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GCN Circular 34518

GRB 230815A: ATCA detection of radio counterpart
2023-08-22T11:44:32Z (9 months ago)
James Leung at U of Sydney/VAST <>
legacy email
J. K. Leung (USyd), G. E. Anderson (Curtin), S. D. Ryder (Macquarie),
A. J. van der Horst (GWU), A. Gulati (USyd), L. Rhodes (Oxford), 
S. Chastain (UNM) on behalf of the PanRadio GRB collaboration

The Australia Telescope Compact Array (ATCA) observed long GRB 230815A 
(Klingler et al., GCN 34434; Mailyan et al., GCN 34440) as part of the 
ATCA "PanRadio GRB" follow-up Large Project C3542 (PI. Anderson) on 
2023-08-17 UT and 2023-08-18 UT. 

No radio sources were detected at the GRB location in the first 
observation conducted from 2023-08-17 02:00 UT for 10 hrs at 5.5, 9.0, 
16.7 and 21.2 GHz. The 3-sigma upper limits were 75, 69, 324, 741 
microJy/beam, respectively. Note the higher than usual rms was due to 
bad weather during the observation.

The second observation was conducted from 2023-08-18 22:00 UT for 6 hrs 
at 5.5, 9.0 and 44 GHz. In our preliminary analysis, we detect a radio 
counterpart with a flux density of 70+/-10 microJy at 9 GHz. The fitted 
position is:

RAJ2000  = 12:18:53.2
DECJ2000 = -58:03:09.0
with an uncertainty of ~0.3". 

This is in broad agreement with previously reported Swift/XRT (Beardmore
et al., GCN 34437) and VLT/HAWK-I (Schneider et al., GCN 34467) 
afterglow positions. There was also a marginal ~3 sigma detection at 
5.5 GHz (rms=14 microJy/beam) and a non-detection at 44 GHz with a
3-sigma upper limit of 111 microJy/beam.

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 
( which is funded by the Australian Government
for operation as a National Facility managed by CSIRO.

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