TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3442 SUBJECT: XRF050509C: Chandra Afterglow Detection DATE: 05/05/20 18:09:04 GMT FROM: Derek Fox at CIT Derek B. Fox (Caltech) reports on behalf of a larger collaboration: "We have observed the afterglow (Gorosabel et al, GCN 3425) of XRF 050509C (Prigozhin et al., GCN 3402) with the Chandra X-ray Observatory and ACIS-S detector, in a single 20-ks pointing beginning at 09:54 UT on May 19, and detect the X-ray afterglow at a count rate of 0.7(2) counts per ksec. This count rate corresponds to a 0.5-10 keV flux of 9E-15 erg cm-2 s-1, assuming a spectrum with power-law photon index alpha=1.5 and Galactic N_H=5.5E+20 cm-2. We note that this flux is consistent with the upper limit from Swift XRT at a similar epoch (Campana et al., GCN 3441)."