GBT observations of SGR J1935+2154 during its recent high-energy bursting activity phase

ATel #15168; Yogesh Maan (NCRA, India), Samayra Straal (NYU Abu Dhabi, UAE), Joeri van Leeuwen (ASTRON, NL) and Ines Pastor-Marazuela (UvA, NL)
on 19 Jan 2022; 05:05 UT
Credential Certification: Yogesh Maan (maan@astron.nl)

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SGR 1935+2154 is known to produce bright radio bursts (ATel #13681, #13684), including bursts with very high, FRB-like, energies (ATel #14074, #14080). After these CHIME and STARE2 detections, FAST also reported radio bursts and pulsed periodic emission at L-band (ATel #14084). With the detection of several high-energy bursts (GCN #21296, ATel #15141, #15162), SGR 1935+2154 entered into its latest outbursting phase on December 24, 2021.

To search for any radio activity in terms of bright radio bursts and/or periodic emission, we observed SGR 1935+2154 on January 05, 2022 using the Green Bank Telescope (GBT) at L-band (1.1 - 1.9 GHz) and S-band (1.6 - 2.4 GHz). The source was observed for 63 minutes at L-band starting at 2022-01-05T19:42:04.00, and 60 minutes at S-band starting at 2022-01-05T18:27:57.001 (date and time are in UTC). At both the bands, we recorded data in coherent dedispersion mode using a DM of 332.66 pc cm^-3, with 2048 channels across a bandwidth of 800 MHz and a sampling time of 40.96 us. The nearby pulsar PSR B1933+16 was also observed as a test pulsar.

We first down-sampled the data to 81.92 us, and 512 frequency sub-bands and then searched for periodic emission, both completely blind and by folding the data around the known period, as well as for bright single pulses, in the DM range of 320 - 345 pc cm^-3. We do not detect any significant periodic or burst emission. After taking into account the time and frequency sections excluded due to radio frequency interference, we place an 8-sigma upper limit on the period-averaged flux density of 12.3 microJy and 12 microJy at L and S-band respectively, assuming a 10% duty cycle. For any burst-like emission, we place 8-sigma upper limits on the pulse-integrated flux density of 51 mJy and 48 mJy at L and S-band respectively, assuming a pulse width of 2 ms.

We note that high-energy bursts from SGR 1935+2154 were also detected by Fermi-GBM about 12.6/11.4 hours before as well as 6.9/8.1 hours after the start of our L/S-band observations (ATel #15162). However, no high-energy burst is reported during our radio observations.

We thank the Green Bank Observatory and staff for their support and the prompt scheduling of our triggered observations.