Deep observation of the NGC 1275 region with MAGIC: Search of diffuse γ -ray emission from cosmic rays in the Perseus cluster

Clusters of galaxies are expected to be reservoirs of cosmic rays (CRs) that should produce diffuse γ-ray emission due to their hadronic interactions with the intra-cluster medium. The nearby Perseus cool-core cluster, identified as the most promising target to search for such an emission, has been observed with the MAGIC telescopes at very-high energies (VHE, E 100 GeV) for a total of 253 h from 2009 to 2014. The active nuclei of NGC 1275, the central dominant galaxy of the cluster, and IC 310, lying at about 0.6° from the centre, have been detected as point-like VHE γ-ray emitters during the first phase of this campaign. We report an updated measurement of the NGC 1275 spectrum, which is described well by a power law with a photon index Γ = 3.6 ± 0.2stat ± 0.2syst between 90 GeV and 1200 GeV. We do not detect any diffuse γ-ray emission from the cluster and so set stringent constraints on its CR population. To bracket the uncertainties over the CR spatial and spectral distributions, we adopt different spatial templates and power-law spectral indexes α. For α = 2.2, the CR-to-thermal pressure within the cluster virial radius is constrained to be 1-2%, except if CRs can propagate out of the cluster core, generating a flatter radial distribution and releasing the CR-to-thermal pressure constraint to 20%. Assuming that the observed radio mini-halo of Perseus is generated by secondary electrons from CR hadronic interactions, we can derive lower limits on the central magnetic field, B0, that depend on the CR distribution. For α = 2.2, B0 5-8 μG, which is below the ~25 μG inferred from Faraday rotation measurements, whereas for α 2.1, the hadronic interpretation of the diffuse radio emission contrasts with our γ-ray flux upper limits independently of the magnetic field strength

MAGIC observations of the diffuse γ -ray emission in the vicinity of the Galactic center

Aims. In the presence of a sufficient amount of target material, γ-rays can be used as a tracer in the search for sources of Galactic cosmic rays (CRs). Here we present deep observations of the Galactic center (GC) region with the MAGIC telescopes and use them to infer the underlying CR distribution and to study the alleged PeV proton accelerator at the center of our Galaxy.Methods. We used data from ≈100 h observations of the GC region conducted with the MAGIC telescopes over five years (from 2012 to 2017). Those were collected at high zenith angles (58−70 deg), leading to a larger energy threshold, but also an increased effective collection area compared to low zenith observations. Using recently developed software tools, we derived the instrument response and background models required for extracting the diffuse emission in the region. We used existing measurements of the gas distribution in the GC region to derive the underlying distribution of CRs. We present a discussion of the associated biases and limitations of such an approach.Results. We obtain a significant detection for all four model components used to fit our data (Sgr A*, “Arc”, G0.9+0.1, and an extended component for the Galactic Ridge). We observe no significant difference between the γ-ray spectra of the immediate GC surroundings, which we model as a point source (Sgr A*) and the Galactic Ridge. The latter can be described as a power-law with index 2 and an exponential cut-off at around 20 TeV with the significance of the cut-off being only 2σ. The derived cosmic-ray profile hints to a peak at the GC position and with a measured profile index of 1.2 ± 0.3 is consistent with the 1/r radial distance scaling law, which supports the hypothesis of a CR accelerator at the GC. We argue that the measurements of this profile are presently limited by our knowledge of the gas distribution in the GC vicinity.</div

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

240siWe 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.nonemixedmagic Collaboration; Other Groups And Collaborators; 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.; Reinthal R.Magic, Collaboration; Other Groups And, Collaborators; 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.; Reinthal, R