processes in the magnetosphere of a spinning BH. The latter induces a magnetospheric poloidal current circuit, generating a decelerating torque on the BH and inducing a toroidal magnetic field. Consequently, rotational energy of the BH is converted to Poynting flux streaming away mainly along the rotational axis and starting the jet. One possibility for particle acceleration near the jet base is realised by magnetospheric vacuum gaps, regions temporarily devoid of plasma, such that an intermittent electric field arises parallel to the magnetic field lines, enabling particle acceleration and contributing to the mass loading of the jets. Magnetised structures, containing bunches of relativistic electrons, propagate away from the galactic nucleus along the jets. Assuming that these electrons emit synchrotron radiation and that they inverse-Compton (IC) up-scatter abundant target photons, which can either be the synchrotron photons themselves or photons from external emitters, the emitted spectrum can be theoretically determined. Additionally taking into account that these emission regions move relativistically themselves and that the emission is Doppler-boosted and beamed in forward direction, the typical two-hump spectral energy distribution (SED) of blazars is recovered. There are however findings that challenge this well-established model. Short-time variability, reaching down to minute scales at very high energy gamma rays, is today known to be a widespread phenomenon of blazars, calling for very compact emission regions. In most models of such optically thick emission regions, the gamma-ray flux is usually pair-absorbed exponentially, without considering the cascade evolving from the pair-produced electrons. From the observed flux, it is often concluded that emission emanates from larger distances where the region is optically thin, especially from outside of the BLR. Only in few blazars gamma-ray attenuation associated with pair absorption in the BLR was clearly reported. With the advent of sophisticated high-energy or very high energy gamma-ray detectors, like the Fermi Large Area Telescope or the Major Atmospheric Gamma-ray Imaging Cherenkov telescopes, besides the extraordinarily fast variability spectral features have been found that cannot be explained by conventional models reproducing the two-hump SED. Two such narrow spectral features are discussed in this work. For the nearby blazar Markarian 501, hints to a sharp peak around 3 TeV have been reported from a multi-wavelength campaign carried out in July 2014, while for 3C 279 a spectral dip was found in 2018 data, that can hardly be described with conventional fitting functions. In this work it is examined whether these spectral peculiarities of blazar jet emission can be explained, if the full radiation reprocessing through an IC pair cascade is accounted for. Such a cascade is the multiple concatenation of IC scattering events and pair production events. In the cascades generally considered in this work, relativistic electrons and high-energy photons are injected into a fixed soft target photon field. A mathematical description for linear IC pair cascades with escape terms is delivered on the basis of preliminary works. The steady-state kinetic equations for the electrons and for the photons are determined, whereby it is paid attention to an explicit formulation and to motivating the correct integration borders of all integrals from kinematic constraints. In determining the potentially observable gamma-ray flux, both the attenuated injected flux and the flux evolving as an effect of IC up-scattering, pair absorption and escape are incorporated, giving the emerging spectra very distinct imprints. Much effort is dedicated to the numerical solution of the electrons' kinetic equation via iterative schemes. It is explained why pointwise iteration from higher to lower Lorentz factors is more efficient than iterating the whole set of sampling points. The algorithm is parallelised at two positions. First, several workers can perform pointwise iterations simultaneously. Second, the most demanding integral is cut into a number of part integrals which can be determined by multiple workers. Through these measures, the Python code can be readily applied to simulate steady-state IC pair cascades with escape. In the case of Markarian 501 the developed framework is as follows. The AGN hosts an advection-dominated accretion flow with a normalised accretion rate of several \(10^{-4}\) and an electron temperature near \(10^{10}\) K. On the one hand, the accretion flow illuminates the few ambient gas clouds with approximate radius \(10^{11}\) m, which reprocess a fraction 0.01 of the luminosity into hydrogen and helium emission lines. On the other hand, the gamma rays from the accretion flow create electrons and positrons in a sporadically active vacuum gap in the BH magnetosphere. In the active gap, a power of roughly 0.001 of the Blandford-Znajek power is extracted from the rotating BH through a gap potential drop of several \(10^{18}\) V, generating ultra-relativistic electrons, which subsequently are multiplied by a factor of about \(10^6\) through interaction with the accretion flow photons. This electron beam propagates away from the central engine and encounters the photon field of one passing ionised cloud. The resulting IC pair cascade is simulated and the evolving gamma-ray spectrum is determined. Just above the absorption troughs due to the hydrogen lines, the spectrum exhibits a narrow bump around 3 TeV. When the cascaded emission is added to the emission generated at larger distances, the observed multi-wavelength SED including the sharp peak at 3 TeV is reproduced, underlining that radiation processes beyond conventional models are motivated by distinct spectral features. The dip in the spectrum of 3C 279 is addressed by a similar cascade model. Three types of injection are considered, varying in the ratio of the photon density to the electron density and varying in the spectral shape. The IC pair cascade is assumed to happen either in the dense BLR photon field with a luminosity of several \(10^{37}\) W and a radial size of few \(10^{14}\) m or in the diluted photon field outside of the BLR. The latter scenario is however rejected as the spectral slope around several 100 MeV and the dip at few 10 GeV cannot be reconciled within this model. The radiation cascaded in the BLR can explain the observational data, irrespective of the assumed injected rate. It is therefore concluded that for this period of gamma-ray emission, the radiation production happens at the edge of the BLR of 3C 279. Both investigations show that IC pair cascades can account for fine structure seen in blazar SEDs. It is insufficient to restrict the radiation transport to pure exponential absorption of an injection term. Pair production and IC up-scattering by all generations of photons and electrons in the optically thick regime critically shape the emerging spectra. As the advent of future improved detectors will provide more high-precision spectra, further observations of narrow spectral features can be expected. It seems therefore recommendable to incorporate cascading into conventional radiation production models or to extend the model developed in this work by synchrotron radiation., Beobachtet man das Firmament im Licht der Gammastrahlung, stellen Blasare die Mehrzahl extragalaktischer Objekte dar. Blasare sind aktive Galaxienkerne mit einem relativistischen Jet, der entlang der Sichtlinie ausgerichtet ist. Galaxien haben einen aktiven Kern, wenn das zentrale supermassereiche Schwarze Loch große Mengen an Umgebungsmaterie und magnetischem Fluss akkretiert. Die nach Innen strömende Masse sammelt sich nahe der Ebene an, die senkrecht zum Drehimpuls des Akkretionsflusses steht. Das akkretierte Material wird durch viskose Reibung aufgeheizt und ein Teil der freigesetzten Energie wird als Schwarzkörper- oder nicht-thermische Strahlung abgestrahlt, deren Leuchtkraft die gesamte stellare Leuchtkraft der Wirtsgalaxie übertreffen kann. Ein Teil der Leuchtkraft des Akkretionsflusses wird in einem umgebenden Feld von ionisierten Gaswolken reprozessiert. Diese Wolken, die um das zentrale Schwarze Loch kreisen, emittieren Doppler-verbreiterte Emissionslinien. Den Teil des aktiven Galaxienkerns, in dem sich diese Wolken befinden, bezeichnet man als BLR (englisch: broad-line region). Ihr Abstand zum zentralen Schwarzen Loch beträgt typischerweise etwa 0,1 pc. Etwa einer von zehn aktiven Galaxienkernen bildet einen Ausfluss von Strahlung und relativistischen Teilchen aus, einen sogenannten relativistischen Jet. Dies wird gemäß dem Blandford-Znajek-Mechanismus durch elektromagnetische Prozesse in den Magnetosphären rotierender Schwarzer Löcher bewerkstelligt. Letztere induzieren einen poloidalen magnetosphärischen Stromkreis, der ein abbremsendes Drehmoment auf das Schwarze Loch ausübt und ein toroidales Magnetfeld erzeugt. Folglich wird die Rotationsenergie des Schwarzen Lochs in Poynting-Fluss umgewandelt, der hauptsächlich entlang der Rotationsachse abfließt und den Jet entstehen lässt. Durch Prozesse, die noch nicht eindeutig identifiziert wurden, werden geladene Teilchen in der Nähe der Jetbasis beschleunigt. Eine Möglichkeit dafür ist Teilchenbeschleunigung in magnetosphärischen Vakuum-Lücken. Dies sind Regionen, die vorübergehend nahezu frei von Plasma sind, sodass zeitweise ein elektrisches Feld parallel zu den Magnetfeldlinien entsteht, das die Teilchenbeschleunigung ermöglicht und zur Aufladung der Jets mit massebehafteten Teilchen beiträgt. Magnetisierte Strukturen, die relativistische Elektronen enthalten, bewegen sich entlang der Jets vom Galaxienkern weg. Unter der Annahme, dass diese Elektronen Synchrotronstrahlung aussenden und dass sie vorhandenen weichen Photonen, die entweder die Synchrotronphotonen selbst oder Photonen von externen Emittern sein können, durch inverse Compton-Streuung höhere Energien verleihen, kann das emittierte Spektrum berechnet werden. Berücksichtigt man zusätzlich, dass sich diese Emissionsgebiete selbst relativistisch bewegen und dass die Emission Doppler-verstärkt ist und bevorzugt in Vorwärtsrichtung abgestrahlt wird, erhält man die typische zweihöckrige spektrale Energieverteilung von Blasaren. Es gibt jedoch Erkenntnisse, die dieses bewährte Modell in Frage stellen. Kurzzeit-Variabilität, die bei sehr hochenergetischer Gammastrahlung bis zu Minuten-Skalen hinunterreicht, ist ein weit verbreitetes Phänomen bei Blasaren und setzt sehr kompakte Emissionsregionen voraus. In den meisten Modellen für solche optisch dicken Emissionsregionen wird der Gammastrahlenfluss durch Paarbildung lediglich exponentiell absorbiert, ohne die Kaskade zu berücksichtigen, die sich durch die erzeugten Elektronen entwickelt. Aus den Beobachtungen wird oft gefolgert, dass die Emission aus optisch dünnen Regionen bei größeren Entfernungen stammt, insbesondere von außerhalb der BLR. Nur bei wenigen Blasaren wurde eine Abschwächung der Gammastrahlung durch Absorption in der BLR eindeutig nachgewiesen. Durch moderne Gammastrahlen-Detektoren, wie das Fermi Large Area Telescope oder den Major Atmospheric Gamma-ray Imaging Cherenkov Teleskopen, wurden neben der Kurzzeit-Variabilität auch spektrale Merkmale gefunden, die nicht durch konventionelle Modelle, die die zweihöckrigen spektralen Energieverteilungen wiedergeben können, erklärt werden können. Zwei solcher besonderen spektralen Merkmale werden in dieser Arbeit diskutiert. Für den Blasar Markarian 501 wurden bei einer im Juli 2014 durchgeführten Multiwellenlängenkampagne Hinweise auf einen schmalen Buckel bei 3 TeV gefunden, während für 3C 279 in Daten von 2018 eine Mulde im Spektrum gefunden wurde, die mit oft verwendeten Fit-Funktionen nur schlecht beschrieben werden kann. In dieser Arbeit wird untersucht, ob diese spektralen Besonderheiten der Blasar-Jet-Emission erklärt werden können, wenn die vollständige Reprozessierung der Strahlung durch eine inverse Compton-Paar-Kaskade berücksichtigt wird. Eine solche Kaskade ist die mehrfache Aneinanderreihung von inverser Compton-Streuung und Paarproduktion. Bei den in dieser Arbeit allgemein betrachteten Kaskaden werden relativistische Elektronen und hochenergetische Photonen in eine Region mit niederenergetischen Photonen konstanter Dichte injiziert. Auf der Grundlage von Vorarbeiten wird eine mathematische Beschreibung für lineare inverse Compton-Paar-Kaskaden mit Entweichtermen ausgearbeitet. Es werden die zeit-unabhängigen kinetischen Gleichungen für Elektronen und Photonen hergeleitet, wobei auf eine vollständige Formulierung und auf die Begründung der korrekten Integrationsgrenzen aller Integrale durch die kinematischen Vorgaben geachtet wird. Bei der Bestimmung des potentiell beobachtbaren Gammastrahlenflusses werden sowohl der teilweise absorbierte, injizierte Fluss als auch der Fluss, der sich als Effekt der inversen Compton-Streuung, der Paar-Absorption und des Entweichens ergibt, einbezogen, was den entstehenden Spektren charakteristische Formen aufprägt. Die kinetische Gleichung der Elektronen wird durch iterative Vorgehensweisen numerisch gelöst. Es wird erklärt, warum eine punktweise Iteration von höheren zu niedrigeren Lorentz-Faktoren effizienter ist als die Iteration des gesamten Satzes von Stützstellen. Der Algorithmus wird an zwei Stellen parallelisiert. Erstens können mehrere Prozessor-Kerne gleichzeitig punktweise Iterationen durchführen. Zweitens wird das rechenintensivste Integral in mehrere Teilintegrale zerlegt, die von mehreren Kernen berechnet werden können. Durch diese Maßnahmen kann der Python-Code zur Simulation von zeitunabhängigen inversen Compton-Paar-Kaskaden eingesetzt werden. Im Fall von Markarian 501 wird folgendes Modell bemüht. Der aktive Galaxienkern hat einen advektionsdominierten Akkretionsfluss mit einer normalisierten Akkretionsrate von mehreren \(10^{-4}\) und einer Elektronentemperatur um \(10^{10}\) K. Einerseits bestrahlt der Akkretionsfluss die wenigen umgebenden Gaswolken mit ungefährem Radius von \(10^{11}\) m, die einen Faktor 0,01 der Leuchtkraft in Form von Wasserstoff- und Helium-Emissionslinien wieder abstrahlen. Andererseits erzeugen die vom Akkretionsfluss stammenden Gammaphotonen in einer zeitweise aktiven Vakuum-Lücke in der Magnetosphäre des Schwarzen Lochs Elektronen und Positronen. In der geöffneten Lücke wird dem rotierenden Schwarzen Loch durch einen Potentialunterschied von mehreren \(10^{18}\) V eine Leistung von etwa 0,001 der Blandford-Znajek-Leistung entzogen, wodurch ultra-relativistische Elektronen erzeugt werden, die anschließend durch Wechselwirkung mit den Photonen des Akkretionsflusses um einen Faktor von etwa \(10^6\) multipliziert werden. Dieser Elektronenstrahl verlässt die Magnetosphäre und trifft auf das Photonenfeld einer vorbeiziehenden ionisierten Wolke. Die daraus resultierende inverse Compton-Paar-Kaskade wird simuliert und das sich ergebende Gammastrahlenspektrum wird berechnet. Unmittelbar oberhalb der durch die Wasserstofflinien verursachten Absorptionströge erscheint bei rund 3 TeV ein schmaler Höcker. Wenn die Strahlung der Kaskade der aus größerer Entfernung stammenden Strahlung überlagert wird, wird die gesamte spektrale Energieverteilung einschließlich des scharfen Buckels bei 3 TeV reproduziert. Das bedeutet, dass schmale spektrale Merkmale für die Relevanz von Strahlungsprozessen sprechen, die über konventionelle Modelle hinausgehen. Der Trog im Spektrum von 3C 279 wird mit einem ähnlichen Kaskadenmodell untersucht. Es werden drei Fälle der Injektion betrachtet, die sich im Verhältnis der Photonen-Anzahl zur Elektronen-Anzahl und im spektralen Verlauf unterscheiden. Es wird angenommen, dass die Kaskade entweder im dichten Photonenfeld der BLR mit einer Leuchtkraft von mehreren \(10^{37}\) W und einer radialen Ausdehnung von einigen \(10^{14}\) m oder im ausgedünnten Photonenfeld außerhalb der BLR stattfindet. Das letztgenannte Szenario muss jedoch verworfen werden, da die spektrale Steigung bei einigen 100 MeV und der Absorptionstrog bei einigen 10 GeV innerhalb dieses Modells nicht miteinander in Einklang gebracht werden können. Die innerhalb der BLR kaskadierte Strahlung kann die Beobachtungsdaten unabhängig von der angenommenen Injektionsrate erklären. Daraus folgt, dass die Gammastrahlung während dieses Emissionsereignisses am Rande der BLR von 3C 279 produziert wird. Beide Untersuchungen zeigen, dass inverse Compton-Paar-Kaskaden Feinstrukturen in der spektralen Energieverteilung von Blasaren erklären können. Es reicht nicht aus, den Strahlungstransport auf reine exponentielle Absorption eines Injektionsterms zu beschränken. Paarbildung und inverse Compton-Streuung im optisch dicken Bereich und über alle Generationen von Photonen und Elektronen hinweg prägen die entstehenden Spektren entscheidend. Da künftige, verbesserte Detektoren detailliertere Spektren liefern werden, darf man weitere Berichte über schmale spektrale Merkmale erwarten. Es erscheint daher empfehlenswert, die Kaskadierung in konventionelle Modelle der Strahlungsproduktion mit einzubeziehen oder das in dieser Arbeit entwickelte Modell um Synchrotronstrahlung zu erweitern.

