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  • 1. Abdollahi, S.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Wood, K. S.
    The Second Catalog of Flaring Gamma-Ray Sources from the Fermi All-sky Variability Analysis2017Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 846, nr 1, artikel-id 34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the second catalog of flaring gamma-ray sources (2FAV) detected with the Fermi All-sky Variability Analysis (FAVA), a tool that blindly searches for transients over the entire sky observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. With respect to the first FAVA catalog, this catalog benefits from a larger data set, the latest LAT data release (Pass 8), as well as from an improved analysis that includes likelihood techniques for a more precise localization of the transients. Applying this analysis to the first 7.4 years of Fermi observations, and in two separate energy bands 0.1-0.8 GeV and 0.8-300 GeV, a total of 4547 flares were detected with significance greater than 6s (before trials), on the timescale of one week. Through spatial clustering of these flares, 518 variable gamma-ray sources were identified. Based on positional coincidence, likely counterparts have been found for 441 sources, mostly among the blazar class of active galactic nuclei. For 77 2FAV sources, no likely gamma-ray counterpart has been found. For each source in the catalog, we provide the time, location, and spectrum of each flaring episode. Studying the spectra of the flares, we observe a harder-when-brighter behavior for flares associated with blazars, with the exception of BL Lac flares detected in the low-energy band. The photon indexes of the flares are never significantly smaller than 1.5. For a leptonic model, and under the assumption of isotropy, this limit suggests that the spectrum of freshly accelerated electrons is never harder than p similar to 2.

  • 2.
    Ackermann, M.
    et al.
    Deutsch Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany..
    Ajello, M.
    Clemson Univ, Dept Phys & Astron, Kinard Lab Phys, Clemson, SC 29634 USA..
    Albert, A.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Atwood, W. B.
    Univ Calif Santa Cruz, Santa Cruz Inst Particle Phys, Dept Phys, Santa Cruz, CA 95064 USA.;Univ Calif Santa Cruz, Dept Astron & Astrophys, Santa Cruz, CA 95064 USA..
    Baldini, L.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Ballet, J.
    Univ Paris Diderot, Lab AIM, CEA IRFU, CNRS,Serv Astrophys,CEA Saclay, F-91191 Gif Sur Yvette, France..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bechtol, K.
    Univ Wisconsin, Dept Phys, Madison, WI 53706 USA..
    Bellazzini, R.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Bissaldi, E.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Blandford, R. D.
    Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Bloom, E. D.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Bonino, R.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Torino, I-10125 Turin, Italy..
    Bottacini, E.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Bregeon, J.
    Univ Turin, Dipartimento Fis Generale Amadeo Avogadro, I-10125 Turin, Italy..
    Bruel, P.
    Univ Montpellier, CNRS IN2P3, Lab Univ & Particules Montpellier, Montpellier, France..
    Buehler, R.
    Deutsch Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany..
    Caliandro, G. A.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;CNRS IN2P3, Ecole polytech, Lab Leprince Ringuet, Palaiseau, France.;CIFS, I-10133 Turin, Italy..
    Cameron, R. A.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Caragiulo, M.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Caraveo, P. A.
    INAF, Ist Astrofis Spaziale & Fis Cosm, I-20133 Milan, Italy..
    Casandjian, J. M.
    Univ Paris Diderot, Lab AIM, CEA IRFU, CNRS,Serv Astrophys,CEA Saclay, F-91191 Gif Sur Yvette, France..
    Cavazzuti, E.
    ASI Sci Data Ctr, I-00133 Rome, Italy..
    Cecchi, C.
    Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy.;Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Charles, E.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Chekhtman, A.
    George Mason Univ, Coll Sci, Fairfax, VA 22030 USA..
    Chiaro, G.
    Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Ciprini, S.
    ASI Sci Data Ctr, I-00133 Rome, Italy.;Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy..
    Cohen-Tanugi, J.
    Conrad, J.
    Stockholm Univ, AlbaNova, Dept Phys, SE-10691 Stockholm, Sweden.;Oskar Klein Ctr Cosmoparticle Phys, AlbaNova, ES-10691 Stockholm, Sweden..
    Cutini, S.
