We present the TESS-based discoveries of planetary systems orbiting the late G dwarfs TOI-2494 and TOI-5143, each of which harbors a hot giant planet and a smaller interior planet. TOI-2494 hosts a transiting mini-Neptune (P = 2.41 days, RP=2.35-0.15+0.16 R circle plus) and a hot Saturn (P = 8.38 days) with grazing transits, while TOI-5143 hosts a transiting mini-Neptune (P = 2.38 days, RP=2.73-0.17+0.19 R circle plus) and a hot Jupiter (P = 5.21 days) with grazing transits. We measure the masses of TOI-2494 c (80 +/- 19 M circle plus) and TOI-5143 c (208 +/- 14 M circle plus), place upper limits on the masses of the smaller planets, and explore the architectures of the planetary systems. TOI-2494 c and TOI-5143 c join a small but growing number of short-period giant planets known to be flanked by smaller companions. While the absence of close neighbors to most hot Jupiters would be consistent with disruptive dynamical evolution, the presence of nearby small planets in some hot Jupiter systems points to a separate, dynamically quiet formation pathway. In support of this conclusion, we present preliminary evidence that hot giant planets with small nearby companions tend to have low mutual orbital inclinations, consistent with the mutual inclination distribution of the dynamically quiet population of compact systems of multiple super-Earths and mini-Neptunes.

Context. The structure and evolution of close-in exoplanets are shaped by atmospheric loss and migration processes, which give rise to key population features such as the hot Neptune desert, ridge, and savanna – regions of the period-radius space whose boundaries offer critical insights into planetary formation and survival. Aims. As part of the KESPRINT collaboration, we selected the TESS transiting planet candidate TOI-3862.01 for radial velocity follow-up to confirm its planetary nature and characterize its mass and bulk properties. This planet candidate is of particular interest due to its position in the middle of the hot Neptune desert, making it a valuable probe for testing theories of planet migration and atmospheric loss. Methods. We confirmed the planetary nature and determined the mass of TOI-3862.01 (hereinafter TOI-3862 b) by performing a joint fit with both transit and radial velocity data, precisely characterizing the bulk properties of this planet. Results. TOI-3862b is a super-Neptune on a 1.56-day orbit around a Sun-like star with an effective temperature of 5300±50 K. It has a mass of 53.7−2.9+2.8 M⊕ and a radius of 5.53 ± 0.18 R⊕, corresponding to a density of 1.7±0.2 g/cm3. This places it among the rare population of hot and dense super-Neptune desert planets. Conclusions. TOI-3862b, residing deep in the hot Neptune desert, represents a rare occurrence in an otherwise sparsely populated region, offering a valuable opportunity to probe the processes that may allow planets to survive in such environments.

We present TOI-2155 b, a massive transiting companion, discovered using data from NASA's Transiting Exoplanet Survey Satellite mission and confirmed with ground-based radial velocity measurements from the Tillinghast Reflector Echelle Spectrograph. We also analyze ground-based follow-up photometric data from the Wendelstein Observatory, Las Cumbres Observatory Global Telescope, and Wild Boar Remote Observatory. TOI-2155 b is a short-period companion with P = 3.7246950 +/- 0.0000014 days. The radius and mass of TOI-2155 b are found to be R-b=0.972(-0.008)(+0.009 )R(J) and M-b=80.6(-1.1)(+1.0 )M(J) , respectively, corresponding to a density of rho(b)=109(-3.3)(+3.1) g cm(-3). The F-type subgiant host star has an effective temperature of T-eff = 6085 +/- 78 K, a radius R-star=1.705(-0.064)(+0.066) R-circle dot, and a mass M-star = 1.33 +/- 0.008 M-circle dot. With a mass close to the hydrogen-burning minimum mass, TOI-2155 b lies at the boundary between brown dwarfs and low-mass stars. Its measured mass, radius, and density place it in a transitional region, where distinguishing between a massive brown dwarf and a very low-mass star is not straightforward. TOI-2155 b therefore provides a valuable benchmark for testing evolutionary models of stellar and substellar structure near the hydrogen-burning limit.