Published
2022
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3. Incremental Fermi Large Area Telescope Fourth Source Catalog

Author

Abdollahi, Soheila, Acero, Fabio, Bloom, Elliott, Orienti, Monica, Orlando, Elena, Paneque, David, Pei, Zhiyuan, Perkins, Jeremy S., Persic, Massimo, Pesce-Rollins, Melissa, Petrosian, Vahe, Pillera, Roberta, Poon, Helen, Bonino, Raffaella, Porter, Troy A., Principe, Giacomo, Raino, Silvia, Rando, Riccardo, Rani, Bindu, Razzano, Massimiliano, Razzaque, Soebur, Reimer, Anita, Reimer, Olaf, Reposeur, Thierry, Brill, Ari, Sanchez-Conde, Miguel A., Saz Parkinson, Pablo M., Scotton, Lorenzo, Serini, Davide, Sgro, Carmelo, Siskind, Eric J., Smith, David A., Spandre, Gloria, Spinelli, Paolo, Sueoka, Kohei, Britto, Richard J., Suson, Dan J., Tajima, Hiro, Tak, Dongguen, Thayer, Jana B., Thompson, David J., Torres, Diego F., Troja, Eleonora, Valverde, Janeth, Wood, Kent, Zaharijas, Gabrijela, Bruel, Philippe, Fermi-LAT Collaboration, Burnett, Toby H., Buson, Sara, Cameron, Rob A., Caputo, Regina, Caraveo, Patrizia A., Baldini, Luca, Castro, Daniel, Chaty, Sylvain, Cheung, Teddy C., Chiaro, Graziano, Cibrario, Nicolo, Ciprini, Stefano, Coronado-Blazquez, Javier, Crnogorcevic, Milena, Cutini, Sara, D'Ammando, Filippo, Ballet, Jean, De Gaetano, Salvatore, Digel, Seth W., Di Lalla, Niccolo, Dirirsa, Feraol F., Di Venere, Leonardo, Dominguez, Alberto, Fallah Ramazani, Vandad, Fegan, Stephen J., Ferrara, Elizabeth C., Fiori, Alessio, Bastieri, Denis, Fleischhack, Henrike, Franckowiak, Anna, Fukazawa, Yasushi, Funk, Stefan, Fusco, Piergiorgio, Galanti, Giorgio, Gammaldi, Viviana, Gargano, Fabio, Garrappa, Simone, Gasparrini, Dario, Bellazzini, Ronaldo, Giacchino, Federica, Giglietto, Nico, Giordano, Francesco, Giroletti, Marcello, Glanzman, Thomas, Green, David, Grenier, Isabelle A., Grondin, Marie-Helene, Guillemot, Lucas, Guiriec, Sylvain, Berenji, Bijan, Gustafsson, Michael, Harding, Alice K., Hays, Liz, Hewitt, John W., Hays, E., Horan, Deirdre, Hou, Xian, Johannesson, Gudlaugur, Karwin, Christopher M., Kayanoki, Taishu, Berretta, Alessandra, Kerr, Matthew T., Kuss, Michael, Landriu, David, Larsson, Stefan, Latronico, Luca, Lemoine-Goumard, Marianne, Li, Jian, Liodakis, Ioannis, Longo, Francesco, Loparco, Francesco, Bissaldi, Elisabetta, Lott, Benoit, Lubrano, Pasquale, Maldera, Simone, Malyshev, Dmitry, Manfreda, Alberto, Marti-Devesa, Guillem, Mazziotta, Mario N., Mereu, Isabella, Meyer, Manuel, Michelson, Peter F., Blandford, Roger D., Mirabal, Nestor, Mitthumsiri, Warit, Mizuno, Tsunefumi, Moiseev, Alex A., Monzani, Maria E., Morselli, Aldo, Moskalenko, Igor V., Negro, Michela, Nuss, Eric, Omodei, Nicola, European Space Agency, National Science Foundation (US), National Aeronautics and Space Administration (US), Department of Energy (US), Agenzia Spaziale Italiana, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, and UAM. Departamento de Física Teórica

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Física, Astronomy and Astrophysics, Galaxies, Astronomi, astrofysik och kosmologi, Space and Planetary Science, BL Lacertae Object, Astronomy, Astrophysics and Cosmology, ddc:520, ddc:530, Física nuclear, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Blazars
Abstract

Abdollahi et al., We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi Large Area Telescope (LAT) catalog of γ-ray sources. Based on the first 12 years of science data in the energy range from 50 MeV to 1 TeV, it contains 6658 sources. The analysis improves on that used for the 4FGL catalog over eight years of data: more sources are fit with curved spectra, we introduce a more robust spectral parameterization for pulsars, and we extend the spectral points to 1 TeV. The spectral parameters, spectral energy distributions, and associations are updated for all sources. Light curves are rebuilt for all sources with 1 yr intervals (not 2 month intervals). Among the 5064 original 4FGL sources, 16 were deleted, 112 are formally below the detection threshold over 12 yr (but are kept in the list), while 74 are newly associated, 10 have an improved association, and seven associations were withdrawn. Pulsars are split explicitly between young and millisecond pulsars. Pulsars and binaries newly detected in LAT sources, as well as more than 100 newly classified blazars, are reported. We add three extended sources and 1607 new point sources, mostly just above the detection threshold, among which eight are considered identified, and 699 have a plausible counterpart at other wavelengths. We discuss the degree-scale residuals to the global sky model and clusters of soft unassociated point sources close to the Galactic plane, which are possibly related to limitations of the interstellar emission model and missing extended sources., The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Études Spatiales in France. This work is performed in part under DOE Contract DE-AC02-76SF00515. This work made extensive use of the ATNF pulsar catalog 102 (Manchester et al. 2005). This research has made use of the NASA/IPAC Extragalactic Database (NED; 2019), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, and of archival data, software, and online services provided by the ASI Science Data Center (ASDC) operated by the Italian Space Agency.

Published
2022
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4. The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope: Data Release 3

Author

collaboration, The Fermi-LAT, Ajello, Marco, Baldini, Luca, Ballet, Jean, Bastieri, Denis, Gonzalez, Josefa Becerra, Bellazzini, Ronaldo, Berretta, Alessandra, Bissaldi, Elisabetta, Bonino, Raffaella, Brill, Ari, Bruel, Philippe, Buson, Sara, Caputo, Regina, Caraveo, Patrizia, Cheung, Teddy, Chiaro, Graziano, Cibrario, Nicolo, Ciprini, Stefano, Crnogorcevic, Milena, Cutini, Sara, D'Ammando, Filippo, De Gaetano, Salvatore, Di Lalla, Niccolo, Di Venere, Leonardo, Dominguez, Alberto, Ramazani, Vandad Fallah, Ferrara, Elizabeth, Fiori, Alessio, Fukazawa, Yasushi, Funk, Stefan, Fusco, Piergiorgio, Gammaldi, Viviana, Gargano, Fabio, Garrappa, Simone, Gasparrini, Dario, Giglietto, Nico, Giordano, Francesco, Giroletti, Marcello, Green, David, Grenier, Isabelle, Guiriec, Sylvain, Horan, Deirdre, Hou, Xian, Kayanoki, Taishu, Kuss, Michael, Larsson, Stefan, Latronico, Luca, Lewis, Tiffany, Li, Jian, Liodakis, Ioannis, Longo, Francesco, Loparco, Francesco, Lott, Benoit, Lovellette, Michael, Lubrano, Pasquale, Madejski, Grzegorz, Maldera, Simone, Manfreda, Alberto, Marti-Devesa, Guillem, Mazziotta, Mario Nicola, Mereu, Isabella, Michelson, Peter, Mirabal, Nestor, Mitthumsiri, Warit, Mizuno, Tsunefumi, Monzani, Maria Elena, Morselli, Aldo, Moskalenko, Igor, Negro, Michela, Ojha, Roopesh, Orienti, Monica, Orlando, Elena, Ormes, Jonathan F., Pei, Zhiyuan, Pena-Herazo, Harold A., Persic, Massimo, Pesce-Rollins, Melissa, Petrosian, Vahe, Pillera, Roberta, Poon, Helen, Porter, Troy, Principe, Giacomo, Raino, Silvia, Rando, Riccardo, Rani, Bindu, Razzano, Massimiliano, Razzaque, Soebur, Reimer, Anita, Reimer, Olaf, Scargle, Jeff, Scotton, Lorenzo, Serini, Davide, Sgro, Carmelo, Siskind, Eric J., Spandre, Gloria, Spinelli, Paolo, Suson, Dan, Tajima, Hiro, Torres, Diego F., Valverde, Janeth, Yassin, Hend, Zaharijas, Gabrijela, UAM. Departamento de Física Teórica, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Deux Infinis Bordeaux (LP2I - Bordeaux), Université de Bordeaux (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), and Fermi-LAT

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Active galactic nuclei, Astrophysics of Galaxies, Active galactic nuclei, Gamma ray astronomy, Blazars, Flat spectrum radio quasars, BL Lacertae objects, Spectral energy distribution, High Energy Astrophysical Phenomena, Astrophysics of Galaxies, FOS: Physical sciences, Física, Astronomy and Astrophysics, Flat spectrum radio quasars, Galaxies, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), BL Lacertae Object, Gamma ray astronomy, BL Lacertae objects, ddc:520, ddc:530, Física nuclear, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Blazars, High Energy Astrophysical Phenomena, Spectral energy distribution
Abstract

The astrophysical journal / Supplement series 263(2), 24 (2022). doi:10.3847/1538-4365/ac9523, An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 yr of E > 50 MeV gamma-ray data, where the spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The new reported AGNs include 587 blazar candidates and four radio galaxies. We describe the properties of the new sample and outline changes affecting the previously published one. We also introduce two new parameters in this release, namely the peak energy of the SED high-energy component and the corresponding flux. These parameters allow an assessment of the Compton dominance, the ratio of the inverse-Compton to the synchrotron-peak luminosities, without relying on X-ray data., Published by Univ. of Chicago Press, Chicago, Ill. [u.a.]

