Kavli Affiliate: Erin Kara
| Summary:
We present results from a comprehensive multi-wavelength monitoring campaign of the changing-look active galactic nucleus 1ES 1927+654 during the onset and evolution of a relativistic radio jet $sim$(May 2022 – August 2025), using observations from XMM-Newton, Swift, TNG, ZTF, VLA, and VLBA. The soft X-ray emission lines at $sim 0.56$ keV and $sim 1$ keV have appeared with variable strength and width during the formation of the nascent jet. We note that the $sim 1$ keV feature has been persisting since the post-2017 flare phase. We also report the detection of a broad ($sim 800$ eV) FeK emission feature at $(6-7)$ keV in the $sim 70$ ks stacked EPIC-pn spectra, marking the first such detection, which historically was lacking in this source. The joint spectral fitting of XMM-Newton EPIC-pn and RGS data reveals the presence of ionized absorbers in 2022 ($logξmathrm/erg cm s^-1sim 1.5pm 0.3$, $mathrmN_H sim 2.5pm 0.9times 10^20 mathrmcm^-2$), but weaker than that detected during the high accretion state in 2018 (Eddington ratio, $λ_rm Edd>1$). The absorption features further weakened in 2023-2025 and were marginally detectable ($mathrmN_H le 10^20mathrmcm^-2$). The entire scenario is suggestive of a real-time transition of the accretion flow (from $λ_rm Edd>1$ to $λ_rm Eddsim 0.3$) during which the winds become weaker and the jet starts to form and evolve. Furthermore, both the soft X-ray $(0.3-2)$ keV and 5 GHz radio fluxes, which increased by factors of $sim 10$ and $sim 60$, respectively, since 2022, have recently plateaued at elevated levels, indicating a stabilized accretion disk, corona, and jet configuration.
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