Strong X-Ray Flaring Activity of PKS 2155-304
ATel #16668; Bidzina Kapanadze (Ilia State University, Tbilisi, Georgia; National Astrophysical Observatory, Abastumani, Georgia)
on 24 Jun 2024; 11:33 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
Since 2024 May, the southern TeV-detected HBL source PKS 2155-304 (z=0.116) is showing a strong flaring activity recorded with X-Ray Telescope onboard Neil Gehrels Swift Observatory. Consequently, the 0.3-10 keV count rate attained to the value of 14.09+/-0.12 cts/s on June 15 (the Swift Target of Opportunity observation triggered by Alicja Wierzcholska) that was very close to the highest historical X-ray state recorded during the exceptional TeV-band outburst of the source in 2006 July (see https://www.swift.psu.edu/monitoring/source.php?source=PKS2155-304 and Kapanadze B. et al. 2014, MNRAS 444, 1077). Afterwards, the 0.3-10 keV brightness declined to the value of 3.90+/-0.08 cts/s (on June 21), but the underwent the subsequent short-term flare and the count rate almost double in about 2 days to 7.65+/-0.10 cts/s (on June 23, our Swift-TOO observation Request Number 20669). Since the further X-ray brightening is anticipated, as well as an enhanced multiwavelength (MWL) activity is predicted also in other spectral ranges in the framework of one-zone SSC scenario, we strongly 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.