Published
2022
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5. New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes*

Author

D. Fidalgo, K. Nishijima, R. Mirzoyan, B. Machado de Oliveira Fraga, P. Majumdar, P. Temnikov, L. Bellizzi, H. Kubo, M. Vazquez Acosta, M. I. Martínez, B. De Lotto, D. Dominis Prester, S. Paiano, I. Šnidarić, C. Nigro, Y. Iwamura, A. Carosi, Stefano Covino, M. Makariev, Alice Donini, A. Rugliancich, P. Munar-Adrover, G. Vanzo, Satoshi Fukami, John Hoang, Massimo Persic, J. Becerra González, Kazuma Ishio, T. Saito, S. Ansoldi, M. Palatiello, V. Fallah Ramazani, Jordi Delgado, C. Maggio, M. Delfino, S. Gasparyan, Elisa Prandini, Francesco Dazzi, Saverio Lombardi, A. Lamastra, Saša Mićanović, A. Berti, V. Vitale, J. Kushida, Kari Nilsson, Dario Hrupec, D. Lelas, A. Arbet Engels, M. Mallamaci, L. Maraschi, Elisa Bernardini, Fabrizio Tavecchio, P. Peñil, Vitaly Neustroev, Elina Lindfors, Ll. Font, M. Peresano, K. Noda, U. Colin, N. Godinović, Mitsunari Takahashi, E. Molina, David Paneque, A. Biland, W. Bednarek, W. Bhattacharyya, A. Fattorini, Ž. Bošnjak, M. Will, Anne M. Lohfink, A. Somero, Luca Tosti, Antonio Stamerra, P. Da Vela, C. Fruck, F. D'Ammando, D. Guberman, Katsuaki Asano, K. Mannheim, R. Carosi, M. Minev, Francesco Longo, Jose Luis Contreras, M. Teshima, A. Hahn, R. J. García López, G. Maneva, L. Nogués, Susumu Inoue, I. Puljak, M. V. Fonseca, Abelardo Moralejo, Nicola Giglietto, J. van Scherpenberg, Juan Cortina, Ferdinando Giordano, Kevin Schmidt, E. Moretti, D. Miceli, U. Barres de Almeida, Victoria Moreno, Valerio Vagelli, B. Banerjee, Shunsuke Sakurai, A. Babić, F. Di Pierro, D. Hadasch, M. Ribó, Oscar Blanch, T. Schweizer, Serena Loporchio, Marina Manganaro, A. De Angelis, A. Chilingaryan, Dominik Baack, M. Strzys, S. Cikota, Daniel Kerszberg, P. G. Prada Moroni, Chiara Righi, V. D'Elia, Wolfgang Rhode, G. Ceribella, M. López, Konstancja Satalecka, D. Mazin, Michele Doro, C. Arcaro, G. Busetto, Ciro Bigongiari, D. Zarić, Matteo Cerruti, R. López-Coto, Tomohiro Inada, J. Herrera, Léa Jouvin, F. Leone, Julian Sitarek, G. Ferrara, D. Dorner, Louis Antonelli, E. Colombo, D. Morcuende, N. Torres-Albà, M. Garczarczyk, I. Vovk, Dorota Sobczyńska, Victor A. Acciari, Y. Chai, Moritz Hütten, D. Strom, J. Rico, R. Paoletti, J. Besenrieder, David H. Green, T. Surić, M. Gaug, L. Di Venere, G. Bonnoli, D. Elsaesser, D. Ninci, Jose Miguel Miranda, E. Do Souto Espiñeira, Tomislav Terzić, S. M. Colak, Juan Abel Barrio, Narek Sahakyan, A. López-Oramas, Yusuke Suda, Carlo Vigorito, L. Saha, J. M. Paredes, Francesco Tombesi, Seiya Nozaki, Davide Depaoli, L. Foffano, M. Mariotti, Laboratoire d'Annecy de Physique des Particules (LAPP/Laboratoire d'Annecy-le-Vieux de Physique des Particules), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), MAGIC, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. A., Asano, K., Baack, D., Babic, A., Banerjee, B., De Almeida, U. B., Barrio, J. A., Gonzalez, J. B., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingaryan, A., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Vela, P. D., Dazzi, F., Angelis, A. D., Lotto, B. D., Delfino, M., Delgado, J., Depaoli, D., Pierro, F. D., Venere, L. D., Souto Espieira, E. D., Prester, D. D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Ramazani, V. F., Fattorini, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Lopez, R. J. G., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Godinovic, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Hutten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jouvin, L., Kerszberg, D., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Loporchio, S., De Oliveira Fraga, B. M., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Mazin, D., Micanovic, S., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogues, L., Nozaki, S., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peil, P., Peresano, M., Persic, M., Moroni, P. G. P., Prandini, E., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Schmidt, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Suric, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Torres-Alb, N., Tosti, L., Vagelli, V., Scherpenberg, J. V., Vanzo, G., Acosta, M. V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Zaric, D., Arcaro, C., Carosi, A., D'Ammando, F., Tombesi, F., Lohfink, A., 30588766 - Arcaro, Cornelia, Laboratoire d'Annecy de Physique des Particules (LAPP), German Research Foundation, Istituto Nazionale di Fisica Nucleare, Swiss National Science Foundation, Ministerio de Economía y Competitividad (España), Department of Atomic Energy (India), Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology (Japan), Academy of Finland, Croatian Science Foundation, University of Rijeka, Polish National Agency for Academic Exchange, and European Commission

Subjects
Non-thermal radiation sources, VHE [gamma ray], Non-thermal radiation source, Astrophysics, 01 natural sciences, Relativistic jet, MAGIC (telescope), 010303 astronomy & astrophysics, model: leptonic, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, astro-ph.HE, education.field_of_study, Gamma ray, gamma ray: emission, quality, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, BL Lacertae objects, Física nuclear, Catalog, Astrophysics and Astronomy, astro-ph.GA, Astrophysics::High Energy Astrophysical Phenomena, Population, energy spectrum, FOS: Physical sciences, Proton Synchrotron, magnetization, BL Lacertae object, leptonic [model], blazar, X-ray, Settore FIS/05 - Astronomia e Astrofisica, emission [gamma ray], 0103 physical sciences, synchrotron, education, Blazar, Active galactic nuclei, Gamma-ray sources, X-ray active galactic nuclei, 010308 nuclear & particles physics, Spectral density, Astronomy and Astrophysics, Catalogues, proton synchrotron, MAGIC, Synchrotron emission, Blazars, Relativistic jets, Catalogs, Automatic Keywords, gamma ray: VHE, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ddc:520, spectral, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs., We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA 2015-68378-P, FPA2017-82729-C6-2-R, FPA2015-69210-C6- 4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016- 76012-C3-1-P, ESP2015-71662-C2-2-P, FPA2017-90566-RE DC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and by the Brazilian MCTIC, CNPq and FAPERJ. E.P. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska–Curie grant agreement No. 664931. M.C. has received financial support through the Postdoctoral Junior Leader Fellowship Programme from la Caixa Banking Foundation, grant No. LCF/BQ/LI18/11630012.

Published
2020

6. The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

Author

Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O’Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babić, A., Banerjee, B., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D’Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Do Souto Espiñera, E., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Fernández-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., García López, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Godinović, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Machado de Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Nöthe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Surić, T., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tsujimoto, S., van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Vovk, I., Will, M., Zarić, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, S. G., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, A. P., Max-Moerbeck, W., Moody, J. Ward, Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., Villata, M., (VERITAS Collaboration), (MAGIC Collaboration), (Multiwavelength Partners), Department of Energy (US), Smithsonian Institution, National Science Foundation (US), National Energy Research Scientific Computing Center (US), German Research Foundation, Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Astrofisica, Ministerio de Economía y Competitividad (España), Department of Atomic Energy (India), Japan Society for the Promotion of Science, Ministry of Education, Culture, Sports, Science and Technology (Japan), Croatian Science Foundation, University of Rijeka, Polish National Agency for Academic Exchange, National Aeronautics and Space Administration (US), Shota Rustaveli National Science Foundation, Boston University, University of Utah, Harvard University, University of California Los Angeles, Columbia University, University of Potsdam, Washington University St. Louis, California Polytechnic State University, San Luis Obispo, Iowa State University, University of Minnesota Twin Cities, Pennsylvania State University, Purdue University, California State University, East Bay, Georgia Institute of Technology, National University of Ireland, Galway, German Electron Synchrotron, University of California Santa Cruz, University of Delaware, University of Iowa, DePauw University, McGill University, Complutense University, University College Dublin, University of Wisconsin-Madison, Universidad de Buenos Aires, Cork Institute of Technology, University of Alabama, University of Chicago, Instituto de Astrofísica de Canarias, University of Udine, INAF, Osservatorio Astronomico di Roma, Swiss Federal Institute of Technology Zurich, Dortmund University, Saha Institute of Nuclear Physics, Centro Brasileiro de Pesquisas Físicas, University of Łódź, University of Siena, National Institute for Nuclear Physics, Max Planck Institute for Physics, Institute for High Energy Physics, University of Padova, University of Pisa, University of Würzburg, University of Turku, Autonomous University of Barcelona, University of Barcelona, National Academy of Sciences of the Republic of Armenia, The University of Tokyo, Bulgarian Academy of Sciences, Fudan University, University of Michigan, Ann Arbor, Western Kentucky University, CNRS, Dublin Institute for Advanced Studies, Ilia State University, Department of Electronics and Nanoengineering, St. Petersburg State University, United States Department of Energy, Universidad de Chile, Brigham Young University, California Institute of Technology, University of Colorado Denver, Aoyama Gakuin University, University of Arizona, Metsähovi Radio Observatory, Aalto-yliopisto, Aalto University, Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babic, A., Banerjee, B., Barres De Almeida, U., Barrio, J. A., Becerra Gonzalez, J., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Do Souto Espiñera, E., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Fernandez-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., Garcia Lopez, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Godinovic, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Machado De Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Nievas Rosillo, M., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogues, L., Nothe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Prada Moroni, P. G., Prandini, E., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Suric, T., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Torres-Alba, N., Tsujimoto, S., Van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Vovk, I., Will, M., Zaric, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, S. G., Kurtanidze, O. M., Kurtanidze, S. O., Lahteenmaki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, A. P., Max-Moerbeck, W., Moody, J. W., Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., and Villata, M.

Subjects
Multiple days, Gamma-ray astronomY, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Flux, Markarian galaxies, Astrophysics, Blazar, 01 natural sciences, 7. Clean energy, BL Lacertae object, High energy astrophysic, law.invention, law, Observatory, BL Lacertae objects, Blazars, High energy astrophysics, Relativistic jets, Gamma-ray astronomy, Time domain astronomy, Relativistic jet, 0103 physical sciences, MAGIC (telescope), BL lacertae objects, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Astronomy and Astrophysics, Light curve, Space and Planetary Science, Markarian galaxie, Electrónica, Electricidad, Flare
Abstract

We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsahovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ⪆ 33) and the size of the emission region (δR≲ 3.8 × 10cm) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model., This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Smithsonian Institution, and NSERC in Canada. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy’s Office of Science, and the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under contract No. DE-AC02- 05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and the collaborating institutions in the construction and operation of the instrument. The MAGIC collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2- R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015- 71662-C2-2-P, FPA201790566REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, and the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV2015-0548 and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782, the University of Rijeka Project 13.12.1.3.02, the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and the Brazilian MCTIC, CNPq, and FAPERJ. This publication makes use of data obtained at Metsähovi Radio Observatory, operated by Aalto University, Finland, and the OVRO 40 m monitoring program, which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST1109911. The UMRAO data were obtained through NSF grant AST 0607523 and NASA Fermi GI award NNX09AU16G. The St. Petersburg University team acknowledges support from Russian RFBR foundation, grant 12-02-00452. The Abastumani Observatory team acknowledges financial support by the Shota Rustaveli National Science Foundation through project FR/577/6-320/13. The Steward Observatory data were obtained under Fermi Guest Investigator Program grant NNX09AU10G. The research at Boston University is supported by NASA grant 80NSSC17K0649 and NSF grant AST-1615796. Software. VEGAS (Cogan 2008), Event Display (Daniel 2008), MARS (Moralejo et al. 2009), Fermi Science Tools81, HEASoft (FTOOLS+XANADU; HEASARC 2014), REX,85 Xspec (Arnaud 1996), emcee (Foreman-Mackey et al. 2013).

