e-MERLIN follow-up of FRB 20250316A and its candidate X-ray counterpart
ATel #17120; G. Bruni, L. Piro, A. L. Thakur (INAF-IAPS, Italy), B. Zhang (U. Nevada, USA), H. Sun, W. Yuan, and Y. Liu (NAO, CAS), X. Wu (PMO, CAS), L. Nicastro, E. Palazzi (INAF-OAS, Italy)
on 29 Mar 2025; 13:36 UT
Credential Certification: Gabriele Bruni (gabriele.bruni@inaf.it)
Subjects: Radio, X-ray, Transient, Fast Radio Burst, Magnetar
We performed an e-MERLIN follow-up of the FRB 20250316A (ATel #17081). Observations were carried out under DDT project RR19005 (PI Bruni) on 2025-03-26, between 03:30 - 12:30 UT, in C-band (4.82-5.33 GHz). The array was pointed to the coordinates of the possible X-ray counterpart identified by the EP collaboration (ATel #17100). Phase referencing was applied. Visibilities were calibrated through the e-Merlin pipeline (Moldon 2021, ascl:2109.006), and imaged in CASA. The image resolution in natural weighting was 57x51 mas.
An RMS of 23 uJy/beam was reached, and no source was detected either within the uncertainty region of the EP coordinates (+/-10 arcsec), or in the more recent CHIME/FRB Outriggers refined position (ATel#17114). This sets a 5-sigma upper limit of 115 uJy for the possible PRS flux density at 5 GHz. At the distance of NGC4141, this translates into a luminosity upper limit of L_nu<1E26 erg/s/Hz, in agreement with the previous one from VLA archival data at 9 GHz from 2012 (ATel #17111). This upper limit is more than two orders of magnitude lower than the luminosity of the PRSs known to date, suggesting that the presence of a PRS associated with FRB 20250316A is unlikely.
We thank the staff of the e-Merlin for their support and assistance 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.
