TITLE: GCN CIRCULAR NUMBER: 40053 SUBJECT: EP250404a: BOOTES-4/JGT optical afterglow detection DATE: 25/04/04 15:31:24 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia ipg@iaa.es
I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M. D. Caballero-Garcia, G. Garcia-Segura, S. Guziy, R. Sanchez-Ramirez and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. de Malaga), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), and D. R. Xiong, J. M. Bai, Y. F. Fan, C. J. Wang, Y. X. Xin, X. H. Zhao, J. R. Mao, B. K. Lun, K. Ye (Yunnan Observatories/CAS, Kunming) on behalf of a larger collaboration, report:
Following the detection of EP250404a by Einstein Probe (Hu et al. GCNC [40051](https://gcn.nasa.gov/circulars/40051)), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically responded to this X-ray transient starting on 2025-04-04 14:39:39UT (20 min after detection and 15 after notification). Series of images in clear filter were gathered and we detect and uncatalogud source constistent with position reported by Xu et al. (GCN [40052](https://gcn.nasa.gov/circulars/40052)). Using GaiaDR3 Gmag as reference we measure an initial magnitude of 14.8 +/- 0.03. Within 20 minutes, the source faded to magnitude 16.1. Further analysis of the additional images is ongoing.
We thank the staff at Lijiang observatory for their excellent support.
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