TITLE: GCN CIRCULAR NUMBER: 44250 SUBJECT: EP260321a: Chandra X-ray Non-detection DATE: 26/04/09 22:11:06 GMT FROM: Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/44250. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...