Chandra Observations of Candidate Sub-Parsec Binary Supermassive Black Holes

Understand

We present analysis of Chandra X-ray observations of seven quasars that were identified as candidate sub-parsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey (CRTS) based on apparent periodicity in their optical light curves.

• Simulations predict close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs, including harder or softer X-ray spectra, ripple-like profiles in the Fe K-$\alpha$ line, and distinct peaks in the spectrum due to the separation of the accretion disk into a circumbinary disk and mini-disks around each SMBH.
• We obtained Chandra observations to test these models and assess whether these quasars could contain binary SMBHs.
• We instead find that the quasar spectra are all well fit by simple absorbed power law models, with the rest frame 2-10 keV photon indices, $\Gamma$, and the X-ray-to-optical power slopes, $\alpha_{\rm OX}$, indistinguishable from the larger quasar population.