663 research outputs found

    TeV flaring activity of the AGN PKS 0625-354 in November 2018

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    International audienceMost Îł\gamma-ray detected active galactic nuclei are blazars with one of their relativistic jets pointing towards the Earth. Only a few objects belong to the class of radio galaxies or misaligned blazars. Here, we investigate the nature of the object PKS 0625-354, its Îł\gamma-ray flux and spectral variability and its broad-band spectral emission with observations from H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S. light curve above 200 GeV shows an outburst in the first night of observations followed by a declining flux with a halving time scale of 5.9h. The γγ\gamma\gamma-opacity constrains the upper limit of the angle between the jet and the line of sight to ∌10∘\sim10^\circ. The broad-band spectral energy distribution shows two humps and can be well fitted with a single-zone synchrotron self Compton emission model. We conclude that PKS 0625-354, as an object showing clear features of both blazars and radio galaxies, can be classified as an intermediate active galactic nuclei. Multi-wavelength studies of such intermediate objects exhibiting features of both blazars and radio galaxies are sparse but crucial for the understanding of the broad-band emission of Îł\gamma-ray detected active galactic nuclei in general

    Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433

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    International audienceSS 433 is a microquasar, a stellar binary system with collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.), finding an energy-dependent shift in the apparent position of the gamma-ray emission of the parsec-scale jets. These observations trace the energetic electron population and indicate the gamma rays are produced by inverse-Compton scattering. Modelling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system at distances of 25 to 30 parsecs and conclude that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons

    TeV flaring activity of the AGN PKS 0625-354 in November 2018

    No full text
    International audienceMost Îł\gamma-ray detected active galactic nuclei are blazars with one of their relativistic jets pointing towards the Earth. Only a few objects belong to the class of radio galaxies or misaligned blazars. Here, we investigate the nature of the object PKS 0625-354, its Îł\gamma-ray flux and spectral variability and its broad-band spectral emission with observations from H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S. light curve above 200 GeV shows an outburst in the first night of observations followed by a declining flux with a halving time scale of 5.9h. The γγ\gamma\gamma-opacity constrains the upper limit of the angle between the jet and the line of sight to ∌10∘\sim10^\circ. The broad-band spectral energy distribution shows two humps and can be well fitted with a single-zone synchrotron self Compton emission model. We conclude that PKS 0625-354, as an object showing clear features of both blazars and radio galaxies, can be classified as an intermediate active galactic nuclei. Multi-wavelength studies of such intermediate objects exhibiting features of both blazars and radio galaxies are sparse but crucial for the understanding of the broad-band emission of Îł\gamma-ray detected active galactic nuclei in general

    Hint for a TeV neutrino emission from the Galactic Ridge with ANTARES

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    International audienceInteractions of cosmic ray protons, atomic nuclei, and electrons in the interstellar medium in the inner part of the Milky Way produce a Îł\gamma-ray flux from the Galactic Ridge. If the Îł\gamma-ray emission is dominated by proton and nuclei interactions, a neutrino flux comparable to the Îł\gamma-ray flux is expected from the same sky region. Data collected by the ANTARES neutrino telescope are used to constrain the neutrino flux from the Galactic Ridge in the 1-100 TeV energy range. Neutrino events reconstructed both as tracks and showers are considered in the analysis and the selection is optimized for the search of an excess in the region ∣l∣<30deg⁥|l| < 30\deg, ∣b∣<2deg⁥|b| < 2\deg. The expected background in the search region is estimated using an off region with similar sky coverage. Neutrino signal originating from a power-law spectrum with slope ranging from ΓΜ=1\Gamma_\nu=1 to 44 is simulated in both channels. The observed energy distributions are fitted to constrain the neutrino emission from the Ridge. The energy distributions in the signal region are inconsistent with the background expectation at ∌96%\sim 96\% confidence level. The mild excess over the background is consistent with a neutrino flux with a power law with a slope 2.45−0.34+0.222.45^{+0.22}_{-0.34} and a flux normalization dNÎœ/dEÎœ=4.0−2.0+2.7×10−16GeV−1cm−2s−1sr−1dN_\nu/dE_\nu = 4.0^{+2.7}_{-2.0} \times 10^{-16} \text{GeV}^{-1} \text{cm}^{-2} \text{s}^{-1} \text{sr}^{-1} at 40 TeV reference energy. Such flux is consistent with the expected neutrino signal if the bulk of the observed Îł\gamma-ray flux from the Galactic Ridge originates from interactions of cosmic ray protons and nuclei with a power-law spectrum extending well into the PeV energy range

