Difference: GCNCIRCULAR21623 ( vs. 1)

T. Nakaoka, K. S. Kawabata, M. Kawabata, H. Nagashima, and Y. Utsumi (Hiroshima University) on behalf of J-GEM collaboration.

We performed H-band imaging of the possible counterpart of G298048, SSS17a in NGC 4993 identified by Coulter et al. (LVC GCN 21529), with HONIR on the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan.

Because of low-elevation observation (height~10 deg) during bright twilight, the foreground sky level was still high and SSS17a was considerably faint (~3 sigma) in our stacked image. We performed a forced aperture photometry and estimated a preliminary magnitude in AB system of

H = 16.7 (2017 August 20.424-429 UT; MJD 57985.424-429)

The magnitude is calibrated against 2MASS field stars. Further analysis is in progress.

-- ShaonGhosh - 20 Aug 2017