TITLE: GCN CIRCULAR NUMBER: 33243 SUBJECT: GRB 221009A: radio afterglow detection with the EVN DATE: 23/02/01 10:41:25 GMT FROM: Stefano Giarratana at University of Bologna S. Giarratana (University of Bologna, INAF-IRA), M. Giroletti (INAF-IRA), T. An (Shanghai A.O.), G. Anderson (Curtin University), P. Atri (ASTRON), J. S. Bright (University of Oxford), R. Fender (University of Oxford), G. Ghirlanda (INAF-OAB), J. K. Leung (University of Sydney, CSIRO), B. Marcote (JIV-ERIC), M. Pérez-Torres (IAA-CSIC), L. Rhodes (University of Oxford), O. S. Salafia (INAF-OAB), J. Yang (OSO) On UT 2022 November 18 and 21 (40 and 43 days post-burst) we observed the radio counterpart of GRB 221009A (Dichiara et al, GCN 32632; Veres et al., GCN 32636) with the European VLBI Network (EVN) at a central frequency of 8.3 and 5 GHz, respectively. From a preliminary analysis, the source is clearly detected at both frequencies with >30 sigma significance. The 8.3 GHz surface brightness peak is ~1.3 mJ/beam. The synthesized beam is 0.9 x 0.5 mas (PA = 7.7 deg). The 5 GHz surface brightness peak is ~1.4 mJy/beam. The synthesized beam is 1.7 x 0.9 mas (PA = 9.25 deg). The source is found at a position within ~1 mas of the one previously reported by Atri et al., GCN 32907 with the VLBA at 15.2 GHz. The offset is most likely accounted for by systematics. All the results presented here are preliminary. Further analysis is in progress. We will report the final results in a forthcoming publication. We would like to thank the directors and staff of all the EVN telescopes for approving, executing, and processing these out-of-session ToO observations. The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code: RG013.