Kapanadze, B.B.KapanadzeDorner, D.D.DornerVERCELLONE, STEFANOSTEFANOVERCELLONEROMANO, PatriziaPatriziaROMANOHughes, P.P.HughesAller, M.M.AllerAller, H.H.AllerReynolds, M.M.ReynoldsKapanadze, S.S.KapanadzeTabagari, L.L.Tabagari2020-11-172020-11-1720180035-8711http://hdl.handle.net/20.500.12386/28403The X-ray variability of the BL Lacertae source 1ES 1959+650 was studied intensively with X-ray telescope (XRT) onboard Swift during 2016 January-August. In this paper, we present the results obtained during this campaign. A long-term high X-ray state was superimposed by shorter-term flares by a factor of 1.9-4.7. We found 35 instances of intra-day variability which showed very fast flux changes by 14-21 per cent occurring within 1 ks and a decline by a factor of 2.3 in 17.2 ks. Similarly to the previous years, this period sometimes was characterized by a lack of correlated X-ray and TeV variability, indicating that the high-energy emission in 1ES 1959+650 was generated in the emission region more complex than a single zone. The source showed a significant X-ray - high-energy flux correlation, while the former was not correlated with the optical-UV fluxes. The best fits of the 0.3-10 keV spectra were mainly obtained using the log-parabola model. Strong spectral variability was detected, shifting the peak of the spectral energy distribution by more than 10 keV that happens rarely in blazars. During some strong short-term flares, the photon index at 1 keV frequently became harder than 1.70, and the spectral evolution was characterized by a harder-when-brighter behaviour.STAMPAenArticle10.1093/mnras/stx24922-s2.0-85044328476000423731200078https://academic.oup.com/mnras/article/473/2/2542/42595772018MNRAS.473.2542KFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems