TITLE: GCN CIRCULAR NUMBER: 40020 SUBJECT: GRB 250402A: LCO optical counterpart detection DATE: 25/04/03 09:09:55 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias ipf@iac.es
I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL)
We report Las Cumbres Observatory Global Telescope network (LCOGT) observations of the SVOM GRB 250402A (Chen et al., GCN circ. 40014; Maggi et al., GCN circ. 40019). We observed the field of GRB 250402A with the three LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Cerro Tololo Inter-American Observatory (Chile) in the SDSS r, g, and i filters, starting at 2025-04-03 02:58:50 UTC, about 3.85 hours after the SVOM trigger.
An uncatalogued source is clearly detected in the three filters at the position of the optical counterpart detected by SVOM/VT (Xin et al., GCN circ. 40015).
We measure the following magnitudes, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction:
Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-03 02:58:50 21.01 0.14 r 300 2025-04-03 03:15:44 21.91 0.17 g 300 2025-04-03 03:21:06 20.80 0.13 i 300
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).
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