Another Strong X-Ray Flare of TeV-Detected Blazar 1ES 0647+250

ATel #13520; bidzina Kapanadze (Ilia State University, Abastumani Astrophysical Observatory, Georgia)
on 24 Feb 2020; 19:29 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)

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In ATel #: 13331, we reported an advent of X-ray flare in the TeV-detected BL Lacertae object of unknown redhsift 1ES 0647+250, which was the strongest for this source since start of the monitoring with X-Ray Telescope onboard Neihl Gehrels Swift Observatory (Swift-XRT). Consequently, the 0.3-10 keV count rate attained to the value of 5.15+/-0.15 cts/s on 2019 December 3 which was the highest historical X-ray brightness for this source (see https://www.swift.psu.edu/monitoring/source.php?source=1ES0647+250). Nearly simultaneously, 1ES 0647+250 exhibited its highest optical-UV brightness since 2005 (as shown by our measurements of the UVOT data and the Tuorla R-band light curve available on http://users.utu.fi/kani/1m/1ES_0647+250.html ). Moreover, the TeV-band observations with MAGIC resulted in the detection of the source with a significance higher than 5 sigma during 2019 December 2-4, corresponding to about 10% of the flux of the Crab Nebula above 100 GeV (Mirzoyan et al. ATel#13324). Afterwards, the source showed brightness fluctuations by a factor of 1.5-2.2 and mean rate of about 3 cts/s (twice higher than that corresponding to the Swift-XRT observations of the source performed before this flare). Eventually, the source showed a brightness drop to 1.18+/-0.05 cts/s (recorded on 2020 February 15). However, the source is showing an onset of another strong X-ray flare: the 0.3-10 keV count rate has boosted by a factor of 3.3 in 8 days (to 3.95 cts/s, recorded on February 23 during the Swift-XRT pointing performed within our TOO request Number 13123). A gradually enhancing optical-UV activity is observed also with the Swift-UVOT instrument. Consequently, intense multiwavelength observations with the satellite and ground based devices 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.