Persistence of the Millihertz X-ray Quasi-Periodic Oscillation in the Active Galactic Nucleus 1ES 1927+654
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| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| author | Masterson, Megan Kara, Erin Alston, William N. Arcodia, Riccardo Begelman, Mitchell Chakraborty, Joheen Fabian, Andrew C. Giustini, Margherita Ingram, Adam Kosec, Peter Laha, Sibasish Miniutti, Giovanni Panagiotou, Christos Pinto, Ciro Ricci, Claudio Sadaula, Dev R. Shuvo, Onic I. Trakhtenbrot, Benny |
| author_facet | Masterson, Megan Kara, Erin Alston, William N. Arcodia, Riccardo Begelman, Mitchell Chakraborty, Joheen Fabian, Andrew C. Giustini, Margherita Ingram, Adam Kosec, Peter Laha, Sibasish Miniutti, Giovanni Panagiotou, Christos Pinto, Ciro Ricci, Claudio Sadaula, Dev R. Shuvo, Onic I. Trakhtenbrot, Benny |
| contents | 1ES 1927+654 is an extreme active galactic nucleus (AGN) that has defied our canonical expectations for how AGN appear across the electromagnetic spectrum and how they vary on short timescales. In 2022, this source began showing a X-ray quasi-periodic oscillation (QPO) at mHz frequencies, along with a newly launched radio jet. Unlike the handful of other known AGN QPOs, the QPO in 1ES 1927+654 showed a significant frequency evolution, spanning from 0.9-2.4 mHz from 2022-2024. In this work, we present the last 1.5 years of monitoring with XMM-Newton (250 ks) up to January 2026, which reveals that the QPO persists but has plateaued at a constant frequency of approximately 2.5 mHz. We perform detailed spectral-timing analyses on this exquisite dataset, consisting of over 900 QPO cycles, more than any AGN QPO to date. Our main findings are: (1) the stacked XMM-Newton power spectra shows no significant second harmonic, (2) a soft (reverberation-like) lag is observed at all frequencies and remains remarkably stable even as the QPO frequency evolved from 2022-2024, and (3) extreme X-ray jumps on the QPO period (up to ~80% baseline flux) persist to present day with a remarkably stable dip-rise-fall pattern. Finally, we also detect the first AGN QPO in NuSTAR observations, which is present from 2023 to 2026 at frequencies consistent with the XMM-Newton detections. While we explore models for eclipses and coupled disk-corona behavior to simultaneously explain the lags, dips, and QPO, these new observations strain such models. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_16688 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Persistence of the Millihertz X-ray Quasi-Periodic Oscillation in the Active Galactic Nucleus 1ES 1927+654 Masterson, Megan Kara, Erin Alston, William N. Arcodia, Riccardo Begelman, Mitchell Chakraborty, Joheen Fabian, Andrew C. Giustini, Margherita Ingram, Adam Kosec, Peter Laha, Sibasish Miniutti, Giovanni Panagiotou, Christos Pinto, Ciro Ricci, Claudio Sadaula, Dev R. Shuvo, Onic I. Trakhtenbrot, Benny High Energy Astrophysical Phenomena 1ES 1927+654 is an extreme active galactic nucleus (AGN) that has defied our canonical expectations for how AGN appear across the electromagnetic spectrum and how they vary on short timescales. In 2022, this source began showing a X-ray quasi-periodic oscillation (QPO) at mHz frequencies, along with a newly launched radio jet. Unlike the handful of other known AGN QPOs, the QPO in 1ES 1927+654 showed a significant frequency evolution, spanning from 0.9-2.4 mHz from 2022-2024. In this work, we present the last 1.5 years of monitoring with XMM-Newton (250 ks) up to January 2026, which reveals that the QPO persists but has plateaued at a constant frequency of approximately 2.5 mHz. We perform detailed spectral-timing analyses on this exquisite dataset, consisting of over 900 QPO cycles, more than any AGN QPO to date. Our main findings are: (1) the stacked XMM-Newton power spectra shows no significant second harmonic, (2) a soft (reverberation-like) lag is observed at all frequencies and remains remarkably stable even as the QPO frequency evolved from 2022-2024, and (3) extreme X-ray jumps on the QPO period (up to ~80% baseline flux) persist to present day with a remarkably stable dip-rise-fall pattern. Finally, we also detect the first AGN QPO in NuSTAR observations, which is present from 2023 to 2026 at frequencies consistent with the XMM-Newton detections. While we explore models for eclipses and coupled disk-corona behavior to simultaneously explain the lags, dips, and QPO, these new observations strain such models. |
| title | Persistence of the Millihertz X-ray Quasi-Periodic Oscillation in the Active Galactic Nucleus 1ES 1927+654 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2604.16688 |