The Advent of X-ray Flare in PG 1553+113
ATel #8998; Bidzina Kapanadze (Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia)
on 27 Apr 2016; 20:33 UT
Credential Certification: Bidzina Kapanadze (bidzina_kapanadze@iliauni.edu.ge)
Referred to by ATel #: 9008
The TeV-detected BL Lac source of unknown redshift PG 1553+113 has been observed 23-times by Swift between 2015 December 24 and 2016 April 19 on the basis of our, Antonio Stemerra's and Abe Falcone's ToO requests of a different priority. During this monitoring, the 0.3 - 10 keV count rate initially increased from 0.82+/-0.03 cts/s to 3.07+/-0.64 cts/s, then it dropped to 0.71+/-0.03 cts/s in 31 d. After the subsequent increase to 80% in 8 d, the count rate showed a permanent drop by a factor of 2.43 till 0.53+/-0.03 cts/s (recorded on 2016 April 14). The today's observation has revealed the count rate of 1.83+/-0.09 cts/s that is by a factor of 3.2 larger than that recorded during the previous Swift pointing of this source performed on April 19. Note that the source exhibited a low X-ray brightness state during the last 1.5 months (with the count rate less than 0.84 cts/s), and since PG 1553+113 shows the advent of X-ray flare, the intensive multiwavelength observations of this object are strongly encouraged to study instable processes and emission mechanisms in this source. Nevertheless, an increasing activity is expected in the UV-radio and gamma-ray parts of the spectrum in the framework of one-zone SSC models.
