TITLE: GCN CIRCULAR NUMBER: 45189 SUBJECT: GRB 260705A: Retraction of optical counterpart DATE: 26/07/20 20:02:38 GMT FROM: James Freeburn at University of North Carolina at Chapel Hill <jamesfreeburn54@gmail.com> James Freeburn (UNC), Tomás Ahumada (NOIRLab), Jillian Rastinejad (UMD), Gokul Srinivasaragavan (UMD/Northwestern), Huei Sears (Rutgers), Anirudh Salgundi (UNC), report on behalf of a larger collaboration: We obtained further imaging of the optical counterpart to GRB 260705A (Saccardi et al., GCN 45079; Hamburg & Veres, GCN 45080) reported in Freeburn et al., GCN 45105. We observed with the Goodman High Throughput Spectrograph (GHTS) in imaging mode at a midpoint of UT 2026-07-11 10:15:00 corresponding to 5.88 days after the trigger and with the Gemini Multi-object Spectrograph (GMOS) mounted on Gemini south at UT 2026-07-08 09:08:46 corresponding to 2.83 days after the trigger. We obtain the following upper limits: | Instrument | MJD | Filter | Upper limit | | ---------- | --------- | ------ | ----------- | | GMOS | 61229.381 | r | 23.7 | | GHTS | 61232.423 | i | 23.0 | | GHTS | 61232.434 | r | 23.3 | We also obtained imaging and spectroscopic data using the GMOS-S instrument mounted on the Gemini South telescope. The acquisition images consisted of a sequence of 20 s and 30 s exposures in the r-band. We acquired 4 x 900 s spectroscopic observations using the B480 grating centered at 520 nm. Data were reduced using DRAGONS. The spectrum is host dominated and shows no prominent transient features. We identify several narrow absorption and emission features at a common redshift of z = 0.1840 +/- 0.0005. Motivated by the photometric and spectroscopic non-detections, we conducted more careful analysis of the images taken on the night of 2026-07-07, detailed in Freeburn et al., GCN 45105. Despite a convincing detection in the coadded image, we found that the source was not present when differencing the individual GMOS exposures. Similarly, in the SOAR data, the source was not reliably recovered when varying the subtraction parameters. We therefore conclude that the source is likely spurious. View this GCN Circular online at https://gcn.nasa.gov/circulars/45189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...