GCN Circular 46209
Subject
EP261105A: Gemini-South/GMOS Optical Upper Limit
Event
Date
2026-11-09T17:01:41Z (14 hours ago)
From
Gokul Srinivasaragavan at Northwestern University <gsriniv2@umd.edu>
Via
Web form
G. Srinivasaragavan (Northwestern) and J. Rastinejad (UMD) report on behalf of a larger collaboration:
We observed the field of EP261105A detected by Einstein Probe (Guo et al., GCN 46155; Guo et al., GCN 46168) with the GMOS instrument on Gemini South (PI: Srinivasaragavan). GMOS observations began on 2026-11-07 at 07:27:15 UT, ~1.9 days after the WXT trigger in r’-band.
The images were calibrated to Legacy Survey DR11 (Dey et al. 2019). We do not detect any source at the position of the reported optical counterpart (Ma et al., GCN 46160; Waseem et al., GCN 46170, GCN 46191) to a 3-sigma limiting magnitude of r > 24.6 AB mag, not corrected for Galactic extinction. If associated with the reported nearby galaxy at z = 0.055 (Waseem et al., GCN 46170), this corresponds to an absolute magnitude upper limit of r > -12.4 AB mag, much fainter than kilonovae similar to AT2017gfo at a similar epoch.
We thank the staff at Gemini observatory for the rapid scheduling and execution of these observations.