GCN Circular 36055

L. Rhodes (Oxford), G. Bruni (INAF-IAPS), L. Piro, G. Gianfagna, A.L. Thakur (INAF-IAPS), J. Bright, F. Carotenuto, S. Smartt, R. Fender (Oxford), P. Jonker (Radboud) report:

We observed the new Fast X-ray Transient EP240315a (Zhang et al., GCN 35931
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) with the e-Merlin radio telescope under the projects DD17003 (PI: Piro) and DD17004 (PI: Rhodes) at 5 GHz for a total of ~16 hours using a combination of two runs in two consecutive nights (from ~17:00 UT to ~01.00 UT, on March 27 and 28, 2024). 

3C286 was used for flux scale calibration, and 0933-0819 for complex gain, respectively. The beam size was 0.15x0.03arcsec. Data was reduced with the eMERLIN pipeline and imaged with CASA. The image RMS was 21 uJy/beam. 

We did not find statistically significant emission at a level above 5-sigma at the position of the optical counterpart (AT2024eju
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, Srivastav et al., GCN 35932
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). Thus, we estimated a 5 sigma upper limit of 105 uJy at 5 GHz. Our upper limit is consistent with the reports by Leung et al., GCN 35968
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 and Ricci et al., GCN 35990
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). 

To search for fainter emission at the position of AT2024eju
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, we concatenated our two e-Merlin epochs (reported here and in Bruni et al., GCN 35980
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). Using a uniform weighting, we find a source with a flux density of about 70 uJy/beam at coordinates consistent with AT2024eju
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. The rms noise in this image is ~20uJy/beam.  

We thank the e-Merlin staff for their excellent support.