TITLE:   GCN CIRCULAR
NUMBER:  37906
SUBJECT: EP241021a: e-MERLIN radio observation
DATE:    24/10/27 10:44:05 GMT
FROM:    Aishwarya L Thakur at INAF-IAPS, Rome <aishth@outlook.com>

G. Gianfagna, G. Bruni, L. Piro, A.L. Thakur (INAF-IAPS) report:

We observed the new Fast X-ray Transient EP241021a (Hu et al., GCN 37834) with the e-MERLIN radio telescope under the project CY18212 (PI: Gianfagna) at 5 GHz starting on Oct. 24, 16:44 UT (~3 days after the EP trigger, GCN 37834) for a total of ~11 hours. 

1331+3030 was used for flux scale calibration, and 0154+0823 for complex gain. The beam size was 104x36 milli-arcsec. Data were reduced with the e-MERLIN pipeline and imaged with CASA. The image RMS was 45 uJy/beam.

We did not find statistically significant emission at a level above 5-sigma at the position of the optical counterpart reported by Fu et al. (GCN 37840, 37842), Li et al. (GCN 37844, 37846), Ror et al. (GCN 37845), Zheng et al. (GCN 37849), Moskvitin & Spiridonova (GCN 37850), Bochenek et al. (GCN 37869), Kumar (GCN 37875), Busmann (GCN 37877), Jin et al. (GCN 37892). Thus, we estimate a 5-sigma upper limit of ~ 0.2 mJy at 5 GHz. Further e-MERLIN observations are planned. 

We thank the e-MERLIN staff, particularly David Williams, for the prompt scheduling and excellent support with these observations. e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC, part of UK Research and Innovation.