论文信息 - VERITAS Observations of the BL Lac Object 1ES 1218+304 - 字舞流文

VERITAS Observations of the BL Lac Object 1ES 1218+304

The VERITAS collaboration reports the detection of very-high-energy 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?) 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 ? = 3.08 ? 0.34stat ? 0.2sys. The integral flux is ?(E>200GeV) = (12.2 ? 2.6) ? 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 very high energy 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 ? = 2.32 ? 0.37stat. 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 ? = 1.86 ? 0.37stat.

R. Guenette | Wei Cui | Stephan LeBohec | D. S. Hanna | R. Mukherjee | R. A. Ong | D. B. Kieda | S. P. Swordy | S. P. Wakely | M. K. Daniel | Henric Krawczynski | M. Beilicke | A. W. Smith | T. B. Humensky | A. Konopelko | V. V. Vassiliev | Martin Pohl | P. Kaaret | J. Quinn | Stephanie Wissel | V. Bugaev | W. Benbow | S. M. Bradbury | A. Cesarini | L. Ciupik | J. P. Finley | J. Grube | C. M. Hui | N. Karlsson | F. Krennrich | M. J. Lang | P. Moriarty | J. S. Perkins | K. Ragan | L. C. Reyes | P. T. Reynolds | M. Schroedter | G. H. Sembroski | T. C. Weekes | R. G. Wagner | Gernot Maier | Jamie Holder | Geza Gyuk | Lucy Fortson | M. Kertzman | H. J. Rose | E. Hays | D. Horan | David A. Williams | V. A. Acciari | K. L. Byrum | M. Wood | J. A. Toner | G. H. Gillanders | J. Kildea | A. McCann | M. McCutcheon | J. E. Ward | B. Zitzer | James Buckley | O. Celik | S. J. Fegan | P. Fortin | E. Aliu | T. Arlen | P. Cogan | A. Imran | D. Pandel | D. Steele | A. Weinstein | R. J. White | Y. C. K. Chow | A. D. Falcone | L. Valcarcel | Y. Butt | T. Nagai | Jacek Niemiec | Pierre Colin | Tulun Ergin | Amy Furniss

[1] HESS Collaboration F. Aharonian,et al. New constraints on the mid-IR EBL from the HESS discovery of VHE gamma-rays from 1ES 0229+200 , 2007, 0709.4584.

[2] M. Böttcher. Modeling the emission processes in blazars , 2006, astro-ph/0608713.

[3] Discovery of very high energy gamma rays from 1ES 1218+30.4 , 2006 .

[4] S. Funk,et al. Background modelling in very-high-energy gamma-ray astronomy , 2006 .

[5] A. R. Bazer-Bachi,et al. An Exceptional Very High Energy Gamma-Ray Flare of PKS 2155–304 , 2007, 0706.0797.

[6] M. Baring,et al. Blazar γ-Rays, Shock Acceleration, and the Extragalactic Background Light , 2007, 0707.4676.

[7] H. Krawczynski,et al. Comparison of techniques to reconstruct VHE gamma-ray showers from multiple stereoscopic Cherenkov images , 1999 .

[8] INTERGALACTIC PHOTON SPECTRA FROM THE FAR IR TO THE UV LYMAN LIMIT FOR 0 < Z < 6 AND THE OPTICAL DEPTH OF THE UNIVERSE TO HIGH ENERGY GAMMA-RAYS , 2005, astro-ph/0510449.

[9] Otaviano Helene,et al. Upper limit of peak area , 1983 .

[10] E. al.,et al. Upper Limits from HESS active galactic nuclei Observations in 2005-2007 , 2007, 0711.3196.

[11] Probing galaxy formation with high energy gamma-rays , 2000, astro-ph/0201119.

[12] Richard L. White,et al. The FIRST Survey: Faint Images of the Radio Sky at twenty centimeters , 1995 .

[13] J. M. Davies,et al. Design of the quartermaster solar furnace , 1957 .

[14] Paolo Giommi,et al. The Connection between X-Ray-- and Radio-selected BL Lacertae Objects , 1995 .

[15] Ti-Pei Li,et al. Analysis methods for results in gamma-ray astronomy , 1983 .

[16] E. L. Wright,et al. Number Counts at 3 μm < λ < 10 μm from the Spitzer Space Telescope , 2004 .

[17] Vladimir Vassiliev,et al. VERITAS: the Very Energetic Radiation Imaging Telescope Array System , 1997 .

[18] et al,et al. Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with HESS and broadband characterisation , 2007, 0705.2946.

[19] Felix A. Aharonian,et al. Simultaneous X-Ray and Gamma-Ray Observations of TEV Blazars: Testing Synchro-Compton Emission Models and Probing the Infrared Extragalactic Background , 1998 .

[20] J. Ellis,et al. Probing Quantum Gravity using Photons from a flare of the active galactic nucleus Markarian 501 Observed by the MAGIC telescope , 2007, 0708.2889.

[21] M. Raue,et al. New limits on the density of the extragalactic background light in the optical to the far-infrared from the spectra of all known TeV blazars , 2007, astro-ph/0701694.

[22] U. Utah,et al. Gamma-Hadron Separation Methods for the VERITAS Array of Four Imaging Atmospheric Cherenkov Telescopes , 2006, astro-ph/0604508.

[23] H. Krawczynski,et al. The first VERITAS telescope , 2006, astro-ph/0604119.

[24] Simon P. Swordy,et al. VERITAS: the Very Energetic Radiation Imaging Telescope Array System , 1999 .

[25] L. Costamante,et al. TeV candidate BL Lac objects , 2001, astro-ph/0112201.

[26] Lucia Pozzetti,et al. Deep galaxy counts, extragalactic background light and the stellar baryon budget , 1999, astro-ph/9907315.

[27] P. J. Boyle,et al. Extremely rapid bursts of TeV photons from the active galaxy Markarian 421 , 1996, Nature.

[28] R. Gould,et al. Pair production in photon-photon collisions. , 1967 .

[29] Felix A. Aharonian,et al. Klein-Nishina effects in the spectra of non-thermal sources immersed in external radiation fields , 2005, astro-ph/0504388.

[30] O. C. de Jager,et al. TeV gamma rays from 3C 279 - A possible probe of origin and intergalactic infrared radiation fields , 1992 .

[31] SIMULTANEOUS CONSTRAINTS ON THE SPECTRUM OF THE EXTRAGALACTIC BACKGROUND LIGHT AND THE INTRINSIC TeV SPECTRA OF MARKARIAN 421, MARKARIAN 501, AND H1426+428 , 2004, astro-ph/0406565.

[32] A. Noutsos,et al. A low level of extragalactic background light as revealed by γ-rays from blazars , 2006, Nature.