TITLE: GCN CIRCULAR NUMBER: 38382 SUBJECT: GRB 241128A: GRANDMA and Kilonova-Catcher Optical Afterglow Detections and Upperlimits DATE: 24/11/29 15:25:01 GMT FROM: Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com> D. Akl (AUS), E. de Bruin (UMN), C. Andrade (UMN), M. Tanasan (NARIT), N. Kochiashvili (AbAO), T. Hussenot-Desenonges (IJCLAB), M. Coughlin (UMN), M. Molham (NRIAG), S. Agayeva (Shamakhy Obs.), S. Antier (OCA), S. Karpov (FZU), D. Turpin (CEA-Saclay/Irfu), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Masek (FZU), A. Klotz (IRAP), M. Boer, S. Gervasoni, C. Limonta (OCA), E. Broens, F. Kugel (KNC), on behalf of the GRANDMA and Kilonova-Catcher collaborations: We observed the field of GRB 241128A (Brivio et al., GCN 38367) detected by Swift-BAT with GRANDMA and its citizen science project Kilonova-catcher (KNC). Our observations were performed with the FRAM-Auger, TAROT-TCA, KNC T400, and KNC-T-BRO telescopes starting from TGRB+108 min. We clearly detect the optical afterglow within the Swift-XRT uncertainty region (Beardmore et al., GCN 38374) and obtain the following magnitudes and 5-sigma upperlimits: +---------------------+-------------+--------+----------------+------------+ | T-mid(UTC) | Exposure(s) | Filter | Mag (AB) | Instrument | +=====================+=============+========+================+============+ | 2024-11-28T18:02:48 | 27x60 | Clear | 19.50 +/- 0.07 | KNC | | 2024-11-28T18:11:15 | 7x180 | Clear | 19.78 +/- 0.22 | KNC | | 2024-11-28T18:38:26 | 11x180 | Clear | 19.67 +/- 0.19 | KNC | | 2024-11-28T19:31:58 | 18x120 | R | 17.84 (U.L.) | FRAM-Auger | | 2024-11-28T19:40:56 | 3x180 | Clear | 17.53 (U.L.) | TAROT-TCA | +---------------------+-------------+--------+----------------+------------+ Our detection is consistent with the optical afterglow detected and reported by Hu et al., GCN 38371. Further, our magnitudes are consistent with those reported by LCO (Izzo and Malesani, GCN 38372) and NOT (Gompertz et al., GCN 38373). All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog, while images taken with a clear filter were calibrated using the Gaia eDR3 Catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/38382. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...