GRB221009A/Swift J1913.1+1946: RT-22 Simeiz observations
ATel #15685; Alexandr Volvach (CRAO, RAS), Tao An (SHAO, CAS), Yulia Sotnikova (SAO, RAS)
on 16 Oct 2022; 10:12 UT
Credential Certification: Alexandr Volvach (volvach@meta.ua)
Subjects: Radio, Gamma-Ray Burst
Referred to by ATel #: 15712
We used the RT-22 Simeiz radio telescope (Volvach et al., A&A 648, A27, 2021) to observe GRB221009A at 22.2 and 36.8 GHz. The observations were carried out on October 11th and 14th, 2022. The observations lasted about 3 hours at each band. The quasar 3C286 was used as the primary flux standard to calibrate the absolute flux scale. A radio source was significantly detected at the first epoch but not clearly detected in the second epoch:
Date | UT F_36.8+/-err (mJy) | UT F_22.2+/-err (mJy)
11.10.2022 | 12:05-15:14 44+/-9 | 15:23-18:33 38+/-12
14.10.2022 | 12:01-15:19 15+/-12 | 15:31-18:46 11+/-13
Compared with previous observational results from RATAN-600 (ATel #15671) and other radio telescopes (ATel #15653, #15655, GCN Circ. #32757), our observations show that the radio counterpart of GRB221109A has entered an optically thin phase above 10 GHz 5 days after the burst, and the turnover frequency appears to have shifted to below 10 GHz. Any radio interferometer follow-up monitoring would be very critical for understanding the rapid evolution of the radio emission of this peculiar GRB as well as the pre-burst environment.
RT-22 Simeiz is a 22-m radio telescope operated by the Radio Astronomy Laboratory of Crimean Astrophysical Observatory RAS. We thank the staff of RT-22 radio telescope for making these observations.
