TITLE:   GCN CIRCULAR
NUMBER:  36249
SUBJECT: GRB 240421B: ATCA radio observations
DATE:    24/04/23 09:50:08 GMT
FROM:    Gemma Anderson at Curtin U <gemma.anderson@curtin.edu.au>

G. E. Anderson (Curtin University), L. Rhodes (U. Oxford), J. K. Leung (U. Toronto/HUJI), S. Chastain (UNM), A. Gulati (U. Sydney), A. J. van der Horst (GWU), on behalf of the PanRadio GRB collaboration

The Australia Telescope Compact Array (ATCA) performed rapid-response observations of GRB 240421B (Williams et al., GCN 36208) at 5.5, 9, 16.7 and 21.2 GHz as part of the Long-term ATCA "PanRadio GRB" follow-up programme C3542 (PI. Anderson). ATCA observed from 2024-04-21 17:00 UT (7.3 hours post-burst) to 2024-04-22 01:40 UT. In our preliminary analysis, we find no radio source coincident with the enhanced XRT position (Beardmore et al., GCN 36213) with 3 sigma upper limits of 57, 54, 60, 90 microJy/beam at 5.5, 9.0, 16.7 and 21.2 GHz, respectively.

We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility
(https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.