We present deep Chandra observations of PSO J231.6576 - 20.8335 , a quasar at redshift z = 6.59 with a nearby ( { \sim } 8 proper kpc ) companion galaxy .
ALMA observed both the quasar and companion to be bright in [ \ion C2 ] , and the system has significant extended Ly \alpha emission around the quasar , suggesting that a galaxy merger is ongoing .
Unlike previous studies of two similar systems , and despite observing the system with Chandra for 140 ks , we do not detect the companion in X-rays .
The quasar itself is detected , but only 13.3 ^ { +4.8 } _ { -3.7 } net counts are observed .
From a basic spectral analysis , the X-ray spectrum of the quasar is soft ( hardness ratio of \mathcal { HR } = -0.60 _ { -0.27 } ^ { +0.17 } , power-law index of \Gamma = 2.6 ^ { +1.0 } _ { -0.9 } ) , which results in a rest-frame X-ray luminosity comparable to other bright quasars ( L _ { 2 - 10 } = 1.09 ^ { +2.20 } _ { -0.70 } \times 10 ^ { 45 } \textrm { erg } \textrm { s } ^ { -1 } ) despite the faint observed X-ray flux .
We highlight two possible interpretations of this result : the quasar has a steep value of \Gamma – potentially related to observed ongoing Eddington accretion – thereby pushing much of the emission out of our observed band , or the quasar has a more normal spectrum ( \Gamma { \sim } 2 ) but is therefore less X-ray luminous ( L _ { 2 - 10 } \sim 0.6 \times 10 ^ { 45 } \textrm { erg } \textrm { s } ^ { -1 } ) .