TITLE:   GCN CIRCULAR
NUMBER:  41767
SUBJECT: GRB 250702B: Late time Chandra observations
DATE:    25/09/09 20:42:37 GMT
FROM:    Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>

R. A. J. Eyles-Ferris (U of Leicester), A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. T. O’Brien (U of Leicester), M. De Pasquale (Univ. Messina), B. P. Gompertz (U. Birmingham), T. Laskar (Utah), D. B. Malesani (DAWN/NBI and Radboud), J. C. Rastinejad (Maryland), S. Schulze (Northwestern), N. R. Tanvir (U of Leicester), P. G. Jonker (Radboud) and D. Watson (DAWN/NBI) report on behalf of a larger collaboration:

We observed the position of the gamma-ray and X-ray transient GRB 250702B/EP250702a (Fermi GBM Team, GCNs 40883, 40886, 40890; Cheng et al., GCN 40906) with the Chandra X-ray Observatory through a Director’s Discretionary Time request (PI: Eyles-Ferris) using ACIS-S. Our observation started at 2025-09-05 23:26:41 UT, approximately 65 days after the initial Fermi trigger, and lasted 39.55 ks.

At the position of GRB 250702B, we detect the X-ray counterpart (Cheng et al., GCN 40906; Kennea et al., GCN 40919; O’Connor et al., GCN 41309) with a preliminary count rate of ~3.1e-4 ct/s. Assuming the same spectrum as derived from Swift/XRT observations, this corresponds to a flux ~6.7e-15 erg/cm^2/s. This is broadly consistent with the alpha ~ 1.9 decay slope measured in both the Swift/XRT light curve and previous Chandra observations (O’Connor et al., GCN 41309). Further analysis of these data is ongoing.

We thank Pat Slane and the Chandra X-ray Center team for approving and scheduling our DDT request.