The Emergence of X-Ray Emission Lines during Relativistic Radio-jet Formation in the Changing-look Active Galactic Nucleus 1ES 1927+654

@article{sadaula2026emergence,
  title = {{The Emergence of X-Ray Emission Lines during Relativistic Radio-jet Formation in the Changing-look Active Galactic Nucleus 1ES 1927+654}},
  author = {Dev R. Sadaula and Sibasish Laha and Eileen T. Meyer and Onic I. Shuvo and Main Pal and Ritesh Ghosh and Matteo Guainazzi and Fabio Pacucci and Stefano Bianchi and Luigi Gallo and Rostom Mbarek and Amelia M. Hankla and Fabio La Franca and Tahir Yaqoob and Megan Masterson and Erin Kara and Missagh Mehdipour and Claudio Ricci and Javier A Garcia and Timothy R. Kallman and Ralf Ballhausen and Mitchell C. Begelman and Alexander Philippov and Suvendu Rakshit and Francesca Panessa and Ehud Behar and S. Bradley Cenko and Federica Ricci and Ilaria Villani and James N. Reeves},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/ae96b4},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae96b4},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - The Emergence of X-Ray Emission Lines during Relativistic Radio-jet Formation in the Changing-look Active Galactic Nucleus 1ES 1927+654
AU  - Dev R. Sadaula
AU  - Sibasish Laha
AU  - Eileen T. Meyer
AU  - Onic I. Shuvo
AU  - Main Pal
AU  - Ritesh Ghosh
AU  - Matteo Guainazzi
AU  - Fabio Pacucci
AU  - Stefano Bianchi
AU  - Luigi Gallo
AU  - Rostom Mbarek
AU  - Amelia M. Hankla
AU  - Fabio La Franca
AU  - Tahir Yaqoob
AU  - Megan Masterson
AU  - Erin Kara
AU  - Missagh Mehdipour
AU  - Claudio Ricci
AU  - Javier A Garcia
AU  - Timothy R. Kallman
AU  - Ralf Ballhausen
AU  - Mitchell C. Begelman
AU  - Alexander Philippov
AU  - Suvendu Rakshit
AU  - Francesca Panessa
AU  - Ehud Behar
AU  - S. Bradley Cenko
AU  - Federica Ricci
AU  - Ilaria Villani
AU  - James N. Reeves
PY  - 2026
DA  - 2026/10/29
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae96b4
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/ae96b4
AB  - We present results from a comprehensive multiwavelength monitoring campaign of the changing-look active galactic nucleus 1ES 1927+654 during the onset and evolution of a relativistic radio jet ∼(2022 May–2025 August), using observations from XMM-Newton, Swift, Telescopio Nazionale Galileo (TNG), the Zwicky Transient Facility (ZTF), Very Large Array (VLA), and Very Long Baseline Array (VLBA). The soft X-ray emission lines at ∼0.56 keV and ∼1 keV have appeared with variable strength and width during the formation of the nascent jet. We note that the ∼1 keV feature has been persisting since the post-2017 flare phase. We also report the detection of a broad (∼800 eV) FeK emission feature at (6–7) keV in the ∼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 Reflection Grating Spectrometer (RGS) data reveals the presence of ionized absorbers in 2022 ( log ξ / erg cm s − 1 ∼ 1.5 ± 0.3 , N H ∼ 2.5 ± 0.9 × 10 ²⁰ cm ⁻² ), but weaker than that detected during the high accretion state in 2018 (Eddington ratio, λ Edd > 1). The absorption features further weakened in 2023–2025 and were marginally detectable ( N H ≤ 10 ²⁰ cm ⁻² ). The entire scenario is suggestive of a real-time transition of the accretion flow (from λ Edd > 1 to λ Edd ∼ 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 ∼10 and ∼60, respectively, since 2022, have recently plateaued at elevated levels, indicating a stabilized accretion disk, corona, and jet configuration.
SN  - 1538-4357
SN  - 0004-637X
ER  -