GCN Circular 37906

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
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) 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
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) 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
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, 37842
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), Li et al. (GCN 37844
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, 37846
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), Ror et al. (GCN 37845
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), Zheng et al. (GCN 37849
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), Moskvitin & Spiridonova (GCN 37850
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), Bochenek et al. (GCN 37869
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), Kumar (GCN 37875
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), Busmann (GCN 37877
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), Jin et al. (GCN 37892
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). 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.