Kavli Affiliate: Erin Kara
| First 5 Authors: Sibasish Laha, Eileen T. Meyer, Dev R. Sadaula, Ritesh Ghosh, Dhrubojyoti Sengupta
| Summary:
We present results from a high cadence multi-wavelength observational
campaign of the enigmatic changing look AGN 1ES 1927+654 from May 2022- April
2024, coincident with an unprecedented radio flare (an increase in flux by a
factor of $sim 60$ over a few months) and the emergence of a spatially
resolved jet at $0.1-0.3$ pc scales (Meyer et al. 2024). Companion work has
also detected a recurrent quasi-periodic oscillation (QPO) in the $2-10$ keV
band with an increasing frequency ($1-2$ mHz) over the same period (Masterson
et al., 2025). During this time, the soft X-rays ($0.3-2$ keV) monotonically
increased by a factor of $sim 8$, while the UV emission remained near-steady
with $<30%$ variation and the $2-10$ keV flux showed variation by a factor
$lesssim 2$. The weak variation of the $2-10$ keV X-ray emission and the
stability of the UV emission suggest that the magnetic energy density and
accretion rate are relatively unchanged, and that the jet could be launched due
to a reconfiguration of the magnetic field (toroidal to poloidal) close to the
black hole. Advecting poloidal flux onto the event horizon would trigger the
Blandford-Znajek (BZ) mechanism, leading to the onset of the jet. The
concurrent softening of the coronal slope (from $Gamma= 2.70pm 0.04$ to
$Gamma=3.27pm 0.04$), the appearance of a QPO, and low coronal temperature
($kT_{e}=8_{-3}^{+8}$ keV) during the radio outburst suggest that the poloidal
field reconfiguration can significantly impact coronal properties and thus
influence jet dynamics. These extraordinary findings in real time are crucial
for coronal and jet plasma studies, particularly as our results are independent
of coronal geometry.
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