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Abstract The “super-puffs” are a population of planets that have masses comparable to that of Neptune but radii similar to Jupiter, leading to extremely low bulk densities (ρ_p ≲ 0.2 g cm⁻³) that are not easily explained by standard core accretion models. Interestingly, several of these super-puffs are found in orbits significantly misaligned with their host stars’ spin axes, indicating past dynamical excitation that may be connected to their low densities. Here, we present new Magellan/Planet Finder Spectrograph radial velocity measurements of WASP-193, a late F star hosting one of the least dense transiting planets known to date ( $M_p=0.112_{-0.034}^{+0.029}{M}_{\mathrm{J}}$, $R_p=1.319_{-0.048}^{+0.056}{R}_{\mathrm{J}}$,ρ_p = 0.060 ± 0.019 g cm⁻³). We refine the bulk properties of WASP-193 b and use interior structure models to determine that the planet can be explained if it consists of roughly equal amounts of metals and H/He, with a metal fraction ofZ= 0.42. The planet is likely substantially reinflated due to its host star’s evolution, and expected to be actively undergoing mass loss. We also measure the projected stellar obliquity using the Rossiter–McLaughlin effect, finding that WASP-193 b is on an orbit well aligned with the stellar equator, with $\lambda =16_{-15}^{+16}$degrees. WASP-193 b is the first Jupiter-sized super-puff on a relatively well-aligned orbit, suggesting a diversity of formation pathways for this population of planets. 

ABSTRACT The time variability and spectra of directly imaged companions provide insight into their physical properties and atmospheric dynamics. We present follow-up R ∼ 40 spectrophotometric monitoring of red companion HD 1160 B at 2.8–4.2 μm using the double-grating 360° vector Apodizing Phase Plate (dgvAPP360) coronagraph and ALES integral field spectrograph on the Large Binocular Telescope Interferometer. We use the recently developed technique of gvAPP-enabled differential spectrophotometry to produce differential light curves for HD 1160 B. We reproduce the previously reported ∼3.2 h periodic variability in archival data, but detect no periodic variability in new observations taken the following night with a similar 3.5 per cent level precision, suggesting rapid evolution in the variability of HD 1160 B. We also extract complementary spectra of HD 1160 B for each night. The two are mostly consistent, but the companion appears fainter on the second night between 3.0–3.2 μm. Fitting models to these spectra produces different values for physical properties depending on the night considered. We find an effective temperature Teff  = $$2794^{+115}_{-133}$$ K on the first night, consistent with the literature, but a cooler Teff  = $$2279^{+79}_{-157}$$ K on the next. We estimate the mass of HD 1160 B to be 16–81 MJup, depending on its age. We also present R = 50 000 high-resolution optical spectroscopy of host star HD 1160 A obtained simultaneously with the PEPSI spectrograph. We reclassify its spectral type to A1 IV-V and measure its projected rotational velocity $$\upsilon \sin i$$ = $$96^{+6}_{-4}$$ km s−1. We thus highlight that gvAPP-enabled differential spectrophotometry can achieve repeatable few per cent level precision and does not yet reach a systematic noise floor, suggesting greater precision is achievable with additional data or advanced detrending techniques. 

Astronomers have found more than a dozen planets transiting stars that are 10–40 million years old1, but younger transiting planets have remained elusive. The lack of such discoveries may be because planets have not fully formed at this age or because our view is blocked by the protoplanetary disk. However, we now know that many outer disks are warped or broken2; provided the inner disk is depleted, transiting planets may thus be visible. Here we report observations of the transiting planet IRAS 04125+2902 b orbiting a 3-million-year-old, 0.7-solar-mass, pre-main-sequence star in the Taurus Molecular Cloud. The host star harbours a nearly face-on (30 degrees inclination) transitional disk3 and a wide binary companion. The planet has a period of 8.83 days, a radius of 10.7 Earth radii (0.96 Jupiter radii) and a 95%-confidence upper limit on its mass of 90 Earth masses (0.3 Jupiter masses) from radial-velocity measurements, making it a possible precursor of the super-Earths and sub-Neptunes frequently found around main-sequence stars. The rotational broadening of the star and the orbit of the wide (4 arcseconds, 635 astronomical units) companion are both consistent with edge-on orientations. Thus, all components of the system are consistent with alignment except the outer disk; the origin of this misalignment is unclear. 

