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GCN Circular 36280

LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
2024-04-24T10:32:21Z (3 months ago)
Dougal Dobie at University of Sydney <>
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D. Dobie, A. Gulati, T. Murphy (U. Sydney/OzGrav), J. Freeburn (Swinburne), A. Anumarlapudi, D.L. Kaplan (UWM) on behalf of a larger collaboration.

We report observations of Mag24a (GCN #36267) and the GW-MMADS source AT2024hdn (GCN #36273) with the Australia Telescope Compact Array (ATCA) on 2024-04-24 using 2x2048 MHz bands centered on 5.5 and 9 GHz.

We observed the position of Mag24a from 03:00-05:34 UTC. We chose to cease observations after independently discovering the red object at the position of the source in archival DECaPS2 data eventually reported in GCN #36274. We then observed the position of AT2024hdn from 05:35-07:40.

We do not find radio emission at the location of either optical source. After preliminary analysis of the data we report 3-sigma upper limits of 

|    Source | Frequency (GHz) | Flux density (uJy) |
| --------- | --------------- | ------------------ |
|    Mag24a |             5.5 |               < 55 |
|    Mag24a |             9.0 |               < 50 |
| AT2024hdn |             5.5 |              < 240 |
| AT2024hdn |             9.0 |               < 60 |

We thank CSIRO staff for rapidly scheduling these observations.

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. We acknowledge the Gomeroi people as the Traditional Owners of the Observatory site.
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