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Long-Term X-Ray Flare in the Blazar 1ES 1959+650

ATel #15433; Bidzina Kapanadze (E. Kharadze National Astrophysical Observatory; Ilia State University, Tbilisi, Georgia; INAF-OAB, Merate, Italy)
on 14 Jun 2022; 19:12 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

Subjects: X-ray, AGN, Blazar

Referred to by ATel #: 15778

Since 2015 August, the TeV-detected blazar 1ES 1959+650 was in a phase of significantly enhanced X-ray activity compared to the previous years, characterized by long-term flares on timescales of a few months and faster flares by a factor of 2-3 lasting 2-4 weeks (Kapanadze et al. 2016, MNRAS, 461, L26; Kapanadze et al. 2018a, MNRAS, 473, 2542; Kapanadze et al. 2018b, ApJS, 238, 13; ATel #9949, # 9694, #9205, # 9121, #8468, # 8342, # 8289, #8014, #10439, #10622; #11059, #11538). After showing a long-term X-ray decline during 2021 October-October and reaching a baseline level of ~2.5 cts/s, the source has undergone another yearly cycle of the 0.3-10 keV flare (observations with the X-Ray Telescope onboard Neil Gehrels Swift Observatory, Swift-XRT; see https://www.swift.psu.edu/monitoring/source.php?source=1ES1959+650). Namely, it showed the count rate of ~(10.5--14.5) cts/s (corresponding to (4.05--4.65)$\times$10^{-10} erg/cm^2/s) during the three Swift-XRT observations performed during 2022 June 12-14. Consequently, intensive multiwavelength observations of 1ES 1959+650 are strongly encouraged for discerning the underlying emission mechanisms and instable processes. 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.