Young planets (<1 Gyr) provide opportunities to directly probe planet formation and evolution processes in action. However, due to heightened stellar activity, there is a lack of known transiting planets in adolescence (similar to 100-500 Myr). Here we present the validation of TIC 150070085 b, a 3.6 R-circle plus planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R-circle plus planet on a 15.90 day orbit. While we are unable to validate the second signal, the proximity to mean-motion resonance (3:2) and transit timing variations observed in the transits of TIC 150070085 b strongly suggest that the signal is planetary. We confirm the host star as a member of Alessi 84 and combine the group's color-magnitude diagram, rotation, and variability properties to update the age to 135 +/- 10 Myr. We additionally use MAROON-X to observe the Rossiter-McLaughlin signal of TIC 150070085 b and measure the sky projected obliquity angle (lambda). We find that TIC 150070085 b is consistent with a near-aligned orbit with its host star (divided by lambda divided by = 18 degrees +/- 12 degrees), in line with similarly aged transiting planets with measured lambda values. Continued discovery and characterization of planets in this age regime are vital to link planetary infancy (<50 Myr) and maturity (>1 Gyr).

We characterize the radius-dependent eccentricity distribution of 347 warm (P = 8-200 days) systems with only one transiting planetary candidate identified during Sectors 1-69 of the TESS mission. Using the “photoeccentric effect” in a hierarchical Bayesian framework, we first model the population using discrete planetary size bins (sub-Neptunes, sub-Saturns, and Jovians). We then develop a continuous mixture model with weights governed by a logistic sigmoid function of radius. We find that the warm-single population is best described by two components: a dominant low-eccentricity mode ( = 0.070-0.068+0.026) and a secondary dynamically excited mode ( = 0.616-0.075+0.091). The fraction of planets belonging to this high-eccentricity component increases strongly with planet radius, characterized by a transition at a break radius of R_br = 9.8-1.1+1.4 R_e. This trend places warm sub-Saturns predominantly on the same low-eccentricity track as sub-Neptunes. In contrast, warm Jovians (8–16 R_e) are frequently eccentric, with 59+-13

We report the discovery and characterisation of NGTS-39 b (TIC 453147896 b), a warm Jupiter transiting a Sun-like star on a 58.2 day, eccentric (e = 0.386 +/- 0.019) orbit. NGTS-39 b was first identified from a TESS single-transit event, and subsequently confirmed with NGTS photometry and radial-velocity measurements from CORALIE and HARPS. The host star is a bright (Tmag = 11.02) F9 dwarf with an effective temperature of Teff = 6053 +67/-30 K. NGTS-39 b is a Jupiter-sized gas giant with a radius of 1.088 +/- 0.012 RJ and a mass of 1.467 +/- 0.081 MJ. Its equilibrium temperature is 519 +6/-5 K, placing it between short-period hot Jupiters and cold, Jupiter-like giants. The high orbital eccentricity and intermediate equilibrium temperature of NGTS-39 b make it a valuable test case for formation and migration models, particularly in the poorly sampled regime of long-period gas giants. The RV data show a linear trend of gamma dot = -17.75 m s^-1 yr^-1, which indicates the presence of an outer companion. The discovery of NGTS-39 b contributes to the small but growing population of transiting warm Jupiters with P > 50 days orbiting bright stars.

The Galactic Be star binary MWC 656 was long considered the only known Be star+black hole (BH) system, making it a critical benchmark for models of massive binary evolution and for the expected X-ray emission of Be+BH binaries. However, recent dynamical measurements cast doubt on the presence of a BH companion. We present new multi-epoch ultraviolet spectroscopy from the Hubble Space Telescope, combined with high-resolution optical spectra, to reassess the nature of the companion. The far-ultraviolet spectra reveal high-ionisation features - including prominent N V and He II lines - which are absent in the spectra of normal Be stars and are indicative of a hot, luminous companion. Spectral modelling shows that these features cannot originate from the Be star or from an accretion disc around a compact object. Instead, we find that the data are best explained by a hot (T-eff approximate to 85 kK), compact, hydrogen-deficient star with strong wind signatures, consistent with an intermediate-mass stripped star. Our revised orbital solution and composite spectroscopic modelling yield a companion mass of M-2 = 1.48(-0.46)(+0.55) M-circle dot, definitively ruling out a BH and disfavouring a white dwarf. MWC 656 thus joins the growing class of Be + stripped star binaries. The system's unusual properties - including a high companion temperature and wind strength - extend the known parameter space of such binaries. The continued absence of confirmed OBe+BH binaries in the Galaxy highlights a growing tension with population synthesis models.

