The Higherst Historical 0.3-10 keV State of the TeV Source 1ES 0647+250

ATel #13324; bidzina Kapanadze (Ilia State University, Abastumani Astrophysical Observatory, Georgia)
on 2 Dec 2019; 06:35 UT
Credential Certification: Bidzina Kapanadze (

Subjects: Blazar

Referred to by ATel #: 13331

The TeV-detected BL Lacertae object of unknown redshift 1ES 0647+250 was targeted with the X-Ray Telescope onboard the Swift satellite (Swift-XRT) on 2019 November 29 in the framework of our Target of Opportunity (TOO) request Number 13123. This observation found the source in the highest X-ray state since the start of its monitoring with Swift (2005 April 1; Moreover, the 0.3-10 keV spectrum was hard with the photon index at 1 keV a=1.85+/-0.09 and showed the presence of the synchrotron SED peak position beyond 2 keV. In the framework of one-zone SSC models, an enhanced activity of 1ES 0647+250 is expected also in the UV-radio and gamma-ray parts of the spectrum, and intensive multiwavelength observations of this source are strongly encouraged. 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.