TITLE: GCN CIRCULAR NUMBER: 40006 SUBJECT: GRB 250327B: Kilonova-Catcher Observations DATE: 25/04/02 01:27:54 GMT FROM: Cristina Andrade at UMN <andra104@umn.edu> E. Broens, F. Dubois, M. Freeberg, A. Lekic, G. Parent, M. Serrau (KNC), C. Andrade (UMN), E. de Bruin (UMN), D. Turpin (CEA-Saclay/Irfu), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250327B (Bouchet et al., GCN 39888) detected by SVOM/ECLAIRs with the citizen science project, Kilonova-Catcher (KNC). These observations were performed by our members using the following telescopes: T-BRO, ODK16 f/6.8, Quatro F4, T180, a Newton telescope T200 and using the Telescope Live Network. In our stacked frames, we detected an optical afterglow at the position reported by SAO/RAS (Moskvitin et al., GCN 39889, Pankov et al. GCN 39906), SVOM/VT (Xin et al., GCN 39890), GOTO (O’Neill et al. GCN 39891), the NOT (Malesani et al., GCN 39893), Mephisto (Lian et al, GCN 39894), the LCOGT (Shrestha et al. GCN 39896, Kumar et al. GCN 39904, Pérez-Fournon et al. GCN 39912), SVOM/COLIBRI (F-GFT) (Ducoin et al., GCN 39897, 39930), the Liverpool telescope (Perley et al., GCN 39902), the OHP/T193 telescope (Dennefeld et al. GCN 39905) and MASTER (Tarasenkov et al., GCN 39913). We report some of our detections and upper limits (5 sigma) in the following table: --------------------------------------------------------------------------------------------- | Tstart-TGRB (hr) | Exposure | Mag | UL (5σ) | Filter | Telescope | --------------------------------------------------------------------------------------------- | 1.62 | 180s | 16.87 ± 0.06 | | Rc (Vega) | T-BRO | | 1.67 | 180s | 17.48 ± 0.10 | | V (Vega) | T-BRO | | 3.29 | 10x60s | 18.98 ± 0.09 | | V (Vega) | ODK16 f/6.8 | | 3.52 | 180s | | 17.8 | V (Vega) | Quatro F4 | | 3.56 | 2x300s | 19.78 ± 0.11 | | g’ (AB) | ODK16 f/6.8 | | 3.58 | 180s | | 17.6 | R (Vega) | Quatro F4 | | 3.81 | 3x300s | 18.93 ± 0.17 | | r’ (AB) | ODK16 f/6.8 | | 4.24 |10x180s | 19.73 ± 0.21 | | V (Vega) | T-BRO | | 6.49 |10x180s | | 20.6 | g’ (AB) | T180 | | 6.51 |15x180s | 20.16 ± 0.36 | | Rc (Vega) | T-BRO | | 6.74 |10x180s | 19.87 ± 0.24 | | r’ (AB) | T180 | | 29.07 |100x40s | | 20.3 | r’ (AB) | Newton T200 | | 76.42 | 59x80s | | 20.5 | V (Vega) | Telescope Live T200 | --------------------------------------------------------------------------------------------- All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022, 2025). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog. Images obtained with sloan filters were calibrated using the PanSTARRS DR1 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/40006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...