Non-detection of short-duration pulses from EP250702a with FAST

ATel #17295; Songbo Zhang (PMO), Xuan Yang (PMO), JinJun Geng (PMO), Yifang Liang (PMO), Yanlong Hua (PMO), Yuanqi Liu (SHAO), Ailing Wang (IHEP, SHAO), Lei Qian (NAOC), Zhichen Pan (NAOC), Tao An (SHAO), Peng Jiang (NAOC), and Xuefeng Wu (PMO)
on 20 Jul 2025; 11:39 UT
Credential Certification: Songbo Zhang (sbzhang@pmo.ac.cn)

Tweet

We report radio follow-up observations of the X-ray transient EP250702a, conducted with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). This event was initially detected by the Einstein Probe and classified as an X-ray transient (ATel #17261) potentially linked to GRB 250702B,D,E (GCN #40883, #40891). Our observations were prompted by the refined localization provided by Swift/XRT (GCN #40919), aiming to search for possible short-duration radio pulses that could indicate associated phenomena. The observations spanned one hour, from 2025-07-06 16::46:00 (UTC) to 17:46:00 (UTC), using the central beam of FAST 19-beam receiver system. The data were recorded in full polarization mode, with a sampling interval of 49.152 us across 4096 channels covering 1.0-1.5 GHz frequency range. To identify potential pulses, we employed the Heimdall software package for single-pulse searches, exploring a dispersion measure (DM) range of 0-2000 pc cm^-3 and pulse widths from 49.152 us to 1.00352 s. No short-duration radio pulses were detected above a signal-to-noise ratio threshold of 7. This corresponds to a flux density upper limit of 0.27 mJy (for a pulse width of 1.00352 s) and a fluence upper limit of 1.93 mJy ms (for a pulse width of 49.152 us), assuming negligible interstellar scattering and a flat spectrum across the observed band. We encourage continued multi-wavelength monitoring, including further radio searches at different frequencies or epochs, to elucidate the nature of this transient. We thank the FAST operations team for their support in scheduling and executing these observations. Contact: Songbo Zhang (PMO)