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Another Very Strong X-ray Flare in 1ES 1959+650

ATel #9694; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia)
on 31 Oct 2016; 21:49 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, Blazar

Referred to by ATel #: 9949, 10430, 10514, 10743, 11059, 11538, 15433, 16087, 16162

The nearby TeV-detected HBL source 1ES 1959+650 (z=0.047) has been observed five times by X-ray Telescope onboard the Swift satellite (Swift-XRT) in the framework of our Target of Opportunity (ToO) requests of different urgencies (ToO Request Number: 8544, 8614, 8623; see https://www.swift.psu.edu/secure/toop/summary.php) which revealed an onset of the third very strong X-ray flare during the last 1 year period. The 0.3-10 keV count rate has shown a permanent increase as follows: October 7 7.21+/-0.09 cts/s October 19 9.92+/-0.12 cts/s October 21 10.93+/-0.12 cts/s October 30 16.95+/-0.15 cts/s October 31 20.46+/-0.15 cts/s Note that the later value is only by 18% smaller than highest historical 0.3-10 keV flux recorded on 2016 July 2 in the framework of the ToO observations triggered by us (ToO Request Number: 8261) and by a factor of 2.8 larger than the weighted mean rate from all XRT observations of this source. 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. 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.