    Hint for a TeV neutrino emission from the Galactic Ridge with ANTARES

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    Interactions of cosmic ray protons, atomic nuclei, and electrons in the interstellar medium in the inner part of the Milky Way produce a Âż-ray flux from the Galactic Ridge. If the Âż-ray emission is dominated by proton and nuclei interactions, a neutrino flux comparable to the Âż-ray flux is expected from the same sky region. Data collected by the ANTARES neutrino telescope are used to constrain the neutrino flux from the Galactic Ridge in the 1-100 TeV energy range. Neutrino events reconstructed both as tracks and showers are considered in the analysis and the selection is optimized for the search of an excess in the region |l| <30Âż, |b| <2Âż. The expected background in the search region is estimated using an off-zone region with similar sky coverage. Neutrino signal originating from a power-law spectrum with spectral index ranging from Âż=1to 4is simulated in both channels. The observed energy distributions are fitted to constrain the neutrino emission from the Ridge. The energy distributions in the signal region are inconsistent with the background expectation at ~96% confidence level. The mild excess over the background is consistent with a neutrino flux with a power law with a spectral index 2.45+0.22 -0.34and a flux normalization dNÂż dEÂż =4.0+2.7 -2.0 ×10-16GeV-1cm-2s-1sr-1 at 40 TeV reference energy. Such flux is consistent with the expected neutrino signal if the bulk of the observed Âż-ray flux from the Galactic Ridge originates from interactions of cosmic ray protons and nuclei with a power-law spectrum extending well into the PeV energy range.The authors acknowledge the financial support of the funding agencies: Centre National de la Recherche Scientifique (CNRS), Commissariat Ă  l'Énergie Atomique et aux Énergies Alternatives (CEA), Commission EuropĂ©enne (FEDER fund and Marie Curie Program), Labex UnivEarthS (ANR-10-LABX-0023 and ANR-18-IDEX-0001), RĂ©gion Alsace (contrat CPER), RĂ©gion Provence-Alpes-CĂŽte d'Azur, DĂ©partement du Var and Ville de La Seyne-sur-Mer, France; Bundesministerium fĂŒr Bildung und Forschung (BMBF), Germany; Istituto Nazionale di Fisica Nucleare (INFN), the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754496, Italy; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), the Netherlands; Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), Romania; Grants PID2021-124591NB-C41, -C42, -C43 funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by “ERDF A way of making Europe”, by the “European Union” or by the “European Union NextGenerationEU/PRTR”, Programa de Planes Complementarios I+D+I (refs. ASFAE/2022/023, ASFAE/2022/014), Programa Prometeo (PROMETEO/2020/019) and GenT (refs. CIDEGENT/2018/034, /2019/043, /2020/049. /2021/23) of the Generalitat Valenciana, Junta de AndalucĂ­a (ref. P18-FR-5057), EU: MSC program (ref. 101025085), Programa MarĂ­a Zambrano (Spanish Ministry of Universities, funded by the European Union, NextGenerationEU), Spain; Ministry of Higher Education, Scientific Research and Training, Morocco, and the Arab Fund for Economic and Social Development, Kuwait. We also acknowledge the technical support of Ifremer, AIM and Foselev Marine for the sea operation and the CC-IN2P3 for the computing facilities.Peer ReviewedArticle signat per 164 autors/es: A. Albert, S. Alves, M. AndrĂ©, M. Ardid , S. Ardid, J.-J. Aubert, J. Aublin, B. Baret, S. Basa, Y. Becherini, B. Belhorma, M. Bendahman, F. Benfenati, V. Bertin, S. Biagi, M. Bissinger, J. Boumaaza, M. Bouta, M.C. Bouwhuis, H. BrĂąnzaƟ, R. Bruijn, J. Brunner, J. Busto, B. Caiffi, D. Calvo, S. Campion, A. Capone, L. Caramete, F. Carenini, J. Carr, V. Carretero, S. Celli, L. Cerisy, M. Chabab, T.N. Chau, R. Cherkaoui El Moursli, T. Chiarusi, M. Circella, J.A.B. Coelho, A. Coleiro, R. Coniglione, P. Coyle, A. Creusot, A.F. DĂ­az, B. De Martino, C. Distefano, I. Di Palma, A. Domi , C. Donzaud, D. Dornic, D. Drouhin, T. Eberl, T. van Eeden, D. van Eijk, S. El Hedri, N. El Khayati, A. Enzenhöfer, M. Fasano, P. Fermani, G. Ferrara, F. Filippini, L. Fusco, S. Gagliardini, J. GarcĂ­a, C. Gatius Oliver, P. Gay, N. Geißelbrecht, H. Glotin, R. Gozzini, R. Gracia Ruiz, K. Graf, C. Guidi, L. Haegel, S. Hallmann, H. van Haren, A.J. Heijboer, Y. Hello, J.J. HernĂĄndez-Rey, J. HĂ¶ĂŸl, J. HofestĂ€dt, F. Huang, G. Illuminati, C.W. James, B. Jisse-Jung, M. de Jong, P. de Jong, M. Kadler, O. Kalekin, U. Katz, A. Kouchner, I. Kreykenbohm, V. Kulikovskiy, R. Lahmann, M. Lamoureux, A. Lazo, D. LefĂšvre, E. Leonora, G. Levi, S. Le Stum, D. Lopez-Coto, S. Loucatos, L. Maderer, J. Manczak, M. Marcelin, A. Margiotta, A. Marinelli, J.A. MartĂ­nez-Mora, P. Migliozzi, A. Moussa, R. Muller, L. Nauta, S. Navas, A. Neronov, E. Nezri, B. Ó Fearraigh, A. Păun, G.E. PăvălaƟ, M. Perrin-Terrin, V. Pestel, P. Piattelli, C. PoirĂš, V. Popa, T. Pradier, N. Randazzo, D. Real, S. Reck, G. Riccobene, A. Romanov, A. SĂĄnchez-Losa, A. Saina, F. Salesa Greus, D.F.E. Samtleben, M. Sanguineti, P. Sapienza, D. Savchenko, J. Schnabel, J. Schumann, F. SchĂŒssler, J. Seneca, M. Spurio, Th. Stolarczyk, M. Taiuti, Y. Tayalati, S.J. Tingay, B. Vallage, G. Vannoye, V. Van Elewyck, S. Viola, D. Vivolo, J. Wilms, S. Zavatarelli, A. Zegarelli, J.D. Zornoza, J. ZĂșñiga.Postprint (published version

