Strong X-Ray Flare in the TeV-Detected Blazar 1ES 1959+650
ATel #16449; Bidzina Kapanadze (Ilia State University, Tbilisi, Georgia; National Astrophysical Observatory, Abastumani, Georgia)
on 14 Feb 2024; 20:10 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
In ATel #16437, a LHAASO detection of strong TeV Gamma-ray Activity from 1ES 1959+650 was reported, starting at MJD 60347.02 and accumulating a significance of 8.7 s.d. (with a flux of ~0.5 Crab Unit above 1 TeV) till 60348.33. Following this detection, we initiated Target of Opportunity observations with Neil Gehrels Swift Observatory (Request Number 20093). The first observation was performed today (since the source was associated with a polar restriction for the Swift satellite) and 1ES 1959+650 has been found in a strong X-ray flaring state: the 0.3-10 keV count rate amounted to 20.35+/-0.12 cts/s which is a factor of ~2.2 higher than that from all observations performed with the X-ray Telescope onboard Swift (Swift-XRT) and corresponding to the unabsorbed 0.3-10 keV flux of (7.60+/-0.05)\times 10^{-10} erg/cm^2/s for the Hydrogen column density of 10^21/cm^2. The spectrum is hard: the photon index at 1 keV $\alpha$=1.88+/-0.02. Due to the opportunity of recording a further X-ray brightening and strong multiwavelength (MWL) activity is expected also in other spectral ranges (in the framework of one-zone SSC scenario), we encourage intense MWL observations with the space and ground-based astronomical 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.
