GCN Circular 35070

Alice P. Curtin (McGill University) for the CHIME/FRB Collaboration:

At 15:36:21 UTC on 15 November 2023, GRB 231115A was detected by Fermi/GBM (Fermi GBM Team, GCN 35035
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 & 35044), INTEGRAL (P. D'Avanzo et al., GCN 35036
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, S. Mereghetti et al., GCN 35037
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), Glowbug (C. C. Cheung et al., GCN 35045
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), and Insight-HXMT (Insight-HXMT team, GCN 35060
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). The position of GRB 231115A (RA=149.00, DEC=69.68 with an uncertainty of 2 arcmin) is consistent with that of the M82 galaxy (S. Mereghetti et al. GCN 35037
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). Additionally, the spectrotemporal properties of GRB 231115A suggest it is likely due to a magnetar giant flare (Fermi/GBM Team, GCN 35044
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, S. Ronchini et al., GCN 35065
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).

At the time of the high-energy (HE) emission, GRB 231115A was ~20 degrees from the meridian of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB). No radio emission was detected from the source at the time of the HE emission. In addition to searching for radio emission at the time of the Fermi/GBM trigger, we also searched within the CHIME/FRB database for bursts from this position within the last two years, yet did not find any definitive astrophysical associations.

Using a pipeline described in Curtin et al. (2023), we constrain the FRB-like radio emission from this source in the 400-800 MHz band to be <260 Jy or <720 Jy ms (assuming a 10 ms pulse width) at the time of the Fermi/GBM trigger. The HE fluence reported by Fermi/GBM in the 10-1000 keV range is (6.3 +/- 0.4)e-7 erg/cm^2  (Fermi/GBM Team, GCN 35044
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). This implies a radio-to-HE emission ratio of <4.5e-9 (unitless assuming a 400 MHz bandwidth). Additionally, using a luminosity distance of 3.5 Mpc to the M82 galaxy (P. D'Avanzo et al. 2023, GCN 35036
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), our derived radio flux limit corresponds to an upper limit on the radio luminosity of <3.8e30 erg s^-1 Hz^-1. 

While GRB 231115A was ~20 degrees from the meridian of CHIME/FRB at the time of the Fermi/GBM trigger, it transited directly overhead CHIME/FRB at 14:18:45 UTC on 15 November 2023. Thus, our best radio constraints for this source are ~80 minutes prior to the Fermi/GBM trigger. As no radio emission was similarly detected at this time, we constrain the radio flux at this time to be <0.5 Jy and the fluence to be <1.2 Jy ms assuming a burst width of 10 ms. This corresponds to a radio luminosity limit of <7.3e27  erg s^-1 Hz^-1 and a radio-to-HE fluence ratio of <7.6e-12 (unitless assuming a 400 MHz bandwidth). 

References
Curtin, A.P., Tendulkar, S.P., Josephy, A., et al., 2023, ApJ, 954, 154. doi:10.3847/1538-4357/ace52f
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