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We report observations of the binary microlensing event OGLE-2018-BLG-0022, provided by the Robotic Observations of Microlensing Events (ROME)/Reactive Event Assessment (REA) Survey, which indicate that the lens is a low-mass binary star consisting of M3 (0.375 ± 0.020 M ⊙) and M7 (0.098 ± 0.005 M ⊙) components. The lens is unusually close, at 0.998 ± 0.047 kpc, compared with the majority of microlensing events, and despite its intrinsically low luminosity, it is likely that adaptive optics observations in the near future will be able to provide an independent confirmation of the lens masses.

We report the discovery of HATS-15 b and HATS-16 b, two massive transiting extrasolar planets orbiting evolved (∼10 Gyr) main-sequence stars. The planet HATS-15 b, which is hosted by a G9 V star (V = 14.8 mag), is a hot Jupiter with mass of 2.17 ± 0.15 MJ and radius of 1.105 ± 0.040 RJ, and it completes its orbit in about 1.7 days. HATS-16 b is a very massive hot Jupiter with mass of 3.27 ± 0.19 MJ and radius of 1.30 ± 0.15 RJ; it orbits around its G3 V parent star (V = 13.8 mag) in ∼2.7 days. HATS-16 is slightly active and shows a periodic photometric modulation, implying a rotational period of 12 days, which is unexpectedly short given its isochronal age. This fast rotation might be the result of the tidal interaction between the star and its planet.

We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120 ± 0.012 MJ, a radius of 0.563-0.034 +0.046 RJ, and an orbital period of 3.1853 days. The host star is a moderately bright (V = 13.340 ± 0.010 mag, KS = 10.976 ± 0.026 mag) K dwarf star with a mass of 0.849 ± 0.027 M⊙, a radius of 0.815-0.035 +0.049 R⊙, and a metallicity of [Fe H] = +0.250 ± 0.080. The star is photometrically quiet to within the precision of the HATSouth measurements, has low RV jitter, and shows no evidence for chromospheric activity in its spectrum. HATS-7b is the second smallest radius planet discovered by a wide-field ground-based transit survey, and one of only a handful of Neptune-size planets with mass and radius determined to 10% precision. Theoretical modeling of HATS-7b yields a hydrogen-helium fraction of 18 ± 4% (rock-iron core and H2-He envelope), or 9 ± 4% (ice core and H2-He envelope), i.e., it has a composition broadly similar to that of Uranus and Neptune, and very different from that of Saturn, which has 75% of its mass in H2-He. Based on a sample of transiting exoplanets with accurately (<20%) determined parameters, we establish approximate powerlaw relations for the envelopes of the mass-density distribution of exoplanets. HATS-7b, which, together with the recently discovered HATS-8b, is one of the first two transiting super-Neptunes discovered in the Southern sky, is a prime target for additional follow-up observations with Southern hemisphere facilities to characterize the atmospheres of Super-Neptunes (which we define as objects with mass greater than that of Neptune, and smaller than halfway between that of Neptune and Saturn, i.e., 0.054 MJ < Mp < 0.18 MJ).