Accurate physical parameters of exoplanet systems are essential for further exploration of planetary internal structure, atmospheres, and formation history. We aim to use simultaneous multicolour ...transit photometry to improve the estimation of transit parameters, to search for transit timing variations (TTVs), and to establish which of our targets should be prioritised for follow-up transmission spectroscopy. We performed time series photometric observations of 12 transits for the hot Jupiters HAT-P-19b, HAT-P-51b, HAT-P-55b, and HAT-P-65b using the simultaneous four-colour camera MuSCAT2 on the Telescopio Carlos Sánchez. We collected 56 additional transit light curves from TESS photometry. To derive transit parameters, we modelled the MuSCAT2 light curves with Gaussian processes to account for correlated noise. To derive physical parameters, we performed EXOFASTv2 global fits to the available transit and radial velocity data sets, together with the Gaia DR3 parallax, isochrones, and spectral energy distributions. To assess the potential for atmospheric characterisation, we compared the multicolour transit depths with a flat line and a clear atmosphere model. We consistently refined the transit and physical parameters. We improved the orbital period and ephemeris estimates, and found no evidence for TTVs or orbital decay. The MuSCAT2 broadband transmission spectra of HAT-P-19b and HAT-P-65b are consistent with previously published low-resolution transmission spectra. We also found that, except for HAT-P-65b, the assumption of a planetary atmosphere can improve the fit to the MuSCAT2 data. In particular, we identified HAT-P-55b as a priority target among these four planets for further atmospheric studies using transmission spectroscopy.
WASP-33b, a hot Jupiter around a hot star, is a rare system in which nodal precession has been discovered. We updated the model for the nodal precession of WASP-33b by adding new observational ...points. Consequently, we found a motion of the nodal precession spanning 11 years. We present homogenous Doppler tomographic analyses of eight datasets, including two new datasets from TS23 and HIDES, obtained between 2008 and 2019, to illustrate the variations in the projected spin-orbit obliquity of WASP-33b and its impact parameter. We also present its impact parameters based on photometric transit observations captured by MuSCAT in 2017 and MuSCAT2 in 2018. We derived its real spin-orbit obliquity \(\psi\), stellar spin inclination \(i_{s}\), and stellar gravitational quadrupole moment \(J_2\) from the time variation models of the two orbital parameters. We obtained \(\psi = 108.19^{+0.95}_{-0.97}\) deg, \(i_s = 58.3^{+4.6}_{-4.2}\) deg, and \(J_2=(1.36^{+0.15}_{-0.12}) \times 10^{-4}\). Our \(J_2\) value was slightly smaller than the theoretically predicted value, which may indicate that its actual stellar internal structure is different from the theoretical one. We derived the nodal precession speed \(\dot{\theta}=0.507^{+0.025}_{-0.022}\) deg year\(^{-1}\), and its period \(P_{\mathrm{pre}}=709^{+33}_{-34}\) years, and found that WASP-33b transits in front of WASP-33 for only \(\sim\) 20 \% of the entire nodal precession period.
Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely ...unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS project's detection of an Earth-sized planet in a 17 h orbit around an ultracool dwarf of M6.5 spectral type located 16.8 pc away. The planet's high irradiation (16 times that of Earth) combined with the infrared luminosity and Jupiter-like size of its host star make it one of the most promising rocky exoplanet targets for detailed emission spectroscopy characterization with JWST. Indeed, our sensitivity study shows that just ten secondary eclipse observations with the Mid-InfraRed Instrument/Low-Resolution Spectrometer on board JWST should provide strong constraints on its atmospheric composition and/or surface mineralogy.
Observations and statistical studies have shown that giant planets are rare around M dwarfs compared with Sun-like stars. The formation mechanism of these extreme systems remains under debate for ...decades. With the help of the TESS mission and ground based follow-up observations, we report the discovery of TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so far with a radius of \(1.22\pm 0.04\ R_J\) and a mass of \(2.48\pm0.09\ M_J\), about 5 times heavier than most other giant planets around M dwarfs. It also has the highest planet-to-star mass ratio (\(q\sim 4\times 10^{-3}\)) among such systems. The host star is an early-M dwarf with a mass of \(0.61\pm0.02\ M_{\odot}\) and a radius of \(0.63\pm0.02\ R_{\odot}\). It has significant super-solar iron abundance (Fe/H=\(0.52\pm 0.08\) dex). However, interior structure modeling suggests that its planet TOI-4201b is metal-poor, which challenges the classical core-accretion correlation of stellar-planet metallicity, unless the planet is inflated by additional energy sources. Building on the detection of this planet, we compare the stellar metallicity distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We find that hot/warm Jupiters show a similar metallicity dependence around G-type stars. For M dwarf host stars, the occurrence of hot Jupiters shows a much stronger correlation with iron abundance, while warm Jupiters display a weaker preference, indicating possible different formation histories.
