GCN Circular 35788

Anna Y. Q. Ho (Cornell), Antonio Rodriguez, Mansi Kasliwal, Shri Kulkarni (Caltech), Daniel Perley (LJMU) report:

Starting at UT 2024 Feb 24 00:26 the Very Large Array (VLA) observed the position of EPW20240219aa, a fast X-ray transient discovered by Einstein Probe (ATel #16463; Yuan et al. 2018, Proc. SPIE, 10699, 1069925) subsequently recognized to have a GRB counterpart (ATel #16473, GCN #35773, 35776, 35784, 35785). The X-band (10 GHz) image RMS was 4 uJy in 34.5 minutes of on-source time.

Several point sources were detected in the 3 arcmin radius localization region of EPW20240219aa, listed in the table below. Two (Source #6 and Source #7) have matches in ZTF deep reference r-band imaging. However, Source #7 has a match in Epoch 1.2 of the VLA Sky Survey (Lacy et al. 2020, PASP, 132, 035001) so is unlikely to be associated with EPW20240219aa.

Source # | RA | Dec | Peak Flux Density (mJy)
1 | 05:20:11.071 | 25:33:35.26 | 0.169 
2 | 05:20:11.950 | 25:32:05.73 | 0.082 
3 | 05:20:04.908 | 25:31:49.33 | 0.157 
4 | 05:20:05.888 | 25:31:20.67 | 0.038
5 | 05:19:59.654 | 25:32:44.65 | 0.049
6 | 05:20:04.705 | 25:33:27.30 | 0.030
7 | 05:19:52.543 | 25:31:48.13 | 0.300 

A link to the ZTF r-band image with a VLA contour overlay can be found here: https://www.dropbox.com/scl/fi/0wk5pqm4nteyiarha6fme/overlayztf.pdf?rlkey=7o4dkhl0ml7ct8d16je67id88&dl=0

A second VLA observation is planned to search for variability and identify any radio counterpart. 

Data were obtained under DDT program VLA 24A-439 (PI Ho). We thank the VLA staff for rapidly approving and scheduling these observations.