Difference: GCNCIRCULAR21597 ( vs. 1)

M. Im, C. Choi, J. Kim, H. M. Lee (SNU), S.-L. Kim, C.-W. Lee (KASI) on behalf of the KU collaboration

We continued to observe the optical counterpart candidate of LIGO/Virgo G298048 (LVC GCNs 210505, 21509, 21513), SSS17a (Coutler et al. LVC GCN 21529), using the KMTNet 1.5m telescopes and other small telescopes. KMTNet is an observing system made of three 1.5m telescopes at the Siding Spring Observatory (SSO), the South African Astronomical Observatory (SAAO), and the Cerro-Tololo Inter-American Observatory (CTIO). BVRI images were taken at each KMTNet site in 2017-08-18 and 08-19 UT.

Preliminary magnitudes in R-band shows continued dimming of SSS17a (e.g., Im et al. LVC GCN 21566), and more interestingly, SSR17a seems to be fading faster in the last epoch data taken at SSO (see also Melandri et al. LVC GCN 21596).

UT R (mag) Site

2017-08-18.71 17.4 +- 0.1 SAAO

2017-08-18.98 17.7 +- 0.1 CTIO

2017-08-19.35 18.4 +- 0.2 SSO

The observation using small telescopes at SSO was carried out too (see Im et al. LVC GCN 21563), and the images taken with these telescopes also suggest faster dimming. The observations using the KMTNet telescopes and the small telescopes are ongoing.

-- ShaonGhosh - 19 Aug 2017