As part of the KESPRINT collaboration, we present the discovery and characterization of three exoplanets in the sub-Neptune to super-Neptune regime, spanning key regions of the exo-Neptunian landscape. TOI-1472c and TOI-1648b are newly discovered sub-Neptunes, while TOI-1472b is a previously known super-Neptune for which we provide an improved mass measurement. These planets have orbital periods of 6–15 days and radii of 2.5–4.1 R_⊕, probing regions where planet formation and atmospheric evolution remain poorly understood. We combine TESS transit photometry with ground-based radial velocities to determine precise masses, radii, and orbital properties. TOI-1472b has a mass of 18.0^+0.84_-0.85 M_⊕ and a radius of 4.06 ± 0.10 R_⊕, TOI-1472c has a mass of 21.1^+0.96_-0.99 M_⊕ and a radius of 3.33 ± 0.08 R_⊕, and TOI-1648b has a mass of 7.4^+1.1_-1.3 M_⊕ and a radius of 2.54^+0.14_-0.12 R_⊕. The planets exhibit a range of eccentricities (0.041–0.178), indicating diverse evolutionary histories. TOI-1648b, with a high Transmission Spectroscopy Metric (TSM ∼59), is a promising target for atmospheric characterization. Together, these three planets provide precise constraints on the structure, composition, and dynamical evolution of small to intermediate-sized exoplanets, enriching our understanding of the exo-Neptunian landscape.

Despite decades of research on hot Jupiters, there are still several theories for their formation. Perhaps hot Jupiters form in several ways. Atmospheric and dynamical studies have the capability to constrain the formation scenarios. However, potential targets have to be well characterized before these observations can further constrain the theories. We present the confirmation and characterization of five hot and warm Jupiters discovered by the TESS space mission. Using TESS data combined with ground-based observations, we determine the masses, radii, and other parameters of TOI-2040 b, TOI-2049 b, TOI-2578 b, TOI-4427 b, and TOI-4458 b. Three of the planets have equilibrium temperatures of about 1800 K while two have temperatures of about 1000 K. Particularly interesting for future atmospheric characterizations are TOI-2578 b and TOI-4427 b, because of their low density and large transmission spectroscopy metric. TOI-4458 b is of special interest because it is in the northern PLATO field. It appears that TOI-2040 b has a small, but measurable eccentricity.

The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits1. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii)2,3. The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5-4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance.

We report the discovery of TOI-7019b, the first transiting brown dwarf (BD) known to orbit a star that is part of the Milky Way's ancient thick disk, as defined chemically ([Fe/H] = -0.79 +/- 0.05 dex, [alpha/Fe] = +0.26 +/- 0.05 dex, [M/H] = -0.59 +/- 0.06 dex) and kinematically (v perpendicular to approximate to 150 +/- 1 km s-1). We estimate a system age tau = 12 +/- 2 Gyr by fitting the host star's spectrum and spectral energy distribution to alpha-enhanced isochrones and independently using the age-metallicity relation of the thick disk. This makes TOI-7019 by far the most metal-poor and ancient BD host known to date. We measure a BD mass of 61.3MJ +/- 2.1MJ and radius of 0.82RJ +/- 0.02RJ from a joint analysis of transit photometry and radial velocity measurements, along with an orbital period of 48.2592 +/- 0.0001 days and an orbital eccentricity of 0.403 +/- 0.002. The measured radius appears to be 12.3% +/- 2.8% larger than predicted relative to standard evolutionary models for old, metal-poor BDs, as well as models that include stellar radiation, hinting at missing physics like the magnetic inhibition of convection. TOI-7019b lowers the probed metallicity regime for transiting BDs by over a factor of two, making it a benchmark system to test evolutionary models in the low-metallicity regime. Future measurements of TOI-7019b's atmosphere will test whether a BD's atmospheric composition tracks its host star's abundances, as expected for binary-like co-formation.

