2019AJ....158..151R

We report the discovery of KMT-2018-BLG-1990Lb, a Jovian planet (m_p=0.57_–0.25^+0.79M_J) orbiting a late M dwarf (M=0.14_–0.06^+0.20M_☉) at a distance of (D_L=1.23_–0.43^+1.06kpc), and projected at 2.6 ± 0.6 times the snow line distance, i.e., a_snow≡2.7au(M/M_☉). This is the second Jovian planet discovered by the Korea Microlensing Telescope Network (KMTNet) in its low-cadence (0.4 hr^–1) fields, demonstrating that this population can be probed based on relatively low-cadence survey-only microlensing data. However, while many Jovian-planet microlensing events will not have caustic crossings (e.g., the previous case, KMT-2016-BLG-1397) and some that do will be well characterized by low-cadence survey observations (e.g., the current case), in general higher-cadence follow-up observations of the caustic crossings are preferable. Such follow-up observations require microlensing alerts, which KMTNet now provides.