TITLE: GCN CIRCULAR NUMBER: 12132 SUBJECT: GRB 110709B: Gemini-South additional analysis and photometry DATE: 11/07/10 02:10:22 GMT FROM: Edo Berger at Harvard E. Berger (Harvard) reports on behalf of a larger collaboration: "Additional inspection and photometry of our Gemini-South r-band image (GCN 12128) reveals a second, fainter source (S2) at the following coordinates (J2000): RA = 10:58:36.955 DEC = -23:27:20.62 with an uncertainty of about 0.8" (due to centroid uncertainty). This position is consistent with the faint source detected by GROND (GCN 12129). Photometry of the two sources using the Gemini-South/GMOS standard photometric zero-point yields the following magnitudes: S1: r = 21.28+/-0.05 mag ("DSS" source) S2: r = 22.18+/-0.12 mag Taken at face value, the brightness of S2 is consistent with the GROND value (r=22.15+/-0.15 mag; GCN 12129), suggesting that S1 has actually faded by about 0.3+/-0.15 mag between 1 and 3.2 hours after the initial trigger. Alternatively, if the offset relative to the GROND photometry of S1 (r=20.9+/-0.1 mag) is due to a zero-point offset, the resulting brightness of S2 is r = 21.9+/-0.1 mag. This is marginally consistent with the GROND value (r=22.15+/-0.15 mag) which was obtained about 2.2 hours earlier than our observations. To determine which scenario is correct relative to the GROND photometry, we measure the brightness of the star at: RA = 10:58:38.053 DEC = -23:26:31.78 to be r = 18.25 mag."