TITLE: GCN CIRCULAR NUMBER: 34556 SUBJECT: Swift J1727.8-1613 (GRB 230824A): Skynet Optical Observations DATE: 23/08/25 21:25:27 GMT FROM: Dylan Dutton at UNC Chapel Hill Dylan Dutton, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, Daryl Janzen, Arie Verveer, John Kennewell, Megan Dubay, Ruide Fu, Logan Selph, and Donovan Schlekat report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill. We observed the field of Swift J1727.8-1613 (GRB 230824A) (Page et al., GCN 34537; Navaneeth et al., GCN 34538, Odeh et al., GCN 34543) with our 0.4m robotic telecope located in Meckering, Australia. The observation began at 14:11:20 UTC on Aug 24 2023, approximately 11 minutes after the first trigger. We obtained multiple expsoures in the B, V, R, and I filters. Exposure lengths were calculated using our automated exposure length scaling model. We detected a bright object, in the same location as Odeh et al., GCN 34543, within the uncertainty radius of the Swift localization, at: R.A. (J2000): 17:27:43.34 Dec. (J2000): -16:12:19.161 Below, we report our photometric measurements. ------------------------------------------- Date TimeTakenUTC ExpTime Filter Mag MagErr ------------------------------------------- 08-24-2023 | 14:11:20 | 25.721s | B | 14.22 | 0.013 08-24-2023 | 14:11:52 | 28.873s | V | 13.88 | 0.011 08-24-2023 | 14:12:29 | 13.756s | R | 13.69 | 0.012 08-24-2023 | 14:12:49 | 10.774s | I | 13.60 | 0.014 08-24-2023 | 14:15:50 | 37.756s | B | 14.25 | 0.010 08-24-2023 | 14:16:34 | 40.014s | V | 13.89 | 0.008 08-24-2023 | 14:17:21 | 19.012s | R | 13.69 | 0.009 08-24-2023 | 14:17:46 | 15.507s | I | 13.67 | 0.012 08-24-2023 | 14:21:35 | 56.372s | V | 13.89 | 0.007 08-24-2023 | 14:25:40 | 63.628s | B | 14.26 | 0.007 08-24-2023 | 14:26:49 | 66.016s | V | 13.88 | 0.006 08-24-2023 | 14:28:02 | 31.063s | R | 13.64 | 0.006 08-24-2023 | 14:28:40 | 24.327s | I | 13.60 | 0.008 08-24-2023 | 14:33:49 | 84.567s | B | 14.25 | 0.006 08-24-2023 | 14:35:19 | 88.210s | V | 13.86 | 0.005 08-24-2023 | 14:36:53 | 40.934s | R | 13.65 | 0.005 08-24-2023 | 14:37:40 | 32.058s | I | 13.63 | 0.007 08-24-2023 | 14:43:26 | 109.523s | B | 14.25 | 0.006 08-24-2023 | 14:45:23 | 113.289s | V | 13.89 | 0.005 08-24-2023 | 14:47:22 | 51.216s | R | 13.67 | 0.005 08-24-2023 | 14:48:20 | 41.685s | I | 13.61 | 0.007 08-24-2023 | 14:54:51 | 140.854s | B | 14.25 | 0.006 08-24-2023 | 14:57:17 | 147.908s | V | 13.88 | 0.005 08-24-2023 | 14:59:52 | 65.83s | R | 13.65 | 0.006 08-24-2023 | 15:01:05 | 53.273s | I | 13.58 | 0.007 08-24-2023 | 15:09:40 | 177.571s | B | 14.15 | 0.005 08-24-2023 | 15:15:54 | 83.812s | R | 13.65 | 0.006 08-24-2023 | 15:17:25 | 67.06s | I | 13.56 | 0.006 08-24-2023 | 15:27:51 | 225.946s | B | 14.23 | 0.006 08-24-2023 | 15:31:42 | 232.571s | V | 13.86 | 0.006 08-24-2023 | 15:35:41 | 105.216s | R | 13.61 | 0.006 08-24-2023 | 15:37:32 | 82.401s | I | 13.60 | 0.007 08-24-2023 | 15:50:16 | 284.651s | B | 14.31 | 0.006 08-24-2023 | 15:55:06 | 293.376s | V | 13.81 | 0.004 08-24-2023 | 16:00:07 | 131.78s | R | 13.57 | 0.005 08-24-2023 | 16:02:25 | 106.593s | I | 13.51 | 0.005 08-24-2023 | 16:30:17 | 164.791s | R | 13.53 | 0.006 08-24-2023 | 16:33:08 | 133.318s | I | 13.50 | 0.009 Our images have been calibrated using stars from the APASS catalog.