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Acciari, VA,Aliu, E,Beilicke, M,Benbow, W,Boltuch, D,Bottcher, M,Bradbury, SM,Bugaev, V,Byrum, K,Cesarini, A,Ciupik, L,Cogan, P,Cui, W,Dickherber, R,Duke, C,Falcone, A,Finley, JP,Finnegan, G,Fortson, L,Furniss, A,Galante, N,Gall, D,Gibbs, K,Guenette, R,Gillanders, GH,Godambe, S,Grube, J,Hanna, D,Hui, CM,Humensky, TB,Imran, A,Kaaret, P,Karlsson, N,Kertzman, M,Kieda, D,Krawczynski, H,Krennrich, F,Lang, MJ,LeBohec, S,Maier, G,McArthur, S,McCann, A,Moriarty, P,Nagai, T,Ong, RA,Otte, AN,Pandel, D,Perkins, JS,Pichel, A,Pohl, M,Quinn, J,Ragan, K,Reyes, LC,Reynolds, PT,Roache, E,Rose, HJ,Schroedter, M,Sembroski, GH,Smith, AW,Steele, D,Swordy, SP,Theiling, M,Thibadeau, S,Vassiliev, VV,Vincent, S,Wakely, SP,Weekes, TC,Weinstein, A,Weisgarber, T,Williams, DA
2010
February
Astrophysical Journal Letters
DISCOVERY OF VARIABILITY IN THE VERY HIGH ENERGY gamma-RAY EMISSION OF 1ES 1218+304 WITH VERITAS
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()
Optional Fields
BL Lacertae objects: individual (1ES 1218+304=VER J1221+301) galaxies: active gamma rays: galaxies ACTIVE GALACTIC NUCLEI EXTRAGALACTIC BACKGROUND LIGHT PEAKED BL-LACERTAE W-COMAE BLAZARS SPECTRA ACCELERATION JET CONSTRAINTS TELESCOPE
709
163
167
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of similar to 6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching similar to 20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices Gamma <= 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical gamma-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.
DOI 10.1088/2041-8205/709/2/L163
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