We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs; E > 100 GeV). Power-law fits of the individual years are compatible with a steady mean photon index Gamma = 4.27 +/- 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma-ray variability. We also performed a temporal analysis of (all available) simultaneous Fermi/Large Area Telescope data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at VHEs with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone synchrotron self-Compton model, which gives the main physical parameters governing the VHE emission in the blazar jet.
PG 1553+113: FIVE YEARS OF OBSERVATIONS WITH MAGIC / Aleksic J; Alvarez EA; Antonelli LA; Antoranz P; Asensio M; Backes M; Barrio JA; Bastieri D; Gonzalez JB; Bednarek W; Berdyugin A; Berger K; Bernardini E; Biland A; Blanch O; Bock RK; Boller A; Bonnoli G; Tridon DB; Braun I; Bretz T; Canellas A; Carmona E; Carosi A; Colin P; Colombo E; Contreras JL; Cortina J; Cossio L; Covino S; Dazzi F; De Angelis A; De Caneva G; del Pozo ED; De Lotto B; Mendez CD; Ortega AD; Doert M; Dominguez A; Prester DD; Dorner D; Doro M; Elsaesser D; Ferenc D; Fonseca MV; Font L; Fruck C; Lopez RJG; Garczarczyk M; Garrido D; Giavitto G; Godinovic N; Hadasch D; Hafner D; Herrero A; Hildebrand D; Ohne-Monch DH; Hose J; Hrupec D; Huber B; Jogler T; Kellermann H; Klepser S; Krahenbuhl T; Krause J; La Barbera A; Lelas D; Leonardo E; Lindfors E; Lombardi S; Lopez M; Lopez-Oramas A; Lorenz E; Makariev M; Maneva G; Mankuzhiyil N; Mannheim K; Maraschi L; Mariotti M; Martinez M; Mazin D; Meucci M; Miranda JM; Mirzoyan R; Miyamoto H; Moldon J; Moralejo A; Munar-Adrover P; Nieto D; Nilsson K; Orito R; Oya I; Paneque D; Paoletti R; Pardo S; Paredes JM; Partini S; Pasanen M; Pauss F; Perez-Torres MA; Persic M; Peruzzo L; Pilia M; Pochon J; Prada F; Moroni PGP; Prandini E; Puljak I; Reichardt I; Reinthal R; Rhode W; Ribo M; Rico J; Rugamer S; Saggion A; Saito K; Saito TY; Salvati M; Satalecka K; Scalzotto V; Scapin V; Schultz C; Schweizer T; Shayduk M; Shore SN; Sillanpaa A; Sitarek J; Sobczynska D; Spanier F; Spiro S; Stamatescu V; Stamerra A; Steinke B; Storz J; Strah N; Suric T; Takalo L; Takami H; Tavecchio F; Temnikov P; Terzic T; Tescaro D; Teshima M; Tibolla O; Torres DF; Treves A; Uellenbeck M; Vankov H; Vogler P; Wagner RM; Weitzel Q; Zabalza V; Zandanel F; Zanin R; Buson S; Horan D; Larsson S; DAmmando F. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 748:1(2012), pp. 46.46-46.55. [10.1088/0004-637X/748/1/46]
PG 1553+113: FIVE YEARS OF OBSERVATIONS WITH MAGIC
D'AMMANDO, FILIPPO
2012
Abstract
We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs; E > 100 GeV). Power-law fits of the individual years are compatible with a steady mean photon index Gamma = 4.27 +/- 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma-ray variability. We also performed a temporal analysis of (all available) simultaneous Fermi/Large Area Telescope data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at VHEs with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone synchrotron self-Compton model, which gives the main physical parameters governing the VHE emission in the blazar jet.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
