GCN Circular 44250

Brendan O'Connor (CMU) and Eleonora Troja (U Rome) on behalf of a larger collaboration:

We observed the position of EP260321a (Huang et al., GCN 44068

) with the Chandra X-ray Observatory (CXO) under GO program 27400339 (PI: O'Connor). Observations were carried out with ACIS-S starting on 2026-04-05 at 22:00 UT, corresponding to ~15.4 d after the EP trigger, for a total of 19.81 ks. We do not detect any coincident X-ray source at this time. With the exception of GW170817, this observation is capable of excluding all known GRB X-ray afterglows from the Swift era, including GRB 060218 which is also located at ~150 Mpc.

Further observations are planned.

We thank the staff of the Chandra X-ray Observatory, including Pat Slane, Dan Schwartz, Jack Steiner, and Vinay Kashyap, for rapidly scheduling these observations.