Very Strong 0.3-10 keV flare in 1ES 1959+650

ATel #16162; Bidzina Kapanadze (Ilia State University, Tbilisi, Gerogia; E. Kharadze National Astrophysical Observatory, Abastumani, Georgia)
on 30 Jul 2023; 12:55 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, #10439, #10622; #11059, #11538, #16087). In ATel#16087 (posted on 2023 June 16), we reported on the onset of another Strong X-Ray Flare in the source with the 0.3-10 keV count rate (CR) of 13.25+/-0.14 cts/s. The subsequent observations with X-Ray Telescope onboard the Neil Gehrels Swift Observatory (Swift-XRT) recorded a further X-ray brightening of the source to the value 22.81+/-0.22 cts/s (on July 4), which is the highest value observed after 2018. After some minor decline, 1ES 1959+650 has re-brightened to the level CR=22.04+/-0.21 recorded during the last XRT visit performed on July 28 (in the framework of our TOO observations; see https://www.swift.psu.edu/monitoring/source.php?source=1ES1959+650). The latter corresponds to the unabsorbed 0.3-10 keV flux of (5.16+/-0.07)$\times$10^{-10} erg/cm^2/s. Due to the opportunity of recording a further X-ray brightening and enhanced multiwavelength (MWL) activity 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.