    ASI Sci Data Ctr, I-00133 Rome, Italy.;Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy.;INAF, Osserv Astronom Roma, I-00040 Rome, Italy..
    D'Ammando, F.
    INAF Ist Radioastron, I-40129 Bologna, Italy.;Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy..
    de Angelis, A.
    Univ Udine, Dipartimento Fis, I-33100 Udine, Italy.;Grp Collegato Udine, Sez Trieste, Ist Nazl Fis Nucl, I-33100 Udine, Italy..
    de Palma, F.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;Univ Telemat Pegaso, Piazza Trieste & Trento 48, I-80132 Naples, Italy..
    Desiante, R.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy.;Univ Udine, I-33100 Udine, Italy..
    Digel, S. W.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Di Venere, L.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Drell, P. S.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Favuzzi, C.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Fegan, S. J.
    Fukazawa, Y.
    Hiroshima Univ, Dept Phys Sci, Hiroshima 7398526, Japan..
    Funk, S.
    Erlangen Ctr Astroparticle Phys, D-91058 Erlangen, Germany..
    Fusco, P.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Gargano, F.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Gasparrini, D.
    ASI Sci Data Ctr, I-00133 Rome, Italy..
    Giglietto, N.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Giordano, F.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Giroletti, M.
    Godfrey, G.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Green, D.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Grenier, I. A.
    Univ Paris Diderot, Lab AIM, CEA IRFU, CNRS,Serv Astrophys,CEA Saclay, F-91191 Gif Sur Yvette, France..
    Guiriec, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Hays, E.
    Hewitt, J. W.
    Univ North Florida, Dept Phys, 1 UNF Dr, Jacksonville, FL 32224 USA..
    Horan, D.
    Johannesson, G.
    Univ Iceland, Inst Sci, IS-107 Reykjavik, Iceland..
    Kuss, M.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Latronico, L.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Li, J.
    IEEC CSIC, Inst Space Sci, Campus UAB, E-08193 Barcelona, Spain..
    Li, L.
    Longo, F.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Loparco, F.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Lovellette, M. N.
    IEEC CSIC, Inst Space Sci, Campus UAB, E-08193 Barcelona, Spain..
    Lubrano, P.
    Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy.;Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Madejski, G. M.
    Maldera, S.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Manfreda, A.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Mayer, M.
    Deutsch Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany..
    Mazziotta, M. N.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Michelson, P. F.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Mitthumsiri, W.
    Naval Res Lab, Div Space Sci, Washington, DC 20375 USA.;Mahidol Univ, Dept Phys, Fac Sci, Bangkok 10400, Thailand..
    Mizuno, T.
    Hiroshima Univ, Hiroshima Astrophys Sci Ctr, Higashihiroshima, Hiroshima 7398526, Japan..
    Monzani, M. E.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Morselli, A.
    Ist Nazl Fis Nucl, Sez Roma Tor Vergata, I-00133 Rome, Italy..
    Moskalenko, I. V.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Murgia, S.
    Univ Calif Irvine, Ctr Cosmol, Dept Phys & Astron, Irvine, CA 92697 USA..
    Nuss, E.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Ormes, J. F.
    Univ Denver, Dept Phys & Astron, Denver, CO 80208 USA..
    Paneque, D.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany..
    Pesce-Rollins, M.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA..
    Petrosian, V.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA..
    Piron, F.
    Pivato, G.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Porter, T. A.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA..
    Raino, S.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy.;M Merlin dellUniv Politecn Bari, Dipartimento Fis, I-70126 Bari, Italy..
    Rando, R.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Razzano, M.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Reimer, A.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Leopold Franzens Univ Innsbruck, Inst Astro & Teilchenphys, A-6020 Innsbruck, Austria.;Leopold Franzens Univ Innsbruck, Inst Theoret Phys, A-6020 Innsbruck, Austria..
    Reimer, O.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Leopold Franzens Univ Innsbruck, Inst Astro & Teilchenphys, A-6020 Innsbruck, Austria.;Leopold Franzens Univ Innsbruck, Inst Theoret Phys, A-6020 Innsbruck, Austria..
    Sanchez-Conde, M.
    Sgro, C.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Siskind, E. J.
    NYCB Real Time Comp Inc, Lattingtown, NY 11560 USA..
