First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654
Abstract
We present a multiwavelength radio study of the changing-look AGN 1ES 1927+654 following its renewed X-ray brightening since mid-2022, combining VLBA imaging with multi-band and time-resolved VLA observations. Our main results are: (i) VLBA observations continue to reveal the bipolar jet structure first reported in Meyer et al. (2025), with new X-band detections confirming the morphology at larger separation and K-band imaging revealing a bridge of emission consistent with a continuous outflow; (ii) the VLBA core exhibits a GHz-peaked spectrum, and VLA/VLITE observations from 340 MHz to 45 GHz show emission from an inhomogeneous synchrotron source, self-absorbed below ~3 GHz and optically thin above; (iii) VLA and VLBA flux densities are consistent above 8 GHz, indicating emission dominated by a compact core; (iv) linear polarization is detected above ~3 GHz, with fractional polarization increasing with frequency from ~0.2% to ~6% and EVPAs exhibiting non-linear lambda^2 behavior; (v) long-term VLA X-band monitoring reveals a large, smooth rotation of the EVPA of ~137 degrees over ~81 days in 2026, followed by a partial return, at stable total intensity and suppressed fractional polarization <~1.4%, consistent with a propagating disturbance crossing the compact emitting region; and (vi) circular polarization is not detected at any epoch. These observations demonstrate that 1ES 1927+654 has transitioned from an X-ray-dominated, non-jetted state to a radio-loud AGN (Laha et al. 2025) hosting a newly launched relativistic jet, a unique laboratory for studying jet birth and early magnetic field evolution.
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BibTeX
@misc{shuvo2026first,
title = {{First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654}},
author = {Onic I. Shuvo and Eileen T. Meyer and Sibasish Laha and Agniva Roychowdhury and Dev R. Sadaula and Tracy E. Clarke and Wendy M. Peters and Mitchell C. Begelman and Markos Georganopoulos and Rostom Mbarek and Amelia M. Hankla and Alexander Philippov and Navin Sridhar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.09539},
eprint = {2609.09539},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09539},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654
AU - Onic I. Shuvo
AU - Eileen T. Meyer
AU - Sibasish Laha
AU - Agniva Roychowdhury
AU - Dev R. Sadaula
AU - Tracy E. Clarke
AU - Wendy M. Peters
AU - Mitchell C. Begelman
AU - Markos Georganopoulos
AU - Rostom Mbarek
AU - Amelia M. Hankla
AU - Alexander Philippov
AU - Navin Sridhar
PY - 2026
DA - 2026/10/10
PB - arXiv
DO - 10.48550/arxiv.2609.09539
UR - https://arxiv.org/abs/2609.09539
AB - We present a multiwavelength radio study of the changing-look AGN 1ES 1927+654 following its renewed X-ray brightening since mid-2022, combining VLBA imaging with multi-band and time-resolved VLA observations. Our main results are: (i) VLBA observations continue to reveal the bipolar jet structure first reported in Meyer et al. (2025), with new X-band detections confirming the morphology at larger separation and K-band imaging revealing a bridge of emission consistent with a continuous outflow; (ii) the VLBA core exhibits a GHz-peaked spectrum, and VLA/VLITE observations from 340 MHz to 45 GHz show emission from an inhomogeneous synchrotron source, self-absorbed below ~3 GHz and optically thin above; (iii) VLA and VLBA flux densities are consistent above 8 GHz, indicating emission dominated by a compact core; (iv) linear polarization is detected above ~3 GHz, with fractional polarization increasing with frequency from ~0.2% to ~6% and EVPAs exhibiting non-linear lambda^2 behavior; (v) long-term VLA X-band monitoring reveals a large, smooth rotation of the EVPA of ~137 degrees over ~81 days in 2026, followed by a partial return, at stable total intensity and suppressed fractional polarization <~1.4%, consistent with a propagating disturbance crossing the compact emitting region; and (vi) circular polarization is not detected at any epoch. These observations demonstrate that 1ES 1927+654 has transitioned from an X-ray-dominated, non-jetted state to a radio-loud AGN (Laha et al. 2025) hosting a newly launched relativistic jet, a unique laboratory for studying jet birth and early magnetic field evolution.
ER -