Trichas, Markos, Green, Paul J., Constantin, Anca, Aldcroft, Thomas L., Kalfountzou, Eleni, Sobolewska, Malgosia, Hyde, Ashley K., Zhou, Hongyan, Kim, Dong-Woo, Haggard, Daryl, and Kelly, Brandon C. 2013. "Empirical Links between XRB and AGN Accretion Using the Complete z < 0.4 Spectroscopic CSC/SDSS Catalog." The Astrophysical Journal 778:188. https://doi.org/10.1088/0004-637X/778/2/188
Striking similarities have been seen between accretion signatures of Galactic X-ray binary (XRB) systems and active galactic nuclei (AGNs). XRB spectral states show a V-shaped correlation between X-ray spectral hardness and Eddington ratio as they vary, and some AGN samples reveal a similar trend, implying analogous processes at vastly larger masses and timescales. To further investigate the analogies, we have matched 617 sources from the Chandra Source Catalog to Sloan Digital Sky Survey spectroscopy, and uniformly measured both X-ray and optical spectral characteristics across a broad range of AGN and galaxy types. We provide useful tabulations of X-ray spectral slope for broad- and narrow-line AGNs, star-forming and passive galaxies, and composite systems, also updating relationships between optical (Ha and [O III]) line emission and X-ray luminosity. We further fit broadband spectral energy distributions with a variety of templates to estimate bolometric luminosity. Our results confirm a significant trend in AGNs between X-ray spectral hardness and Eddington ratio expressed in X-ray luminosity, albeit with significant dispersion. The trend is not significant when expressed in the full bolometric or template-estimated AGN luminosity. We also confirm a relationship between the X-ray/optical spectral slope aox and Eddington ratio, but it may not follow the trend predicted by analogy with XRB accretion states.