FAST detected repeated bursts from FRB 20251229A

ATel #17591; Dejiang Zhou (NAOC), Jiarui Niu (NAOC), Wanjin Lu (NAOC), Shiqian Zhao (GZHU), Jintao Xie (SUSE), Dengke Zhou (Zhejiang Lab), Heng Xu (NAOC), Suo Cao (NAOC), Longxuan Zhang (HUST), Yuhao Zhu (NAOC), Jiaheng Zhang (CCNU), Yuanpei Yang (YNU), Dongzi Li (THU), WeiWei Zhu (NAOC), Bing Zhang (HKU), Jinlin Han (NAOC), Jinhuang Cao (NAOC), Yi Feng (Zhejiang Lab), Yuxiang Huang (YNAO), Di Li (THU), Rui Luo (GZHU), Fayin Wang (NJU), Pei Wang (NAOC), Xuan Yang (PMO), Ye Li (PMO), Wenfei Yu (SHAO), Songbo Zhang (PMO)
on 11 Jan 2026; 10:19 UT
Credential Certification: Weiwei Zhu (zhuww@nao.cas.cn)

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We carried out follow-up observations of the recently discovered repeating fast radio burst FRB 20251229A (ATel#17574) for 40 minutes on 2026 January 6, 2 hours on 2026 January 7, and 30 minutes each on 2026 January 8 and 9, using the Five-hundred-meter Aperture Spherical radio Telescope (FAST, Nan et al. 2011) with the 19-beam receiver covering a frequency bandwidth from 1.0 GHZ to 1.5 GHz (Jiang et al. 2020). Polarization Data were recorded for 4.7 hours in total with a 49.152 \mu s sampling time, and we detected 9 bursts, as listed below:

DATE | TOA | S/N |Width(ms)| Fluence (mJy ms)
2026-01-06 | 61046.355822639 | 28.6 | 3.8 | 1018.4
2026-01-06 | 61046.355822871 | 54.7 | 3.3 | 1933.3
2026-01-06 | 61046.361141021 | 57.7 | 4.4 | 299.8
2026-01-06 | 61046.361315179 | 20.2 | 8.1 | 183.3
2026-01-06 | 61046.374163996 | 14.7 | 3.2 | 136.9
2026-01-07 | 61047.298726257 | 10.6 | 7.1 | 47.4
2026-01-07 | 61047.305362873 | 272.8 | 2.1 |1997.3
2026-01-08 | 61048.252010508 | 12.3 | 5.3 | 39.4
2026-01-09 | 61049.317006043 | 15.1 | 7.0 | 111.1

We applied the structure-maximizing techniques (Hessels et al. 2019) to the highest S/N burst detected on 2026-01-07, and obtained a consistent but more accurate dispersion measure of DM = 192.91 +/- 0.15 pc cm^{-3} than that given by the HyperFlash and ECLAT (ATel#17588). The time of arrival (TOA) has been converted to the infinite frequency using this DM value. Signal-to-noise ratios (S/N) and fluences were measured following standard FAST single-pulse analysis procedures (Zhou et al. 2023). The rotation measure is also derived from polarization data of this brightest burst: RM = -77.7 +/- 1.8 rad m^{-2}.

References:
Hessels, J.~W.~T., Spitler, L.~G., Seymour, A.~D., et al.\ 2019, ApJL, 876, 2, L23.
Jiang, P., Tang, N.-Y., Hou, L.-G., et al.\ 2020, RAA, 20, 5, 064.
Nan, R., Li, D., Jin, C., et al. 2011, INT J MOD PHYS D, 20, 6, 989.
Zhou, D.J., Han, J.L., Xu, J., et al. 2023, RAA,23, 104001