We report the discovery and characterisation of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in TESS photometry. To characterise the system, we ...performed and retrieved CHEOPS, TESS, and ground-based photometry, HARPS high-resolution spectroscopy, and Gemini speckle imaging. We characterise the host star and determine \(T_{\rm eff, \star}=4734\pm67\) K, \(R_{\star}=0.726\pm0.007\) \(R_{\odot}\), and \(M_{\star}=0.748\pm0.032\) \(M_{\odot}\). We present a novel detrending method based on PSF shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of \(P_{\rm b}=6.44387\pm0.00003\) d, a radius of \(R_{\rm b}=2.59\pm0.04\) \(R_{\oplus}\), and a mass of \(M_{\rm b}=13.5_{-1.8}^{+1.7}\) \(M_{\oplus}\), whilst TOI-1064 c has an orbital period of \(P_{\rm c}=12.22657^{+0.00005}_{-0.00004}\) d, a radius of \(R_{\rm c}=2.65\pm0.04\) \(R_{\oplus}\), and a 3\(\sigma\) upper mass limit of 8.5 \({\rm M_{\oplus}}\). From the high-precision photometry we obtain radius uncertainties of \(\sim\)1.6%, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterised sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further RVs are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of mass-radius space, and it allows us to identify a trend in bulk density-stellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets.
As an all-sky survey, NASA's \(TESS\) mission is able to detect the brightest and rarest types of transiting planetary systems, including young planets that enable study of the evolutionary processes ...that occur within the first billion years. Here, we report the discovery of a young, multi-planet system orbiting the bright K4.5V star, TOI-712 (\(V = 10.838\), \(M_\star = 0.733_{-0.025}^{+0.026} M_\odot\), \(R_\star = 0.674\pm0.016 R_\odot\), \(T_{\rm eff} = 4622_{-60}^{+61}\) K). From the \(TESS\) light curve, we measure a rotation period of 12.48 days, and derive an age between about \(500\) Myr and 1.1 Gyr. The photometric observations reveal three transiting mini-Neptunes (\(R_b = 2.049^{+0.12}_{-0.080} R_\oplus\), \(R_c = 2.701^{+0.092}_{-0.082} R_\oplus\), \(R_d = 2.474^{+0.090}_{-0.082} R_\oplus \)), with orbital periods of \(P_b = 9.531\) days, \(P_c = 51.699\) days, and \(P_d = 84.839\) days. After modeling the three-planet system, an additional Earth-sized candidate is identified, TOI-712.05 (\(P = 4.32\) days, \(R_P = 0.81 \pm 0.11 R_\oplus\)). We calculate that the habitable zone falls between 0.339 and 0.844 au (82.7 and 325.3 days), placing TOI-712 d near its inner edge. Among planetary systems harboring temperate planets, TOI-712 (\(T = 9.9\)) stands out as a relatively young star bright enough to motivate further characterization.
We report the discovery of five transiting companions near the hydrogen-burning mass limit in close orbits around main sequence stars originally identified by the Transiting Exoplanet Survey ...Satellite (TESS) as TESS Objects of Interest (TOIs): TOI-148, TOI-587, TOI-681, TOI-746, and TOI-1213. Using TESS and ground-based photometry as well as radial velocities from the CORALIE, CHIRON, TRES, and FEROS spectrographs, we found the companions have orbital periods between 4.8 and 27.2 days, masses between 77 and 98 \(\mathrm{M_{Jup}}\), and radii between 0.81 and 1.66 \(\mathrm{R_{Jup}}\). These targets have masses near the uncertain lower limit of hydrogen core fusion (\(\sim\)73-96 \(\mathrm{M_{Jup}}\)), which separates brown dwarfs and low-mass stars. We constrained young ages for TOI-587 (0.2 \(\pm\) 0.1 Gyr) and TOI-681 (0.17 \(\pm\) 0.03 Gyr) and found them to have relatively larger radii compared to other transiting companions of a similar mass. Conversely we estimated older ages for TOI-148 and TOI-746 and found them to have relatively smaller companion radii. With an effective temperature of 9800 \(\pm\) 200 K, TOI-587 is the hottest known main-sequence star to host a transiting brown dwarf or very low-mass star. We found evidence of spin-orbit synchronization for TOI-148 and TOI-746 as well as tidal circularization for TOI-148. These companions add to the population of brown dwarfs and very low-mass stars with well measured parameters ideal to test formation models of these rare objects, the origin of the brown dwarf desert, and the distinction between brown dwarfs and hydrogen-burning main sequence stars.
