TITLE: GCN CIRCULAR NUMBER: 36767 SUBJECT: EP240626a: BOOTES-7 optical upper limit DATE: 24/06/26 20:28:27 GMT FROM: ipg@iaa.es

I. Perez-Garcia, S.-Y. Wu, , E. Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar, A. Castellon, A. Reina (Univ. de Malaga),Y.-D. Hu (INAF-OAB, Brera), L. Hernandez-Garcia (Univ. de Valparaiso), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:

Following the detection of the fast X-ray transient EP240626a by the Einstein Probe (Wu et al. GCNC 36766), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the fast X-ray transient location starting on June 26, 08:11 UT (~ 1.7 h after trigger) in different optical bands. Conditions were non-optimal as the target was at low altitude above horizon (and setting). No new optical source is detected on the co-added images (clear-filter) within the EP/WXT 2 arcmin radius error box down to 19.0 mag.

We thank the staff at San Pedro de Atacama Celestial Explorations observatory for their excellent support.

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