    Spada, F.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Spandre, G.
    Univ Wisconsin, Wisconsin IceCube Particle Astrophys Ctr, Madison, WI 53706 USA..
    Spinelli, P.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Tajima, H.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA.;Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi 4648601, Japan..
    Takahashi, H.
    Thayer, J. B.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Tibaldo, L.
    Max Planck Inst Kernphys, D-69029 Heidelberg, Germany..
    Torres, D. F.
    ICREA, Barcelona, Spain..
    Tosti, G.
    Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy.;Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Troja, E.
    Vianello, G.
    Stanford Univ, WW Hansen Expt Phys Lab, Kavli Inst Particle Astrophys & Cosmol, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Wood, K. S.
    Zimmer, S.
    Rephaeli, Y.
    Tel Aviv Univ, POB 39040, IL-6997801 Tel Aviv, Israel.;Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA..
    Search for Gamma-Ray Emission from the Coma Cluster with Six Years of Fermi-LAT Data (vol 819, 149, 2016)2018Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 860, nr 1, artikel-id 85Artikel i tidskrift (Refereegranskat)
  • 3. Ackermann, M.
    et al.
    Ajello, M.
    Albert, A.
    Atwood, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bellazzini, R.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonino, R.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Bruel, P.
    Buehler, R.
    Burnett, T. H.
    Cameron, R. A.
    Caputo, R.
    Caragiulo, M.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Chiappo, A.
    Chiaro, G.
    Ciprini, S.
    Conrad, J.
    Costanza, F.
    Cuoco, A.
    Cutini, S.
    D'Ammando, F.
    De Palma, F.
    Desiante, R.
    Digel, S. W.
    Di Lalla, N.
    Di Mauro, M.
    Di Venere, L.
    Drell, P. S.
    Favuzzi, C.
    Fegan, S. J.
    Ferrara, E. C.
    Focke, W. B.
    Franckowiak, A.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Gomez-Vargas, G. A.
    Green, D.
    Grenier, I. A.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Gustafsson, M.
    Harding, A. K.
    Hays, E.
    Hewitt, J. W.
    Horan, D.
    Jogler, T.
    Johnson, A. S.
    Kamae, T.
    Kocevski, D.
    Kuss, M.
    La Mura, G.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Latronico, L.
    Li, J.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Magill, J. D.
    Maldera, S.
    Malyshev, D.
    Manfreda, A.
    Martin, P.
    Mazziotta, M. N.
    Michelson, P. F.
    Mirabal, N.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Negro, M.
    Nuss, E.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Perkins, J. S.
    Persic, M.
    Pesce-Rollins, M.
    Piron, F.
    Principe, G.
    Rainò, S.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Sánchez-Conde, M.
    Sgrò, C.
    Simone, D.
    Siskind, E. J.
    Spada, F.
    Spandre, G.
    Spinelli, P.
    Suson, D. J.
    Tajima, H.
    Tanaka, K.
    Thayer, J. B.
    Tibaldo, L.
    Torres, D. F.
    Troja, E.
    Uchiyama, Y.
    Vianello, G.
    Wood, K. S.
    Wood, M.
    Zaharijas, G.
    Zimmer, S.
    The Fermi Galactic Center GeV Excess and Implications for Dark Matter2017Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 840, nr 1, artikel-id 43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The region around the Galactic Center (GC) is now well established to be brighter at energies of a few GeV than what is expected from conventional models of diffuse gamma-ray emission and catalogs of known gamma-ray sources. We study the GeV excess using 6.5 yr of data from the Fermi Large Area Telescope. We characterize the uncertainty of the GC excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the Milky Way, and uncertainties due to a potential contribution from the Fermi bubbles. We also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. The GC is of particular interest, as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter (DM) particles. However, control regions along the Galactic plane, where a DM signal is not expected, show excesses of similar amplitude relative to the local background. Based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross-section as a function of particle mass and annihilation channel.

  • 4.
    Ahnen, M. L.
    et al.
    Swiss Fed Inst Technol, CH-8093 Zurich, Switzerland..
