GCN 43889: EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
2026-03-01T13:18:28.764Z | rev 0
Yuan Fang, Hong Guang Li, Shiyan Zhong, Qinhao Shao, Jian Cui, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Guowang Du, Jinghua Zhang, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The 50cm Telescope of the Yunnan University was triggered on 2026-02-26T14:42:36 (~52.6 min after the EP/WXT trigger) to observe the field of EP-WXT trigger 01709258652 (Yang et al., GCN 43849; Wu et al., GCN 43857). A sequence of g, r, i and z-band images was obtained about 51 min. The photometry of suggested flare star LP 435-538 (High Proper Motion Star; Yang et al., GCN 43849) shows a decline from 14.41 to 14.89 mag (AB, calibrated against Gaia XP) in g-band over ~47 min. The fading was relatively gradual during this observation period. These results further support the previous finding by Wu et al. (GCN 43857) that EP X-ray trigger was associated with a stellar flare.
The 50cm telescope is located at the Lijiang Observatory, China and is part of 50cm array facility. The camera employs an ON Semi KAF-50100 sensor, with 8176 x 6132 pixels of size 6μm (corresponding to 0.3 arcsec projected on the sky). The telescope is utilized for a prompt monitoring of transients and also serves as the supporting facility for monitoring the Mephisto detected targets (Chen et al. 2024, Yang et al. 2024).
GCN 43857: EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
2026-02-27T02:06:29.241Z | rev 0
C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team:
We observed the field of trigger 01709258652 detected by EP/WXT (Yang et al., GCN 43849) with LATIOS on SVOM/C-GFT. Observations started at 2026-02-26T13:56:46 UTC, ~6.77 min after the trigger.
A sequence of g-, r-, and i-band images was obtained over ~110 min. Photometry of the suggested flare star LP 435-538 (High Proper Motion Star; Yang et al., GCN 43849) shows a decline from ~13.8 to ~15.4 mag in g-band over ~110 min. The fading was initially fast, then slowed, and was flatter in the r and i bands. This confirms the EP X-ray trigger is associated with a stellar flare.
The photometry was calibrated against nearby Pan-STARRS1 stars and no correction for Galactic dust extinction was applied.
We thank the observation assistants Hong-Xv Xue and Bo-Wen Li at Jilin ob-servatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.