Very-High-Energy $\gamma$-Ray Observations of the Blazar 1ES 2344+514 with VERITAS

Abstract

We present very-high-energy $\gamma$-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above background of $20.8\sigma$ in $47.2$ hours (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations the temporal properties of 1ES 2344+514 are studied on short and long times scales. We fit a constant flux model to nightly- and seasonally-binned light curves and apply a fractional variability test, to determine the stability of the source on different timescales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly-binned light curves and for the long-term seasonally-binned light curve at the $>3\sigma$ level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (${\chi }^2/NDF=7.89/6$) by a power-law function with index $\Gamma =2.46\pm 0.06_{stat}\pm 0.20_{sys}$ and extends to at least 8 TeV. The extragalactic-background-light-deabsorbed spectrum is adequately fit (${\chi }^2/NDF=6.73/6$) by a power-law function with index $\Gamma =2.15\pm 0.06_{stat}\pm 0.20_{sys}$ while an F-test indicates that the power-law with exponential cutoff function provides a marginally-better fit (${\chi }^2/NDF$ = $2.56/5$) at the 2.1$\sigma$ level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source.

arXiv comment7 pages, 2 figures. Published in Monthly Notices of the Royal Astronomical Society

References in corpus (27)

• On characterising the variability properties of X-ray light curves from active galaxies
• The extragalactic optical-infrared background radiations, their time evolution and the cosmic photon-photon opacity
• The Connection between X-ray- and Radio-Selected BL Lacertae Objects
• Constraints on the Physical Parameters of TeV Blazars
• Modeling the Emission Processes in Blazars
• The First VERITAS Telescope
• The Extragalactic Background Light and the Gamma-ray Opacity of the Universe
• Very High Energy Gamma-Rays from AGN: Cascading on the Cosmic Background Radiation Fields and the Formation of Pair Halos
• The extragalactic background light, the Hubble constant, and anomalies: conclusions from 20 years of TeV gamma-ray observations
• Discovery of >350 GeV Gamma Rays from the BL Lacertae Object 1ES 2344+514
• The Sixth VLBA Calibrator Survey: VCS6
• VERITAS Observations of the gamma-Ray Binary LS I +61 303
• Observation of very high energy gamma-rays from the AGN 1ES 2344+514 in a low emission state with the MAGIC telescope
• Search for Magnetically Broadened Cascade Emission From Blazars with VERITAS
• Observations of 54 Active Galactic Nuclei with the HEGRA System of Cherenkov Telescopes
• Non-thermal Cosmic Backgrounds from Blazars: the contribution to the CMB, X-ray and gamma-ray Backgrounds
• Multiwavelength Observations of the VHE Blazar 1ES 2344+514
• The Simultaneous Low State Spectral Energy Distribution of 1ES 2344+514 from Radio to Very High Energies
• A Very High Energy Gamma-Ray Spectrum of 1ES 2344+514
• VERITAS detection of $\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations
• A New Mirror Alignment System for the VERITAS Telescopes
• Constraining the parameter space of the one-zone synchrotron-self-Compton model for GeV-TeV detected BL Lac objects
• Gamma-ray Observations Under Bright Moonlight with VERITAS
• The VERITAS Upgraded Telescope-Level Trigger Systems: Technical Details and Performance Characterization
• Very High Energy $\gamma$-ray and Near Infrared observations of 1ES2344+514 during 2004-05
• Highlights from the VERITAS AGN Observation Program
• Blazar Duty-Cycle at gamma-ray Frequecies: Constraints from Extragalactic Background Radiation and Prospects for AGILE and GLAST

Cited by in corpus (13)

• Improved limits on Lorentz invariance violation from astrophysical gamma-ray sources
• Multi-TeV flaring from high energy blazars: An evidence of the photohadronic process
• An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state
• Prospects for a Multi-TeV Gamma-ray Sky Survey with the LHAASO Water Cherenkov Detector Array
• Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES~2344+514
• Photohadronic interpretation of the different incarnation of 1ES 2344+514
• Propagation of very-high-energy $\gamma$-rays from distant blazars
• The `blazar sequence' in TeV band
• Prospects of additional contribution at Optical-NIR band of EBL in the light of VHE spectra
• Properties and Possible Physical Origins of $\gamma$-ray Emission in Extreme Synchrotron Blazars
• Revisiting the evidences for spectral anomalies in distant blazars: new data on the photon-ALP mixing
• Broadband Spectral Analysis of 1ES2344+514: A Multi-epoch study
• Multi-Band Optical Variability of Blazar 1ES 2344+514 on Diverse Time-Scales