TITLE:   GCN CIRCULAR
NUMBER:  35866
SUBJECT: GRB240218A: ATCA observation of the radio counterpart
DATE:    24/03/04 19:10:37 GMT
FROM:    Aishwarya L Thakur at INAF-IAPS, Rome <aishth@outlook.com>

A.L. Thakur (INAF-IAPS), R. Ricci (INAF-IRA), G. Bruni, L. Piro, G. Gianfagna (INAF-IAPS), M. Wieringa (ATNF) report:

We observed the high-redshift GRB240218A (Page et al. GCN 35742, Veres and Meegan et al. GCN 35755, Svinkin et al. GCN 37558, D’Avanzo et al. GCN 35747, Saccardi et al. GCN 35756) with the Australian Telescope Compact Array under program C3546 (PI Thakur) on 4 March 2024 at a mean epoch of ~ 15 days post-burst. Observations were performed in the C-band for a total duration of ~6 hours.

Given the declination of the radio counterpart, the ATCA beam in the current array configuration is highly elongated on the North-South axis. We performed a check for potential confusing sources using a VLASS field at 3 GHz, centred on the position of the radio afterglow as detected by the VLA at RA=10:47:11.480 Dec=+01:16:35.29 (Schroeder et al., GCN 35794). No confusing sources are visible down to an rms of 130 uJy/beam.

In the preliminary 5.5 GHz ATCA image, we detect a source with a flux of ~ 0.2 mJy at a position consistent with the VLA detection.

Further monitoring of this counterpart is planned.

We thank CSIRO Space and Astronomy staff, particularly Jamie Stevens, for excellent support in planning and performing 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.