TITLE:   GCN CIRCULAR
NUMBER:  37038
SUBJECT: EP240804a: LCOGT optical counterpart detection
DATE:    24/08/05 09:02:09 GMT
FROM:    Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>

F. Poidevin, I. Pérez-Fournon, D. S. Aguado, J. A. Acosta-Pulido, A. López-Oramas, D. Nespral (IAC and ULL), and F. Acero (CEA Saclay and IAC)

We report on optical follow-up observations of the Einstein Probe (EP) fast X-ray transient EP240804a (Wang et al., GCN 37034) using one of the Las Cumbres Observatory Global Telescope Network (LCOGT) 1-m telescopes located at the Cerro Tololo Inter-American Observatory (Chile) LCOGT node, with a single 300 sec exposure in the SDSSr filter. The observation started at 07:03:14 UT on 2024-08-05, i.e. 9.44 hr after the EP trigger.

We detect an uncatalogued source with r = 20.30 +/- 0.25 at a position consistent with the optical counterpart reported by An et al. (GCN 37035). For the calibration we used the Gaia synthetic photometry generated from the Gaia BP/RP mean spectra (Gaia DR3 Part 6. Performance verification).
The magnitude is not corrected for Galactic extinction.

This work makes use of observations from the Las Cumbres Observatory global telescope network (program IAC2024B-004).