TITLE: GCN CIRCULAR NUMBER: 35506 SUBJECT: GRB 230818A: further radio observations with the VLA DATE: 24/01/09 13:30:14 GMT FROM: Stefano Giarratana at University of Bologna <s.giarratana@ira.inaf.it> S. Giarratana (University of Bologna, INAF-IRA), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.) At 22:56:54 UT on 2023 September 18 (T_mid = 31.0 days post-burst) and at 17:12:33 UT on 2023 November 28 (T_mid = 101.8 days post-burst) the Karl G. Jansky VLA started observing the field of GRB 230818A (Fermi GBM team, GCN 34478; Tohuvavohu et al., GCN 34479) at a central frequency of 6 and 10 GHz. The standard J1331+3030 (3C286) was used as bandpass and flux density calibrator, while J1912+3740 was used as complex gain calibrator. From a preliminary analysis, we do not detect the radio counterpart of GRB 230818A. We derive the following upper limits (UL; 3sigma). ===================================================== T_mid Freq UL r.m.s. Beam PA [days] [GHz] [uJy] [uJy/b] [arcsec] [deg] ===================================================== 31.0 6 24 8 0.34x0.31 -64 31.0 10 24 8 0.22x0.19 -75 101.8 6 30 10 13.2x9.94 -87 101.8 10 24 8 9.05x6.06 -82 ===================================================== We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF161095, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/35506. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...