We perform an in-depth analysis of the recently validated TOI-3884 system, an M4-dwarf star with a transiting super-Neptune. Using high-precision light curves obtained with the 3.5 m Apache Point Observatory and radial velocity observations with the Habitable-zone Planet Finder, we derive a planetary mass of 32.6(-7.4)(+7.3) M-circle plus and radius of 6.4 +/- 0.2 R-circle plus. We detect a distinct starspot crossing event occurring just after ingress and spanning half the transit for every transit. We determine this spot feature to be wavelength dependent with the amplitude and duration evolving slightly over time. Best-fit starspot models show that TOI-3884b possesses a misaligned (lambda = 75 degrees +/- 10 degrees) orbit that crosses a giant pole spot. This system presents a rare opportunity for studies into the nature of both a misaligned super-Neptune and spot evolution on an active mid-M dwarf.

We confirm the planetary nature of two gas giants discovered by TESS to transit M dwarfs with stellar companions at wide separations. TOI-3984 A (J = 11.93) is an M4 dwarf hosting a short-period (4.353326 +/- 0.000005 days) gas giant (M-p = 0.14 +/- 0.0 3 M-J and R-p = 0.71 +/- 0.02 R-J) with a wide-separation white dwarf companion. TOI-5293 A (J = 12.47) is an M3 dwarf hosting a short-period (2.930289 +/- 0.000004 days) gas giant (M-p = 0.54 +/- 0.07 M-J and R-p = 1.06 +/- 0.04 R-J) with a wide-separation M dwarf companion. We characterize both systems using a combination of ground- and space-based photometry, speckle imaging, and high-precision radial velocities from the Habitable-zone Planet Finder and NEID spectrographs..TOI-3984 A b (T-eq = 563 +/- 15 K and = TSM138(-27)(+29)) and TOI-5293 A b (T-eq=675(-30)(+42) K and TSM = 92 +/- 14) are two of the coolest gas giants among the population of hot Jupiter-sized gas planets orbiting M dwarfs and are favorable targets for atmospheric characterization of temperate gas giants and 3D obliquity measurements to probe system architecture and migration scenarios.

Using both ground-based transit photometry and high-precision radial velocity spectroscopy, we confirm the planetary nature of TOI-3785 b. This transiting Neptune orbits an M2-Dwarf star with a period of similar to 4.67 days, a planetary radius of 5.14 +/- 0.16 R-circle plus, a mass of 14.95(-3.92)(+ 4.10) M-circle plus, and a density of rho = 0.61(-0.17)(+0.18) g cm(-3). TOI-3785 b + belongs to a rare population of Neptunes (4 R-circle plus < R-p < 7 R-circle plus) orbiting cooler, smaller M-dwarf host stars, of which only similar to 10 have been confirmed. By increasing the number of confirmed planets, TOI-3785 b offers an opportunity to compare similar planets across varying planetary and stellar parameter spaces. Moreover, with a high-transmission spectroscopy metric of similar to 150 combined with a relatively cool equilibrium temperature of T-eq = 582 +/- 16 K and an inactive host star, TOI-3785 b is one of the more promising low-density M-dwarf Neptune targets for atmospheric follow up. Future investigation into atmospheric mass-loss rates of TOI-3785 b may yield new insights into the atmospheric evolution of these low-mass gas planets around M dwarfs.

We present an analysis of Sun-as-a-star observations from four different high-resolution, stabilized spectrographs-HARPS, HARPS-N, EXPRES, and NEID. With simultaneous observations of the Sun from four different instruments, we are able to gain insight into the radial velocity precision and accuracy delivered by each of these instruments and isolate instrumental systematics that differ from true astrophysical signals. With solar observations, we can completely characterize the expected Doppler shift contributed by orbiting Solar System bodies and remove them. This results in a data set with measured velocity variations that purely trace flows on the solar surface. Direct comparisons of the radial velocities measured by each instrument show remarkable agreement with residual intraday scatter of only 15-30 cm s-1. This shows that current ultra-stabilized instruments have broken through to a new level of measurement precision that reveals stellar variability with high fidelity and detail. We end by discussing how radial velocities from different instruments can be combined to provide powerful leverage for testing techniques to mitigate stellar signals.

Warm Jupiters are close-in giant planets with relatively large planet-star separations (i.e., 10 < a/R* < 100). Given their weak tidal interactions with their host stars, measurements of stellar obliquity may be used to probe the initial obliquity distribution and dynamical history for close-in gas giants. Using spectroscopic observations, we confirm the planetary nature of TOI-1859b and determine the stellar obliquity of TOI-1859 to be ? = 38.9(-2.7)(+2.8 degrees) relative to its planetary 2.8 -companion using the Rossiter-McLaughlin effect. TOI-1859b is a 64 day warm Jupiter orbiting around a late F dwarf and has an orbital eccentricity of 0.57 ( +0.12)(-0.16) inferred purely from transit light curves. The eccentric and misaligned orbit of TOI-0.12 -1859b is likely an outcome of dynamical interactions, such as planet-planet scattering and planet-disk resonance crossing.

