TITLE: GCN CIRCULAR NUMBER: 10435 SUBJECT: GRB 100216A: XRT Refined Analysis DATE: 10/02/19 23:51:55 GMT FROM: Antonia Rowlinson at U.of Leicester A. Rowlinson (U. Leicester), K. Page (U. Leicester) and N. Lyons (U. Leicester) report on behalf of the Swift-XRT team: We have analysed 9.9 ks of XRT data for GRB 100216A (Cummings et al. GCN Circ. 10428), from 214.4 ks to 249.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. We do not detect any fading source within the BAT refined error circle of Cummings et al. (GCN Circ. 10428). A source is detected within the BAT refined error circle at RA, Dec = 154.25836, +35.56772 which is equivalent to: RA (J2000): 10h 17m 2.0s Dec (J2000): +35d 34' 3.8'' with an uncertainty of 5 arcsec (radius, 90% confidence) and is likely to be the known X-ray source 1RXS J101702.9+353404. This source has a count rate of 0.004 count s^-1, corresponding to a flux of 2.6e-13 erg cm^-2 s^-1, however fading cannot be determined at this time and futher observations are being planned. The three sigma upper limit 0.3 - 10 keV count rate for a source at any other position within the BAT error circle is 6e-4 count s^-1, which corresponds to an observed flux limit of 2.3e-14 erg cm^-2 s^-1 (assuming a typical count-to-observed flux conversion factor of 3.8e-11 erg cm^-2 ct^-1, Evans et al., 2009, MNRAS, 397, 1177). The results of the XRT-team automatic analysis are available at http://www.swift.acc.uk/xrt_products/00020127. This circular is an official product of the Swift-XRT team.