Published
2020

7. Unraveling the Complex Behavior of Mrk 421 with Simultaneous X-Ray and VHE Observations during an Extreme Flaring Activity in 2013 April

Author

Simonetta Puccetti, D. Dominis Prester, M. Makariev, Alice Donini, Sofia O. Kurtanidze, G. Bonnoli, Julian Sitarek, D. Dorner, Yoshiki Ohtani, J. Becerra González, S. Ventura, S. Ansoldi, L. Nogués, J. Besenrieder, A. Rugliancich, P. Munar-Adrover, Jose Luis Contreras, B. Jordan, I. Puljak, Pawel Gliwny, L. V. Larionova, L. Di Venere, Sunay Ibryamov, Abelardo Moralejo, M. I. Martínez, B. De Lotto, Juan Cortina, A. A. Mokrushina, E. Moretti, Kaya Mori, Maria Petropoulou, Elena G. Larionova, J. Rico, Juan Abel Barrio, Narek Sahakyan, A. Fattorini, C. Fruck, F. Del Puppo, F. Verrecchia, Victoria Moreno, Chiara Righi, M. V. Fonseca, Elina Lindfors, Justin D. Finke, D. A. Morozova, V. D'Elia, A. López-Oramas, M. G. Nikolashvili, John Hoang, Susumu Inoue, L. Maraschi, R. Paoletti, R. Reinthal, A. Strigachev, Saverio Lombardi, T. Schweizer, E. Do Souto Espiñeira, Tomislav Terzić, Ferdinando Giordano, Fabrizio Tavecchio, C. Nigro, B. Banerjee, Bernd Schleicher, A. Hahn, R. G. Chanishvili, Francesco Longo, M. Will, Shunsuke Sakurai, Ll. Font, Takeshi Oka, Davide Depaoli, Alan P. Marscher, L. Saha, D. Elsaesser, Antonio Stamerra, R. Carosi, G. Ceribella, Joni Tammi, V. Fallah Ramazani, D. Lelas, T. Guever, M. Teshima, J. M. Paredes, Dorota Sobczyńska, Zeljka Bosnjak, Chakali Eswaraiah, A. C. R. Readhead, G. Busetto, Jorge Otero-Santos, Mislav Baloković, J. L. Richards, R. A. Chigladze, Y. Chai, J. Kushida, Seiya Nozaki, Kari Nilsson, U. Barres de Almeida, L. Foffano, Ciro Bigongiari, Saša Mićanović, V. Vitale, Wen Ping Chen, P. Temnikov, T. Saito, Andrei Berdyugin, David H. Green, D. Strom, F. Di Pierro, E. N. Kopatskaya, Stefano Covino, D. Miceli, S. Gasparyan, D. Blinov, G. Maneva, E. Molina, S. G. Jorstad, T. Surić, M. Mariotti, I. Šnidarić, Satoshi Fukami, H. Kubo, M. Vazquez Acosta, R. López-Coto, Kazuma Ishio, Y. Iwamura, M. Gaug, A. Lamastra, A. C. Sadun, J. Herrera, G. Vanzo, Oscar Blanch, T. S. Grishina, Walter Max-Moerbeck, Anne Lähteenmäki, S. M. Colak, Valeri M. Larionov, C. M. Raiteri, C. Maggio, O. M. Kurtanidze, S. Cikota, D. Ninci, G. Ferrara, A. De Angelis, Rumen Bachev, Yu. V. Troitskaya, M. Minev, Georgi Latev, Elisa Bernardini, Other groups, L. Pavletić, Elisa Prandini, Goran Damljanović, Evgeni Semkov, M. Delfino, Wolfgang Rhode, Yusuke Suda, Massimo Persic, Carlo Vigorito, A. Berti, Paul S. Smith, K. Noda, Dario Hrupec, C. Leto, Victor A. Acciari, K. Nishijima, B. Machado de Oliveira Fraga, Mitsunari Takahashi, P. Peñil, L. Bellizzi, Serena Loporchio, Jose Miguel Miranda, N. Godinović, M. Strzys, Ashot Chilingarian, N. Giglietto, U. Colin, W. Bednarek, Simone Mender, Moritz Hütten, W. Bhattacharyya, I. Agudo, R. Mirzoyan, Louis Antonelli, Dominik Baack, P. Majumdar, G. M. Madejski, A. Arbet Engels, Vitaly Neustroev, J. W. Moody, Luca Tosti, M. Villata, D. Morcuende, N. Torres-Albà, I. Vovk, Jordi Delgado, H. C. Lin, Kevin Schmidt, Talvikki Hovatta, D. Hadasch, M. Palatiello, Y. Kajiwara, Francesco Dazzi, M. Mallamaci, O. Vince, M. Peresano, Yosuke Kobayashi, P. Da Vela, F. D'Ammando, K. Mannheim, R. J. García López, Ivan S. Troitsky, Tjark Miener, David Paneque, A. Biland, Marina Manganaro, P. G. Prada Moroni, Merja Tornikoski, Matteo Cerruti, M. López, Konstancja Satalecka, D. Mazin, Michele Doro, J. Barnes, F. Leone, M. Ribó, J. van Scherpenberg, A. Babić, Alessia Spolon, Léa Jouvin, Manasvita Joshi, Vassil Verguilov, Daniel Kerszberg, V. Ramakrishnan, D. Zarić, Tomohiro Inada, E. Colombo, M. Perri, M. Garczarczyk, Federal Ministry of Education and Research (Germany), Istituto Nazionale di Astrofisica, Swiss National Science Foundation, Istituto Nazionale di Fisica Nucleare, Ministerio de Economía y Competitividad (España), European Commission, Department of Atomic Energy (India), Ministry of Education, Culture, Sports, Science and Technology (Japan), Japan Society for the Promotion of Science, Ministry of Education, Youth and Science (Bulgaria), Academy of Finland, Croatian Science Foundation, University of Rijeka, German Research Foundation, National Centre for Research and Development (Poland), Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, National Aeronautics and Space Administration (US), Department of Energy (US), Centre National de la Recherche Scientifique (France), Russian Science Foundation, Gordon and Betty Moore Foundation, John Templeton Foundation, Shota Rustaveli National Science Foundation, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Metsähovi Radio Observatory, Department of Electronics and Nanoengineering, Aalto-yliopisto, Aalto University, Magic, Collaboration, Other Groups And, Collaborator, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. A., Baack, D., Babic, A., Banerjee, B., De Almeida, U. B., Barrio, J. A., Gonzalez, J. B., Bednarek, W., Bellizzi, L. K., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Vela, P. D., Dazzi, F., Angelis, A. D., Lotto, B. D., Puppo, F. D., Delfino, M., Delgado, J., Depaoli, D., Pierro, F. D., Venere, L. D., Souto Espiñeira, E. D., Prester, D. D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Ramazani, V. F., Fattorini, A., Ferrara, G., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Lopez, R. J. G., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinovic, N., Green, D., Hadasch, D., Hahn, A., Hassan, T., Herrera, J., Hoang, J., Hrupec, D., Hutten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jouvin, L., Kajiwara, Y., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Loporchio, S., De Oliveira Fraga, B. M., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Mazin, D., Mender, S., Micanovic, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogues, L., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletic, L., Peñil, P., Peresano, M., Persic, M., Moroni, P. G. P., Prandini, E., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Suric, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Torres-Alba, N., Tosti, L., Scherpenberg, J. V., Vanzo, G., Acosta, M. V., Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Zaric, D., Petropoulou, M., Finke, J., D'Ammando, F., Balokovic, M., Madejski, G., Mori, K., Puccetti, S., Leto, C., Perri, M., Verrecchia, F., Villata, M., Raiteri, C. M., Agudo, I., Bachev, R., Berdyugin, A., Blinov, D. A., Chanishvili, R., Chen, W. P., Chigladze, R., Damljanovic, G., Eswaraiah, C., Grishina, T. S., Ibryamov, S., Jordan, B., Jorstad, S. G., Joshi, M., Kopatskaya, E. N., Kurtanidze, O. M., Kurtanidze, S. O., Larionova, E. G., Larionova, L. V., Larionov, V. M., Latev, G., Lin, H. C., Marscher, A. P., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Semkov, E., Smith, P. S., Strigachev, A., Troitskaya, Y. V., Troitsky, I. S., Vince, O., Barnes, J., Guver, T., Moody, J. W., Sadun, A. C., Hovatta, T., Richards, J. L., Max-Moerbeck, W., Readhead, A. C. S., Lahteenmaki, A., Tornikoski, M., Tammi, J., Ramakrishnan, V., and Reinthal, R.

Subjects
Individual sources Mrk 421, Flux, Astrophysics, Blazar, 7. Clean energy, 01 natural sciences, Imaging Atmospheric Cherenkov observations, Gamma-ray, Active galaxie, Relativistic jet, MAGIC (telescope), BL lacertae objects, BL Lacertae objects, Blazars, Active galaxies, Markarian galaxies, Gamma-ray detectors, Gamma-rays, Relativistic jets, High energy astrophysics, Observational astronomy, 010303 astronomy & astrophysics, astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gamma ray, X-ray, Markarian galaxie, Física nuclear, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics and Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Individual sources Mrk 421, Imaging Atmospheric Cherenkov observations, MAGIC, BL Lacertae objects, Blazars, Active galaxies, Markarian galaxies, Gamma-ray detectors, Gamma-rays, Relativistic jets, High energy astrophysics, Observational astronomy, Plasmoid, Astrophysics::Cosmology and Extragalactic Astrophysics, BL Lacertae object, High energy astrophysic, 0103 physical sciences, Gamma-ray detector, 010308 nuclear & particles physics, Astronomy and Astrophysics, Magnetic reconnection, Light curve, MAGIC, 13. Climate action, Space and Planetary Science, ddc:520, High Energy Astrophysical Phenomena
Abstract

We report on a multiband variability and correlation study of the TeV blazar Mrk 421 during an exceptional flaring activity observed from 2013 April 11 to 19. The study uses, among others, data from GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT), Swift, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Large Area Telescope, Very Energetic Radiation Imaging Telescope Array System (VERITAS), and Major Atmospheric Gamma Imaging Cherenkov (MAGIC). The large blazar activity and the 43 hr of simultaneous NuSTAR and MAGIC/VERITAS observations permitted variability studies on 15 minute time bins over three X-ray bands (3-7 keV, 7-30 keV, and 30-80 keV) and three very-high-energy (VHE; >0.1 TeV) gamma-ray bands (0.2-0.4 TeV, 0.4-0.8 TeV, and >0.8 TeV). We detected substantial flux variations on multi-hour and sub-hour timescales in all of the X-ray and VHE gamma-ray bands. The characteristics of the sub-hour flux variations are essentially energy independent, while the multi-hour flux variations can have a strong dependence on the energy of the X-rays and the VHE gamma-rays. The three VHE bands and the three X-ray bands are positively correlated with no time lag, but the strength and characteristics of the correlation change substantially over time and across energy bands. Our findings favor multi-zone scenarios for explaining the achromatic/chromatic variability of the fast/slow components of the light curves, as well as the changes in the flux-flux correlation on day-long timescales. We interpret these results within a magnetic reconnection scenario, where the multi-hour flux variations are dominated by the combined emission from various plasmoids of different sizes and velocities, while the sub-hour flux variations are dominated by the emission from a single small plasmoid moving across the magnetic reconnection layer. © 2020. The American Astronomical Society. All rights reserved., The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2017-87859-P, FPA2017-85668-P, FPA2017-82729-C6-2-R, FPA2017-827 29-C6-6-R, FPA2017-82729-C6-5-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2017-87055-C2-2-P, and FPA 201790566REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO-1153/28.08.2018 and the Academy of Finland grant No. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia "Severo Ochoa" SEV-20160588 and SEV-2015-0548, and Unidad de Excelencia "Maria de Maeztu" MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and by the Brazilian MCTIC, CNPq and FAPERJ. The Fermi-LAT.Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K..A..Wallenberg Foundation, the Swedish Research Council, and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC; Italy) and the California Institute of Technology (USA). D.P. and A.B. are grateful to Amy Furniss and Wystan Benbow for providing the VERITAS VHE gamma-ray fluxes and for useful discussions about them. M.P. acknowledges support from the Lyman Jr. Spitzer Postdoctoral Fellowship and NASA Fermi grant No. 80NSSC18K1745., and J.F. is partially supported by NASA under contract S-15633Y. M.B. acknowledges support from NASA Headquarters under the NASA Earth and Space Science Fellowship Program (grant NNX14AQ07H) and the black hole Initiative at Harvard University, which is funded in part by the Gordon and Betty Moore Foundation (grant GBMF8273) and in part by the John Templeton Foundation. This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants DN 18-13/2017, DN 18-10/2017, KP06-H28/3 (2018), and KP-06-PN38/1 (2019), as well as for the Spanish MIMECO (AYA2016-80889-P, RYC-2013-14511) and the IAA-CSIC "Severo Ochoa" program SEV2017-0709. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. The Abastumani team acknowledges financial support of the project FR/638/6-320/12 by the Shota Rustaveli National Science Foundation under contract 31/77. T.G. acknowledges support from Istanbul University (Project numbers 49429 and 48285), Bilim Akademisi (BAGEP program), and TUBITAK (project numbers 13AT100-431, 13AT100-466, and 13AT60-430). The Boston University effort was supported in part by NASA grants NNX12AO90G and NNX14AQ58G. Data from the Steward Observatory spectropolarimetric monitoring project were used in this paper. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09 AU10G, NNX12AO93G, and NNX15AU81G. The OVRO 40 m monitoring program is supported in part by NASA grants NNX08AW31G and NNX11A043G and NSF grants AST-0808050 and AST-1109911. The Metsahovi team acknowledges the support from the Academy of Finland to our observing projects (numbers 212656, 210338, 121148, and others). W.M. acknowledges support from CONICYT project Basal AFB-170002.

