The Lowest Historical 0.3-10 keV State of the TeV-Detected Blazar 1ES 1011+496
ATel #15936; Bidzina Kapanadze (Ilia State University, Tbilisi, Gerogia; E. Kharadze National Astrophysical Observatory, Abastumani, Georgia)
on 7 Mar 2023; 19:49 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
The TeV-detected blazar 1ES 1011+496 (z=0.212) has been observed 70 times with X-Ray Telescope onboard the Neil Gehrels Swift Observatory (Swift-XRT), revealing a large variability in the 0.3-10 keV count rate between 0.15+/-0.01 cts/s and 5.51+/-0.15 cts/s with four X-ray flares by a factor of 2-5 during the densely-sampled Swift campaigns (see https://www.swift.psu.edu/monitoring/source.php?source=1ES1011+496). The lowest Historical 0.3-10 keV State was recorded during the last XRT visit to the source performed on 2023 March, in the framework of our Target-of-Opportunity Request Number 12871. 1ES 1011+496 did not show a variability during the 2.9-ks exposure (in the photon counting mode), which was distributed over the three different Swift orbits with a total time span of 19 ks (including the 'blank' intervals between the subsequent visits). Note that the observation of such an instance is anticipated in the lowest ('quiescent') state when the variable flux from the very very fast instable process, occurring in the accretion disc, is not overwhelmed by a strong emission produced at the front of the relativistic shock front propagating through the blazar jet (in flaring states). The x-ray keV spectrum was very soft with the photon index of 2.58+/-10 and unabsorbed 0.3-10 keV flux of (456+/-0.29)x10^{-12} erg/cm^2/s.
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.
