VERITAS observations of the BL Lac 1ES 1218+304
Abstract
The VERITAS collaboration reports the detection of very-high-energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 1218+304 located at a redshift of z=0.182. A gamma-ray signal was detected with a statistical significance of 10.4 standard deviations (10.4 sigma) for the observations taken during the first three months of 2007, confirming the discovery of this object made by the MAGIC collaboration. The photon spectrum between ~160 GeV and ~1.8 TeV is well described by a power law with an index of Gamma = 3.08 +/- 0.34_stat +/- 0.2_sys. The integral flux is Phi(E > 200 GeV) = (12.2 +/- 2.6) X 10^-12 cm^-2 s^-1, which corresponds to ~6% of that of the Crab Nebula. The light curve does not show any evidence for VHE flux variability. Using lower limits on the density of the extragalactic background light in the near to mid-infrared we are able to limit the range of intrinsic energy spectra for 1ES 1218+304. We show that the intrinsic photon spectrum has an index that is harder than Gamma = 2.32 +/- 0.37_stat. When including constraints from the spectra of 1ES 1101-232 and 1ES 0229+200, the spectrum of 1ES 1218+304 is likely to be harder than Gamma = 1.86 +/- 0.37_stat.
Keywords
Cite
@article{arxiv.0901.4561,
title = {VERITAS observations of the BL Lac 1ES 1218+304},
author = {VERITAS Collaboration and V. A. Acciari and E. Aliu and T. Arlen and M. Beilicke and W. Benbow and S. M. Bradbury and J. H. Buckley and V. Bugaev and Y. Butt and K. L. Byrum and O. Celik and A. Cesarini and L. Ciupik and Y. C. K. Chow and P. Cogan and P. Colin and W. Cui and M. K. Daniel and T. Ergin and A. D. Falcone and S. J. Fegan and J. P. Finley and P. Fortin and L. F. Fortson and A. Furniss and G. H. Gillanders and J. Grube and R. Guenette and G. Gyuk and D. Hanna and E. Hays and J. Holder and D. Horan and C. M. Hui and T. B. Humensky and A. Imran and P. Kaaret and N. Karlsson and M. Kertzman and D. B. Kieda and J. Kildea and A. Konopelko and H. Krawczynski and F. Krennrich and M. J. Lang and S. LeBohec and G. Maier and A. McCann and M. McCutcheon and P. Moriarty and R. Mukherjee and T. Nagai and J. Niemiec and R. A. Ong and D. Pandel and J. S. Perkins and M. Pohl and J. Quinn and K. Ragan and L. C. Reyes and P. T. Reynolds and H. J. Rose and M. Schroedter and G. H. Sembroski and A. W. Smith and D. Steele and S. P. Swordy and J. A. Toner and L. Valcarcel and V. V. Vassiliev and R. Wagner and S. P. Wakely and J. E. Ward and T. C. Weekes and A. Weinstein and R. J. White and D. A. Williams and S. A. Wissel and M. Wood and B. Zitzer},
journal= {arXiv preprint arXiv:0901.4561},
year = {2014}
}
Comments
Accepted for publication in The Astrophysical Journal