Published
2020

8. The Peculiar Light Curve of J1415+1320: A Case Study in Extreme Scattering Events

Author

Mark Gurwell, Harish Vedantham, Roger Blandford, Rodrigo Reeves, Talvikki Hovatta, J. A. Zensus, T. J. Pearson, Walter Max-Moerbeck, Anne Lähteenmäki, Anthony C. S. Readhead, Merja Tornikoski, Léon V. E. Koopmans, Joseph L. Richards, Vasiliki Pavlidou, Vikram Ravi, and Astronomy

Subjects
PKS-1413+135, Opacity, ISM: structure, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, BL LACERTAE OBJECT, law, 0103 physical sciences, ABSORPTION, PLASMA LENSES, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Scattering, BL Lacertae objects: individual: PKS 1413+135, scattering, Astronomy and Astrophysics, Plasma, galaxies: jets, Light curve, PKS 1413+135, Astrophysics - Astrophysics of Galaxies, Lens (optics), Interstellar medium, Wavelength, HOST GALAXY, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Physics::Space Physics, Astrophysics - High Energy Astrophysical Phenomena, Parallax
Abstract

The radio light-curve of J1415+1320 (PKS 1413+135) shows time-symmetric and recurring U-shaped features across the cm-wave and mm-wave bands. The symmetry of these features points to lensing by an intervening object as the cause. U-shaped events in radio light curves in the cm-wave band have previously been attributed to Extreme scattering events (ESE). ESEs are thought to be the result of lensing by compact plasma structures in the Galactic interstellar medium, but the precise nature of these plasma structures remains unknown. Since the strength of a plasma lens evolves with wavelength $\lambda$ as $\lambda^2$, the presence of correlated variations at over a wide wavelength range casts doubt on the canonical ESE interpretation for J1415+1320. In this paper, we critically examine the evidence for plasma lensing in J1415+1320. We compute limits on the lensing strength, and the associated free-free opacity of the putative plasma lenses. We compare the observed and model ESE light curves, and also derive a lower limit on the lens distance based on the effects of parallax due to the Earth's orbit around the Sun. We conclude that plasma lensing is not a viable interpretation for J1415+1320's light curves and that symmetric U-shaped features in the radio light curves of extragalactic sources do not present {\em prima facie} evidence for ESEs. The methodology presented here is generic enough to be applicable to any plasma lensing candidate., Comment: Submitted version

Published
2017

9. Two New Catalogs of Blazar Candidates in the WISE Infrared Sky

Author

Fabio La Franca, Marco Landoni, Francesco Massaro, V. H. Chavushyan, Nuria Alvarez Crespo, Dan Milisavljevic, N. Masetti, Raffaele D'Abrusco, Alessandro Paggi, Federica Ricci, Riccardo Campana, Howard A. Smith, ITA, USA, D’Abrusco, Raffaele, Álvarez Crespo, Nuria, Massaro, Francesco, Campana, Riccardo, Chavushyan, Vahram, Landoni, Marco, La Franca, Fabio, Masetti, Nicola, Milisavljevic, Dan, Paggi, Alessandro, Ricci, Federica, and Smith, Howard A.

Subjects
BL Lacertae objects: general, Catalogs, Galaxies: active, Radiation mechanisms: non-thermal Supporting material: FITS files, catalog, Infrared, media_common.quotation_subject, Population, FOS: Physical sciences, Astrophysics, 01 natural sciences, BL Lacertae object, 0103 physical sciences, Blazar, education, 010303 astronomy & astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, education.field_of_study, 010308 nuclear & particles physics, active, radiation mechanisms: non-thermal [BL Lacertae objects, catalogs, galaxies], Astronomy and Astrophysics, radiation mechanisms: non-thermal, Space and Planetary Science, Sky, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

We present two catalogs of radio-loud candidate blazars whose WISE mid-infrared colors are selected to be consistent with the colors of confirmed gamma-ray emitting blazars. The first catalog is the improved and expanded release of the WIBRaLS catalog presented by D'Abrusco et al. (2014): it includes sources detected in all four WISE filters, spatially cross-matched with radio source in one of three radio surveys and radio-loud based on their q22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, FSRQs or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6] and [12]) only, whose mid-infrared colors are similar to those of confirmed, gamma-ray BL Lacs. KDBLLACS members area also required to have a radio counterpart and be radio-loud based on the parameter q12, defined similarly to q22 used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We crossmatch the two new catalogs with the most recent catalogs of gamma-ray sources detected by Fermi LAT instrument. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of gamma-ray unassociated sources confirmed that ~90% of these candidates are blazars, we anticipate that these new catalogs will play again an important role in the identification of the gamma-ray sky., 20 pages, 7 figures. Accepted for publication in The Astrophysical Journal Supplement Series

Published
2019

10. A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

Author

Becerra, Gonzalez Josefa, Finke, Justin D., Ojha, Roopesh, Carpenter, Bryce, Lindfors, Elina, Krauss, Felicia, Desiante, Rachele, Longo, Francesco, McEnery, Julie E., Buson, Sara, Nisson, Kari, Fallah, Ramazani Vandad, Reinthal, Riho, Takalo, Leo, Pursimo, Tapio, Boschin, Walter, Tanaka, Yasuyuki T., Itoh, Ryosuke, Inoue, Yoshiyuki, Shiki, Kensei, Fukazawa, Yasushi, Tanaka, Yasuyuki T., Gonzalez, Josefa Becerra, Itoh, Ryosuke, Finke, Justin D., Inoue, Yoshiyuki, Ojha, Roopesh, Carpenter, Bryce, Lindfors, Elina, Krauss, Felicia, Desiante, Rachele, Shiki, Kensei, Fukazawa, Yasushi, Longo, Francesco, Mcenery, Julie E., Buson, Sara, Nilsson, Kari, Ramazani, Vandad Fallah, Reinthal, Riho, Takalo, Leo, Pursimo, Tapio, and Boschin, Walter

Subjects
High energy, Photon, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, Jets-gamma ray, Astrophysics, 01 natural sciences, BL Lacertae object, Galaxie, Active-galaxies, law.invention, Jets-gamma rays, law, BL Lacertae objects, Galaxies, Galaxies-X-rays, Individual (S4 0954+65)-galaxies, Astronomy and Astrophysics, Space and Planetary Science, gamma rays: galaxies, 0103 physical sciences, Active-galaxie, BL Lacertae objects: individual (S4 0954+65), Blazar, 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), ta115, 010308 nuclear & particles physics, galaxies: jets, Astronomy and Astrophysic, Synchrotron, Individual (S4 0954+65)-galaxie, X-rays: galaxies, Galaxies-X-ray, Hardening (metallurgy), Astrophysics - High Energy Astrophysical Phenomena, Flare
Abstract

著者人数: 21名, Accepted: 2016-04-12, 資料番号: SA1160134000

Published
2016

11. The cluster-scale environment of PKS 2155-304

Author

Farina, E, Fumagalli, M, Decarli, R, Fanidakis, N, Farina E. P., Fumagalli M., Decarli R., Fanidakis N., Farina, E, Fumagalli, M, Decarli, R, Fanidakis, N, Farina E. P., Fumagalli M., Decarli R., and Fanidakis N.

Abstract

PKS 2155-304 is one of the brightest extragalactic source in the X-ray and EUV bands, and is a prototype for the BL Lac class of objects. In this paper, we investigate the large-scale environment of this source using new multi-object as well as long-slit spectroscopy, together with archival spectra and optical images. We find clear evidence of a modest overdensity of galaxies at z = 0.116 10 ± 0.000 06, consistent with previous determinations of the BL Lac redshift. The galaxy group has a radial velocity dispersion of 250-40+80 km s-1 and a virial radius of 0.22 Mpc, yielding a role-of-thumb estimate of the virial mass of Mvir ~ 1.5 × 1013 M⊙, i.e. one order of magnitude less than that observed in similar objects. This result hints towards a relatively wide diversity in the environmental properties of BL Lac objects.

Published
2016

12. Optical spectroscopic observations of gamma-ray blazar candidates. IV. results of the 2014 follow-up campaign

Author

Francesco Massaro, Howard A. Smith, Marco Landoni, Dan Milisavljevic, Federica Ricci, Raffaele D'Abrusco, Alessandro Paggi, N. Masetti, Daniel Stern, Gino Tosti, Ricci, Federica, Massaro, F., Landoni, M., D'Abrusco, R., Milisavljevic, D., Stern, D., Masetti, N., Paggi, A., Smith, Howard A., Tosti, G., ITA, USA, and RICCI, FEDERICA

Subjects
Active galactic nucleus, Radio galaxy, radiation mechanism, galaxies: active, FOS: Physical sciences, BL Lacertae objects: general , galaxies: active , radiation mechanisms: non-thermal, active, Astrophysics, BL Lacertae object, Observatory, galaxies, Blazar, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), galaxie, Quasar, Astronomy and Astrophysics, BL Lacertae objects: general, radiation mechanisms: non-thermal, BL Lacertae objects, general, non-thermal, radiation mechanisms, Redshift, Galaxy, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

The extragalactic gamma-ray sky is dominated by the emission arising from blazars, one of the most peculiar classes of radio-loud active galaxies. Since the launch of Fermi several methods were developed to search for blazars as potential counterparts of unidentified gamma-ray sources (UGSs). To confirm the nature of the selected candidates, optical spectroscopic observations are necessary. In 2013 we started a spectroscopic campaign to investigate gamma-ray blazar candidates selected according to different procedures. The main goals of our campaign are: 1) to confirm the nature of these candidates, and 2) whenever possible determine their redshifts. Optical spectroscopic observations will also permit us to verify the robustness of the proposed associations and check for the presence of possible source class contaminants to our counterpart selection. This paper reports the results of observations carried out in 2014 in the Northern hemisphere with Kitt Peak National Observatory (KPNO) and in the Southern hemisphere with the Southern Astrophysical Research (SOAR) telescopes. We also report three sources observed with the Magellan and Palomar telescopes. Our selection of blazar-like sources that could be potential counterparts of UGSs is based on their peculiar IR colors and on their combination with radio observations both at high and low frequencies (i.e., above and below ~ 1 GHz) in publicly available large radio surveys. We present the optical spectra of 27 objects. [....] We also report the case for WISE J173052.85-035247.2, candidate counterpart of the source 2FGL J1730.6-0353, which has no radio counterpart in the major radio surveys. We confirm that our selection of gamma-ray blazars candidates can successfully indentify low-energy counterparts to Fermi unassociated sources and allow us to discover new blazars., 20 pages, 30 figures, 1 table, AJ accepted for publication (pre-proof version), Abstract cut

