TITLE: GCN CIRCULAR NUMBER: 42174 SUBJECT: GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up DATE: 25/10/09 11:20:11 GMT FROM: Youdong HU at INAF-OAB <huyoudong072@hotmail.com> Y.-D. Hu (GXU), F. Aceituno, A. J. Castro-Tirado, E. Fernandez-Garcia, I. Perez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, and S. Guziy (IAA-CSIC) and A. Fernández-Martín (CAHA) on behalf of a larger collaboration, report: Following the detection of GRB 251007A by Swift (Ambrosi et al. GCNC 42146), we triggered the 1.5m OSN telescope in Granada (Spain) starting on Oct. 08 at 04:17:06 UT (~8.8 hrs post burst), a series of I-band image was gathered. In the stacked image, the optical afterglow is detected within the Swift/XRT error region (Beardmore et al. GCNC 42161) with I=21.21+-0.19. About 20 mins later, the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain) also triggered to start taking images with Sloan-griz filters. The optical afterglow is detected in the stacked image with i=22.0+-0.3. These detections are consistent with the reports from UVOT (Ambrosi et al. GCNC 42146), MASTER (Lipunov et al. GCNC 42149), SVOM/C-GFT (Wu et al. GCNC 42154), AKO (Odeh et al. GCNC 42157), NOT (Malesani et al. GCNC 42158) and SVOM/VT (Li et al. GCNC 42163). We thank the staff at OSN and Calar Alto observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42174. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...