Hot Jupiters were many of the first exoplanets discovered in the 1990s, but in the decades since their discovery, the mysteries surrounding their origins remain. Here, we present nine new hot ...Jupiters (TOI-1855 b, TOI-2107 b, TOI-2368 b, TOI-3321 b, TOI-3894 b, TOI-3919 b, TOI-4153 b, TOI-5232 b, and TOI-5301 b) discovered by NASA's TESS mission and confirmed using ground-based imaging and spectroscopy. These discoveries are the first in a series of papers named the Migration and Evolution of giant ExoPlanets (MEEP) survey and are part of an ongoing effort to build a complete sample of hot Jupiters orbiting FGK stars, with a limiting Gaia \(G\)-band magnitude of 12.5. This effort aims to use homogeneous detection and analysis techniques to generate a set of precisely measured stellar and planetary properties that is ripe for statistical analysis. The nine planets presented in this work occupy a range of masses (0.55 Jupiter masses (M\(_{\rm{J}}\)) \(<\) M\(_{\rm{P}}\) \(<\) 3.88 M\(_{\rm{J}}\)) and sizes (0.967 Jupiter radii (R\(_{\rm{J}}\)) \(<\) R\(_{\rm{P}}\) \(<\) 1.438 R\(_{\rm{J}}\)) and orbit stars that range in temperature from 5360 K \(<\) Teff \(<\) 6860 K with Gaia \(G\)-band magnitudes ranging from 11.1 to 12.7. Two of the planets in our sample have detectable orbital eccentricity: TOI-3919 b (\(e = 0.259^{+0.033}_{-0.036}\)) and TOI-5301 b (\(e = 0.33^{+0.11}_{-0.10}\)). These eccentric planets join a growing sample of eccentric hot Jupiters that are consistent with high-eccentricity tidal migration, one of the three most prominent theories explaining hot Jupiter formation and evolution.
We report the mass determination of TOI-519 b, a transiting substellar object around a mid-M dwarf. We carried out radial velocity measurements using Subaru / InfraRed Doppler (IRD), revealing that ...TOI-519 b is a planet with a mass of \(0.463^{+0.082}_{-0.088}~M_{\rm Jup}\). We also find that the host star is metal rich (\(\rm Fe/H = 0.27 \pm 0.09\) dex) and has the lowest effective temperature (\(T_{\rm eff}=3322 \pm 49\) K) among all stars hosting known close-in giant planets based on the IRD spectra and mid-resolution infrared spectra obtained with NASA Infrared Telescope Facility / SpeX. The core mass of TOI-519 b inferred from a thermal evolution model ranges from \(0\) to \(\sim30~M_\oplus\), which can be explained by both the core accretion and disk instability models as the formation origins of this planet. However, TOI-519 is in line with the emerging trend that M dwarfs with close-in giant planets tend to have high metallicity, which may indicate that they formed in the core accretion model. The system is also consistent with the potential trend that close-in giant planets around M dwarfs tend to be less massive than those around FGK dwarfs.
