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Another X-ray Flare in TeV-detected blazar 1ES 1959+650

ATel #10430; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia)
on 27 May 2017; 15:57 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, AGN, Blazar

Referred to by ATel #: 10514, 10530

Since 2015 August, the nearby TeV-detected HBL source 1ES 1959+650 (z=0.048) is in a phase of enhanced X-ray activity compared to the previous years (Kapanadze et al. 2016, MNRAS, 461, L26; ATel #8014, #8289, #8342, #8468, #9121, #9205, #9694, #9949, and http://www.swift.psu.edu/monitoring/source.php?source=1ES1959+650 for the historical 0.3-10 keV light curve). After the end of the resticted visibility of the source by Swift (on 2017 May 23), we have resumed its monitoring with the X-Ray Telescope onboard the satellite Swift (Swift-XRT), based on our Target of Opportunity (ToO) request Number 9432. The first observation of this campaign, performed on May 27, has found the source to be in a flaring state: the 0.3-10 keV count rate amounts to 12.93+/-0.10 cts/s which is by 76 per cent higher than the weighted mean rate from all XRT observations of this source. In the framework of one-zone SSC models, an enhanced 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.