GCN Circular 41954
Subject
EP250911a: e-MERLIN radio observations
Event
Date
2025-09-23T12:59:20Z (a day ago)
From
Giulia Gianfagna at INAF-IAPS <giulia.gianfagna@inaf.it>
Via
Web form
G. Gianfagna, G. Bruni, L. Piro, A. L. Thakur (INAF-IAPS) report:
We observed the Fast X-ray Transient EP250911a (Liang et al., GCN 41788) with the e-MERLIN radio telescope under the project CY20206 (PI: Gianfagna) at 5 GHz starting on Sep. 17, 16:00 UT (~6 days after the EP trigger) for a total of 11 hours.
1331+3030 was used for flux scale calibration, and 2344+2952 for complex gain. The beam size was 63x37 milli-arcsec. Data was reduced with the e-MERLIN pipeline and imaged with CASA. The image RMS was 18 uJy/beam.
We did not find statistically significant emission at a level above 5-sigma at the position of the optical counterpart reported by Quirola-Vasquez et al. (GCN 41790), Angulo et al (GCN 41793), Lai et al. (GCN 41801), Moskvitin et al. (GCN 41805), Ma et al. (GCN 41807), Malesani et al. (GCN 41811). Thus, we estimate a 5-sigma upper limit of ~ 90 uJy at 5 GHz. Further e-Merlin observations are planned.
We thank the e-Merlin staff for the prompt scheduling of 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.