{
  "bibcode": "2015GCN.17358....1C",
  "body": "R. Chornock (Ohio University) and W. Fong (University of Arizona) report:\n\nWe re-imaged the field of the possibly-short GRB 150120A (D'Elia et al.,\nGCN 17310) with the Gemini Multi-Object Spectrograph (GMOS) mounted on the \nGemini-North 8-m telescope starting on 2015 Jan 22.284 UT (2.16 days\npost-burst and 49.8 hr after our first Gemini observations; Fong et al.,\nGCN 17313). We obtained a total of 2160s of observations in r-band in\n1.0\" seeing at an airmass of 1.6. Image subtraction using the ISIS package \nreveals no residuals in or around the enhanced XRT position (Evans et al.,\nGCN 17317). Based on the 3-sigma limit of the second epoch, which is not\ndeep as our first epoch due to poorer conditions, we place a limit of r(AB)>25.0 \nmag on the optical afterglow of GRB 150120A at 2.0 hr\npost-burst.\n\nWe note that the enhanced XRT position (Evans et al., GCN 17317) shifted\nrelative to the prompt enhanced XRT position (Evans, GCN 17311) and now \nencompasses Source A of Perley & Cenko (GCN 17312), while Source B is now\njust outside the XRT error circle.  We placed a spectroscopic slit across\nboth Sources A and B and obtained a pair of 900s GMOS spectra on 2014 Jan.\n27 with the R400 grating (range 4900-9200 Angs).  Both galaxies exhibit\nnebular emission lines (H-beta, [O III]) at the same common redshift of\nz=0.460.\n\nWe thank the staff at Gemini for their assistance scheduling and\nperforming these observations.",
  "circularId": 17358,
  "createdOn": 1422484807000,
  "email": "chornock@ohio.edu",
  "subject": "GRB 150120A: Gemini-N imaging and host redshift",
  "submitter": "Ryan Chornock at Ohio U  <chornock@ohio.edu>",
  "eventId": "GRB 150120A"
}