EP J171203.4-333221.5: Archival radio observations from ASKAP VAST

ATel #17268; Akash Anumarlapudi (UWM), David Kaplan (UWM), Dougal Dobie (U. Sydney/OzGrav), and Tara Murphy (U. Sydney), on behalf of the VAST collaboration.
on 5 Jul 2025; 03:27 UT
Credential Certification: Akash Anumarlapudi (aakash@uwm.edu)

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On June 23, 2025, Einstein Probe (EP) discovered a X-ray transient EP250623a (EP J171203.4-333221.5; ATel #17247). Follow-up observations by the Follow-up X-ray Telescope (FXT) on board EP and the Swift X-ray telescope (XRT) revealed that the source is likely Galactic (ATel #17255) and could be an eclipsing neutron-star binary system. Following this, MeerKAT performed radio observations of this source at 1.4 GHz and found a weak radio source (5.3 sigma) with a flux density of 108 uJy (ATel #17258) at the location of the EP transient.

Here we report the archival radio observations of this source taken at the Australian SKA Pathfinder (ASKAP) observations as part of the Variable And Slow Transients Survey (VAST; Murphy et al. 2021) at 887.5 MHz.

The position of the source was observed for 64 epochs, roughly with a two-week cadence between January 2020 and October 2024. Each observation lasted approximately 12 minutes, reaching a sensitivity (noise level) of 250 uJy. The source was not detected in any of the single-epoch images. We stacked the individual exposures, which also resulted in a non-detection. The 1-sigma noise level at the location of the source is 40 uJy, a factor 2-3 deeper than the transient's brightness reported by MeerKAT in the ATel #17258, although at a slightly different frequency.