Enhanced X-ray Activity of the UHBL Source 1ES 0033+595
ATel #11494; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia; INAF-OAB, Merate, Italy)
on 1 Apr 2018; 21:16 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
The TeV-detected ultra-high-energy peaked BL Lacertae source (UHBL) 1ES 0033+595 was observed 87 times with X-Ray Telescope (XRT) onboard the Neil Geherels Swift Observatory since 2005 April 1 with a total exposure of 117 ks (Mostly, in the framework of our ToO requests). During this monitoring, 1ES 0033+595 was one of the bright BL Lac sources in X-rays with the 0.3-10 keV count rate ranging between 1.39+/-0.04 cts/s and 9.24+/-0.13 cts/s, and exhibiting fast X-ray flares by a factor of 2.2--2.8 (see http://www.swift.psu.edu/monitoring /source.php?source=1ES0033+595; Kapanadze et al. 2015, Atel#8107). During these instances, the source also showed a fast flux and spectral variability down to the sub-hour timescales. Furthermore, 1ES 0033+595 generally showed very hard X-ray spectra with the photon index at 1 keV a=0.93-1.45 and the position of the synchrotron SED peak sometimes moved beyond 10 keV (that occurs very rarely among BL Lacs; see Kapanadze et al. 2016, 831, 102; 2017, ApJ, 848; 103; MNRAS, 469, 1655; MNRAS, 473, 2542). This property is explained in the framework of hadronic models more easily than via the leptonic ones (Sukla et al. 2015, ApJ, 798,2). The last XRT observation performed on 2018 April 1 has evealed a brightening by 36% to 2.50+/-0.08 cts/s in 4 day. The corresponding 0.3-10 keV spectrum shows a good fit with the log-parabolic model (the reduced Chi-squared of 1.04 with 52 degrees-f-freedom; the hydrogen column density fixed to the Galactic value 4.13\times10^{21} from Kalberla er al. 2005, A&A, 440, 775) yielding a=0.99+/-0.24, b=1.06+/-0.31 and the de-absorbed 0.3-10 keV flux of 1.2\times10^{-10} erg/cm^2/s. In the framework of one-zone SSC models, enhanced activity of 1ES 0033+595 is also expected in the UV-radio and gamma-ray parts of the spectrum, and intensive multiwavelength observations of this source are strongly encouraged.
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.