TITLE:   GCN CIRCULAR
NUMBER:  43552
SUBJECT: EP260128a: LCO optical upper limits
DATE:    26/01/29 07:47:19 GMT
FROM:    Jonathan Quirola at Radboud University <jaquirola1990@gmail.com>

J. A. Quirola-Vasquez (Radboud), J. N. D. van Dalen (Radboud), J. Chacón(PUC), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud), and F. E. Bauer (SSI and UTA) report on behalf of a larger collaboration:

We observed the field of the fast X-ray transient EP260128a (Zhou  et al., GCN 43549) using an LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. A series of 6x300 s exposures was taken in each of the SDSS-r filter, starting on 2026-01-29 at 02:05:48 UT (2.43 hr after the trigger).

No new source is detected within or at the border of the EP/FXT uncertainty region (Zhou et al., GCN 43549) compared to Legacy DR11. From the stacked images, we obtain the following 3-sigma upper limits:


r > 22.5

These upper limits are in AB magnitudes, calibrated using nearby stars from the Pan-STARRS catalog, and are not corrected for Galactic extinction.