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تسجيل مستخدم جديدDiscovery of very-high-energy emission from RGB J2243+203 and derivation of its redshift upper limit
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Very-high-energy (VHE; $>$ 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 21 and 24 December 2014. The VERITAS energy spectrum from this source can be fit by a power law with a photon index of $4.6 pm 0.5$, and a flux normalization at 0.15 TeV of $(6.3 pm 1.1) times 10^{-10} ~ textrm{cm}^{-2} textrm{s}^{-1} textrm{TeV}^{-1}$. The integrated textit{Fermi}-LAT flux from 1 GeV to 100 GeV during the VERITAS detection is $(4.1 pm 0.8) times 10^{textrm{-8}} ~textrm{cm}^{textrm{-2}}textrm{s}^{textrm{-1}}$, which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, ($4.0 pm 0.1 times 10^{textrm{-9}} ~ textrm{cm}^{textrm{-2}}textrm{s}^{textrm{-1}}$). The detection with VERITAS triggered observations in the X-ray band with the textit{Swift}-XRT. However, due to scheduling constraints textit{Swift}-XRT observations were performed 67 hours after the VERITAS detection, not simultaneous with the VERITAS observations. The observed X-ray energy spectrum between 2 keV and 10 keV can be fitted with a power-law with a spectral index of $2.7 pm 0.2$, and the integrated photon flux in the same energy band is $(3.6 pm 0.6) times 10^{-13} ~textrm{cm}^{-2} textrm{s}^{-1}$. EBL model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z $<~0.9$ to z $<~1.1$.
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