Warm Jupiters are close-in giant planets with relatively large planet-star separations (i.e., \(10< a/R_\star <100\)). 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 \(\lambda = 38.9^{+2.8}_{-2.7}\deg\) relative to its planetary 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-1859b is likely an outcome of dynamical interactions, such as planet-planet scattering and planet-disk resonance crossing.
Understanding the distribution and occurrence rate of small planets was a fundamental goal of the Kepler transiting exoplanet mission, and could be improved with K2 and TESS. Deriving accurate ...exoplanetary radii requires accurate measurements of the host star radii and the planetary transit depths, including accounting for any "third light" in the system due to nearby bound companions or background stars. High-resolution imaging of Kepler and K2 planet candidate hosts to detect very close (within ~0.5") background or bound stellar companions has been crucial for both confirming the planetary nature of candidates, and the determination of accurate planetary radii and mean densities. Here we present an investigation of the effect of close companions, both detected and undetected, on the observed (raw count) exoplanet radius distribution. We demonstrate that the recently detected "gap" in the observed radius distribution (also seen in the completeness-corrected distribution) is fairly robust to undetected stellar companions, given that all of the systems in the sample have undergone some kind of vetting with high-resolution imaging. However, while the gap in the observed sample is not erased or shifted, it is partially filled in after accounting for possible undetected stellar companions. These findings have implications for the most likely core composition, and thus formation location, of super-Earth and sub-Neptune planets. Furthermore, we show that without high-resolution imaging of planet candidate host stars, the shape of the observed exoplanet radius distribution will be incorrectly inferred, for both Kepler- and TESS-detected systems.
We report on the discovery and validation of a transiting long-period mini-Neptune orbiting a bright (V = 9.0 mag) G dwarf (TOI 4633; R = 1.05 RSun, M = 1.10 MSun). The planet was identified in data ...from the Transiting Exoplanet Survey Satellite by citizen scientists taking part in the Planet Hunters TESS project. Modeling of the transit events yields an orbital period of 271.9445 +/- 0.0040 days and radius of 3.2 +/- 0.20 REarth. The Earth-like orbital period and an incident flux of 1.56 +/- 0.2 places it in the optimistic habitable zone around the star. Doppler spectroscopy of the system allowed us to place an upper mass limit on the transiting planet and revealed a non-transiting planet candidate in the system with a period of 34.15 +/- 0.15 days. Furthermore, the combination of archival data dating back to 1905 with new high angular resolution imaging revealed a stellar companion orbiting the primary star with an orbital period of around 230 years and an eccentricity of about 0.9. The long period of the transiting planet, combined with the high eccentricity and close approach of the companion star makes this a valuable system for testing the formation and stability of planets in binary systems.
We present high angular resolution imaging observations of 517 host stars of TESS exoplanet candidates using the `Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists ...mainly of bright F, G, K stars at distances of less than 500 pc. Our speckle observations span angular resolutions of ~20 mas out to 1.2 arcsec, yielding spatial resolutions of <10 to 500 AU for most stars, and our contrast limits can detect companion stars 5-9 magnitudes fainter than the primary at optical wavelengths. We detect 102 close stellar companions and determine the separation, magnitude difference, mass ratio, and estimated orbital period for each system. Our observations of exoplanet host star binaries reveal that they have wider separations than field binaries, with a mean orbital semi-major axis near 100 AU. Other imaging studies have suggested this dearth of very closely separated binaries in systems which host exoplanets, but incompleteness at small separations makes it difficult to disentangle unobserved companions from a true lack of companions. With our improved angular resolution and sensitivity, we confirm that this lack of close exoplanet host binaries is indeed real. We also search for a correlation between planetary orbital radii vs. binary star separation, but given the very short orbital periods of the TESS planets, we do not find any clear trend. We do note that in exoplanet systems containing binary host stars, there is an observational bias against detecting Earth-size planet transits due to transit depth dilution caused by the companion star.
