EP240904a: NOT optical upper limit
ATel #16807; S. Y. Fu, J. An, S. Q. Jiang, X. Liu, Z. P. Zhu, D. Xu (NAOC, CAS), J. P.U. Fynbo (DAWN/NBI), A. Diaz (NOT) on behalf of a large collaboration
on 8 Sep 2024; 06:38 UT
Credential Certification: Dong Xu (dxu@nao.cas.cn)
Subjects: Optical, Soft Gamma-ray Repeater, Transient, Magnetar
We observed the field of EP240904a detected by Einstein Probe (EP, Cheng et al., ATel #16805), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 20:42:54 UT on 2024-09-07, i.e. 3.14 days after the trigger, and 4 x 180 s frames were obtained in the SDSS-r band.
No uncatalogued optical transient is found within or beside the 10-arcsec EP/FXT error circle, down to a 5-sigma limiting magnitude of r ~ 23.4 (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction. Also there is no apparently brightening catalogued source within or beside the 10-arcsec EP/FXT error circle.
