TITLE:   GCN CIRCULAR
NUMBER:  21538
SUBJECT: LIGO/Virgo G298048: Las Cumbres Observatory Detection of The Possible Optical Counterpart in NGC 4993
DATE:    17/08/18 04:06:31 GMT
FROM:    Iair Arcavi at LCOGT  <iarcavi@lcogt.net>

I. Arcavi, D. A. Howell, C. McCully, G. Hosseinzadeh, S. Vasylyev (UCSB/Las
Cumbres Obs), M. Zalzman, D. Poznanski (TAU), L.P. Singer (NASA/GSFC), S.
Valenti (UC Davis), T. Piran (HUJI), D. Kasen, J. Barnes (UC Berkeley) and
W-f. Fong (UA) report an independent detection of the possible optical
counterpart reported by Coulter et al. (LVC GCN 21529), Chornock et al.
(LVC GCN 21530), Valenti et al. (LVC GCN 21531) and Melandri et al. (LVC
GCN 21532).

In the course of Las Cumbres Observatory galaxy-targeted LIGO followup we
observed NGC 4993 from one of our 1-meter telescopes at the Cerro Tololo
Inter-American Observatory in Chile. An imaging 5-minute exposure starting
at 2017-08-18 00:15:23 UT in the w (=g+r+i) filter clearly shows the
candidate.

Analysis of the image is ongoing and followup is planned when the field
becomes visible to our Siding Spring telescopes starting at 2017-08-18
08:32 UT.