NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

摘要: We present NuSTAR (Nuclear Spectroscopic Telescope Array) observations of four active galactic nuclei (AGNs) located within 15 Mpc. These AGNs, namely ESO 121-G6, NGC 660, 3486, and 5195, have observed X-ray luminosities L_(2–10 keV,obs) ≲ 10³⁹ erg s⁻¹, classifying them as low-luminosity AGN (LLAGN). perform broad-band spectral analysis for the by combining our data with Chandra or XMM–Newton to directly measure their column densities (N_H) infer intrinsic power. complement archival new high-angular resolution mid-infrared (mid-IR) all objects, except 5195. Based on analysis, we found that both 121-G6 660 are heavily obscured (N_H > 10²³ cm⁻²; L_(2–10 keV,int) ∼ 10⁴¹ s⁻¹), may be Compton thick. also note flux slope significantly changed over last decade, indicating significant changes in obscuration potentially accretion rate. On other hand, 3486 5195 appear unobscured just mildly obscured, respectively, s⁻¹ λ_(Edd) ≳ 10⁻³, detected mid-IR imaging, presence obscuring dust nuclear scale. however, is undetected high-resolution current do not provide stringent constraints absence AGN.