We use WIYN/NEID radial velocity measurements to confirm the planetary nature and measure the mass of the TESS transiting exoplanet candidate around the mid-K dwarf GJ 523 (V=9.23, K=6.525). We find that GJ 523b is on a 17.75 day orbit and has a radius of 2.55±0.15 R_⊕, a mass of 23.5±3.3 M_⊕, and a zero-albedo equilibrium temperature of 538 K. GJ 523b's high bulk density of 7.8±1.8 g cm^-3 and position on a mass-radius diagram implies a surprising low atmospheric mass fraction despite its relatively large mass. Additionally, we determine that the system has an age of 169^+100_-48 Myr through a gyrochronological analysis of GJ 523 and its comoving companions. We also use the SED-derived stellar radius, the photometric rotation period, and the spectroscopic vsin i_⋆ to derive a stellar inclination of 17.6±5.0 degrees, implying that GJ 523b has a minimum orbital obliquity of 71.4_-5.0^+4.7 degrees. GJ 523b's high mass, apparent lack of a gas envelope, young age, and high orbital obliquity present a challenge to typical planet formation pathways, and at the moment there is not enough data on the system to definitively determine how GJ 523b formed. Finally, we present a new observational classification for ultra-dense, sub-Neptune-sized exoplanets similar to GJ 523b: the mega-Earths, planets with R_p ≥2.1 R_⊕ and ρ_p ≥ 5.5 g cm^-3.

Astrometry and radial velocities (RVs) from Gaia DR3 yielded orbits for hundreds of thousands of binary systems, including several samples proposed to contain black holes (BHs), neutron stars (NSs), and white dwarfs (WDs). We present results of a systematic spectroscopic follow-up program targeting these objects. Beginning with a sample of 227 sources, we used a combination of archival data and many-epoch spectroscopic follow-up to characterize more than 200. We obtained 1292 high-quality RVs over a period of four years using the TRES and FEROS spectrographs, achieving a typical precision of 50 m/s and at least 10 RVs for 60 sources. We use these data to test the Gaia orbital solutions and tighten constraints on orbital parameters and component masses. Joint fitting of astrometry and RVs allows us to directly constrain flux ratios, verifying that undetected companions are genuinely dark. We find that 60

We report the discovery of a low-mass transiting brown dwarf orbiting TOI-6884 (TIC 156514476, T-mag = 11.4) from NASA's Transiting Exoplanet Survey Satellite (TESS) mission. The TESS light curves initially suggested an orbital period of similar to 14.42 days; however, our high-precision ground-based radial velocity measurements and multi-epoch time-series photometry reveal this to be a harmonic alias. We determine the true orbital period to be 4.808264(-0.000014)(+0.000015) days and confirm the substellar nature of the companion. TOI-6884b has a mass of 26.32(-0.93)(+0.98)MJ, a radius of 0.927(-0.52)(+0.51)RJ, and resides on a nearly circular orbit (e=0.067(-0.012)(+0.010)). Its host star is a late F-type slightly evolved star with M-* =1.410(-0.069)(+0.075)M(circle dot), R-* =1.840(-0.073)(+0.072) R-circle dot, log g=4.057(-0.039)(+0.045), [Fe/H]=0.094(-0.068)(+0.073) dex, and T-eff=6330(-160)(+180) K. TOI-6884b is a key addition to the small population of well-characterized transiting brown dwarfs orbiting host stars that have left the main sequence. The detection of such systems will contribute to our understanding of dynamical histories and structural evolution of short-period substellar companions around evolved stars.

