MULTIWAVELENGTH OBSERVATIONS OF THE VERY HIGH ENERGY BLAZAR 1ES 2344+514
- Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States)
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
- Department of Physics, Washington University, St. Louis, MO 63130 (United States)
- School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
- Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)
- Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)
- Physics Department, University of Utah, Salt Lake City, UT 84112 (United States)
- Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
- Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)
- Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States)
Multiwavelength observations of the high-frequency-peaked blazar 1ES 2344+514 were performed from 2007 October to 2008 January. The campaign represents the first contemporaneous data on the object at very high energy (VHE, E >100 GeV) {gamma}-ray, X-ray, and UV energies. Observations with VERITAS in VHE {gamma}-rays yield a strong detection of 20{sigma} with 633 excess events in a total exposure of 18.1 hr live time. A strong VHE {gamma}-ray flare on 2007 December 7 is measured at F(>300 GeV) = (6.76 {+-} 0.62) x 10{sup -11} photons cm{sup -2} s{sup -1}, corresponding to 48% of the Crab Nebula flux. Excluding this flaring episode, nightly variability at lower fluxes is observed with a time-averaged mean of F(>300 GeV) = (1.06 {+-} 0.09) x 10{sup -11} photons cm{sup -2} s{sup -1} (7.6% of the Crab Nebula flux). The differential photon spectrum between 390 GeV and 8.3 TeV for the time-averaged observations excluding 2007 December 7 is well described by a power law with a photon index of {Gamma} = 2.78 {+-} 0.09{sub stat} {+-} 0.15{sub syst}. On the flaring night of 2007 December 7 the measured VHE {gamma}-ray photon index was {Gamma} = 2.43 {+-} 0.22{sub stat} {+-} 0.15{sub syst}. Over the full period of VERITAS observations contemporaneous X-ray and UV data were taken with Swift and RXTE. The measured 2-10 keV flux ranged by a factor of {approx}7 during the campaign. On 2007 December 8 the highest ever observed X-ray flux from 1ES 2344+514 was measured by Swift X-ray Telescope at a flux of F(2-10 keV) = (6.28 {+-} 0.31) x 10{sup -11} erg cm{sup -2} s{sup -1}. Evidence for a correlation between the X-ray flux and VHE {gamma}-ray flux on nightly timescales is indicated with a Pearson correlation coefficient of r = 0.60 {+-} 0.11. Contemporaneous spectral energy distributions (SEDs) of 1ES 2344+514 are presented for two distinct flux states. A one-zone synchrotron self-Compton (SSC) model describes both SEDs using parameters consistent with previous SSC modeling of 1ES 2344+514 from non-contemporaneous observations.
- OSTI ID:
- 21584860
- Journal Information:
- Astrophysical Journal, Vol. 738, Issue 2; Other Information: DOI: 10.1088/0004-637X/738/2/169; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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