TITLE: GCN CIRCULAR NUMBER: 10606 SUBJECT: GRB 100414A: Gemini-N candidate and redshift DATE: 10/04/17 08:16:49 GMT FROM: Antonino Cucchiara at PSU A. Cucchiara and D. B. Fox (PSU) report on behalf of a larger collaboration: "Starting on 2010 April 17.26 UT we used the GMOS spectrograph on the Gemini North 8-m telescope to observe the field of the Fermi-LAT GRB 100414A (Takahashi et al. GCN 10594). In our 5 min i'-band observation we detected a bright source inside the refined XRT error circle (Page et al., GCN 10605) at the following coordinate: RA: 12:48:29.96 Dec: +8:41:34.91 with 0.5" uncertainty in both directions. Using two USNO-B1 stars we obtain i' = 20.37 +- 0.03 mag for this object. A sequence of 2x1200s spectra were also obtained with the same instrument, covering a spectral range of 4000-8000A. A series of metal absorption features were identified (FeII2374, FeII2383,FeII2587,MnII2594, FeII2600, MgII2796,2803,MgI2853) at the common redshift of z= 1.368. We therefore suggest this as the redshift of GRB 100414A. Further observations are planned. We thank the Gemini staff for performing this observation, in particular A. Fritz."