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GCN Circular 21533

Subject
LIGO/Virgo G298048: Optical Candidate Shows No Evidence for Previous Activity in Archival ASAS-SN Data
Date
2017-08-18T02:06:30Z (7 years ago)
From
Philip Cowperthwaite at Harvard U <pcowperthwaite@cfa.harvard.edu>
P. S. Cowperthwaite (Harvard),  R. J. Foley (UCSC), E. Berger (Harvard),

We investigate ASAS-SN public data at the position of the transient source
SSS17a (RA = 13:09:48.09 DECL. = -23:22:53.35, Coulter et al. 2017 GCN
21529). This source is also seen in DECam observations (Chornock et al. GCN
21530) and DLT data (Yang et al. GCN 21531).

We search the last 100 days of available data, finding no strong evidence
for variability at this position. The most recent observation is UT =
2017-08-14.9933703 (HJD = 2457980.49073), approximately 2 days before the
GW trigger.

The data can be found here:

https://asas-sn.osu.edu/public/light_curve/ede9a693-78be-4049-85a0-7de11bc61c3a

The photometry is generated by placing an aperture at the indicated
coordinates, and therefore includes light from the host galaxy.

The light curve is flat with a mean magnitude of 13.45 mag with a scatter
of 0.05 mag. This indicates that the transient is most likely a young
source.

This circular makes use of ASAS-SN public data obtained from
https://asas-sn.osu.edu/ (Shappee, B. J., Prieto, J. L., Grupe, D.,
et al. 2014, ApJ, 788, 48; Kochanek, C. S., Shappee, B. J., Stanek, K.
Z., et al. 2017, PASP, 129, 104502).

[GCN OPS NOTE(18oct17):  Per author's request, the last paragraph was added.]
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