Determine whether the magnetic-field configuration was permanently altered by the EVPA event

Determine whether the magnetic-field configuration in the compact emitting region of 1ES\,1927+654 was permanently altered following the approximately 137° EVPA rotation observed during 2026 through simultaneous multi-frequency polarimetric monitoring before and after the event.

Background

The VLA X-band monitoring reveals a smooth EVPA rotation of approximately 137° over 81 days in 2026, followed by a partial return, while the total intensity remains stable and the fractional polarization is suppressed. The authors interpret this behavior as consistent with a transient disturbance propagating through the compact emitting region, although the long-term effect on the magnetic field remains unresolved.

The paper states that approved simultaneous multi-frequency polarimetric observations will test whether the event produced a lasting change in the field configuration.

References

Simultaneous multi-frequency polarimetric follow-up observations, which have been approved, will show whether the field configuration was permanently altered.

— First Detection of Radio Polarization During Jet Formation in the Changing-Look AGN 1ES 1927+654  (2609.09539 - Shuvo et al., 8 Sep 2026) in Conclusions, Section “VLA X-band Monitoring and Polarimetric Evolution”