Enhanced X-Ray Activity of the HBL Source 1ES 0033+595
ATel #10187; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University)
on 20 Mar 2017; 17:45 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
The TeV-detected high-energy peaked BL Lacertae object (HBL) 1ES 0033+595 was observed 64-times by X-Ray Telescope (XRT) onboard Swift since 2005 April 1, mostly in the framework of our Target of Opportunity (ToO) observations. During this monitoring, it was one of the bright HBLs with the 0.3-10 keV count rate ranging between 1.49+/-0.04 cts/s and 9.24+/-0.13 cts/s, and exhibiting two strong X-ray flares by a factor of 2.4--2.8 (see http://www.swift.psu.edu/monitoring /source.php?source=1ES0033+595; Kapanadze 2015, Atel#8107). During these flares, the source also underwent a fast flux and spectral variability (even on subhour timescales which are observed rarely in BLLs). Furthermore, 1ES 0033+595 generally showed very hard spectra with the photon index at 1 keV smaller than a=1.5 and the position of the synchrotron SED peak sometimes beyond 10 keV that occurs very rarely among HBLs. During the last three XRT observations of 1ES 0033+595, performed between 2017 February 18 and March 18 (our ToOs of a low urgency), the source showed the lowest historical 0.3-10 keV count rate which was twice larger during the last observation. During the latter, the source showed a very hard spectrum again, fitted well with the logparabola model (with the Hydrogen column density fixed to 4.13\times10^{21}, adopted from Karberl a et al. 2005, A&A, 440, 775) and yielding the photon index at 1 keV a=1.25+/-0.17, the curvature parameter b=0.63+/-0.22, the position of the SED peak Ep=3.94+/-1.09 keV. Intensive multiwavelength observations of 1ES 0033+595 are encouraged to study instable processes and emission mechanisms in this extreme HBL source.
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.