    Constraints on the intergalactic magnetic field using Fermi-LAT and H.E.S.S. blazar observations

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    International audienceMagnetic fields in galaxies and galaxy clusters are believed to be the result of the amplification of intergalactic seed fields during the formation of large-scale structures in the universe. However, the origin, strength, and morphology of this intergalactic magnetic field (IGMF) remain unknown. Lower limits on (or indirect detection of) the IGMF can be obtained from observations of high-energy gamma rays from distant blazars. Gamma rays interact with the extragalactic background light to produce electron-positron pairs, which can subsequently initiate electromagnetic cascades. The γ\gamma-ray signature of the cascade depends on the IGMF since it deflects the pairs. Here we report on a new search for this cascade emission using a combined data set from the Fermi Large Area Telescope and the High Energy Stereoscopic System. Using state-of-the-art Monte Carlo predictions for the cascade signal, our results place a lower limit on the IGMF of B>7.1×10−16B > 7.1\times10^{-16} G for a coherence length of 1 Mpc even when blazar duty cycles as short as 10 yr are assumed. This improves on previous lower limits by a factor of 2. For longer duty cycles of 10410^4 (10710^7) yr, IGMF strengths below 1.8×10−141.8\times10^{-14} G (3.9×10−143.9\times10^{-14} G) are excluded, which rules out specific models for IGMF generation in the early universe

    The vanishing of the primary emission region in PKS 1510-089

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    International audienceIn July 2021, PKS 1510-089 exhibited a significant flux drop in the high-energy gamma-ray (by a factor 10) and optical (by a factor 5) bands and remained in this low state throughout 2022. Similarly, the optical polarization in the source vanished, resulting in the optical spectrum being fully explained through the steady flux of the accretion disk and the broad-line region. Unlike the aforementioned bands, the very-high-energy gamma-ray and X-ray fluxes did not exhibit a significant flux drop from year to year. This suggests that the steady-state very-high-energy gamma-ray and X-ray fluxes originate from a different emission region than the vanished parts of the high-energy gamma-ray and optical jet fluxes. The latter component has disappeared through either a swing of the jet away from the line-of-sight or a significant drop in the photon production efficiency of the jet close to the black hole. Either change could become visible in high-resolution radio images