    Jóhannesson, Gudlaugur
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Yassine, M.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    et al.,
    MAGIC and Fermi-LAT gamma-ray results on unassociated HAWC sources2019Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, nr 1, s. 356-366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The HAWC Collaboration released the 2HWC catalogue of TeV sources, in which 19 show no association with any known high-energy (HE; E greater than or similar to 10 GeV) or very-high-energy (VHE; E greater than or similar to 300 GeV) sources. This catalogue motivated follow-up studies by both the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) and Fermi-LAT (Large Area Telescope) observatories with the aim of investigating gamma-ray emission over a broad energy band. In this paper, we report the results from the first joint work between High Altitude Water Cherenkov (HAWC), MAGIC, and Fermi-LAT on three unassociated HAWC sources: 2HWC J2006+341, 2HWC J1907+084*, and 2HWC J1852+013*. Although no significant detection was found in the HE and VHE regimes, this investigation shows that a minimum 1 degrees extension (at 95 per cent confidence level) and harder spectrum in the GeV than the one extrapolated from HAWC results are required in the case of 2HWC J1852+013*, whilst a simply minimum extension of 0.16 degrees (at 95 per cent confidence level) can already explain the scenario proposed by HAWC for the remaining sources. Moreover, the hypothesis that these sources are pulsar wind nebulae is also investigated in detail.

  • 5. Ahnen, Max L.
    et al.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics.
    Grishina, T. S.
    et.al.,
    Multiwavelength observations of a VHE gamma-ray flare from PKS 1510-089 in 20152017Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 603, artikel-id A29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. PKS 1510-089 is one of only a few flat spectrum radio quasars detected in the very-high-energy (VHE, > 100 GeV) gamma-ray band. Aims. We study the broadband spectral and temporal properties of the PKS 1510-089 emission during a high gamma-ray state. Methods. We performed VHE gamma-ray observations of PKS 1510-089 with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes during a long, high gamma-ray state in May 2015. In order to perform broadband modeling of the source, we have also gathered contemporaneous multiwavelength data in radio, IR, optical photometry and polarization, UV, X-ray, and GeV gamma-ray ranges. We construct a broadband spectral energy distribution (SED) in two periods, selected according to VHE gamma-ray state. Results. PKS 1510-089 was detected by MAGIC during a few day-long observations performed in the middle of a long, high optical and gamma-ray state, showing for the first time a significant VHE gamma-ray variability. Similarly to the optical and gamma-ray high state of the source detected in 2012, it was accompanied by a rotation of the optical polarization angle and the emission of a new jet component observed in radio. However, owing to large uncertainty on the knot separation time, the association with the VHE gamma-ray emission cannot be firmly established. The spectral shape in the VHE band during the flare is similar to those obtained during previous measurements of the source. The observed flux variability sets constraints for the first time on the size of the region from which VHE gamma rays are emitted. We model the broadband SED in the framework of the external Compton scenario and discuss the possible emission site in view of multiwavelength data and alternative emission models.

  • 6.
    Ajello, M.
    et al.
    Clemson Univ, Kinard Lab Phys, Dept Phys & Astron, Clemson, SC 29634 USA..
    Baldini, L.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Barbiellini, G.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Bastieri, D.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Bellazzini, R.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Bissaldi, E.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Blandford, R. D.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Bonino, R.
    Ist Nazl Fis Nucl, Sez Torino, I-10125 Turin, Italy.;Univ Turin, Dipartimento Fis, I-10125 Turin, Italy..
    Bottacini, E.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA.;Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Bregeon, J.
    Univ Montpellier, CNRS IN2P3, Lab Univers & Particules Montpellier, F-34095 Montpellier, France..
    Bruel, P.
    CNRS IN2P3, Ecole Polytech, Lab Leprince Ringuet, F-91128 Palaiseau, France..
    Buehler, R.
    DESY, D-15738 Zeuthen, Germany..
    Cameron, R. A.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Caputo, R.
    CRESST, Greenbelt, MD 20771 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Caraveo, P. A.
    INAF Ist Astrofis Spaziale & Fis Cosm Milano, Via E Bassini 15, I-20133 Milan, Italy..
    Chiaro, G.
    INAF Ist Astrofis Spaziale & Fis Cosm Milano, Via E Bassini 15, I-20133 Milan, Italy..
