Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions

article Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions published yes Hiromichi Tagawa author Zoltán Haiman author 7c006e8c-cc0d-11ee-8322-cb904ef76f360000-0003-3633-5403 Shigeo S. Kimura author Hassen M. Yesuf author Hengxiao Guo author ZoHa department Accretion disks in active galactic nuclei (AGN) are promising sites for mergers of stellar-mass black holes (BHs) detectable via gravitational waves (GWs). These environments facilitate both in situ formation and dynamical capture of compact objects and their subsequent mergers. The uncertain origin of GW events detected by LIGO, Virgo, and KAGRA motivates searching for accompanying electromagnetic (EM) signatures. Here, we investigate postmerger EM flares associated with jets launched from merger remnants, as well as from the shocked ambient gas as the jet breaks out of the disk. We find that jet breakout produces luminous gamma-ray emission, detectable with MeV-band telescopes. Cooling emission from a shocked circum-BH minidisk, winds, and background AGN disk peaks in the UV and optical, with durations ranging from about an hour to a month, and can be identified through year-long monitoring of ∼103 AGNs with luminosities ranging from ∼1044 to ∼1045 erg s−1. With a single set of parameters, this postmerger jet model produces gamma-ray, hard X-ray, and optical flares similar to those claimed to be associated with GW events. Furthermore, by incorporating a transition from a high- to low-angular-momentum accretion state after the merger, the model avoids excessive BH growth, alleviating tensions with hyper-Eddington accretion scenarios. https://research-explorer.ista.ac.at/download/22616/22630/2026_AstrophysicalJournal_Tagawa.pdf application/pdfno IOP Publishing2026 eng The Astrophysical Journal 0004-637X 1538-435710.3847/1538-4357/ae7d29 10062 Tagawa, Hiromichi, et al. “Electromagnetic Flares from Compact-Object Mergers in Active Galactic Nucleus Disks: Signatures and Predictions.” The Astrophysical Journal, vol. 1006, no. 2, 121, IOP Publishing, 2026, doi:<a href="https://doi.org/10.3847/1538-4357/ae7d29">10.3847/1538-4357/ae7d29</a>. Tagawa, H., Haiman, Z., Kimura, S. S., Yesuf, H. M., & Guo, H. (2026). Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions. The Astrophysical Journal. IOP Publishing. <a href="https://doi.org/10.3847/1538-4357/ae7d29">https://doi.org/10.3847/1538-4357/ae7d29</a> H. Tagawa, Z. Haiman, S.S. Kimura, H.M. Yesuf, H. Guo, The Astrophysical Journal 1006 (2026). H. Tagawa, Z. Haiman, S. S. Kimura, H. M. Yesuf, and H. Guo, “Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions,” The Astrophysical Journal, vol. 1006, no. 2. IOP Publishing, 2026. Tagawa, Hiromichi, Zoltán Haiman, Shigeo S. Kimura, Hassen M. Yesuf, and Hengxiao Guo. “Electromagnetic Flares from Compact-Object Mergers in Active Galactic Nucleus Disks: Signatures and Predictions.” The Astrophysical Journal. IOP Publishing, 2026. <a href="https://doi.org/10.3847/1538-4357/ae7d29">https://doi.org/10.3847/1538-4357/ae7d29</a>. Tagawa H, Haiman Z, Kimura SS, Yesuf HM, Guo H. Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions. The Astrophysical Journal. 2026;1006(2). doi:<a href="https://doi.org/10.3847/1538-4357/ae7d29">10.3847/1538-4357/ae7d29</a> Tagawa H, Haiman Z, Kimura SS, Yesuf HM, Guo H. 2026. Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions. The Astrophysical Journal. 1006(2), 121. 226162026-08-02T22:01:52Z2026-08-03T08:00:54Z