A Strong X-Ray Flare in the TeV-Detected Blazar 1ES 1959+650

ATel #16087; Bidzina Kapanadze (Ilia State University, Tbilisi, Gerogia; E. Kharadze National Astrophysical Observatory, Abastumani, Georgia)
on 16 Jun 2023; 21:38 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

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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, #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 long-term enhanced 0.3-10 keV activity. The 0.3-10 keV observation, performed on June 15 with the X-Ray Telescope onboard the Neil Gehrels Swift Observation (Swift-XRT; on the basis of our Target-of-Opportunity Request Number 18948), detected the in a strong X-ray flaring state corresponding to 13.25+/-0.14 cts/s. The latter is about twice higher than that recorded during the previous Swift-XRT visit to the source (2023 February 2). Due to the opportunity of recording another strong X-ray flare and enhanced multiwavelength (MWL) activity is predicted also in other spectral ranges in the framework of one-zone SSC scenario, we encourage intense MWL observations with the space and ground-based astronomical instruments. 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.