Difference: GCNCIRCULAR21529 ( vs. 1)

D. A. Coulter, C. D. Kilpatrick, M. R. Siebert, R. J. Foley (UCSC), B. J. Shappee, M. R. Drout, J. S. Simon, and A. L. Piro (Carnegie)

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.

-- ThomasKupfer - 18 Aug 2017