A radio, optical, UV and X-ray view of the enigmatic changing look Active Galactic Nucleus 1ES~1927+654 from its pre- to post-flare states

Abstract

The nearby type-II AGN 1ES1927+654 went through a violent changing-look (CL) event beginning December 2017 during which the optical and UV fluxes increased by four magnitudes over a few months, and broad emission lines newly appeared in the optical/UV. By July 2018 the X-ray coronal emission had completely vanished, only to reappear a few months later. In this work we report the evolution of the radio, optical, UV and X-rays from the pre-flare state through mid-2021 with new and archival data from the Very Long Baseline Array (VLBA), the European VLBI Network, the Very Large Array (VLA), the Telescopio Nazionale Galileo (TNG), Gran Telescopio Canarias (GTC), The Neil Gehrels Swift observatory and XMM-Newton. The main results from our work are: (1) The source has returned to its pre-CL state in optical, UV, and X-ray; the disk-corona relation has been re-established as has been in the pre-CL state, with an ${\alpha }_{\mathrm{OX}}\sim 1.02$. The optical spectra are dominated by narrow emission lines. (2) The UV light curve follows a shallower slope of $\propto t^{-0.91\pm 0.04}$ compared to that predicted by a tidal disruption event. We conjecture that a magnetic flux inversion event is the possible cause for this enigmatic event. (3) The compact radio emission which we tracked in the pre-CL (2014), during CL (2018) and post-CL(2021) at spatial scales $<1$ pc was at its lowest level during the changing look event in 2018, nearly contemporaneous with a low $2-10$ keV emission. The radio to X-ray ratio of the compact source $L_{\mathrm{Radio}}/L_{\mathrm{X}-\mathrm{ray}}\sim 10^{-5.5}$, follows the Gudel-Benz relation, typically found in coronally active stars, and several AGN. (4) We do not detect any presence of nascent jets at the spatial scales of $\sim 5-10$ pc.

Resubmitted to ApJ following minor comments from the referee

References in corpus (25)

• The Host Galaxies and Classification of Active Galactic Nuclei
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
• The corona contracts in a black-hole transient
• On the origin of radio emission in radio quiet quasars
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• Ionized outflows from active galactic nuclei as the essential elements of feedback
• The destruction and recreation of the X-ray corona in a changing-look Active Galactic Nucleus
• Driving extreme variability: The evolving corona and evidence for jet launching in Markarian 335
• The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars
• Radio Variability in Seyfert Nuclei
• The Close AGN Reference Survey (CARS) - What is causing Mrk1018's return to the shadows after 30 years?
• Indecent Exposure in Seyfert 2 Galaxies: A Close Look
• The 450 days X-ray monitoring of the changing-look AGN 1ES 1927+654
• NuSTAR/XMM-Newton monitoring of the Seyfert 1 galaxy HE 1143-1810. Testing the two-corona scenario
• Magnetic flux inversion in a peculiar changing look AGN
• Evidence for an emerging disc wind and collimated outflow during an X-ray flare in the narrow-line Seyfert 1 galaxy Mrk 335
• The variable and non-variable X-ray absorbers in Compton-thin type-II Active Galactic Nuclei
• HST unveils a compact mildly relativistic Broad Line Region in the candidate true type 2 NGC 3147
• Daily variability at milli-arcsecond scales in the radio quiet NLSy1 Mrk 110
• A broadband X-ray spectral study of the Seyfert 1 galaxy ESO 141--G055 with XMM-Newton and NuSTAR
• A parsec-scale faint jet in the nearby changing-look Seyfert galaxy Mrk 590
• Investigating the origin of the Fe emission lines of the Seyfert 1 galaxy Mrk~205
• A weakening Compton hump and soft X-ray excess detected in the Seyfert-1 galaxy MCG-02-58-22

Cited by in corpus (5)

• Evolution of a Relativistic Outflow and X-ray Corona in the Extreme Changing-Look AGN 1ES 1927+654
• Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko
• The outburst of the changing-look AGN IRAS23226-3843 in 2019
• Multiple Flares in the Changing-Look AGN NGC 5273
• Quantum contribution to luminosity of quasars