We statistically validated a sample of hot Neptune candidates applying a two-step vetting technique using DAVE and TRICERATOPS. We performed a systematic validation of 250 transit-like events in the ...Transiting Exoplanet Survey Satellite (TESS) archive in the parameter region defined by \(P\leq 4\) d and \(3R_\oplus\leq R\leq 5R_\oplus\). Through our analysis, we identified 18 hot Neptune-sized candidates, with a false positive probability \(<50\%\). Nine of these planet candidates still need to be confirmed. For each of the nine targets we retrieved the stellar parameters using ARIADNE and derived constraints on the planetary parameters by fitting the lightcurves with the juliet package. Within this sample of nine candidates, we statistically validated (i.e, with false positive probability < \(0.3\%\)) two systems (TOI-277 b and TOI-1288 b) by re-processing the candidates with TRICERATOPS along with follow-up observations. These new validated exoplanets expand the known hot Neptunes population and are high-priority targets for future radial velocities follow-up.
We report the discovery and Doppler mass measurement of a 7.4-day 2.3-\(R_\oplus\) mini-Neptune around a metal-poor K dwarf BD+29 2654 (TOI-2018). Based on a high-resolution Keck/HIRES spectrum, the ...Gaia parallax, and multi-wavelength photometry from the ultraviolet to the mid-infrared, we found that the host star has \(T_{\text{eff}}=4174^{+34}_{-42}\) K, \(\log{g}=4.62^{+0.02}_{-0.03}\), \(\text{Fe/H}=-0.58\pm0.18\), \(M_{\ast}=0.57\pm0.02~M_{\odot}\), and \(R_{\ast}=0.62\pm0.01~R_{\odot}\). Precise Doppler measurements with Keck/HIRES revealed a planetary mass of \(M_{\text{p}}=9.2\pm2.1~M_{\oplus}\) for TOI-2018 b. TOI-2018 b has a mass and radius that are consistent with an Earth-like core with a \(\sim1\%\)-by-mass hydrogen/helium envelope, or an ice-rock mixture. The mass of TOI-2018 b is close to the threshold for run-away accretion and hence giant planet formation. Such a threshold is predicted to be around 10\(M_\oplus\) or lower for a low-metallicity (low-opacity) environment. If TOI-2018 b is a planetary core that failed to undergo run-away accretion, it may underline the reason why giant planets are rare around low-metallicity host stars (one possibility is their shorter disk lifetimes). With a K-band magnitude of 7.1, TOI-2018 b may be a suitable target for transmission spectroscopy with the James Webb Space Telescope. The system is also amenable to metastable Helium observation; the detection of a Helium exosphere would help distinguish between a H/He enveloped planet and a water world.
Hot jupiters (P < 10 d, M > 60 \(\mathrm{M}_\oplus\)) are almost always found alone around their stars, but four out of hundreds known have inner companion planets. These rare companions allow us to ...constrain the hot jupiter's formation history by ruling out high-eccentricity tidal migration. Less is known about inner companions to hot Saturn-mass planets. We report here the discovery of the TOI-2000 system, which features a hot Saturn-mass planet with a smaller inner companion. The mini-neptune TOI-2000 b (\(2.70 \pm 0.15 \,\mathrm{R}_\oplus\), \(11.0 \pm 2.4 \,\mathrm{M}_\oplus\)) is in a 3.10-day orbit, and the hot saturn TOI-2000 c (\(8.14^{+0.31}_{-0.30} \,\mathrm{R}_\oplus\), \(81.7^{+4.7}_{-4.6} \,\mathrm{M}_\oplus\)) is in a 9.13-day orbit. Both planets transit their host star TOI-2000 (TIC 371188886, V = 10.98, TESS magnitude = 10.36), a metal-rich (Fe/H = \(0.439^{+0.041}_{-0.043}\)) G dwarf 174 pc away. TESS observed the two planets in sectors 9-11 and 36-38, and we followed up with ground-based photometry, spectroscopy, and speckle imaging. Radial velocities from CHIRON, FEROS, and HARPS allowed us to confirm both planets by direct mass measurement. In addition, we demonstrate constraining planetary and stellar parameters with MIST stellar evolutionary tracks through Hamiltonian Monte Carlo under the PyMC framework, achieving higher sampling efficiency and shorter run time compared to traditional Markov chain Monte Carlo. Having the brightest host star in the V band among similar systems, TOI-2000 b and c are superb candidates for atmospheric characterization by the JWST, which can potentially distinguish whether they formed together or TOI-2000 c swept along material during migration to form TOI-2000 b.
