We report the detection of redshifted iron K \alpha absorption lines in the Chandra LETG spectrum of the narrow-line quasar , PG 1211+143 .
The absorption lines are observed at 4.22 keV and 4.93 keV in the quasar spectrum , corresponding to 4.56 keV and 5.33 keV in the rest frame of PG 1211+143 .
From Monte Carlo simulations , the chance probability of both lines being false detections is low at 1.36 \times 10 ^ { -4 } .
Highly redshifted ionized iron K \alpha ( Fe xxv or Fe xxvi ) is the most plausible identification for the lines at their observed energies .
If identified with H-like iron K \alpha at 6.97 keV , then the relativistic velocity shifts required are 0.40c and 0.26c .
The extreme velocities can be explained by pure gravitational redshift if the matter exists in a stable orbit within 6 gravitational radii of the black hole .
This would require a Kerr metric for the black hole .
Alternatively the absorption may be the result of matter infalling directly onto the black hole , with a maximum observed velocity of 0.38c at 6 R _ { g } in the Schwarzschild metric .
This matter may originate in a failed outflow or jet , which does not escape the gravitational potential of the black hole .