GREENBURST discovery of FRB 20261029A

ATel #18131; Duncan Lorimer (WVU) On Behalf of the GREENBURST collaboration
on 30 Oct 2026; 21:46 UT
Credential Certification: Duncan Lorimer (duncan.lorimer@mail.wvu.edu)

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We report the detection of a fast radio burst, FRB 20261029A, with the Green Bank Telescope using the GREENBURST commensal FRB detection system (Surnis et al. 2019, PASA, 36, e032; Agarwal et al. 2020, MNRAS, 497, 352; Kania et al. 2026, MNRAS, 548, 665). The burst was detected at 10:50:08 UTC on 2026 October 29 (MJD 61342.4514862337) carried out as part of project GBT 26A-554. The burst was detected across the frequency range 960-1920 MHz at a dispersion measure of 456.7 ± 0.1 pc/cc, with a signal-to-noise ratio of 8.3 and an observed pulse width of approximately 8 ms. The telescope pointing gives a nominal position of RA = 04h28m28s, Dec = +26d32m31s (J2000), with an uncertainty of approximately 9 arcmin. The DM substantially exceeds the maximum Galactic contribution along this sightline of ~100 pc/cc as predicted by NE2025 (Ocker & Cordes 2026, ApJ, 1002, 1), implying an extragalactic DM excess of ~360 pc/cc. No counterparts are evident in the second CHIME/FRB catalog (CHIME/FRB Collaboration et al. 2026, ApJS, 283, 1) within 2 degrees. A search of the NASA/IPAC Extragalactic Database within 20 arcmin of the burst position identifies a single galaxy, SDSS J042845.76+263028.5, at an angular separation of 4.6 arcmin, with a spectroscopic redshift of z = 0.555 ± 0.001 (Albareti et al. 2017, ApJS, 233, 25). We note that the photometric redshift (z = 0.181 ± 0.088) is significantly discrepant and the spectral fit quality flag raises some uncertainty about the spectroscopic value. If z ~ 0.18 is adopted, the DM excess is broadly consistent with standard models (Macquart et al. 2020, Nature, 581, 391). Follow-up observations are encouraged.

Dedispersed pulse and waterfall plot.