TITLE:   GCN CIRCULAR
NUMBER:  41559
SUBJECT: EP250827a: BOOTES-7 early optical dectection
DATE:    25/08/27 10:21:40 GMT
FROM:    I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>

M. Gritsevich (Univ. of Helsinki), I. Perez-Garcia, E.  Fernandez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC,  Granada), C. Perez del Pulgar (Univ. of Malaga), D.-R. Xiong (YNAO, Kumming), Y.-D. Hu (GXU, Guanxi), B.-B. Zhang (Nanjing Univ.), and A. Maury (Space Obs., San Pedro de Atacama), on behalf of a larger  collaboration, report:

Following the detection of EP250827a by Einstein Probe (Hua et al., GCNC 41553), the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) automatically observed the X-ray transient location starting on Aug. 27, 07:47:36 UT (i.e. 413 s after trigger). A series of images in clear filter were gathered for 2 h and the optical counterpart reported by Levan et al. (GCNC 41554), Li et al. (GCNC 41555) and Lipunov et al. (GCNC 41558) was detected at early times in our dataset. We measure a magnitude of 18.67 +/- 0.05 on a co-added image (60s x 5 exposures) at 07:53:11 UT mid time. Further data analysis is ongoing.

We would like to thank the staff at San Pedro de Atacama Space Observatory for their excellent support.