Warm Jupiters -- defined here as planets larger than 6 Earth radii with orbital periods of 8--200 days -- are a key missing piece in our understanding of how planetary systems form and evolve. It is ...currently debated whether Warm Jupiters form in situ, undergo disk or high eccentricity tidal migration, or have a mixture of origin channels. These different classes of origin channels lead to different expectations for Warm Jupiters' properties, which are currently difficult to evaluate due to the small sample size. We take advantage of the \TESS survey and systematically search for Warm Jupiter candidates around main-sequence host stars brighter than the \TESS-band magnitude of 12 in the Full-Frame Images in Year 1 of the \TESS Prime Mission data. We introduce a catalog of 55 Warm Jupiter candidates, including 19 candidates that were not originally released as \TESS Objects of Interest (TOIs) by the \TESS team. We fit their \TESS light curves, characterize their eccentricities and transit-timing variations (TTVs), and prioritize a list for ground-based follow-up and \TESS Extended Mission observations. Using hierarchical Bayesian modeling, we find the preliminary eccentricity distributions of our Warm-Jupiter-candidate catalog using a Beta distribution, a Rayleigh distribution, and a two-component Gaussian distribution as the functional forms of the eccentricity distribution. Additional follow-up observations will be required to clean the sample of false positives for a full statistical study, derive the orbital solutions to break the eccentricity degeneracy, and provide mass measurements.
TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS Mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). ...Precise characterization of the planets' masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial velocity measurements using HARPS, FEROS, and PFS break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in the 2:1 resonance with a moderate libration amplitude of 60 +/- 2 degrees; small but significant free eccentricity of 0.0222 +0.0005/-0.0003 for TOI-216b; and small but significant mutual inclination of 1.2-3.9 degrees (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet.
We report the discovery of a transiting, temperate, Neptune-sized exoplanet orbiting the nearby (\(d\) = 27.5 pc), M3V star TOI-1231 (NLTT 24399, L 248-27, 2MASS J10265947-5228099). The planet was ...detected using photometric data from the Transiting Exoplanet Survey Satellite and followed up with observations from the Las Cumbres Observatory and the Antarctica Search for Transiting ExoPlanets program. Combining the photometric data sets, we find that the newly discovered planet has a radius of 3.65\(^{+0.16}_{-0.15}\) R\(_{\oplus}\), and an orbital period of 24.246 days. Radial velocity measurements obtained with the Planet Finder Spectrograph on the Magellan Clay telescope confirm the existence of the planet and lead to a mass measurement of 15.5\(\pm\)3.3 M\(_{\oplus}\). With an equilibrium temperature of just 330K TOI-1231 b is one of the coolest small planets accessible for atmospheric studies thus far, and its host star's bright NIR brightness (J=8.88, K\(_{s}\)=8.07) make it an exciting target for HST and JWST. Future atmospheric observations would enable the first comparative planetology efforts in the 250-350 K temperature regime via comparisons with K2-18 b. Furthermore, TOI-1231's high systemic radial velocity (70.5 k\ms) may allow for the detection of low-velocity hydrogen atoms escaping the planet by Doppler shifting the H I Ly-alpha stellar emission away from the geocoronal and ISM absorption features.
We present the discovery of TOI-2136b, a sub-Neptune planet transiting every
7.85 days a nearby M4.5V-type star, identified through photometric measurements
from the TESS mission. The host star is ...located $33$ pc away with a radius of
$R_{\ast} = 0.34\pm0.02\ R_{\odot}$, a mass of $0.34\pm0.02\ M_{\odot}$ and an
effective temperature of $\rm 3342\pm100\ K$. We estimate its stellar rotation
period to be $75\pm5$ days based on archival long-term photometry. We confirm
and characterize the planet based on a series of ground-based multi-wavelength
photometry, high-angular-resolution imaging observations, and precise radial
velocities from CFHT/SPIRou. Our joint analysis reveals that the planet has a
radius of $2.19\pm0.17\ R_{\oplus}$, and a mass measurement of $6.4\pm2.4\
M_{\oplus}$. The mass and radius of TOI2136b is consistent with a broad range
of compositions, from water-ice to gas-dominated worlds. TOI-2136b falls close
to the radius valley for low-mass stars predicted by the thermally driven
atmospheric mass loss models, making it an interesting target for future
studies of its interior structure and atmospheric properties.
