Do radio active galactic nuclei reflect X-ray binary spectral states?

Moravec, Emily; Svoboda, Jiří; Borkar, Abhijeet; Boorman, Peter; Kynoch, Daniel; Panessa, Francesca; Mingo, Beatriz and Guainazzi, Matteo (2022). Do radio active galactic nuclei reflect X-ray binary spectral states? Astronomy & Astrophysics, 662, article no. A28.



Context. Over recent years there has been mounting evidence that accreting supermassive black holes in active galactic nuclei (AGNs) and stellar mass black holes have similar observational signatures: thermal emission from the accretion disk, X-ray coronas, and relativistic jets. Further, there have been investigations into whether or not AGNs have spectral states similar to those of X-ray binaries (XRBs) and what parallels can be drawn between the two using a hardness-intensity diagram (HID).

Aims. To address whether AGN jets might be related to accretion states as in XRBs, we explore whether populations of radio AGNs classified according to their (a) radio jet morphology, Fanaroff-Riley classes I and II (FR I and II), (b) excitation class, high- and low-excitation radio galaxies (HERG and LERG), and (c) radio jet linear extent, compact to giant, occupy different and distinct regions of the AGN HID (total luminosity vs. hardness).

Methods. We do this by cross-correlating 15 catalogs of radio galaxies with the desired characteristics from the literature with XMM-Newton and Swift X-ray and ultraviolet (UV) source catalogs. We calculate the luminosity and hardness from the X-ray and UV photometry, place the sources on the AGN HID, and search for separation of populations and analogies with the XRB spectral state HID.

Results. We find that (a) FR Is and IIs, (b) HERGs and LERGs, and (c) FR I-LERGs and FR II-HERGs occupy distinct areas of the HID at a statistically significant level (p-value < 0.05), and we find no clear evidence for population distinction between the different radio jet linear extents. The separation between FR I-LERG and FR II-HERG populations is the strongest in this work.

Conclusions. Our results indicate that radio-loud AGNs occupy distinct areas of the HID depending on the morphology and excitation class, showing strong similarities to XRBs.

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