DOI

https://doi.org/10.48717/h9k1-gc09

Project

RB008

Title

e-EVN: EW031C, RG013F, EG123D, RB008, SE001A

Abstract

The formerly type-II AGN 1ES 1927+654 is widely considered one of the most unusual and extreme CL-AGN yet discovered, exhibiting an extreme 4 magnitude flare in the optical in late 2017 concurrent with the first-ever appearance of broad emission lines. Multi-wavelength monitoring since the event has shown strong variability in the soft X-rays corresponding to the twice-repeated destruction and reappearance of the X-ray corona. Ongoing X-ray monitoring now shows that the soft X-ray flux is again rising and a very recent VLBA observation on 27 April shows an unprecedented factor-of-20 increase in the VLBA radio flux to match the X-rays. We have then started a daily VLA+Swift+NICER campaign of 1ES 1927 since 20 May 2022. The daily VLA C-band observations have shown that the source radio flux jumped to 30 mJy in April, and to 60 mJy on 20 May. On 21 May it went down slightly to 54 mJy, but again it raised to 61 mJy on 22nd May. The VLA observations were paired with three observations with the VLBA (C and X band) at roughly the start, middle, and end of the period (∼1 week separation, 10 hr total request). We request one epoch EVN observations at K-band to complement our dataset at high frequency, in order to be able to test different scenarios, such as magnetically driven expanding plasma, an emerging radio component or coronal variability. For all of them the information at high frequency is crucial.