Published
2015

13. The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies

Author

MAGIC Collaboration, J. Aleksić(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), S. Ansoldi(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), L. A. Antonelli(INAF National Institute for Astrophysics, I-00136 Rome, Italy), P. Antoranz(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), A. Babic(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), P. Bangale(Max-Planck-Institut für Physik, D-80805 München, Germany), U. Barres de Almeida(Max-Planck-Institut für Physik, D-80805 München, Germany), J. A. Barrio(Universidad Complutense, E-28040 Madrid, Spain), J. Becerra González(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), W. Bednarek(University of Lodz, PL-90236 Lodz, Poland), K. Berger(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), E. Bernardini(Deutsches Elektronen-Synchrotron), A. Biland(ETH Zurich, CH-8093 Zurich, Switzerland), O. Blanch(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), R. K. Bock(Max-Planck-Institut für Physik, D-80805 München, Germany), S. Bonnefoy(Universidad Complutense, E-28040 Madrid, Spain), G. Bonnoli(INAF National Institute for Astrophysics, I-00136 Rome, Italy), F. Borracci(Max-Planck-Institut für Physik, D-80805 München, Germany), T. Bretz(Universität Würzburg, D-97074 Würzburg, Germany), E. Carmona(Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid, Spain), A. Carosi(INAF National Institute for Astrophysics, I-00136 Rome, Italy), D. Carreto Fidalgo(Universität Würzburg, D-97074 Würzburg, Germany), P. Colin(Max-Planck-Institut für Physik, D-80805 München, Germany), E. Colombo(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), J. L. Contreras(Universidad Complutense, E-28040 Madrid, Spain), J. Cortina(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), S. Covino(INAF National Institute for Astrophysics, I-00136 Rome, Italy), P. Da Vela(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), F. Dazzi(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), A. De Angelis(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), G. De Caneva(Deutsches Elektronen-Synchrotron), B. De Lotto(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), C. Delgado Mendez(Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid, Spain), M. Doert(Technische Universität Dortmund, D-44221 Dortmund, Germany), A. Domínguez(Inst. de Astrofísica de Andalucía), D. Dominis Prester(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), D. Dorner(Universität Würzburg, D-97074 Würzburg, Germany), M. Doro(Università di Padova and INFN, I-35131 Padova, Italy), S. Einecke(Technische Universität Dortmund, D-44221 Dortmund, Germany), D. Eisenacher(Universität Würzburg, D-97074 Würzburg, Germany), D. Elsaesser(Universität Würzburg, D-97074 Würzburg, Germany), E. Farina(Università dell'Insubria, Como, I-22100 Como, Italy), D. Ferenc(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), M. V. Fonseca(Universidad Complutense, E-28040 Madrid, Spain), L. Font(Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain), K. Frantzen(Technische Universität Dortmund, D-44221 Dortmund, Germany), C. Fruck(Max-Planck-Institut für Physik, D-80805 München, Germany), R. J. García López(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), M. Garczarczyk(Deutsches Elektronen-Synchrotron), D. Garrido Terrats(Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain), M. Gaug(Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain), G. Giavitto(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), N. Godinović(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), A. González Mu\ noz(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), S. R. Gozzini(Deutsches Elektronen-Synchrotron), A. Hadamek(Technische Universität Dortmund, D-44221 Dortmund, Germany), D. Hadasch(Institut de Ciències de l'Espai), A. Herrero(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), D. Hildebrand(ETH Zurich, CH-8093 Zurich, Switzerland), J. Hose(Max-Planck-Institut für Physik, D-80805 München, Germany), D. Hrupec(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), W. Idec(University of Lodz, PL-90236 Lodz, Poland), V. Kadenius(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), H. Kellermann(Max-Planck-Institut für Physik, D-80805 München, Germany), M. L. Knoetig(ETH Zurich, CH-8093 Zurich, Switzerland), J. Krause(Max-Planck-Institut für Physik, D-80805 München, Germany), J. Kushida(Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan), A. La Barbera(INAF National Institute for Astrophysics, I-00136 Rome, Italy), D. Lelas(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), N. Lewandowska(Universität Würzburg, D-97074 Würzburg, Germany), E. Lindfors(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), F. Longo(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), S. Lombardi(INAF National Institute for Astrophysics, I-00136 Rome, Italy), M. López(Universidad Complutense, E-28040 Madrid, Spain), R. López-Coto(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), A. López-Oramas(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), E. Lorenz(Max-Planck-Institut für Physik, D-80805 München, Germany), I. Lozano(Universidad Complutense, E-28040 Madrid, Spain), M. Makariev(Inst. for Nucl. Research and Nucl. Energy, BG-1784 Sofia, Bulgaria), K. Mallot(Deutsches Elektronen-Synchrotron), G. Maneva(Inst. for Nucl. Research and Nucl. Energy, BG-1784 Sofia, Bulgaria), N. Mankuzhiyil(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), K. Mannheim(Universität Würzburg, D-97074 Würzburg, Germany), L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy), B. Marcote(Universitat de Barcelona), M. Mariotti(Università di Padova and INFN, I-35131 Padova, Italy), M. Martínez(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), D. Mazin(Max-Planck-Institut für Physik, D-80805 München, Germany), U. Menzel(Max-Planck-Institut für Physik, D-80805 München, Germany), M. Meucci(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), J. M. Miranda(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), R. Mirzoyan(Max-Planck-Institut für Physik, D-80805 München, Germany), A. Moralejo(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), P. Munar-Adrover(Universitat de Barcelona), D. Nakajima(Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan), A. Niedzwiecki(University of Lodz, PL-90236 Lodz, Poland), K. Nilsson(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), N. Nowak(6,32,*), R. Orito(Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan), A. Overkemping(Technische Universität Dortmund, D-44221 Dortmund, Germany), S. Paiano(Università di Padova and INFN, I-35131 Padova, Italy), M. Palatiello(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), D. Paneque(6,*), R. Paoletti(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), J. M. Paredes(Universitat de Barcelona), X. Paredes-Fortuny(Universitat de Barcelona), S. Partini(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), M. Persic(Università di Udine, and INFN Trieste, I-33100 Udine, Italy), F. Prada(Inst. de Astrofísica de Andalucía), P. G. Prada Moroni(Università di Pisa, and INFN Pisa, I-56126 Pisa, Italy), E. Prandini(Università di Padova and INFN, I-35131 Padova, Italy), S. Preziuso(Università di Siena, and INFN Pisa, I-53100 Siena, Italy), I. Puljak(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), R. Reinthal(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), W. Rhode(Technische Universität Dortmund, D-44221 Dortmund, Germany), M. Ribó(Universitat de Barcelona), J. Rico(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), J. Rodriguez Garcia(Max-Planck-Institut für Physik, D-80805 München, Germany), S. Rügamer(Universität Würzburg, D-97074 Würzburg, Germany), A. Saggion(Università di Padova and INFN, I-35131 Padova, Italy), K. Saito(Japanese MAGIC Consortium, Division of Physics and Astronomy, Kyoto University, Japan), M. Salvati(INAF National Institute for Astrophysics, I-00136 Rome, Italy), K. Satalecka(Universidad Complutense, E-28040 Madrid, Spain), V. Scalzotto(Università di Padova and INFN, I-35131 Padova, Italy), V. Scapin(Universidad Complutense, E-28040 Madrid, Spain), C. Schultz(Università di Padova and INFN, I-35131 Padova, Italy), T. Schweizer(Max-Planck-Institut für Physik, D-80805 München, Germany), S. N. Shore(Università di Pisa, and INFN Pisa, I-56126 Pisa, Italy), A. Sillanpää(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), J. Sitarek(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), I. Snidaric(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), D. Sobczynska(University of Lodz, PL-90236 Lodz, Poland), F. Spanier(Universität Würzburg, D-97074 Würzburg, Germany), V. Stamatescu(IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain), A. Stamerra(INAF National Institute for Astrophysics, I-00136 Rome, Italy), T. Steinbring(Universität Würzburg, D-97074 Würzburg, Germany), J. Storz(Universität Würzburg, D-97074 Würzburg, Germany), S. Sun(Max-Planck-Institut für Physik, D-80805 München, Germany), T. Surić(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), L. Takalo(Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Department of Physics, University of Oulu, Finland), F. Tavecchio(INAF National Institute for Astrophysics, I-00136 Rome, Italy), P. Temnikov(Inst. for Nucl. Research and Nucl. Energy, BG-1784 Sofia, Bulgaria), T. Terzić(Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia), D. Tescaro(Inst. de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain), M. Teshima(Max-Planck-Institut für Physik, D-80805 München, Germany), J. Thaele(Technische Universität Dortmund, D-44221 Dortmund, Germany), O. Tibolla(Universität Würzburg, D-97074 Würzburg, Germany), D. F. Torres(Institut de Ciències de l'Espai), T. Toyama(Max-Planck-Institut für Physik, D-80805 München, Germany), A. Treves(Università dell'Insubria, Como, I-22100 Como, Italy), M. Uellenbeck(Technische Universität Dortmund, D-44221 Dortmund, Germany), P. Vogler(ETH Zurich, CH-8093 Zurich, Switzerland), R. M. Wagner(Max-Planck-Institut für Physik, D-80805 München, Germany), F. Zandanel(Inst. de Astrofísica de Andalucía), R. Zanin(Universitat de Barcelona), VERITAS collaboration(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), (Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), S. Archambault(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), B. Behera(Deutsches Elektronen-Synchrotron), M. Beilicke(Department of Physics, Washington University, St. Louis, MO 63130, USA), W. Benbow(Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA), R. Bird(School of Physics, University College Dublin, Belfield, Dublin 4, Ireland), J. H. Buckley(Department of Physics, Washington University, St. Louis, MO 63130, USA), V. Bugaev(Department of Physics, Washington University, St. Louis, MO 63130, USA), M. Cerruti(Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA), X. Chen(Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany), L. Ciupik(Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605, USA), E. Collins-Hughes(School of Physics, University College Dublin, Belfield, Dublin 4, Ireland), W. Cui(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), J. Dumm(School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA), J. D. Eisch(Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA), A. Falcone(Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802, USA), S. Federici(DESY, Platanenallee 6, 15738 Zeuthen, Germany), Q. Feng(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), J. P. Finley(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), H. Fleischhack(Deutsches Elektronen-Synchrotron), P. Fortin(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA), L. Fortson(School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA), A. Furniss(Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064, USA), S. Griffin(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), S. T. Griffiths(Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242, USA), J. Grube(Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605, USA), G. Gyuk(Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605, USA), D. Hanna(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), J. Holder(Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716, USA), G. Hughes(Deutsches Elektronen-Synchrotron), T. B. Humensky(Physics Department, Columbia University, New York, NY 10027, USA), C. A. Johnson(Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064, USA), P. Kaaret(Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242, USA), M. Kertzman(Department of Physics and Astronomy, DePauw University, Greencastle, IN 46135-0037, USA), Y. Khassen(School of Physics, University College Dublin, Belfield, Dublin 4, Ireland), D. Kieda(Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA), H. Krawczynski(Department of Physics, Washington University, St. Louis, MO 63130, USA), F. Krennrich(Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA), S. Kumar(Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716, USA), M. J. Lang(School of Physics, National University of Ireland Galway, University Road, Galway, Ireland), G. Maier(Deutsches Elektronen-Synchrotron), S. McArthur(Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA), K. Meagher(School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, 837 State Street NW, Atlanta, GA 30332-0430), P. Moriarty(Department of Life and Physical Sciences, Galway-Mayo Institute of Technology, Dublin Road, Galway, Ireland), R. Mukherjee(Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027, USA), R. A. Ong(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA), A. N. Otte(School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, 837 State Street NW, Atlanta, GA 30332-0430), N. Park(Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA), A. Pichel(Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67 - Sucursal 28), M. Pohl(Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany), A. Popkow(Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA), H. Prokoph(Deutsches Elektronen-Synchrotron), J. Quinn(School of Physics, University College Dublin, Belfield, Dublin 4, Ireland), K. Ragan(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), J. Rajotte(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), P. T. Reynolds(Department of Applied Physics and Instrumentation, Cork Institute of Technology, Bishopstown, Cork, Ireland), G. T. Richards(School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, 837 State Street NW, Atlanta, GA 30332-0430), E. Roache(Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA), A. C. Rovero(Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67 - Sucursal 28), G. H. Sembroski(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), K. Shahinyan(School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA), D. Staszak(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), I. Telezhinsky(Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany), M. Theiling(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), J. V. Tucci(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), J. Tyler(Physics Department, McGill University, Montreal, QC H3A 2T8, Canada), A. Varlotta(Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA), S. P. Wakely(Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA), T. C. Weekes(Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645, USA), A. Weinstein(Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA), R. Welsing(Deutsches Elektronen-Synchrotron), A. Wilhelm(Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany), D. A. Williams(Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064, USA), B. Zitzer(Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA), External collaborators(INAF, Osservatorio Astronomico di Torino, I-10025 Pino Torinese), (INAF, Osservatorio Astronomico di Torino, I-10025 Pino Torinese), M. Villata(INAF, Osservatorio Astronomico di Torino, I-10025 Pino Torinese), C. Raiteri(INAF, Osservatorio Astronomico di Torino, I-10025 Pino Torinese), H. D. Aller(Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042, USA), M. F. Aller(Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042, USA), W. P. Chen(Graduate Institute of Astronomy, National Central University, Jhongli 32054, Taiwan), B. Jordan(School of Cosmic Physics, Dublin Institute for Advanced Studies, Dublin, 2, Ireland), E. Koptelova(Graduate Institute of Astronomy, National Central University, Jhongli 32054, Taiwan), O. M. Kurtanidze(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia), A. Lähteenmäki(Aalto University Metsähovi Radio Observatory Metsähovintie 114 FIN-02540 Kylmälä Finland), B. McBreen(University College Dublin, Belfield, Dublin 4, Ireland), V. M. Larionov(Isaac Newton Institute of Chile, St. Petersburg Branch, St. Petersburg, Russia), C. S. Lin(Graduate Institute of Astronomy, National Central University, Jhongli 32054, Taiwan), M. G. Nikolashvili(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia), E. Angelakis(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany), M. Capalbi(ASI-Science Data Center, Via del Politecnico, I-00133 Rome, Italy), A. Carrami\ nana(Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla 72840, Mexico), L. Carrasco(Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla 72840, Mexico), P. Cassaro(INAF Istituto di Radioastronomia, Sezione di Noto, Contrada Renna Bassa, 96017 Noto), A. Cesarini(Department of Physics, University of Trento, I38050, Povo, Trento, Italy), L. Fuhrmann(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany), M. Giroletti(INAF Istituto di Radioastronomia, 40129 Bologna, Italy), T. Hovatta(Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125), T. P. Krichbaum(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany), H. A. Krimm(Astro Space Center of the Lebedev Physical Institute, 117997 Moscow, Russia), W. Max-Moerbeck(Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125), J. W. Moody(Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA), G. Maccaferri(INAF Istituto di Radioastronomia, Stazione Radioastronomica di Medicina, I-40059 Medicina), Y. Mori(Department of Physics, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551, Japan), I. Nestoras(Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany), A. Orlati(INAF Istituto di Radioastronomia, Stazione Radioastronomica di Medicina, I-40059 Medicina), C. Pace(Indiana University, Department of Astronomy, Swain Hall West 319, Bloomington, IN 47405-7105, USA), R. Pearson(Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA), M. Perri(INAF National Institute for Astrophysics, I-00136 Rome, Italy), A. C. S. Readhead(Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125), J. L. Richards(Department of Physics, Purdue University, 525 Northwestern Ave, West Lafayette, IN 47907), A. C. Sadun(Department of Physics, University of Colorado, Denver, CO 80220, USA), T. Sakamoto(Department of Physics and Mathematics, College of Science and 952 Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuoku, Sagamihara-shi Kanagawa 252-5258, Japan), J. Tammi(Aalto University Metsähovi Radio Observatory Metsähovintie 114 FIN-02540 Kylmälä Finland), M. Tornikoski(Aalto University Metsähovi Radio Observatory Metsähovintie 114 FIN-02540 Kylmälä Finland), Y. Yatsu(Department of Physics, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551, Japan), A. Zook(Department of Physics and Astronomy, Pomona College, Claremont CA 91711-6312, USA), Aleksić, J, Ansoldi, Stefano, Antonelli, L. A., Antoranz, P., Babic, A., Bangale, P., Barres De Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Carreto Fidalgo, D., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Einecke, S., Eisenacher, D., Elsaesser, D., Farina, E., Ferenc, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., García López, R. J., Garczarczyk, M., Garrido Terrats, D., Gaug, M., Giavitto, G., Godinović, N., González Muñoz, A., Gozzini, S. R., Hadamek, A., Hadasch, D., Herrero, A., Hildebrand, D., Hose, J., Hrupec, D., Idec, W., Kadenius, V., Kellermann, H., Knoetig, M. L., Krause, J., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Longo, Francesco, Lombardi, S., López, M., López Coto, R., López Oramas, A., Lorenz, E., Lozano, I., Makariev, M., Mallot, K., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Meucci, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Munar Adrover, P., Nakajima, D., Niedzwiecki, A., Nilsson, K., Nowak, N., Orito, R., Overkemping, A., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes Fortuny, X., Partini, S., Persic, M., Prada, F., Prada Moroni, P. G., Prandini, E., Preziuso, S., Puljak, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Rodriguezgarcia, J., Rügamer, S., Saggion, A., Saito, K., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Spanier, F., Stamatescu, V., Stamerra, A., Steinbring, T., Storz, J., Sun, S., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Tibolla, O., Torres, D. F., Toyama, T., Treves, A., Uellenbeck, M., Vogler, P., Wagner, R. M., Zandanel, F., Zanin, R., Archambault, S., Behera, B., Beilicke, M., Benbow, W., Bird, R., Buckley, J. H., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins Hughes, E., Cui, W., Dumm, J., Eisch, J. D., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., Mcarthur, S., Meagher, K., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Park, N., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., Villata, M., Raiteri, C., Aller, H. D., Aller, M. F., Chen, W. P., Jordan, B., Koptelova, E., Kurtanidze, O. M., Lähteenmäki, A., Mcbreen, B., Larionov, V. M., Lin, C. S., Nikolashvili, M. G., Angelakis, E., Capalbi, M., Carramiñana, A., Carrasco, L., Cassaro, P., Cesarini, A., Fuhrmann, L., Giroletti, M., Hovatta, T., Krichbaum, T. P., Krimm, H. A., Max Moerbeck, W., Moody, J. W., Maccaferri, G., Mori, Y., Nestoras, I., Orlati, A., Pace, C., Pearson, R., Perri, M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Tammi, J., Tornikoski, M., Yatsu, Y., Zook, A., Department of Radio Science and Engineering, Aalto-yliopisto, Aalto University, and Universitat de Barcelona

