We present multi-wavelength observations of the afterglow of the short GRB 111117A , and follow-up observations of its host galaxy .
From rapid optical and radio observations we place limits of r \gtrsim 25.5 mag at \delta t \approx 0.55 d and F _ { \nu } ( 5.8 { GHz } ) \lesssim 18 \mu Jy at \delta t \approx 0.50 d , respectively .
However , using a Chandra observation at \delta t \approx 3.0 d we locate the absolute position of the X-ray afterglow to an accuracy of 0.22 ^ { \prime \prime } ( 1 \sigma ) , a factor of about 6 times better than the Swift /XRT position .
This allows us to robustly identify the host galaxy and to locate the burst at a projected offset of 1.25 \pm 0.20 ^ { \prime \prime } from the host centroid .
Using optical and near-IR observations of the host galaxy we determine a photometric redshift of z = 1.3 ^ { +0.3 } _ { -0.2 } , one of the highest for any short GRB , and leading to a projected physical offset for the burst of 10.5 \pm 1.7 kpc , typical of previous short GRBs .
At this redshift , the isotropic \gamma -ray energy is E _ { \gamma,iso } \approx 3.0 \times 10 ^ { 51 } erg ( rest-frame 23 - 2300 keV ) with a peak energy of E _ { pk } \approx 850 - 2300 keV ( rest-frame ) .
In conjunction with the isotropic X-ray energy , GRB 111117AÂ appears to follow our recently-reported E _ { x,iso } - E _ { \gamma,iso } - E _ { pk } universal scaling .
Using the X-ray data along with the optical and radio non-detections we find that for a blastwave kinetic energy of E _ { K,iso } \approx E _ { \gamma,iso } erg , the circumburst density is n _ { 0 } \approx 3 \times 10 ^ { -4 } -1 cm ^ { -3 } ( for a range of \epsilon _ { B } = 0.001 - 0.1 ) .
Similarly , from the non-detection of a break in the X-ray light curve at \delta t \lesssim 3 d , we infer a minimum opening angle for the outflow of \theta _ { j } \gtrsim 3 - 10 ^ { \circ } ( depending on the circumburst density ) .
We conclude that Chandra observations of short GRBs are effective at determining precise positions and robust host galaxy associations in the absence of optical and radio detections .