Abstract Cold Jovian planets play an important role in sculpting the dynamical environment in which inner terrestrial planets form. The core accretion model predicts that giant planets cannot form around low-mass M dwarfs, although this idea has been challenged by recent planet discoveries. Here, we investigate the occurrence rate of giant planets around low-mass (0.1–0.3M_⊙) M dwarfs. We monitor a volume-complete, inactive sample of 200 such stars located within 15 pc, collecting four high-resolution spectra of each M dwarf over six years and performing intensive follow-up monitoring of two candidate radial velocity variables. We use TRES on the 1.5 m telescope at the Fred Lawrence Whipple Observatory and CHIRON on the Cerro Tololo Inter-American Observatory 1.5 m telescope for our primary campaign, and MAROON-X on Gemini-North for high-precision follow up. We place a 95% confidence upper limit of 1.5% (68% confidence limit of 0.57%) on the occurrence ofM_Psini> 1M_Jgiant planets out to the water snow line and provide additional constraints on the giant planet population as a function ofM_Psiniand period. Beyond the snow line (100 K <T_eq< 150 K), we place 95% confidence upper limits of 1.5%, 1.7%, and 4.4% (68% confidence limits of 0.58%, 0.66%, and 1.7%) for 3M_J<M_Psini< 10M_J, 0.8M_J<M_Psini< 3M_J, and 0.3M_J<M_Psini< 0.8M_Jgiant planets, respectively; i.e., Jupiter analogs are rare around low-mass M dwarfs. In contrast, surveys of Sun-like stars have found that their giant planets are most common at these Jupiter-like instellations. 

Abstract We present the discovery of TOI 762 A b and TIC 46432937 b, two giant planets transiting M-dwarf stars. Transits of both systems were first detected from observations by the NASA TESS mission, and the transiting objects are confirmed as planets through high-precision radial velocity observations carried out with Very Large Telescope/ESPRESSO. TOI 762 A b is a warm sub-Saturn with a mass of 0.251 ± 0.042M_J, a radius of 0.744 ± 0.017R_J, and an orbital period of 3.4717 days. It transits a mid-M-dwarf star with a mass of 0.442 ± 0.025M_☉and a radius of 0.4250 ± 0.0091R_☉. The star TOI 762 A has a resolved binary star companion, TOI 762 B, that is separated from TOI 762 A by 3.″2 (∼319 au) and has an estimated mass of 0.227 ± 0.010M_☉. The planet TIC 46432937 b is a warm super-Jupiter with a mass of 3.20 ± 0.11M_Jand radius of 1.188 ± 0.030R_J. The planet’s orbital period isP= 1.4404 days, and it undergoes grazing transits of its early M-dwarf host star, which has a mass of 0.563 ± 0.029M_☉and a radius of 0.5299 ± 0.0091R_☉. TIC 46432937 b is one of the highest-mass planets found to date transiting an M-dwarf star. TIC 46432937 b is also a promising target for atmospheric observations, having the highest transmission spectroscopy metric or emission spectroscopy metric value of any known warm super-Jupiter (mass greater than 3.0M_J, equilibrium temperature below 1000 K). 