Fundamental to our understanding of planetary bulk compositions is the relationship between their masses and radii, two properties that are often not simultaneously known for most exoplanets. However, while many previous studies have modeled the two-dimensional relationship between planetary mass and radii, this approach largely ignores the dependencies on other properties that may have influenced the formation and evolution of the planets. In this work, we extend the existing nonparametric and probabilistic framework of MRExo to jointly model distributions beyond two dimensions. Our updated framework can now simultaneously model up to four observables, while also incorporating asymmetric measurement uncertainties and upper limits in the data. We showcase the potential of this multidimensional approach to three science cases: (i) a four-dimensional joint fit to planetary mass, radius, insolation, and stellar mass, hinting of changes in planetary bulk density across insolation and stellar mass; (ii) a three-dimensional fit to the California Kepler Survey sample showing how the planet radius valley evolves across different stellar masses; and (iii) a two-dimensional fit to a sample of Class-II protoplanetary disks in Lupus while incorporating the upper limits in dust mass measurements. In addition, we employ bootstrap and Monte Carlo sampling to quantify the impact of the finite sample size as well as measurement uncertainties on the predicted quantities. We update our existing open-source user-friendly MRExo Python package with these changes, which allows users to apply this highly flexible framework to a variety of data sets beyond what we have shown here.

Theories of planet formation predict that low-mass stars should rarely host exoplanets with masses exceeding that of Neptune. We used radial velocity observations to detect a Neptune-mass exoplanet orbiting LHS 3154, a star that is nine times less massive than the Sun. The exoplanet's orbital period is 3.7 days, and its minimum mass is 13.2 Earth masses. We used simulations to show that the high planet-to-star mass ratio (>3.5 * 10-4) is not an expected outcome of either the core accretion or gravitational instability theories of planet formation. In the core-accretion simulations, we show that close-in Neptune-mass planets are only formed if the dust mass of the protoplanetary disk is an order of magnitude greater than typically observed around very low-mass stars.

TOI-1899 b is a rare exoplanet, a temperate warm Jupiter orbiting an M dwarf, first discovered by Canas et al. (2020) from a TESS single-transit event. Using new radial velocities (RVs) from the precision RV spectrographs HPF and NEID, along with additional TESS photometry and ground-based transit follow-up, we are able to derive a much more precise orbital period of P = 29.090312(-0.000035)(+0.000036) days, along with a radius of R-p = 0.99 +/- 0.03 R-J. We have also improved the constraints on planet mass, M-p = 0.67 +/- 0.04 M-J, and eccentricity, which is consistent with a circular orbit at 2 sigma (e = 0.044(-0.027)(+0.029)). TOI-1899 b occupies a unique region of parameter space as the coolest known (T-eq approximate to 380 K) Jovian-sized transiting planet around an M dwarf; we show that it has great potential to provide clues regarding the formation and migration mechanisms of these rare gas giants through transmission spectroscopy with JWST, as well as studies of tidal evolution.

NEID is a high-resolution red-optical precision radial velocity (RV) spectrograph recently commissioned at the WIYN 3.5 m telescope at Kitt Peak National Observatory, Arizona, USA. NEID has an extremely stable environmental control system, and spans a wavelength range of 380-930 nm with two observing modes: a High Resolution mode at R & SIM; 112,000 for maximum RV precision, and a High Efficiency mode at R & SIM; 72,000 for faint targets. In this paper we present a detailed description of the components of NEID's optical fiber feed, which include the instrument, exposure meter, calibration system, and telescope fibers. Many parts of the optical fiber feed can lead to uncalibratable RV errors, which cannot be corrected for using a stable wavelength reference source. We show how these errors directly cascade down to performance requirements on the fiber feed and the scrambling system. We detail the design, assembly, and testing of each component. Designed and built from the bottom-up with a single-visit instrument precision requirement of 27 cm s(-1), close attention is paid to the error contribution from each NEID subsystem. Finally, we include the lab and on-sky tests performed during instrument commissioning to test the illumination stability, and discuss the path to achieving the instrumental stability required to search for a true Earth twin around a solar-type star.

We confirm the planetary nature of TOI-5344 b as a transiting giant exoplanet around an M0-dwarf star. TOI-5344 b was discovered with the Transiting Exoplanet Survey Satellite photometry and confirmed with ground-based photometry (the Red Buttes Observatory 0.6 m telescope), radial velocity (the Habitable-zone Planet Finder), and speckle imaging (the NN-Explore Exoplanet Stellar Speckle Imager). TOI-5344 b is a Saturn-like giant planet (rho = 0.80 -0.15+0.17 g cm-3) with a planetary radius of 9.7 +/- 0.5 R circle plus (0.87 +/- 0.04 R Jup) and a planetary mass of 135-18+17M circle plus (0.42 -0.06+0.05MJup ). It has an orbital period of 3.792622-0.000010+0.000010 days and an orbital eccentricity of 0.06-0.04+0.07 . We measure a high metallicity for TOI-5344 of [Fe/H] = 0.48 +/- 0.12, where the high metallicity is consistent with expectations from formation through core accretion. We compare the metallicity of the M-dwarf hosts of giant exoplanets to that of M-dwarf hosts of nongiants (less than or similar to 8 R circle plus). While the two populations appear to show different metallicity distributions, quantitative tests are prohibited by various sample caveats.