TITLE: GCN CIRCULAR NUMBER: 31335 SUBJECT: GRB 211229A: Swift ToO observations DATE: 21/12/29 15:06:32 GMT FROM: Phil Evans at U of Leicester pae9@leicester.ac.uk

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 211229A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021475

Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT-GUANO event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.