We report the discovery of TOI-2119b, a transiting brown dwarf (BD) that orbits and is completely eclipsed by an active M-dwarf star. Using light curve data from the Transiting Exoplanet Survey ...Satellite mission and follow-up high-resolution Doppler spectroscopic observations, we find the BD has a radius of \(R_b = 1.08 \pm 0.03{\rm R_J}\), a mass of \(M_b = 64.4 \pm 2.3{\rm M_J}\), an orbital period of \(P = 7.200865 \pm 0.00002\) days, and an eccentricity of \(e=0.337\pm 0.002\). The host star has a mass of \(M_\star = 0.53 \pm 0.02{\rm M_\odot}\), a radius of \(R_\star= 0.50 \pm 0.01{\rm R_\odot}\), an effective temperature of \(T_{\rm eff} = 3621 \pm 48\)K, and a metallicity of \(\rm Fe/H=+0.06\pm 0.08\). TOI-2119b joins an emerging population of transiting BDs around M-dwarf host stars, with TOI-2119 being the ninth such system. These M-dwarf--brown dwarf systems typically occupy mass ratios near \(q = M_b/M_\star \approx 0.1-0.2\), which separates them from the typical mass ratios for systems with transiting substellar objects and giant exoplanets that orbit more massive stars. The nature of the secondary eclipse of the BD by the star enables us to estimate the effective temperature of the substellar object to be \(2030\pm 84\)K, which is consistent with predictions by substellar evolutionary models.
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO (\(J\)=2--1) line emission from the protoplanetary disk around T-Tauri star SU Aurigae (hereafter SU Aur). ...Previous observations in optical and near infrared wavelengths find a unique structure in SU Aur. One of the highlights of the observational results is that an extended tail-like structure is associated with the disk, indicating mass transfer from or into the disk. Here we report the discovery of the counterpart of the tail-like structure in CO gas extending more than 1000 au long. Based on geometric and kinematic perspectives, both of the disk and the tail-like structure components physically connect to each other. Several theoretical studies predicted the observed tail-like structure via the following possible scenarios, 1) a gaseous stream from the molecular cloud remnant, 2) collision with a (sub)stellar intruder or a gaseous blob from the ambient cloud, and 3) ejection of a planetary or brown dwarf mass object due to gravitational instability via multi-body gravitational interaction. Since the tail-like structures associated with the SU Aur disk is a new example following RW Aurigae, some disks may experience the internal or external interaction and drastically lose mass during disk evolution.
Transiting exoplanets orbiting young nearby stars are ideal laboratories for testing theories of planet formation and evolution. However, to date only a handful of stars with age <1 Gyr have been ...found to host transiting exoplanets. Here we present the discovery and validation of a sub-Neptune around HD 18599, a young (300 Myr), nearby (d=40 pc) K star. We validate the transiting planet candidate as a bona fide planet using data from the TESS, Spitzer, and Gaia missions, ground-based photometry from IRSF, LCO, PEST, and NGTS, speckle imaging from Gemini, and spectroscopy from CHIRON, NRES, FEROS, and Minerva-Australis. The planet has an orbital period of 4.13 d, and a radius of 2.7Rearth. The RV data yields a 3-sigma mass upper limit of 30.5Mearth which is explained by either a massive companion or the large observed jitter typical for a young star. The brightness of the host star (V~9 mag) makes it conducive to detailed characterization via Doppler mass measurement which will provide a rare view into the interior structure of young planets.
We present the discovery and validation of a temperate sub-Neptune around the
nearby mid-M dwarf TIC 470381900 (TOI-1696), with a radius of $3.09 \pm 0.11
\,R_\oplus$ and an orbital period of $2.5 ...\,\rm{days}$, using a combination of
TESS and follow-up observations using ground-based telescopes. Joint analysis
of multi-band photometry from TESS, MuSCAT, MuSCAT3, Sinistro, and KeplerCam
confirmed the transit signal to be achromatic as well as refined the orbital
ephemeris. High-resolution imaging with Gemini/'Alopeke and high-resolution
spectroscopy with the Subaru/IRD confirmed that there are no stellar companions
or background sources to the star. The spectroscopic observations with IRD and
IRTF/SpeX were used to determine the stellar parameters, and found the host
star is an M4 dwarf with an effective temperature of $T_{eff} = 3185 \pm
76\,\rm{K}$ and a metallicity of Fe/H $=0.336 \pm 0.060 \,\rm{dex}$. The
radial velocities measured from IRD set a $2$-$\sigma$ upper limit on the
planetary mass to be $48.8 \,M_\oplus$. The large radius ratio ($R_p/R_\star
\sim 0.1$) and the relatively bright NIR magnitude ($J=12.2 \,\rm{mag}$) make
this planet an attractive target for further followup observations. TOI-1696b
is one of the planets belonging to the Neptunian desert with the highest
transmission spectroscopy metric discovered to date, making it an interesting
candidate for atmospheric characterizations with JWST.
