GCN Circular 6974
E. Berger (Princeton/OCIW) and R. Covarrubias (LCO) report: "We observed the XRT error circle of GRB 071021 (GCNs 6963,6966) in the i-band using the LDSS3 instrument on the Magellan/Clay telescope. In a coadded image of 1120 sec we do not detect any object within the XRT error circle to a 3-sigma limit of i>23 mag. Since no z-band magnitude was reported in GCN 6972 we cannot determine whether our limits are significantly deeper. However, our non-detection in r- and i-band appears to indicate a redshift of z~6-6.5 (for i-band effective wavelength = 7600A and FWHM = 1300A). Further observations are in progress."