The detection of exoplanets using astrometry has long been an area of interest, but is fraught with challenges. The Gaia mission is fundamentally reshaping this field thanks to its unprecedentedly precise all-sky astrometric observations. The 2022 release of Gaia DR3 brought the first exoplanets discovered from the Gaia astrometry, including a new candidate around the bright (V = 6.6) solar-type star HD 12800. However, two years after announcement, the Gaia exoplanet candidate was retracted. In this work we report radial velocity observations of HD 12800 acquired with the TRES spectrograph, which we began immediately after the release of Gaia DR3. Our observations failed to detect the planet candidate; nonetheless, we emphasize that the originally proposed companion would have been easily detected in our radial velocity observations. We conclude with a discussion on the role of intermediate-precision (approximate to 10 m s(-1)) RV spectrographs in the follow-up of Gaia astrometric exoplanet candidates, relevant to the forthcoming release of Gaia Data Release 4. We argue that such observations may play an important role in planet confirmation for stars between approximately 8 < G < 12, likely to represent a significant fraction of Gaia exoplanet discoveries.

Transiting warm Jupiters orbiting bright stars are scarcely known, but a substantial number of these planets have been uncovered by the TESS mission. In this work, we report the discovery and confirmation of a transiting warm Jupiter orbiting the bright ( V = 8.70) subgiant star HD 715 (TOI-6893). HD 715 b was originally identified from a single transit event in TESS Sector 70. We acquired two seasons of radial velocity follow-up using the PFS, TRES, and MINERVA-Australis spectrographs, which clearly detect the planetary orbit. At M _* = 1.60 ± 0.04 M _⊙ , HD 715 thus becomes one of the most massive stars known to host a transiting warm Jupiter. From a joint fit to the TESS transit and our RVs, we find that HD 715 b has a $56.4{0}_{-0.23}^{+0.19}$ day orbital period and measure a precise mass and radius of 0.635 ± 0.056 M _J and 1.07 ± 0.04 R _J , rendering it a relatively typical member of the warm Jupiter population. The moderate orbital eccentricity of $0.2{1}_{-0.08}^{+0.07}$ contrasts with the higher eccentricities of other similar warm Jupiters orbiting evolved stars, indicating a greater diversity in orbital eccentricities than previously known. The absence of additional transits in preceding TESS observations in Sectors 42 and 43 allows us to further refine the range of possible orbital periods to [56.01, 56.35] days. Though the ephemeris uncertainty remains substantial, future photometric observations may nonetheless allow for recovery of the transit of HD 715 b.

Theoretical models predict that subgiants within a narrow mass regime can retain detectable lithium enrichment signatures from planetary engulfment. We test this prediction using TOI-5882, selected because it occupies this favorable subgiant parameter space and hosts a massive brown dwarf (22 MJ, P = 7.1 days) companion capable of dynamically perturbing inner planets. We investigate whether (1) TOI-5882 exhibits lithium enhancement among similar subgiants, (2) planetary material would be deposited in the convective zone, and (3) the required engulfed mass lies within a plausible range for planetary engulfment. Using spectra from the Tillinghast Reflector Echelle Spectrograph, we measured a Li I equivalent width of 75.39 +/- 3.58 m & Aring; and an abundance of A(Li) = 2.49 +/- 0.12 dex. Comparing these values to a control sample of 61 subgiants from the GALactic Archaeology with HERMES (GALAH)DR4 survey, we find that TOI-5882 ranks in the 98.4th percentile in both metrics, confirming significant lithium enrichment. We evaluate the engulfment scenario by modeling convective zone deposition and estimating the mass required to reproduce the observed enhancement relative to the control sample. We perform an estimate of the engulfed planetary mass incorporating CI chondritic Li abundances, as planets formed via core accretion are enriched in heavy elements and lithium partitions with these metals. This yields a required engulfed mass of 9-95 M circle plus-an order of magnitude lower than the 5.6 MJ implied by protosolar assumptions. TOI-5882's lithium excess can plausibly result from the ingestion of a super-Earth to Neptune-mass planet, motivating further studies to test this scenario.

