GCN Circular 17899
P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'a� (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 150530B (Cummings et al. GCN Circ. 17895), collecting 4.8 ks of Photon Counting (PC) mode data between T0+239.2 ks and T0+247.3 ks. No X-ray sources have been detected inside or close to the Swift/BAT error region. The 3-sigma upper limit in the field ranges from ~0.003 to ~0.004 ct s^-1, corresponding to a 0.3-10 keV observed flux of 1.0e-13 to 1.5e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). Four uncatalogued sources were detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020522. This circular is an official product of the Swift-XRT team.