BASS. XLIX. Characterization of Highly Luminous and Obscured AGNs: Local X-Ray and [Ne V]λ3426 Emission in Comparison with the High-redshift Universe

We present a detailed analysis of the most luminous and obscured active galactic nuclei (AGNs) detected in the ultra-hard X-ray band (14–195 kev) by the Swift/Burst Alert Telescope. Our sample comprises 21 X-ray luminous ( log L X / erg s − 1 > 44.6 , 2–10 keV) AGNs at z < 0.6, optically classified as Seyfert 1.9 and 2. Using NuSTAR, XMM-Newton, Suzaku, and Chandra data, we constrain AGN properties such as absorption column density N H , photon index Γ, intrinsic L X , covering factor, and iron K α equivalent width. We find median line-of-sight log N H / cm − 2 = 23 . 5 − 1.2 + 0.5 and 2–10 keV rest-frame, de-absorbed log L X / erg s − 1 = 44 . 7 − 0.6 + 0.8 , at the 5th and 95th percentiles. For sources with black hole mass estimates (12/20), we find a weak correlation between Γ and Eddington ratio ( λ Edd ). Of these, six (50% ± 13%) lie in the N H - λ Edd “forbidden region” and exhibit a combined higher prevalence of N H variability and outflow signatures, suggesting a transitional phase where AGN feedback may be clearing the obscuring material. For the 13/21 sources with multi-epoch X-ray spectroscopy, 85 − 15 + 5 % exhibit variability in either 2–10 keV flux ( 77 − 15 + 8 % ) or line-of-sight N H ( 3 3 − 10 + 15 % ). For the 20/21 sources with available near-UV/optical spectroscopy, we detect [Ne v] λ 3426 in 17 ( 8 5 − 11 + 5 %), confirming its reliability to probe AGN emission even in heavily obscured systems. When renormalized to the same [O iii ] λ 5007 peak flux as z = 2−9 narrow-line AGNs identified with JWST, our sample exhibits significantly stronger [Ne v] λ 3426 emission, suggesting that high-redshift obscured AGNs may be intrinsically weaker in [Ne v] λ 3426 or that [Ne v] λ 3426 is more challenging to detect in those environments. The sources presented in this work serve as a benchmark for high-redshift analogs, showing the potential of [Ne v] λ 3426 to reveal obscured AGNs and the need for future missions to expand X-ray studies into the high-redshift Universe.