We present the characterization of HIP 61637 b (TOI-5401 b), a brown dwarf discovered by TESS to transit an A-type star. HIP 61637 is the most massive and the brightest star known to host a transiting brown dwarf to date. The companion lies in the middle of the "brown dwarf desert". We perform a joint analysis of light curves from NASA's TESS mission and our high-resolution spectroscopy from the Tillinghast Reflector Echelle Spectrograph. We determine that HIP 61637 b has a radius of R_BD = 1.149^+0.049_-0.038 R_J, a mass of M_BD = 47.8^+1.5_-1.4 M_J, and transits its host star every 6.829104 ± 0.000011 days in a near-circular orbit (e = 0.054 ± 0.013). The host star has a mass of 2.86± 0.12 M_⊙, a radius of 4.33 ± 0.17 R_⊙, and an effective temperature of T_eff = 9180^+240_-230 K. We find that the host is nearing the end of its time on the main sequence and has begun to evolve, allowing for a precise age estimation of 396 ± 46 Myr for the system using stellar evolution models. This adds an important data point to the handful of well-characterized transiting brown dwarfs with reliable age estimates, allowing us to test the latest substellar evolution models. Theory of tidal evolution predicts that tidal dissipation mechanisms have circularized the orbit, consistent with the observed near-zero eccentricity.

Of the > 500 confirmed transiting hot jupiters and approximately 2000 additional candidates today, only ten are known to have nearby companion planets. The survival of nearby companions means that these hot jupiters cannot have migrated to their present location via dynamically disruptive high-eccentricity migration but instead have undergone disk migration or formed in situ. The occurrence rate for these nearby companions, therefore, constrains the relative efficiency of different hot jupiter formation pathways. Here, we perform a uniform box least-squares search for nearby transiting companions to hot jupiters in the first five years of TESS data. Accounting for observational completeness and detection efficiency, we arrive at an occurrence rate of (7.6^+5.5_-3.8)%, which is a lower limit on the fraction of hot jupiters that underwent disk migration or in situ formation. Comparing this rate with that derived from transit-timing variation searches suggests that hot jupiters are likely mostly aligned with their nearby companions, but their apparently higher incidence of grazing transits may point to a slight preferential misalignment. We also synthesize evidence that hot jupiters with nearby companions may have cold companions at a rate similar to that of other hot jupiters. Comprehensive transit, radial velocity, and stellar obliquity measurements in hot jupiter systems with nearby companions will be necessary to fully account for the relative prevalence of proposed hot jupiter formation pathways.

We report the discovery of a sub-Neptune and a Neptune-like planet (R (b)=2.48(-0.10)(+0.14) R (circle plus), R (c)=4.03(-0.15)(+0.23 )R (circle plus)) orbiting the F-type star TOI-4495. The planets have orbital periods of 2.567 and 5.185 days, lying close to a 2:1 mean-motion resonance (MMR). Our photodynamical analysis of the TESS light curves constrains the planetary masses to M (b) = 7.7 +/- 1.4 M (circle plus)and M (c) = 23.2 +/- 4.7 M (circle plus). The measured masses and radii indicate the presence of volatile-rich gaseous envelopes on both planets. The Rossiter-McLaughlin effect and the Doppler shadow of TOI-4495 c reveal a well-aligned orbit with a projected stellar obliquity of lambda=-2.3(-7.8)(+8.3)degrees . Combined with the low mutual inclination constrained by the photodynamical analysis (Delta I < 8.7 degrees), the planetary orbits are likely coplanar and aligned with the host star's spin axis. We show that the planets are near, but not in, the 2:1 MMR, with a circulating resonant angle. We also find substantial free eccentricity for the inner planet, TOI-4495 b ( e(b)=0.078(-0.013)(+0.02) ). Given the observed proximity to the 2:1 resonance and the more massive outer planet, TOI-4495 b and c are particularly susceptible to resonant overstability, which in turn can explain the observed eccentricity by converting resonantly excited eccentricity into free eccentricity. However, additional mechanisms (e.g., planetesimal scattering) may be required to further excite the eccentricity by similar to 4%. To prevent tidal damping from reducing the eccentricity below the observed level over the star's lifetime (1.9 Gyr), the reduced tidal quality factor of TOI-4495 b must be Q 'greater than or similar to 10(5) , consistent with the presence of a thick envelope on the planet.