The Emergence of X-Ray Emission Lines during Relativistic Radio-jet Formation in the Changing-look Active Galactic Nucleus 1ES 1927+654
Abstract 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.
Authors
- Ehud Behar (ORCID: https://orcid.org/0000-0001-9735-4873)
- Erin Kara (ORCID: https://orcid.org/0000-0003-0172-0854)
- F. Panessa (ORCID: https://orcid.org/0000-0003-0543-3617)
- Luigi Gallo (ORCID: https://orcid.org/0009-0006-4968-7108)
- Eileen T. Meyer (ORCID: https://orcid.org/0000-0002-7676-9962)
- Cláudio Ricci (ORCID: https://orcid.org/0000-0001-5231-2645)
- Amelia Hankla (ORCID: https://orcid.org/0000-0001-9725-5509)
- Fabio Pacucci (ORCID: https://orcid.org/0000-0001-9879-7780)
- Missagh Mehdipour (ORCID: https://orcid.org/0000-0002-4992-4664)
- T. R. Kallman (ORCID: https://orcid.org/0000-0002-5779-6906)
- Fabio La Franca (ORCID: https://orcid.org/0000-0002-1239-2721)
- Onic I. Shuvo (ORCID: https://orcid.org/0000-0003-4727-2209)
- James N. Reeves (ORCID: https://orcid.org/0000-0003-3221-6765)
- Mitchell C. Begelman (ORCID: https://orcid.org/0000-0003-0936-8488)
- Main Pal (ORCID: https://orcid.org/0000-0001-6523-6522)
- M. Guainazzi (ORCID: https://orcid.org/0000-0002-1094-3147)
- Megan Masterson (ORCID: https://orcid.org/0000-0003-4127-0739)
- Ralf Ballhausen (ORCID: https://orcid.org/0000-0002-1118-8470)
- Dev R. Sadaula (ORCID: https://orcid.org/0000-0002-9163-8653)
- Suvendu Rakshit (ORCID: https://orcid.org/0000-0002-8377-9667)
- S. Bianchi (ORCID: https://orcid.org/0000-0002-4622-4240)
- Rostom Mbarek (ORCID: https://orcid.org/0000-0001-9475-5292)
- S. B. Cenko
- Tahir Yaqoob
- Ilaria Villani (ORCID: https://orcid.org/0009-0006-7483-0463)
- Federica Ricci (ORCID: https://orcid.org/0000-0001-5742-5980)
- Ritesh Ghosh
- Sibasish Laha
- Alexander Philippov (ORCID: https://orcid.org/0000-0001-7801-0362)
- Javier A Garcia
Institutions
- University of Delhi (IN)
- Roma Tre University (IT)
- Space Telescope Science Institute (US)
- National Institute of Standards and Technology (US)
- Harvard University (US)
- Princeton University (US)
- Peking University (CN)
- University of Michigan (US)
- Astronomical Observatory of Rome (IT)
- European Space Agency (FR)
- Aryabhatta Research Institute of Observational Sciences (IN)
- Institute for Space Astrophysics and Planetology (IT)
- Center for Astrophysics Harvard & Smithsonian (US)
- Massachusetts Institute of Technology (US)
- Saint Mary's University (CA)
- University of Maryland, College Park (US)
- University of Maryland, Baltimore County (US)
- Catholic University of America (US)
- National Institute for Astrophysics (IT)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2026-10-29
- DOI
- https://doi.org/10.3847/1538-4357/ae96b4
- Primary Topic
- Astrophysical Phenomena and Observations
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- United States-Israel Binational Science Foundation
- Goddard Space Flight Center