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GCN Circular 25539

Subject
LIGO/Virgo S190814bv: VLA observation of ASKAP J005547-270433/AT2019osy
Date
2019-08-29T07:33:40Z (5 years ago)
From
Kunal Mooley at NRAO,Caltech <kmooley@caltech.edu>
Kunal Mooley (NRAO, Caltech), Gregg Hallinan (Caltech), Dale Frail 
(NRAO), Alessandra Corsi (TTU), Kenta Hotokezaka (Princeton), Mansi 
Kasliwal (Caltech), Dougal Dobie (U. Sydney, CSIRO), Tara Murphy (U. 
Sydney), David Kaplan (UWM) report on behalf of the JAGWAR collaboration

We observed ASKAP J005547-270433 (GCN 25487) with the VLA between 1-12 
GHz on 2019 Aug 28.3. We find that the spectrum between the observed 
frequencies is consistent with a single power law. The derived spectral 
index is -0.42, and the extrapolated 943 MHz flux density is 490+/-20 
uJy (compare with 550+/-34 uJy from ASKAP Aug 23). The radio source 
appears to be unresolved on 100 mas scales, and its coordinates are 
consistent with the optical centroid (obtained from DECaLS DR8) of 
2dFGRS TGS211Z177 to 0.1 arcsec. The 3 GHz luminosity is 3e28 erg/s/Hz, 
assuming association with the 2dFGRS galaxy. The radio spectral index, 
source position and size, and luminosity of ASKAP J0055-27 are 
consistent with a low luminosity AGN, and variability observed by ASKAP 
consistent with refractive interstellar scintillation.

Although a radio AGN is the likely explanation, we cannot completely 
rule out the association of ASKAP J0055-27 with S190814bv. The radio 
spectrum is rather hard for a merger afterglow (implying the electron 
power-law index p to be <2), however additional epochs are encouraged to 
separate any possible afterglow component from AGN scintillation.

We thank the NRAO staff for scheduling the VLA observation.
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