    Ciprini, S.
    Agenzia Spaziale Italiana, Space Sci Data Ctr, Via Politecn, I-00133 Rome, Italy..
    Cohen-Tanugi, J.
    Univ Montpellier, CNRS IN2P3, Lab Univers & Particules Montpellier, F-34095 Montpellier, France..
    Costantin, D.
    Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    D'Ammando, F.
    INAF Ist Radioastron, I-40129 Bologna, Italy.;Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy..
    de Palma, F.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy.;Univ Telemat Pegaso, Piazza Trieste & Trento 48, I-80132 Naples, Italy..
    Di Lalla, N.
    Univ Pisa, I-56127 Pisa, Italy.;Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Di Mauro, M.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Di Venere, L.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Dominguez, A.
    Univ Complutense Madrid, Grp Altas Energias, E-28040 Madrid, Spain..
    Favuzzi, C.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Franckowiak, A.
    DESY, D-15738 Zeuthen, Germany..
    Fukazawa, Y.
    Hiroshima Univ, Dept Phys Sci, Higashihiroshima, Hiroshima 7398526, Japan..
    Funk, S.
    Friedrich Alexander Univ Erlangen Nurnberg, Erlangen Ctr Astroparticle Phys, Erwin Rommel Str 1, D-91058 Erlangen, Germany..
    Fusco, P.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Gargano, F.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Gasparrini, D.
    Agenzia Spaziale Italiana, Space Sci Data Ctr, Via Politecn, I-00133 Rome, Italy.;Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy..
    Giglietto, N.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Giordano, F.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Giroletti, M.
    INAF Ist Radioastron, I-40129 Bologna, Italy..
    Green, D.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Grenier, I. A.
    Univ Paris Diderot, Lab AIM, CEA IRFU, CNRS,Serv Astrophys,CEA Saclay, F-91191 Gif Sur Yvette, France..
    Guiriec, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;George Washington Univ, Dept Phys, 725 21st St NW, Washington, DC 20052 USA..
    Holt, C.
    Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA.;Univ Maryland Baltimore Cty, Ctr Space Sci & Technol, Baltimore, MD 21250 USA..
    Horan, D.
    CNRS IN2P3, Ecole Polytech, Lab Leprince Ringuet, F-91128 Palaiseau, France..
    Johannesson, G.
    Univ Iceland, Sci Inst, IS-107 Reykjavik, Iceland.;NORDITA, Roslagstullsbacken 23, SE-10691 Stockholm, Sweden..
    Kocevski, D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Kuss, M.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    La Mura, G.
    Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Li, J.
    Inst Space Sci CSICIEEC, Campus UAB,Carrer Magrans S-N, E-08193 Barcelona, Spain..
    Longo, F.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy..
    Loparco, F.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Lubrano, P.
    Ist Nazl Fis Nucl, Sez Perugia, I-06123 Perugia, Italy..
    Magill, J. D.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Maldera, S.
    Stanford Univ, SLAC Natl Accelerator Lab, Stanford, CA 94305 USA..
    Manfreda, A.
    Univ Pisa, I-56127 Pisa, Italy..
    Mazziotta, M. N.
    Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Michelson, P. F.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Mizuno, T.
    Hiroshima Univ, Hiroshima Astrophys Sci Ctr, Higashihiroshima, Hiroshima 7398526, Japan..
    Monzani, M. E.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Morselli, A.
    Ist Nazl Fis Nucl, Sez Roma Tor Vergata, I-00133 Rome, Italy..
    Negro, M.
    Ist Nazl Fis Nucl, Sez Torino, I-10125 Turin, Italy.;Univ Turin, Dipartimento Fis, I-10125 Turin, Italy..
    Nuss, E.
    Univ Montpellier, CNRS IN2P3, Lab Univers & Particules Montpellier, F-34095 Montpellier, France..
    Omodei, N.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Orienti, M.
    INAF Ist Radioastron, I-40129 Bologna, Italy..
    Orlando, E.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Paliya, V. S.
    Clemson Univ, Kinard Lab Phys, Dept Phys & Astron, Clemson, SC 29634 USA..
    Perkins, J. S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Persic, M.
