TITLE: GCN CIRCULAR NUMBER: 15206 SUBJECT: GRB 130828A: Further Swift XRT observations DATE: 13/09/09 21:13:13 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe (PSU) reports on behalf of the Swift team: We report on two follow-up observations of the field of GRB 130828A which was discovered by the FERMI LAT as reported by Vianello & Sonbas (GCN circ 15128). The first Swift observation was performed on 2013-09-04 (obsID 20293) for 2.6ks and was centered on the X-ray source reported in Grupe et al. (GCN circ. 15135). This X-ray source is still present in the new observation suggesting that these X-rays are emitted from the Seyfert 1.9 galaxy SDSS J171855.44+275947.4 as suggested by Grupe et al. Support for this assumption comes from new IPN measurements by Hurley et al. (GCN circ. 15138) who published a new IPN error box. The X-ray source associated with SDSS J171855.44+275947.4 is significantly outside this error box. We re-examined the Swift observation of the field which contains the IPN error box (obsID 20289) and found enhanced X-ray emission within the IPN error box reported by Hurley et al. Applying the Bayesian statistics as described by Kraft et al. (1991, ApJ, 374, 344) suggesting a source detection at the 3sigma level of (2.4+4.2-2.1)e-3 counts/s. The position of this marginally detected source is: RA(hh mm ss.s) = 17h19m09.24s Dec(dd mm ss.s) = +28:13:14.05 with an uncertainty of 8". We re-observed the position of this source with Swift on 2013-09-07 for a total of 5157s (obsID 20295). No source was detected in this observation. The 3sigma upper limit at the position of the previously detected X-ray source within the IPN error box is 1.3e-3 counts/s. This may suggest that the X-ray source found within the IPN error box during observation 20289 is the X-ray afterglow of GRB 130828A. Note, however, that considering the 3sigma errors given above, this upper limit is non-conclusive. No further Swift observations are planned of this GRB. This circular is an official product of the Swift team.