Abstract M-dwarf stars provide us with an ideal opportunity to study nearby small planets. The HUnting for M Dwarf Rocky planets Using MAROON-X (HUMDRUM) survey uses the MAROON-X spectrograph, which is ideally suited to studying these stars, to measure precise masses of a volume-limited (<30 pc) sample of transiting M-dwarf planets. TOI-1450 is a nearby (22.5 pc) binary system containing a M3 dwarf with a roughly 3000 K companion. Its primary star, TOI-1450A, was identified by the Transiting Exoplanet Survey Satellite (TESS) to have a 2.04 days transit signal, and is included in the HUMDRUM sample. In this paper, we present MAROON-X radial velocities (RVs) which confirm the planetary nature of this signal and measure its mass at nearly 10% precision. The 2.04 days planet, TOI-1450A b, hasR_b= 1.13 ± 0.04R_⊕andM_b= 1.26 ± 0.13M_⊕. It is the second-lowest-mass transiting planet with a high-precision RV mass measurement. With this mass and radius, the planet’s mean density is compatible with an Earth-like composition. Given its short orbital period and slightly sub-Earth density, it may be amenable to JWST follow-up to test whether the planet has retained an atmosphere despite extreme heating from the nearby star. We also discover a nontransiting planet in the system with a period of 5.07 days and a $M\sin i_c=1.53\pm 0.18M_{\oplus }$. We also find a 2.01 days signal present in the systems’s TESS photometry that likely corresponds to the rotation period of TOI-1450A’s binary companion, TOI-1450B. TOI-1450A, meanwhile, appears to have a rotation period of approximately 40 days, which is in line with our expectations for a mid-M dwarf. 

We report the discovery of TOI-4641b, a warm Jupiter transiting a rapidly rotating F-type star with a stellar effective temperature of 6560 K. The planet has a radius of 0.73 RJup, a mass smaller than 3.87 MJup(3σ), and a period of 22.09 d. It is orbiting a bright star (V=7.5 mag) on a circular orbit with a radius and mass of 1.73 R⊙ and 1.41 M⊙. Follow-up ground-based photometry was obtained using the Tierras Observatory. Two transits were also observed with the Tillinghast Reflector Echelle Spectrograph, revealing the star to have a low projected spin-orbit angle (λ=$$1.41^{+0.76}_{-0.76}$$°). Such obliquity measurements for stars with warm Jupiters are relatively few, and may shed light on the formation of warm Jupiters. Among the known planets orbiting hot and rapidly rotating stars, TOI-4641b is one of the longest period planets to be thoroughly characterized. Unlike hot Jupiters around hot stars which are more often misaligned, the warm Jupiter TOI-4641b is found in a well-aligned orbit. Future exploration of this parameter space can add one more dimension to the star–planet orbital obliquity distribution that has been well sampled for hot Jupiters. 

Abstract Although all-sky surveys have led to the discovery of dozens of young planets, little is known about their atmospheres. Here, we present multiwavelength transit data for the super-Neptune sized exoplanet, K2-33b—the youngest (∼10 Myr) transiting exoplanet to date. We combined photometric observations of K2-33 covering a total of 33 transits spanning >2 yr, taken from K2, MEarth, the Hubble Space Telescope (HST), and Spitzer. The transit photometry spanned from the optical to the near-infrared (0.6–4.5μm), enabling us to construct a transmission spectrum of the planet. We find that the optical transit depths are nearly a factor of 2 deeper than those from the near-infrared. This difference holds across multiple data sets taken over years, ruling out issues of data analysis and unconstrained systematics. Surface inhomogeneities on the young star can reproduce some of the difference, but required spot coverage fractions (>60%) are ruled out by the observed stellar spectrum (<20%). We find a better fit to the transmission spectrum using photochemical hazes, which were predicted to be strong in young, moderate-temperature, and large-radius planets like K2-33b. A tholin haze with CO as the dominant gaseous carbon carrier in the atmosphere can reasonably reproduce the data with small or no stellar surface inhomogeneities, consistent with the stellar spectrum. The HST data quality is insufficient for the detection of any molecular features. More observations would be required to fully characterize the hazes and spot properties and confirm the presence of CO suggested by current data.