Studying the Extreme Behaviour of 1ES 2344+51.4

Abstract

The BL Lac type object 1ES 2344+51.4 (redshift $z=0.044$) was one of the first sources to be included in the extreme high-peaked BL Lac (EHBL) family. EHBLs are characterised by a broadband spectral energy distribution (SED) featuring the synchrotron peak above $\sim 10^{17}$ Hz. From previous studies of 1ES 2344+51.4 in the very-high-energy (VHE, $>$100 GeV) gamma-ray range, its inverse Compton (IC) peak is expected around 200 GeV. 1ES 2344+51.4 was first detected in the VHE range by Whipple in 1995 during a very bright outburst showing around 60 % of the flux of the Crab Nebula above 350 GeV. In 1996, during another flare in the X-ray band, observations with Beppo-SAX revealed a large 0.1-10 keV flux variability on timescales of a few hours and an impressive frequency shift of the synchrotron peak to above $10^{18}$ Hz. Later on, this extreme behaviour of the source motivated several multiwavelength campaigns, during most of which the source appeared to be in a low state and showing no clear signs of "extremeness". In August 2016, FACT detected 1ES 2344+51.4 in a high state and triggered multiwavelength observations. The VHE observations show a flux level similar to the historical maximum of 1995. The combination of MAGIC, FACT, and Fermi-LAT spectra provides an unprecedented characterisation of the IC peak. It is the first time that simultaneous HE and VHE data are presented for this object during a flaring episode. We find an atypically hard spectrum in the VHE $\gamma$-rays as well as a hard X-ray spectrum, revealing a renewed extreme behaviour.

arXiv comment8 pages, 3 figures, 36th International Cosmic Ray Conference (ICRC2019), July 24th-August 1st, 2019. Madison, WI, U.S.A

References in corpus (13)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• Modeling the Emission Processes in Blazars
• Design and Operation of FACT -- The First G-APD Cherenkov Telescope
• Extreme synchrotron BL Lac objects
• Discovery of >350 GeV Gamma Rays from the BL Lacertae Object 1ES 2344+514
• Fermi observations of TeV-selected AGN
• The extreme HBL behaviour of Markarian 501 during 2012
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• 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
• FACT - Monitoring Blazars at Very High Energies