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GCN Circular 21529

LIGO/Virgo G298048: Potential optical counterpart discovered by Swope telescope
2017-08-18T01:05:23Z (7 years ago)
Edo Berger at Harvard U <>
D. A. Coulter, C. D. Kilpatrick, M. R. Siebert, R. J. Foley (UCSC), B. J.
Shappee, M. R. Drout, J. S. Simon, A. L. Piro (Carnegie), and A. Rest (STScI)

report on behalf of the One-Meter Two-Hemisphere (1M2H) collaboration:

On 2017 Aug 18 UT in the process of observing several galaxies coincident
with the highest-likelihood localization region for the LIGO/Virgo G298048
trigger (LVC GCNs 21509, 21513) with the 1-m Swope telescope at Las
Campanas Observatory, we detect a source 5.3�� E and 8.8�� N of NGC 4993, an
S0 galaxy in the NGC 4993 / ESO 508-G018 group at a distance of ~40 Mpc 
(Tully-Fisher distance to the group; Freedman et al., ApJ, 553, 47, 2001).
The object is:

SSS17a  13:09:48.089  -23:22:53.35

and had a brightness of i = 16.0 mag.

We have checked the minor planet center and previous SN discoveries, and
have found no cross-matches.  This source could possibly be optical
emission associated with the LIGO/Virgo G298048 trigger. 

Spectroscopic observations are under way.  Additional photometry has been
obtained and is being analyzed. Additional observations are encouraged.

The contact person for this circular is Ryan Foley (

[GCN OPS NOTE(28sep17):  Per a combination of requests and editorial
policy: (1) AR was added to the author list. (2) The contact-name sentence
was added.  The editor notes that RF was having sign-up problems with the
LV-EM Forum and E.Berger offered to submit in his place since
publication latency was important.  (3) And the EB signature block
was removed.]
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