Long-Term X-Ray Flare in the Southern Blazar 1ES 1101-232
ATel #16396; Bidzina Kapanadze (Ilia State University, Tbilisi, Georgia; National Astrophysical Observatory, Abastumani, Georgia)
on 8 Jan 2024; 09:46 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
In ATel#16322 (posted by us on 2023 November 6), we reported a flaring X-ray state of the southern TeV-detected blazar 1ES 1101-232. Afterwards, the source continued an X-ray brightening and attained to the new highest historical 0.3-10 keV count rate of 3.18+/-0.09 cts/s (corresponding to the unabsorbed flux of about 7.7\times10^{-11}erg/cm^2/s^{-1}). This state was followed by low-amplitude brightness fluctuations, and 1ES 1101-232 regained the aforementioned highest brightness state during the last Swift-XRT visit to the source on 2024 January 4 (our TOO observations; Request Numbers 19587 and 19626). Similar to the results reported within ATel#16322, the source is showing curved 0.3-10 keV spectra characterized by hard or very hard photon index at 1 keV ($a$~1.7--1.9) and high spectral curvature ($b$~0.4--0.6). These properties can be explained in the framework of the first-order Fermi acceleration shifting the electron population with very low initial energy predominantly to the energies capable of producing photons around E~1 keV and relatively less frequently to the higher energies (Kapanadze B. et al. 2022, A&A, 668, 75). This yields the spectral hardening at the reference energy and derivation of very hard and extremely hard $a$ values, as well as establishment of a large spectral curvature. Due to the flaring X-ray state and extreme spectral properties of 1ES 1101-232, we strongly encourage intense MWL observations with the space and ground-based 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.