Subjects
Astrofísica, Brightness, Ciencias Físicas, blazars, Astrophysics, telescope, x-ray variability, 01 natural sciences, Spectral line, BL Lacertae objects, individual, Mrk 421, purl.org/becyt/ford/1 [https], Raigs gamma, emission, MAGIC (telescope), 010303 astronomy & astrophysics, Physics, astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), individual: Mrk 421 [BL Lacertae objects], Galaxies: BL Lacertae objects: individual: Markarian 421, Spectral energy distribution, Electrónica, Electricidad, Astrophysics - High Energy Astrophysical Phenomena, CIENCIAS NATURALES Y EXACTAS, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, power spectra, BL Lacertae object, tev photons, 0103 physical sciences, Nucli galàctic actiu, bl lacertae objects: individual: mrk 421, Blazar, Astronomy and Astrophysics, Space and Planetary Science, Active galactic nuclei, 010308 nuclear & particles physics, light curves, Gamma rays, Institut für Physik und Astronomie, purl.org/becyt/ford/1.3 [https], Light curve, Galaxies, Galàxies, Astronomía, Crab Nebula, optical variability, active galactic nuclei, Galàxies actives, Active galaxies, markarian-421, ddc:520
Abstract

We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk421 during non-flaring activity. Such a temporally extended X-ray/VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies., Comment: Accepted for publication in A&A, 18 pages, 14 figures (v2 has a small modification in the acknowledgments, and also corrects a typo in the field "author" in the metadata)

Published
2015
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14. The host galaxy and Fermi-LAT counterpart of HESS J1943+213

Author

W. Gässler, W. Domainko, D. Peter, A. van der Wel, D. A. Sanchez, Laboratoire d'Annecy de Physique des Particules (LAPP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), and HESS

Subjects
[PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, LARGE-AREA TELESCOPE, cD, [radiation mechanisms], BL LACERTAE OBJECT, SPECTRA, Blazar, HESS - Abteilung Hofmann, Astrophysics::Galaxy Astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), CALIBRATION, Physics, SPECTROSCOPY, IDENTIFICATION, Astrophysics::Instrumentation and Methods for Astrophysics, GAMMA-RAYS, Gamma ray, Astronomy and Astrophysics, [BL Lacertae objects], Radius, BLAZARS, Astrophysics - Astrophysics of Galaxies, Galaxy, non-thermal, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Physics and Astronomy, Space and Planetary Science, Sky, Astrophysics of Galaxies (astro-ph.GA), DISCOVERY, galaxies [gamma rays], HIGH-ENERGY EMISSION, HESS J1943+213 [individual], Astrophysics - High Energy Astrophysical Phenomena, elliptical and lenticular [galaxies], BL Lac object, Fermi Gamma-ray Space Telescope
Abstract

Context. The very-high energy (VHE, E > 100 GeV) gamma-ray sky shows diverse Galactic and extragalactic source populations. For some sources the astrophysical object class could not be identified so far. Aims. The nature (Galactic or extragalactic) of the VHE gamma-ray source HESS J1943+213 is explored. We specifically investigate the proposed near-infrared counterpart 2MASS J19435624+2118233 of HESS J1943+213 and investigate the implications of a physical association. Methods. We present K-band imaging from the 3.5 m CAHA telescope of 2MASS J19435624+2118233. Furthermore, 5 years of Fermi-LAT data were analyzed to search for a high-energy (HE, 100 MeV < E < 100 GeV) counterpart. Results. The CAHA observations revealed that the near-infrared counterpart is extended with an intrinsic half light radius of 2"-2.5". These observations also show a smooth, centrally concentrated light profile that is typical of a galaxy, and thus point toward an extragalactic scenario for the VHE gamma-ray source, assuming that the near-infrared source is the counterpart of HESS J1943+213. A high-Sersic index profile provides a better fit than an exponential profile, indicating that the surface brightness profile of 2MASS J19435624+ 2118233 follows that of a typical, massive elliptical galaxy more closely than that of a disk galaxy. With Fermi-LAT a HE counterpart is found with a power-law spectrum above 1 GeV, with a normalization of (3.0 +/- 0.8(stat) +/- 0.6(sys)) x 10(-15)cm(-2)s(-1)MeV(-1) at the decorrelation energy E-dec = 15.1 GeV and a spectral index of Gamma = 1.59 +/- 0.19(stat) +/- 0.13(sys). This gamma-ray spectrum shows a rather sharp break between the HE and VHE regimes of Delta Gamma = 1.47 +/- 0.36. Conclusions. The infrared and HE data strongly favor an extragalactic origin of HESS J1943+213, where the infrared counterpart traces the host galaxy of an extreme blazar and where the rather sharp spectral break between the HE and VHE regime indicates attenuation on extragalactic background light. The source is most likely located at a redshift between 0.03 and 0.45 according to extension and EBL attenuation arguments.

Published
2014

15. The jet-disc connection in AGN

Author

Paolo Padovani, Tullia Sbarrato, Gabriele Ghisellini, Sbarrato, T, Padovani, P, and Ghisellini, G

Subjects
Accretion, Active galactic nucleus, Radiation mechanisms: non-thermal, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, BL Lacertae object, Accretion rate, Accretion disc, Astrophysics::Solar and Stellar Astrophysics, Emission spectrum, Blazar, General, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astronomy, Astronomy and Astrophysics, Accretion (astrophysics), Large sample, Quasars: general, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Gamma-rays: general
Abstract

We present our latest results on the connection between accretion rate and relativistic jet power in AGN, by using a large sample which includes mostly blazars, but contains also some radio--galaxies. The jet power can be traced by $\gamma$--ray luminosity in the case of blazars, and radio luminosity for both classes. The accretion disc luminosity is instead traced by the broad emission lines. Among blazars, we find a correlation between broad line emission and the $\gamma$--ray or radio luminosities, suggesting a direct tight connection between jet power and accretion rate. We confirm that the observational differences between blazar subclasses reflect differences in the accretion regime, but with blazars only we cannot properly access the low--accretion regime. By introducing radio--galaxies, we succeed in observing the fingerprint of the transition between radiatively efficient and inefficient accretion discs in the jetted AGN family. The transition occurs at the standard critical value $L_{\rm d}/L_{\rm Edd}\sim10^{-2}$ and it appears smooth. Below this value, the ionizing luminosity emitted by the accretion structure drops significantly., Comment: 11 pages, 6 figures. Accepted for publication in MNRAS

Published
2014

16. Multiwavelength observations of the AGN 1ES 0414+009 with veritas, FERMI-LAT, SWIFT-XRT, AND MDM

Author

E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, M. Böttcher, A. Bouvier, V. Bugaev, A. Cannon, A. Cesarini, L. Ciupik, E. Collins-Hughes, M. P. Connolly, W. Cui, R. Dickherber, J. Dumm, M. Errando, A. Falcone, S. Federici, Q. Feng, J. P. Finley, G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, S. Godambe, S. Griffin, J. Grube, G. Gyuk, D. Hanna, J. Holder, H. Huan, G. Hughes, C. M. Hui, A. Imran, O. Jameil, P. Kaaret, N. Karlsson, M. Kertzman, J. Kerr, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, K. Lee, A. S. Madhavan, P. Majumdar, S. McArthur, A. McCann, P. Moriarty, R. Mukherjee, T. Nelson, A. O'Faoláin de Bhróithe, R. A. Ong, M. Orr, A. N. Otte, N. Park, J. S. Perkins, A. Pichel, M. Pohl, J. Quinn, K. Ragan, P. T. Reynolds, E. Roache, J. Ruppel, D. B. Saxon, M. Schroedter, G. H. Sembroski, G. D. Şentürk, A. W. Smith, D. Staszak, M. Stroh, I. Telezhinsky, G. Tešić, M. Theiling, S. Thibadeau, K. Tsurusaki, A. Varlotta, V. V. Vassiliev, M. Vivier, S. P. Wakely, J. E. Ward, A. Weinstein, R. Welsing, D. A. Williams, and B. Zitzer

Subjects
stars, Photon, Ciencias Físicas, Astrophysics::High Energy Astrophysical Phenomena, blazars, Flux, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, telescope, 01 natural sciences, Power law, purl.org/becyt/ford/1 [https], gamma-ray astronomy, 0103 physical sciences, gamma rays: galaxies, emission, bl lacertae objects: individual (1es 0414+009, erj0416+011), Nuclear Experiment, 010303 astronomy & astrophysics, Cherenkov radiation, Physics, search, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Institut für Physik und Astronomie, Astronomy and Astrophysics, purl.org/becyt/ford/1.3 [https], sample, Astronomía, Crab Nebula, individual (1ES 0414+009, VERJ0416+011) [BL Lacertae objects], Space and Planetary Science, bl lacertae object, galaxies [gamma rays], Spectral energy distribution, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, CIENCIAS NATURALES Y EXACTAS, discovery, Fermi Gamma-ray Space Telescope, BL Lac object
Abstract

We present observations of the BL Lac object 1ES 0414+009 in the >200 GeV gamma-ray band by the VERITAS array of Cherenkov telescopes. 1ES 0414+009 was observed by VERITAS between January 2008 and February 2011, resulting in 56.2 hours of good quality pointed observations. These observations resulted in a detection of 822 events from the source corresponding to a statistical significance of 6.4 standard deviations (6.4 sigma) above the background. The source flux, showing no evidence for variability, is measured as 5.2 +/- 1.1_stat +/- 2.6_sys * 10^-12 photons cm^-2 s^-1 above 200 GeV, equivalent to approximately 2% of the Crab Nebula flux above this energy. The differential photon spectrum from 230 GeV to 850 GeV is well fit by a power law with an photon index of Gamma 3.4 +/- 0.5_stat +/- 0.3_sys and a flux normalization of 1.6 +/- 0.3_stat +/- 0.8_sys * 10^-11 photons cm^-2 s^-1 at 300 GeV. We also present multiwavelength results taken in the optical (MDM), X-ray (Swift-XRT), and GeV (Fermi-LAT) bands and use these results to construct a broadband spectral energy distribution (SED). Modeling of this SED indicates that homogenous one-zone leptonic scenarios are not adequate to describe emission from the system, with a lepto-hadronic model providing a better fit to the data., Accepted for publication in The Astrophysical Journal

