KMT-2018-BLG-1743: Planetary Microlensing Event Occurring on Two Source
  Stars
  We present the analysis of the microlensing event KMT-2018-BLG-1743. The
light curve of the event, with a peak magnification $A_{\rm peak}\sim 800$,
exhibits two anomaly features, one around the peak and the other on the falling
side of the light curve. An interpretation with a binary lens and a single
source (2L1S) cannot describe the anomalies. By conducting additional modeling
that includes an extra lens (3L1S) or an extra source (2L2S) relative to a 2L1S
interpretation, we find that 2L2S interpretations with a planetary lens system
and a binary source best explain the observed light curve with
$\Delta\chi^2\sim 188$ and $\sim 91$ over the 2L1S and 3L1S solutions,
respectively. Assuming that these $\Delta\chi^2$ values are adequate for
distinguishing the models, the event is the fourth 2L2S event and the second
2L2S planetary event. The 2L2S interpretations are subject to a degeneracy,
resulting in two solutions with $s>1.0$ (wide solution) and $s<1.0$ (close
solution). The masses of the lens components and the distance to the lens are
$(M_{\rm host}/M_\odot, M_{\rm planet}/M_{\rm J}, D_{\rm L}/{\rm kpc}) \sim
(0.19^{+0.27}_{-0.111}, 0.25^{+0.34}_{-0.14}, 6.48^{+0.94}_{-1.03})$ and $\sim
(0.42^{+0.34}_{-0.25}, 1.61^{+1.30}_{-0.97}, 6.04^{+0.93}_{-1.27})$ according
to the wide and close solutions, respectively. The source is a binary composed
of an early G dwarf and a mid M dwarf. The values of the relative lens-source
proper motion expected from the two degenerate solutions, $\mu_{\rm wide}\sim
2.3 $mas yr$^{-1}$ and $\mu_{\rm close} \sim 4.1 $mas yr$^{-1}$, are
substantially different, and thus the degeneracy can be broken by resolving the
lens and source from future high-resolution imaging observations.
