Quasars at early redshifts ($z > 6$) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416$-$21.2339, a $z=6.23$ quasar with a merging companion galaxy identified in [C II] and rest-frame UV emission. With $72.3^{ +9.6}_{ -8.6}$ net counts, we find that PSO J308.0416$-$21.2339 is powerful ($L_X = 2.31^{ +1.14}_{ -0.76} \times 10^{ 45}\ \textrm{ erg}\,\textrm{ s}^{ -1}\,\textrm{ cm}^{ -2}$ in rest-frame $2.0-10.0$ keV) yet soft (spectral power-law index $\Gamma=2.39^{ +0.37}_{ -0.36}$ and optical-to-X-ray slope $\alpha_{ \rm OX} = -1.41 \pm 0.11$). In addition, we detect three hard-energy photons $2.''0$ to the west of the main quasar, cospatial with the brightest UV emission of the merging companion. As no soft-energy photons are detected in the same area, this is potentially indicative of a highly-obscured source. With conservative assumptions, and accounting for both background fluctuations and the extended wings of the quasar's emission, these photons only have a probability $P=0.021$ of happening by chance. If confirmed by deeper observations, this system is the first high redshift quasar and companion individually detected in X-rays and is likely a dual AGN.
Categories: astro-ph.GA astro-ph.HE