GCN Circular 25621
Dougal Dobie (University of Sydney/CSIRO), Emil Lenc (CSIRO), Ian Brown (UWM), Tara Murphy (University of Sydney), Adam Stewart (University of Sydney), David Kaplan (UWM), Kunal Mooley (Caltech), Gregg Hallinan (Caltech) and the OzGrav, JAGWAR and GROWTH collaborations. We observed ASKAP J005547.4-270433/AT2019osy (GCN 25487) with the Australia Telescope Compact Array (ATCA) on 2019 August 29 from 14:00-22:00 UT. We report flux densities of: 369+/-23 uJy at 5.0 GHz 335+/-19 uJy at 6.0 GHz 307+/-15 uJy at 8.5 GHz 278+/-14 uJy at 9.5 GHz Fitting a power-law to these values we find a spectral index of alpha=-0.39+/-0.11, consistent with the value of -0.42 found by Mooley et al. (GCN 25539). Comparing to the VLA observations reported by Mooley et al. (GCN 25539), we find that the flux density has increased by ~40% in 1.5 days across 4.5-10 GHz. Additional epochs are required to separate intrinsic variability from contamination from propagation effects and systematics due to differing spatial resolution between the ATCA, VLA and ASKAP. Thank you to CSIRO staff for supporting these observations.