TITLE: GCN CIRCULAR NUMBER: 39715 SUBJECT: LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST DATE: 25/03/14 03:56:23 GMT FROM: gaosj@smail.nju.edu.cn

Shi-Jie Gao (NJU), Xiang-Dong Li (NJU), Yi-Xuan Shao (NJU), Ping Zhou (NJU) and Pei Wang (NAOC) report:

Following the detection of the binary compact object merger event S250206dm by the LIGO-Virgo-KAGRA Collaboration (GCN [39175](https://gcn.nasa.gov/circulars/39175)), the CHIME/FRB collaboration reported a fast radio burst, FRB 20250206A (GCN [39216](https://gcn.nasa.gov/circulars/39216)). The burst occurred less than one minute after S250206dm, with an estimated spatial coincidence probability of 0.1%.

We conducted a follow-up observation using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) on 2025-02-27, starting at MJD 60733.130141 (convert to infinite frequency in TDB scale). The observation used the L-band (1.25 GHz, 500 MHz bandwidth) 19-beam receiver, with the central beam pointed at R.A. = 22:34:48.72, Decl. = +12:10:11.6. The total integration time was 4800 s.

No radio pulsation was detected in either the central beam or the surrounding beams. The non-detection places an upper limit of ~10 mJy on millisecond-duration pulses.

This work was made use of the data from FAST (Five-hundred-meter Aperture Spherical radio Telescope, https://cstr.cn/31116.02.FAST). FAST is a Chinese national mega-science facility, operated by National Astronomical Observatories, Chinese Academy of Sciences.

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