Published
2012

17. Long-term monitor of Mrk 421 TeV emission using ARGO-YBJ experiment

Author

B. Bartoli, X. J. Bi, C. Bleve, I. Bolognino, P. Branchini, A. Budano, A. K. Calabrese Melcarne, P. Camarri, Z. Cao, A. Cappa, R. Cardarelli, S. Catalanotti, C. Cattaneo, P. Celio, S. Z. Chen, T. L. Chen, Y. Chen, P. Creti, S. W. Cui, B. Z. Dai, G. D’Alı Staiti, Danzengluobu, M. Dattoli, B. D’Ettorre Piazzoli, T. Di Girolamo, X. H. Ding, G. Di Sciascio, C. F. Feng, Zhaoyang Feng, Zhenyong Feng, F. Galeazzi, P. Galeotti, E. Giroletti, Q. B. Gou, Y. Q. Guo, H. H. He, Haibing Hu, Hongbo Hu, Q. Huang, M. Iacovacci, R. Iuppa, I. James, H. Y. Jia, Labaciren, H. J. Li, J. Y. Li, X. X. Li, G. Liguori, C. Liu, C. Q. Liu, J. Liu, M. Y. Liu, H. Lu, X. H. Ma, S. M. Mari, S. Mastroianni, P. Montini, C. C. Ning, A. Pagliaro, B. Panico, P. Pistilli, X. B. Qu, E. Rossi, F. Ruggieri, P. Salvini, R. Santonico, P. R. Shen, X. D. Sheng, F. Shi, C. Stanescu, A. Surdo, Y. H. Tan, P. Vallania, S. Vernetto, C. Vigorito, B. Wang, H. Wang, C. Y. Wu, H. R. Wu, B. Xu, L. Xue, Y. X. Yan, Q. Y. Yang, X. C. Yang, Z. G. Yao, A. F. Yuan, M. Zha, H. M. Zhang, Jilong Zhang, Jianli Zhang, L. Zhang, P. Zhang, X. Y. Zhang, Y. Zhang, Zhaxiciren, Zhaxisangzhu, X. X. Zhou, F. R. Zhu, Q. Q. Zhu, G. Zizzi, BERNARDINI, Paolo, DE MITRI, Ivan, MANCARELLA, Giovanni, MARSELLA, GIOVANNI, MARTELLO, Daniele, PANAREO, Marco, PERRONE, Lorenzo, B., Bartoli, Bernardini, Paolo, X. J., Bi, C., Bleve, I., Bolognino, P., Branchini, A., Budano, A. K., Calabrese Melcarne, P., Camarri, Z., Cao, A., Cappa, R., Cardarelli, S., Catalanotti, C., Cattaneo, P., Celio, S. Z., Chen, T. L., Chen, Y., Chen, P., Creti, S. W., Cui, B. Z., Dai, G., D’Alı Staiti, Danzengluobu, M., Dattoli, DE MITRI, Ivan, B., D’Ettorre Piazzoli, T., Di Girolamo, X. H., Ding, G., Di Sciascio, C. F., Feng, Zhaoyang, Feng, Zhenyong, Feng, F., Galeazzi, P., Galeotti, E., Giroletti, Q. B., Gou, Y. Q., Guo, H. H., He, Haibing, Hu, Hongbo, Hu, Q., Huang, M., Iacovacci, R., Iuppa, I., Jame, H. Y., Jia, Labaciren, H. J., Li, J. Y., Li, X. X., Li, G., Liguori, C., Liu, C. Q., Liu, J., Liu, M. Y., Liu, H., Lu, X. H., Ma, Mancarella, Giovanni, S. M., Mari, Marsella, Giovanni, Martello, Daniele, S., Mastroianni, P., Montini, C. C., Ning, A., Pagliaro, Panareo, Marco, B., Panico, Perrone, Lorenzo, P., Pistilli, X. B., Qu, E., Rossi, F., Ruggieri, P., Salvini, R., Santonico, P. R., Shen, X. D., Sheng, F., Shi, C., Stanescu, A., Surdo, Y. H., Tan, P., Vallania, S., Vernetto, C., Vigorito, B., Wang, H., Wang, C. Y., Wu, H. R., Wu, B., Xu, L., Xue, Y. X., Yan, Q. Y., Yang, X. C., Yang, Z. G., Yao, A. F., Yuan, M., Zha, H. M., Zhang, Jilong, Zhang, Jianli, Zhang, L., Zhang, P., Zhang, X. Y., Zhang, Y., Zhang, Zhaxiciren, Zhaxisangzhu, X. X., Zhou, F. R., Zhu, Q. Q., Zhu, and G., Zizzi

Subjects
gamma ray observations, Markarian 421, BL Lacertae object
Abstract

ARGO-YBJ is an air shower detector array with a fully covered layer of Resistive Plate Chambers. It is operated with a high duty cycle and a large field of view. It monitors continuously the northern sky at energies above 0.3 TeV. In this paper, we report a long-term monitoring of Mrk 421 over the period from November 2007 to February 2010. Meanwhile, this source was observed by the satellite-borne experiments RXTE and Swift in the X-ray band. Mrk 421 was very active especially in the first half of 2008. Many flares are observed in both X-ray and gamma-ray bands simultaneously. The gamma-ray flux observed by ARGO-YBJ has a clear correlation with the X-ray flux. No lag longer than 1 day between the X-ray and gamma-ray photons is found. The evolution of the spectral energy distribution is investigated by measuring indices at four different flux levels. Hardening of the spectra is observed in both X-ray and gamma-ray bands. The gamma-ray flux increases quadratically with the simultaneously measured X-ray flux. All these observational results strongly favor the synchrotron self-Compton process as the underlying radiative mechanism.

Published
2011

18. Gamma-Ray Flares from Mrk421 in 2008 observed with the ARGO-YBJ detector

Author

Aielli, G., Bacci, C., Bartoli, B., Bernardini, P., Xj, B., Bleve, C., Branchini, P., Budano, A., Bussino, S., Calabrese Melcarne, A., Camarri, P., Cao, Z., Cappa, A., Cardarelli, R., Catalanotti, S., Cattaneo, C., Celio, P., Chen, S., Chen, Y., Cheng, N., Creti, P., Cui, S., Dai, B., D'Ali'Staiti, G., Danzengluobu, Dattoli, M., De Mitri, I., D’Ettorre Piazzoli, B., De Vincenzi, M., Di Girolamo, T., Ding, X., Di Sciascio, G., Feng, C., Feng, Z., Galeazzi, F., Galeotti, P., Gargana, R., Gou, Q., Guo, Y., Hh, H., Hbi, H., Hbo, H., Huang, Q., Iacovacci, M., Iuppa, R., James, I., Jia, H., Labaciren, Hj, L., Jy, L., Xx, L., Liberti, B., Liguori, G., Liu, C., Liu, J., Liu, M., Lu, H., Xh, M., Mancarella, G., Mari, S., Marsella, G., Martello, D., Mastroianni, S., Meng, X., Montini, P., Ning, C., Pagliaro, A., Panareo, M., Perrone, L., Pistilli, P., Xb, Q., Rossi, E., Ruggieri, F., Saggese, L., Salvini, P., Santonico, R., Shen, P., Sheng, X., Shi, F., Stanescu, C., Surdo, A., Tan, Y., Vallania, P., Vernetto, S., Vigorito, C., Wang, B., Wang, H., Cy, W., Hr, W., Xu, B., Xue, L., Yan, Y., Yang, Q., Yang, X., Yuan, A., Zha, M., Zhang, H., Zhang, J., Zhang, L., Zhang, P., Zhang, X., Zhang, Y., Zhaxisangzhu, Zhou, X., Zhu, F., Zhu, Q., Zizzi, G., G., Aielli, C., Bacci, B., Bartoli, Bernardini, Paolo, X. J., Bi, C., Bleve, P., Branchini, A., Budano, S., Bussino, A. K., CALABRESE MELCARNE, P., Camarri, Z., Cao, A., Cappa, R., Cardarelli, S., Catalanotti, C., Cattaneo, P., Celio, S. Z., Chen, Y., Chen, N., Cheng, P., Creti, S. W., Cui, B. Z., Dai, G., D’ALÍ STAITI, Danzengluobu, M., Dattoli, DE MITRI, Ivan, B., D’ETTORRE PIAZZOLI, M., DE VINCENZI, T., DI GIROLAMO, X. H., Ding, G., DI SCIASCIO, C. F., Feng, Zhaoyang, Feng, Zhenyong, Feng, F., Galeazzi, P., Galeotti, R., Gargana, Q. B., Gou, Y. Q., Guo, H. H., He, Haibing, Hu, Hongbo, Hu, Q., Huang, M., Iacovacci, R., Iuppa, I., Jame, H. Y., Jia, Labaciren, H. J., Li, J. Y., Li, X. X., Li, B., Liberti, G., Liguori, C., Liu, C. Q., Liu, M. Y., Liu, J., Liu, H., Lu, X. H., Ma, Mancarella, Giovanni, S. M., Mari, Marsella, Giovanni, Martello, Daniele, S., Mastroianni, X. R., Meng, P., Montini, C. C., Ning, A., Pagliaro, Panareo, Marco, Perrone, Lorenzo, P., Pistilli, X. B., Qu, E., Rossi, F., Ruggieri, L., Saggese, P., Salvini, R., Santonico, P. R., Shen, X. D., Sheng, F., Shi, C., Stanescu, A., Surdo, Y. H., Tan, P., Vallania, S., Vernetto, C., Vigorito, B., Wang, H., Wang, C. Y., Wu, H. R., Wu, B., Xu, L., Xue, Y. X., Yan, Q. Y., Yang, X. C., Yang, A. F., Yuan, M., Zha, H. M., Zhang, Jilong, Zhang, Jianli, Zhang, L., Zhang, P., Zhang, X. Y., Zhang, Y., Zhang, Zhaxisangzhu, X. X., Zhou, F. R., Zhu, Q. Q., Zhu, Zizzi, Giovanni, Aielli, G, Bacci, C, Bartoli, B, Bernardini, P, Bi, XJ, Bleve, C, Branchini, P, Budano, A, Bussino, S, Calabrese Melcarne, AK, Camarri, P, Cao, Z, Cappa, A, Cardarelli, R, Catalanotti, S, Cattaneo, C, Celio, P, Chen, SZ, Chen, Y, Cheng, N, Creti, P, Cui, SW, Dai, BZ, D’Ali Staiti, G, Dattoli, M, De Mitri, I, D’Ettorre Piazzoli, B, De Vincenzi, M, Di Girolamo, T, Ding, XH, Di Sciascio, G, Feng, CF, Feng, ZYa, Feng, ZYo, Galeazzi, F, Galeotti, P, Gargana, R, Gou, QB, Guo, YQ, He, HH, Hu, HBi, Hu, HBo, Huang, Q, Iacovacci, M, Iuppa, R, James, I, Jia, HY, Li, HJ, Li, JY, Li, XX, Liberti, B, Liguori, G, Liu, C, Liu, CQ, Liu, J, Liu, MY, Lu, H, Ma, XH, Mancarella, G, Mari, SM, Marsella, G, Martello, D, Mastroianni, S, Meng, XR, Montini, P, Ning, CC, Pagliaro, A, Panareo, M, Perrone, L, Pistilli, P, Qu, XB, Rossi, E, Ruggieri, F, Saggese, L, Salvini, P, Santonico, R, Shen, PR, Sheng, XD, Shi, F, Stanescu, C, Surdo, A, Tan, YH, Vallania, P, Vernetto, S, Vigorito, C, Wang, B, Wang, H, Wu, CY, Wu, HR, Xu, B, Xue, L, Yan, YX, Yang, QY, Yang, XC, Yuan, AF, Zha, M, Zhang, HM, Zhang, JLi, Zhang, JLo, Zhang, L, Zhang, P, Zhang, XY, Zhang, Y, Zhou, XX, Zhu, FR, Zhu, QQ, Zizzi, G, Bi, Xj, Bussino, Severino Angelo Maria, Melcarne, Akc, Chen, Sz, Cui, Sw, Dai, Bz, Staiti, Gd, Piazzoli, Bd, Ding, Xh, Feng, Cf, Feng, Zy, Gou, Qb, Guo, Yq, He, Hh, Hu, Hb, Jia, Hy, Li, Hj, Li, Jy, Li, Xx, Liu, Cq, Liu, My, Ma, Xh, Mari, Stefano Maria, Meng, Xr, Ning, Cc, Qu, Xb, Shen, Pr, Sheng, Xd, Tan, Yh, Wu, Cy, Wu, Hr, Yan, Yx, Yang, Qy, Yang, Xc, Yuan, Af, Zhang, Hm, Zhang, Jl, Zhang, Xy, Zhou, Xx, Zhu, Fr, Zhu, Qq, Zizzi, G., Bartoli, Bruno, Catalanotti, Sergio, D'ETTORRE PIAZZOLI, Benedetto, DI GIROLAMO, Tristano, Iacovacci, Michele, and Mastroianni, Stefano

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Flux, Astrophysics, BL Lacertae object, Settore FIS/05 - Astronomia E Astrofisica, Extended Air showers, Settore FIS/05 - Astronomia e Astrofisica, general" ["gamma rays], Blazar, BL Lacertae objects, Markarian 421, gamma rays, Cherenkov radiation, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, individual (Markarian 421)" ["BL Lacertae objects], Settore FIS/01 - Fisica Sperimentale, Gamma ray, individual (Markarian 421) - gamma rays: observations [BL Lacertae objects], Astronomy and Astrophysics, Air shower, Crab Nebula, Space and Planetary Science, gamma ray, Intergalactic travel, Astrophysics - High Energy Astrophysical Phenomena
Abstract

In 2008 the blazar Markarian 421 entered a very active phase and was one of the brightest sources in the sky at TeV energies, showing frequent flaring episodes. Using the data of ARGO-YBJ, a full coverage air shower detector located at Yangbajing (4300 m a.s.l., Tibet, China), we monitored the source at gamma ray energies E > 0.3 TeV during the whole year. The observed flux was variable, with the strongest flares in March and June, in correlation with X-ray enhanced activity. While during specific episodes the TeV flux could be several times larger than the Crab Nebula one, the average emission from day 41 to 180 was almost twice the Crab level, with an integral flux of (3.6 +-0.6) 10^-11 photons cm^-2 s^-1 for energies E > 1 TeV, and decreased afterwards. This paper concentrates on the flares occurred in the first half of June. This period has been deeply studied from optical to 100 MeV gamma rays, and partially up to TeV energies, since the moonlight hampered the Cherenkov telescope observations during the most intense part of the emission. Our data complete these observations, with the detection of a signal with a statistical significance of 3.8 standard deviations on June 11-13, corresponding to a gamma ray flux about 6 times larger than the Crab one above 1 TeV. The reconstructed differential spectrum, corrected for the intergalactic absorption, can be represented by a power law with an index alpha = -2.1 extending up to several TeV. The spectrum slope is fully consistent with previous observations reporting a correlation between the flux and the spectral index, suggesting that this property is maintained in different epochs and characterizes the source emission processes., Accepted for publication on ApJL

Published
2010

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