Bright optical outbursts of the FSRQ Ton 599 and 3C 345
ATel #11624; F. Jankowsky, S. Wagner (LSW Heidelberg)
on 9 May 2018; 11:48 UT
Credential Certification: Felix Jankowsky (f.jankowsky@lsw.uni-heidelberg.de)
Subjects: Optical, Gamma Ray, >GeV, TeV, VHE, AGN, Blazar, Quasar
Optical observations of the flat-spectrum radio quasar Ton 599 (4C 29.45, PKS 1156+295; z=0.7) with the Automatic Telescope for Optical Monitoring (ATOM) show a bright optical state. R-band observations conducted between 21 March 2018 and 8 May 2018 with ATOM reveal a continuous increase in flux from magnitude 15 to 13 – the highest recorded with ATOM since 2006. This includes rapid brightening by 0.5 magnitudes over 24 hours (between MJD 58245.4 and 58246.4). Ton 599 has recently shown increased activity in November 2017 in gamma-ray (ATel #10931, #10937) and optical bands (ATel #10948). Following that event, it has also been detected by Cherenkov telescopes in December (ATel #11061, #11075).
Furthermore, ATOM observations of the flat-spectrum radio-quasar 3C 345 (PKS 1641+399; z=0.6) also show an increase in optical flux. R-band observations conducted between 10 April 2018 and 8 May 2018 show an increase from magnitude 17.2 to 16.0. This is the brightest optical state since 2010. A previous bright gamma-ray state has been observed in May/June 2017 with Fermi-LAT (ATel #10453) – which, however, was not accompanied by a significant optical counter-part.
ATOM is a 75 cm telescope located at the H.E.S.S. site in the Khomas Highlands in Namibia. It regularly monitors galactic and extragalactic gamma-ray emitters and will continue observations of both Ton 599 and 3C 345.