TITLE: GCN CIRCULAR NUMBER: 30358 SUBJECT: GRB 210702A: Swift-XRT refined Analysis DATE: 21/07/03 08:49:45 GMT FROM: Phil Evans at U of Leicester V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB) and A.Y. Lien report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 210702A (Lien et al. GCN Circ. 30351), from 84 s to 38.4 ks after the BAT trigger. The data comprise 310 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 4559 s of PC mode data and 10 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 168.57877, -36.74715 which is equivalent to: RA (J2000): 11h 14m 18.91s Dec(J2000): -36d 44' 49.7" with an uncertainty of 1.9 arcsec (radius, 90% confidence). The light curve can be modelled with an initial power-law decay with an index of alpha=1.005 (+0.014, -0.013), followed by a break at T+7161 s to an alpha of 1.68 (+0.11, -0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.570 (+0.018, -0.015). The best-fitting absorption column is consistent with the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.95 (+/-0.07) and a best-fitting absorption column of 1.8 (+/-1.0) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.2 x 10^21 cm^-2 Intrinsic column: 1.8 (+/-1.0) x 10^21 cm^-2 at z=1.16 Photon index: 1.95 (+/-0.07) If the light curve continues to decay with a power-law decay index of 1.68, the count rate at T+24 hours will be 0.044 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-12 (2.0 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01058804. This circular is an official product of the Swift-XRT team.