    Ist Nazl Fis Nucl, Sez Trieste, I-34127 Trieste, Italy.;Ist Nazl Astrofis, Osservatorio Astron Trieste, I-34143 Trieste, Italy..
    Pesce-Rollins, M.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Piron, F.
    Univ Montpellier, CNRS IN2P3, Lab Univers & Particules Montpellier, F-34095 Montpellier, France..
    Principe, G.
    Friedrich Alexander Univ Erlangen Nurnberg, Erlangen Ctr Astroparticle Phys, Erwin Rommel Str 1, D-91058 Erlangen, Germany..
    Racusin, J. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Raino, S.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Rando, R.
    Ist Nazl Fis Nucl, Sez Padova, I-35131 Padua, Italy.;Univ Padua, Dipartimento Fis & Astron G Galilei, I-35131 Padua, Italy..
    Razzano, M.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Razzaque, S.
    Univ Johannesburg, Dept Phys, POB 524, ZA-2006 Auckland Pk, South Africa..
    Reimer, A.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA.;Leopold Franzens Univ Innsbruck, Inst Astro & Teilchenphys, A-6020 Innsbruck, Austria.;Leopold Franzens Univ Innsbruck, Inst Theoret Phys, A-6020 Innsbruck, Austria..
    Reimer, O.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA.;Leopold Franzens Univ Innsbruck, Inst Astro & Teilchenphys, A-6020 Innsbruck, Austria.;Leopold Franzens Univ Innsbruck, Inst Theoret Phys, A-6020 Innsbruck, Austria..
    Sgro, C.
    Siskind, E. J.
    NYCB Real Time Comp Inc, Lattingtown, NY 11560 USA..
    Spandre, G.
    Ist Nazl Fis Nucl, Sez Pisa, I-56127 Pisa, Italy..
    Spinelli, P.
    Univ Politecn Bari, Dipartimento Fis M Merlin, I-70126 Bari, Italy.;Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy..
    Tak, D.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Thayer, J. B.
    Stanford Univ, Kavli Inst Particle Astrophys & Cosmol, WW Hansen Expt Phys Lab, Dept Phys, Stanford, CA 94305 USA..
    Torres, D. F.
    ICREA, E-08010 Barcelona, Spain..
    Tosti, G.
    Univ Perugia, Dipartimento Fis, I-06123 Perugia, Italy..
    Valverde, J.
    CNRS IN2P3, Ecole Polytech, Lab Leprince Ringuet, F-91128 Palaiseau, France..
    Vogel, M.
    Calif State Univ Los Angeles, Dept Phys & Astron, Los Angeles, CA 90032 USA..
    Wood, K.
    Praxis Inc, Alexandria, VA 22303 USA.;Naval Res Lab, Washington, DC 20375 USA..
    Investigating the Nature of Late-time High-energy GRB Emission through Joint Fermi/Swift Observations2018Ingår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 863, nr 2, artikel-id 138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use joint observations by the Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveals that LAT nondetections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the nondetected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.

  • 7. Sitarek, J.
    et al.
    González, J. B.
    Ramazani, V. F.
    Lindfors, E.
    Pedaletti, G.
    Tavecchio, F.
    Acosta, M. V.
    Larsson, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Baliyan, K.
    Kaur, N.
    Sameer,
    Jorstad, S.
    Raiteri, C.
    Collaborations, MAGIC and Fermi-LAT
    MAGIC observations of variable very-high-energy gamma-ray emission from PKS1510-089 during May 2015 outburst2017Ingår i: Proceedings of Science, Sissa Medialab Srl , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    PKS1510-089 is a flat spectrum radio quasar located at a redshift of 0.36. It is one of only a few such sources detected in very-high-energy (VHE, >100 GeV) gamma rays. Though PKS1510-089 is highly variable at GeV energies, until recently no variability has been observed in the VHE band. In 2015 May PKS1510-089 showed a high state in optical and in the GeV range. A VHE gamma-ray flare was detected with MAGIC at that time, showing the first instance of VHE gamma-ray flux variability on the time scale of days in this source. We will present the MAGIC results from this observation, discuss their temporal and spectral properties in the multi-wavelength context and present modelling of such emission in the external Compton scenario. 

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