Long-term X-Ray Flare and Extremely Hard Spectra in TeV-Detected Blazar H1426+428
ATel #16879; Bidzina Kapanadze (Ilia State University, Tbilisi, Georgia; National Astrophysical Observatory, Abastumani, Georgia)
on 29 Oct 2024; 08:20 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
In Atel#16871 (posted on 2024 October 21), we reported an elevated X-ray state in the TeV-detected BLazar H1426+428 (z=0.129). The subsequent observation performed with the X-Ray Telescope onboard Neil Gehrels Swift Observatory (Swift-XRT) on October 26 showed a subsequent brightening of the source: the observation-binned 0.3-10 keV count rate amounted to 3.10+/-0.08 cts/s, which is about 25 and 45 per cent higher than that recorded during the previous Swift visit to H1426+428 (on October 20) and
the mean rate from all 217 XRT observations to the source carried out since 2004 December 22, respectively. Note also that the current 0.3-10 keV level is about twice higher than that recorded in the beginning of 2024 September, achieved via the long-term gradual brightness increase. The 0.3-10 keV spectrum is even more hard spectrum during the previous observation (reported to be very hard; see Atel#16871), with the photon-index at 1 keV $a$=1.64+/-0.05, the curvature parameter $b$=0.16+/-0.10 and the synchrotron SED peak to be situated beyond 10 keV. The latter result has been recorded rarely even high-energy-peaked BL Lacerate obsjects (HBLs, a blazar group incorporating our target). This may serve as an indication of the significant contribution of the photons produced within different hadronic cascades (see, e.g., Kapanadze 2023, Universe, 9, 344). Since the source has shoving an X-ray flaring activity and a similar behaviour is expected in the framework of one-zone synchrotron self-Compton scenarios, the intense multiwavelength observations of H1426+428 are strongly encouraged for discerning the underlying emission mechanisms and instable processes.
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.