We present the discovery of TOI-1420b, an exceptionally low-density (\(\rho = 0.08\pm0.02\) g cm\(^{-3}\)) transiting planet in a \(P = 6.96\) day orbit around a late G dwarf star. Using transit ...observations from TESS, LCOGT, OPM, Whitin, Wendelstein, OAUV, Ca l'Ou, and KeplerCam along with radial velocity observations from HARPS-N and NEID, we find that the planet has a radius of \(R_p\) = 11.9 \(\pm\) 0.3 \(R_\Earth\) and a mass of \(M_p\) = 25.1 \(\pm\) 3.8 \(M_\Earth\). TOI-1420b is the largest-known planet with a mass less than \(50M_\Earth\), indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b's envelope mass fraction to be \(f_{env} = 82^{+7}_{-6}\%\), suggesting that runaway gas accretion occurred when its core was at most \(4-5\times\) the mass of the Earth. TOI-1420b is similar to the planet WASP-107b in mass, radius, density, and orbital period, so a comparison of these two systems may help reveal the origins of close-in low-density planets. With an atmospheric scale height of 1950 km, a transmission spectroscopy metric of 580, and a predicted Rossiter-McLaughlin amplitude of about \(17\) m s\(^{-1}\), TOI-1420b is an excellent target for future atmospheric and dynamical characterization.
To date, thousands of planets have been discovered, but there are regions of the orbital parameter space that are still bare. An example is the short period and intermediate mass/radius space known ...as the Neptunian desert, where planets should be easy to find but discoveries remain few. This suggests unusual formation and evolution processes are responsible for the planets residing here. We present the discovery of TOI-332 b, a planet with an ultra-short period of \(0.78\) d that sits firmly within the desert. It orbits a K0 dwarf with an effective temperature of \(5251 \pm 71\) K. TOI-332 b has a radius of \(3.20^{+0.16}_{-0.12}\) R\(_{\oplus}\), smaller than that of Neptune, but an unusually large mass of \(57.2 \pm 1.6\) M\(_{\oplus}\). It has one of the highest densities of any Neptune-sized planet discovered thus far at \(9.6^{+1.1}_{-1.3}\) gcm\(^{-3}\). A 4-layer internal structure model indicates it likely has a negligible hydrogen-helium envelope, something only found for a small handful of planets this massive, and so TOI-332 b presents an interesting challenge to planetary formation theories. We find that photoevaporation cannot account for the mass loss required to strip this planet of the Jupiter-like envelope it would have been expected to accrete. We need to look towards other scenarios, such as high-eccentricity migration, giant impacts, or gap opening in the protoplanetary disc, to try and explain this unusual discovery.
With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase improvements to the MIT Quick-Look Pipeline (QLP) through the discovery and validation of a multi-planet system around ...M-dwarf TOI 4342 (\(T_{mag}=11.032\), \(M_* = 0.63 M_\odot\), \(R_* = 0.60 R_\odot\), \(T_{eff} = 3900\) K, \(d = 61.54\) pc). With updates to QLP, including a new multi-planet search, as well as faster cadence data from TESS' First Extended Mission, we discovered two sub-Neptunes (\(R_b = 2.266_{-0.038}^{+0.038} R_\oplus\) and \(R_c = 2.415_{-0.040}^{+0.043} R_\oplus\); \(P_b\) = 5.538 days and \(P_c\) = 10.689 days) and validated them with ground-based photometry, spectra, and speckle imaging. Both planets notably have high transmission spectroscopy metrics (TSMs) of 36 and 32, making TOI 4342 one of the best systems for comparative atmospheric studies. This system demonstrates how improvements to QLP, along with faster cadence Full-Frame Images (FFIs), can lead to the discovery of new multi-planet systems.
