The sensitivities of radial velocity (RV) surveys for exoplanet detection are extending to increasingly long orbital periods, where companions with periods of several years are now being regularly discovered. Companions with orbital periods that exceed the duration of the survey manifest in the data as an incomplete orbit or linear trend, a feature that can either present as the sole detectable companion to the host star, or as an additional signal overlain on the signatures of previously discovered companion(s). A diagnostic that can confirm or constrain scenarios in which the trend is caused by an unseen stellar, rather than planetary, companion is the use of high-contrast imaging observations. Here, we present RV data from the Anglo-Australian Planet Search (AAPS) for twenty stars that show evidence of orbiting companions. Of these, six companions have resolved orbits, with three that lie in the planetary regime. Two of these (HD 92987b and HD 221420b) are new discoveries. Follow-up observations using the Differential Speckle Survey Instrument (DSSI) on the Gemini South telescope revealed that five of the twenty monitored companions are likely stellar in nature. We use the sensitivity of the AAPS and DSSI data to place constraints on the mass of the companions for the remaining systems. Our analysis shows that a planetary-mass companion provides the most likely self-consistent explanation of the data for many of the remaining systems.

We report the discovery of TOI-2180 b, a 2.8 M J giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8 ± 0.6 days, revealed an orbital eccentricity of 0.368 ± 0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.

We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source-lens baseline object. The planet's mass, M p =13.4±0.9 M J , places it right at the deuteriumburning limit, i.e., the conventional boundary between "planets" and "brown dwarfs." Its existence raises the question of whether such objects are really "planets" (formed within the disks of their hosts) or "failed stars" (lowmass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf, M host =0.89±0.07 M e , and the planet has a semimajor axis a∼2.0 au. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth-Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultradense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over <1% of an orbital period.

Radial velocity (RV) surveys have discovered giant exoplanets on au-scale orbits with a broad distribution of eccentricities. Those with the most eccentric orbits are valuable laboratories for testing theories of high-eccentricity migration. However, few such exoplanets transit their host stars, thus removing the ability to apply constraints on formation from their bulk internal compositions. We report the discovery of Kepler-1704 b, a transiting 4.15 M J giant planet on a 988.88 day orbit with an extreme eccentricity of -+ 0.921 0.015 0.010 . Our decade-long RV baseline from the Keck I telescope allows us to measure the orbit and bulk heavy-element composition of Kepler-1704 b and place limits on the existence of undiscovered companions. A failed hot Jupiter, Kepler-1704 b was likely excited to high eccentricity by scattering events that possibly began during its gas accretion phase. Its final periastron distance was too large to allow for tidal circularization, so now it orbits its host from distances spanning 0.16-3.9 au. The maximum difference in planetary equilibrium temperature resulting from this elongated orbit is over 700 K. A simulation of the thermal phase curve of Kepler-1704 b during periastron passage demonstrates that it is a remarkable target for atmospheric characterization from the James Webb Space Telescope, which could potentially also measure the planet's rotational period as the hot spot from periastron rotates in and out of view. Continued characterization of the Kepler-1704 system promises to refine theories explaining the formation of hot Jupiters and cool giant planets like those in the solar system.

The discovery of terrestrial exoplanets is uncovering increasingly diverse architectures. Of particular interest are those systems that contain exoplanets at a variety of star–planet separations, allowing direct comparison of exoplanet evolution (comparative planetology). The Kepler-1649 system contains two terrestrial planets similar both in size and insolation flux to Venus and Earth, although their eccentricities remain largely unconstrained. Here we present results of dynamical studies of the system and the potential effects on climate. The eccentricities of the Kepler-1649 system are poorly constrained, and we show that there are dynamically viable regions for further terrestrial planets in between the two known planets for a limited range of eccentricities. We investigate the effect of eccentricity of the outer planet on the dynamics of both planets and show that this results in high-frequency (1000–3000 years) eccentricity oscillations in long-term stable configurations. We calculate the resulting effect of these eccentricity variations on insolation flux and present the results of 3D climate simulations for the habitable zone planet. Our simulations demonstrate that, despite large eccentricity variations, the planet can maintain stable climates with relatively small temperature variations on the substellar hemisphere for a variety of initial climate configurations. Such systems thus provide key opportunities to explore alternative Venus/Earth climate evolution scenarios.

The search for habitable planets has revealed many planets that can vary greatly from an Earth analog environment. These include highly eccentric orbits, giant planets, different bulk densities, relatively active stars, and evolved stars. This work catalogs all planets found to reside in the habitable zone (HZ) and provides HZ boundaries, orbit characterization, and the potential for spectroscopic follow-up observations. Demographics of the HZ planets are compared with a full catalog of exoplanets. Extreme planets within the HZ are highlighted, and how their unique properties may affect their potential habitability is discussed. Kepler-296 f is the most eccentric ≤2 R ⊕ planet that spends 100% of its orbit in the HZ. HD 106270 b and HD 38529 c are the most massive planets (≤13 M J) that orbit within the HZ, and are ideal targets for determining the properties of potential hosts of HZ exomoons. These planets, along with the others highlighted, will serve as special edge cases to the Earth-based scenario, and observations of these targets will help test the resilience of habitability outside the standard model. The most promising observational HZ target that is known to transit is GJ 414 A b. Of the transiting, ≤2 R ⊕ HZ planets, LHS 1140 b, TRAPPIST-1 d, and K2-3 d are the most favorable. Of the nontransiting HZ planets, HD 102365 b and 55 Cnc f are the most promising, and the best nontransiting candidates that have ≤2 R ⊕ are GJ 667 C c, Wolf 1061 c, Ross 508 b, Teegarden’s Star b, and Proxima Cen b.

Radial velocity (RV) searches for exoplanets have surveyed many of the nearest and brightest stars for long-term velocity variations indicative of a companion body. Such surveys often detect highamplitude velocity signatures of objects that lie outside the planetary mass regime, most commonly those of a low-mass star. Such stellar companions are frequently discarded as false-alarms to the main science goals of the survey, but high-resolution imaging techniques can be employed to either directly detect or place significant constraints on the nature of the companion object. Here, we present the discovery of a compact companion to the nearby star HD 118475. Our Anglo-Australian Telescope (AAT) RV data allow the extraction of the full Keplerian orbit of the companion, found to have a minimum mass of 0.445 M ⊙ . Follow-up speckle imaging observations at the predicted time of maximum angular separation rule out a main-sequence star as the source of the RV signature at the 3.3σ significance level, implying that the companion must be a low-luminosity compact object, most likely a white dwarf. We provide an isochrone analysis combined with our data that constrain the possible inclinations of the binary orbit. We discuss the eccentric orbit of the companion in the context of tidal circularization timescales and show that non-circular orbit was likely inherited from the progenitor. Finally, we emphasize the need for utilizing such an observation method to further understand the demographics of white dwarf companions around nearby stars.

Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the "microlens parallax." We report the discovery of a 30-65M J brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ∼5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ∼0.25 au or ∼45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events.