    KM3NeT broadcast optical data transport system

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    International audienceThe optical data transport system of the KM3NeT neutrino telescope at the bottom of the Mediterranean Sea will provide more than 6000 optical modules in the detector arrays with a point-to-point optical connection to the control stations onshore. The ARCA and ORCA detectors of KM3NeT are being installed at a depth of about 3500 m and 2500 m, respectively and their distance to the control stations is about 100 kilometers and 40 kilometers. In particular, the two detectors are optimised for the detection of cosmic neutrinos with energies above about 1 TeV (ARCA) and for the detection of atmospheric neutrinos with energies in the range 1 GeV–1 TeV (ORCA). The expected maximum data rate is 200 Mbps per optical module. The implemented optical data transport system matches the layouts of the networks of electro-optical cables and junction boxes in the deep sea. For efficient use of the fibres in the system the technology of Dense Wavelength Division Multiplexing is applied. The performance of the optical system in terms of measured bit error rates, optical budget are presented. The next steps in the implementation of the system are also discussed

    Constraining the cosmic-ray pressure in the inner Virgo Cluster using H.E.S.S. observations of M 87

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    International audienceThe origin of the gamma-ray emission from M87 is currently a matter of debate. This work aims to localize the VHE (100 GeV-100 TeV) gamma-ray emission from M87 and probe a potential extended hadronic emission component in the inner Virgo Cluster. The search for a steady and extended gamma-ray signal around M87 can constrain the cosmic-ray energy density and the pressure exerted by the cosmic rays onto the intra-cluster medium, and allow us to investigate the role of the cosmic rays in the active galactic nucleus feedback as a heating mechanism in the Virgo Cluster. H.E.S.S. telescopes are sensitive to VHE gamma rays and have been utilized to observe M87 since 2004. We utilized a Bayesian block analysis to identify M87 emission states with H.E.S.S. observations from 2004 until 2021, dividing them into low, intermediate, and high states. Because of the causality argument, an extended (≳\gtrsimkpc) signal is allowed only in steady emission states. Hence, we fitted the morphology of the 120h low state data and found no significant gamma-ray extension. Therefore, we derived for the low state an upper limit of 58"(corresponding to ≈\approx4.6kpc) in the extension of a single-component morphological model described by a rotationally symmetric 2D Gaussian model at 99.7% confidence level. Our results exclude the radio lobes (≈\approx30 kpc) as the principal component of the VHE gamma-ray emission from the low state of M87. The gamma-ray emission is compatible with a single emission region at the radio core of M87. These results, with the help of two multiple-component models, constrain the maximum cosmic-ray to thermal pressure ratio XCR,max.X_{{CR,max.}}â‰Č\lesssim0.320.32 and the total energy in cosmic-ray protons (CRp) to UCRU_{CR}â‰Č\lesssim5×1058\times10^{58} erg in the inner 20kpc of the Virgo Cluster for an assumed CRp power-law distribution in momentum with spectral index αp\alpha_{p}=2.1

    Searches for neutrinos in the direction of radio-bright blazars with the ANTARES telescope

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    International audienceActive galaxies, especially blazars, are among the most promising neutrino source candidates. To date, ANTARES searches for these objects considered GeV-TeV Îł\gamma-ray bright blazars. Here, a statistically complete radio-bright blazar sample is used as the target for searches of origins of neutrinos collected by the ANTARES neutrino telescope over 13 years of operation. The hypothesis of a neutrino-blazar directional correlation is tested by pair counting and by a complementary likelihood-based approach. The resulting post-trial pp-value is 3.0%3.0\% (2.2σ2.2\sigma in the two-sided convention), possibly indicating a correlation. Additionally, a time-dependent analysis is performed to search for temporal clustering of neutrino candidates as a mean of detecting neutrino flares in blazars. None of the investigated sources alone reaches a significant flare detection level. However, the presence of 18 sources with a pre-trial significance above 3σ3\sigma indicates a p=1.4%p=1.4\% (2.5σ2.5\sigma in the two-sided convention) detection of a time-variable neutrino flux. An \textit{a posteriori} investigation reveals an intriguing temporal coincidence of neutrino, radio, and Îł\gamma-ray flares of the J0242+1101 blazar at a p=0.5%p=0.5\% (2.9σ2.9\sigma in the two-sided convention) level. Altogether, the results presented here suggest a possible connection of neutrino candidates detected by the ANTARES telescope with radio-bright blazars
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