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A strong X-ray Flare in TeV blazar 1ES 1959+650

ATel #8289; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia)
on 16 Nov 2015; 14:47 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, Blazar

Referred to by ATel #: 8337, 8342, 9148, 9949, 10430, 10514, 10743, 11059

The nearby TeV-detected blazar 1ES 1959+650 (z=0.047) shows a prolonged X-ray flaring activity since 2015 August 1, and the 0.3-10 keV count rate reached the value of 20.62+/-0.20 cts/s on November 15 (in the framework of our ToO observation of a medium urgency). Note that this rate corresponds to the highest historical X-ray flux value recorded since the start of Swift monitoring of 1ES 1959+650 (2005 April 19) - it is by 46% higher compared the previous highest one obtained on 2015 October 11 (see http://www.swift.psu.edu/monitoring/source.php?source=1ES1959+650 ) and by a factor of 3.2 larger than the weighted mean 0.3-10 keV count rate from the 138 Swift-XRT observations of this source. To date, 1ES 1959+650 has become the third blazar exceeding the level of 20 cts/s (after Mrk 421 and Mrk 501). The spectral analysis shows the presence of the spectral curvature with b=0.31+/-0.09, photon index at 1 keV a=1.78+/-0.06, synchrotron SED peak location 2.26+/0.16 keV. The unabsorbed 0.3-10 keV flux is equal to (6.17+/-0.16)\times10^{-10} erg/cm^2/s corresponding to the isotropic luminosity of 6.22\times10^{45} erg/s. In the framework of one-zone SSC models, an increased activity is also expected in the UV-radio and gamma-ray parts of the spectrum and intensive multiwavelength observations of 1ES 1959+650 are strongly encouraged to study instable processes and emission mechanisms in this source.