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A New Highest Historical 0.3-10 keV Brightness State of TeV-detected Blazar 1ES 1959+650

ATel #10530; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia)
on 25 Jun 2017; 08:32 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, Blazar

In Atel#10430 and Atel#10514, posted on 2017 May 27 and June 20, respectively, we reported the gradually enhancing X-ray flaring activity of the nearby TeV-detected blazar 1ES 1959+650 (z=0.048). Afterwards, the source has been observed seven times with the X-Ray Telescope (XRT) onboard the satellite Swift, and it underwent an extreme X-ray flux variability (see http://www.swift.psu.edu/monitoring/source.php?source=1ES1959+650 ). Namely, the 0.3-10 keV count rate initially declined by 40% to 10.70+/-0.18 cts/s in 0.6 d (June 20), then a gradual increase of the brightness by a factor of 3.2 in 3.2 d was observed. The count rate attained the value of 34.0+/-0.20 cts/s (June 24) which is by 36% higher then its highest historical value recorded on 2016 July 2. Afterwards, the X-ray brightness has declined to 19.10+/-015 cts/s in 0.95 d, although the latter value is by a factor of 2.4 higher than the weighted mean rate from all XRT observations of this source. In the framework of one-zone SSC models, a flaring activity of our target 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. Nevertheless, it's familiar to this object to re-flare after some brightness drop during the high X-ray states (see Kapanadze et al. 2016a, MNRAS, 461, L26). XRT is one of the Swift instruments along with Burst Alert Telescope (BAT) and UV/Optical Telescope (UVOT). It is a JET-X Wolter I type telescope, developed jointly by Pennsylvania State University, Brera Astronomical Observatory (OAB) and University of Leicester. Thanks to the unique characteristics, good photon statistics and low background counts of this instrument (in combination with EEV CCD2 detector), we can investigate a flux variability on different time-scales from minutes to years, obtain high-quality spectra for the majority of the observations, derive different spectral parameters, and study their timing behaviour in the 0.3-10 keV range of the electromagnetic spectrum. The Swift Satellite is operated by Pennsylvania State University.