TY - JOUR
T1 - A Reemerging Bright Soft X-Ray State of the Changing-look Active Galactic Nucleus 1ES 1927+654
T2 - A Multiwavelength View
AU - Ghosh, Ritesh
AU - Laha, Sibasish
AU - Meyer, Eileen
AU - Roychowdhury, Agniva
AU - Yang, Xiaolong
AU - Acosta-Pulido, J. A.
AU - Rakshit, Suvendu
AU - Pandey, Shivangi
AU - González, Josefa Becerra
AU - Behar, Ehud
AU - Gallo, Luigi C.
AU - Panessa, Francesca
AU - Bianchi, Stefano
AU - La Franca, Fabio
AU - Scepi, Nicolas
AU - Begelman, Mitchell C.
AU - Longinotti, Anna Lia
AU - Lusso, Elisabeta
AU - Oates, Samantha
AU - Nicholl, Matt
AU - Cenko, S. Bradley
AU - O’Connor, Brendan
AU - Hammerstein, Erica
AU - Jose, Jincen
AU - Gabányi, Krisztina Éva
AU - Ricci, Federica
AU - Chattopadhyay, Sabyasachi
N1 - Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/9/1
Y1 - 2023/9/1
N2 - 1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio variability of the source in its postflare state (2022 January-2023 May). First, we detect an increase in the soft X-ray (0.3-2 keV) flux from 2022 May to 2023 May by almost a factor of 5, which we call the bright soft state. The hard X-ray 2-10 keV flux increased by a factor of 2, while the UV flux density did not show any significant changes (≤30%) in the same period. The integrated energy pumped into the soft and hard X-rays during this period of 11 months is ∼3.57 × 1050 erg and 5.9 × 1049 erg, respectively. From the energetics, it is evident that whatever is producing the soft excess (SE) is pumping out more energy than either the UV or hard X-ray source. Since the energy source presumably is ultimately the accretion of matter onto the supermassive black hole, the SE-emitting region must be receiving the majority of this energy. In addition, the source does not follow the typical disk-corona relation found in AGNs, neither in the initial flare (from 2017 to 2019) nor in the current bright soft state (2022-2023). We found that the core (<1 pc) radio emission at 5 GHz gradually increased until 2022 March, but showed a dip in 2022 August. The Güdel-Benz relation (L radio/L X-ray ∼ 10−5), however, is still within the expected range for radio-quiet AGNs, and further follow-up radio observations are currently being undertaken.
AB - 1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio variability of the source in its postflare state (2022 January-2023 May). First, we detect an increase in the soft X-ray (0.3-2 keV) flux from 2022 May to 2023 May by almost a factor of 5, which we call the bright soft state. The hard X-ray 2-10 keV flux increased by a factor of 2, while the UV flux density did not show any significant changes (≤30%) in the same period. The integrated energy pumped into the soft and hard X-rays during this period of 11 months is ∼3.57 × 1050 erg and 5.9 × 1049 erg, respectively. From the energetics, it is evident that whatever is producing the soft excess (SE) is pumping out more energy than either the UV or hard X-ray source. Since the energy source presumably is ultimately the accretion of matter onto the supermassive black hole, the SE-emitting region must be receiving the majority of this energy. In addition, the source does not follow the typical disk-corona relation found in AGNs, neither in the initial flare (from 2017 to 2019) nor in the current bright soft state (2022-2023). We found that the core (<1 pc) radio emission at 5 GHz gradually increased until 2022 March, but showed a dip in 2022 August. The Güdel-Benz relation (L radio/L X-ray ∼ 10−5), however, is still within the expected range for radio-quiet AGNs, and further follow-up radio observations are currently being undertaken.
UR - http://www.scopus.com/inward/record.url?scp=85172783342&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aced92
DO - 10.3847/1538-4357/aced92
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AN - SCOPUS:85172783342
SN - 0004-637X
VL - 955
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 3
ER -