The brightness and oscillations of this nucleus have behaved unpredictably and so become the subject of special observation and study in the optical, radio, ultraviolet and X-ray spectrums. Academic papers analysing its unusual characteristics have challenged conventional theories aboutaccretion disks and black hole environments.[6][7][8][9][10]
1ES 1927+654 is the catalog reference for the object in the Einstein Slew Survey – a scan of the sky in the X-ray spectrum which was performed by theEinstein Observatory and first published in 1992.
1ES 1927+654 has captured the attention of astronomers due to its unpredictable behavior. Its sudden changes have made it a target for multi-wavelength observation campaigns, drawing data from X-ray, optical, and radio observatories around the world.[11][12][2][13]
1ES 1927+654 was first cataloged during the Einstein Slew Survey, which aimed to identify X-ray sources in the sky. It was classified as a Seyfert galaxy due to its emission-line features.[14]
A dramatic increase in brightness was detected in 2017, with the galaxy brightening by a factor of about 40 in the ultraviolet spectrum. This event triggered follow-up studies to investigate the cause.[8] In 2018, detailed observations by X-ray and ultraviolet telescopes revealed that the AGN's accretion disk had undergone a partial or total disruption.[13] TheQuasi-periodic oscillation (QPO) period shrank from 18 to 7.1 minutes over two years, showing unique evolution.[15] Future X-ray and gravitational-wave observations are planned to test possible explanations.[15]
In 2020, studies suggested that the extreme variability could be linked to magnetic field instabilities around the black hole. The event challenged models of black hole accretion and inspired new theories about AGN outbursts.[16]
This illustration shows theaccretion disk,corona (pale, conical swirls above the disk), andsupermassive black hole of 1ES 1927+654 Credit: NASA/Sonoma State University, Aurore Simonnet
Artist's concept Matter is stripped from a white dwarf (sphere at lower right) orbiting within the innermost accretion disk surrounding 1ES 1927+654'ssupermassive black hole.
^Cao, Xinwu; You, Bei; Wei, Xing (October 14, 2023), "An accretion disc with magnetic outflows triggered by a sudden mass accretion event in changing-look active galactic nucleus 1ES 1927+654",Monthly Notices of the Royal Astronomical Society,526 (2): 2331,arXiv:2309.10610,Bibcode:2023MNRAS.526.2331C,doi:10.1093/mnras/stad2877
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