GCN Circular 34843
Subject
GRB 230911C: ATCA detection of possible radio counterpart
Event
Date
2023-10-19T17:29:14Z (2 years ago)
From
Sarah Chastain at University of New Mexico <sarahichastain@gmail.com>
Via
Web form
S. Chastain (UNM), G. E. Anderson (Curtin), J. K. Leung (UofT/HUJI), S. D. Ryder (Macquarie), A. J. van der Horst (GWU), A. Gulati (USyd), and L. Rhodes (Oxford) on behalf of the ATCA PanRadio GRB collaboration
The Australia Telescope Compact Array (ATCA) observed long GRB 230911C (E. Sonbas et al., GCN 34655) as part of the ATCA "PanRadio GRB" Large Project C3542 (PI: G. Anderson) on 2023-09-11 UT, 2023-09-13 UT, 2023-09-26 UT, and 2023-10-16 UT.
We detect a possible radio afterglow at 9 GHz in the second epoch, which continues to brighten in the third, and fourth epoch. At 5.5 GHz this source is not detected in any of the observations.
In the fourth epoch at 5.5 GHz, we find 3-sigma upper limit of 105 microJy/beam. In the fourth epoch at 9.0 GHz, the source detected in the previous observations is detected at 150 +/- 35 microJy/beam.
The fitted position is:
RAJ2000 = 15:07:13 +/- 8 arcseconds
DECJ2000 = -41:19:51 +/- 1 arcsecond
This is approximately 18 arcseconds away from the reported Swift/XRT enhanced position (P. A. Evans et al., GCN 34658).
Further observations are planned.
We thank the CSIRO Space and Astronomy staff for supporting these observations.
We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.