Search for: All records

Abstract We describe the discovery and characterization of TOI-7149 b, a 0.705 ± 0.075M_J, 1.18 ± 0.045R_Jgas giant on a ∼2.65 days period orbit transiting an M4V star with a mass of 0.344 ± 0.030M_⊙and an effective temperature of 3363 ± 59 K. The planet was first discovered using NASA’s TESS mission, which we confirmed using a combination of ground-based photometry, radial velocities, and speckle imaging. The planet has one of the deepest transits of all known main-sequence planet hosts at ∼12% (R_p/R_⋆∼ 0.33). Pushing the bounds of previous discoveries of giant exoplanets around M-dwarf stars (GEMS), TOI-7149 is one of the lowest mass M-dwarfs to host a transiting giant planet. We compare the sample of transiting GEMS to stars within 200 pc with a Gaia color–magnitude diagram and find that the GEMS hosts are likely to be high metallicity stars. We also analyze the sample of transiting giant planets using the nonparametricMRExoframework to compare the bulk density of warm Jupiters across stellar masses. We confirm our previous result that transiting Jupiters around early M-dwarfs have similar masses and densities to warm Jupiters around FGK stars, and extend this to mid M-dwarfs, thereby suggesting a potential commonality in their formation mechanisms. 

Abstract We present the discovery of TOI-6303b and TOI-6330b, two massive transiting super-Jupiters orbiting a M0 and a M2 dwarf star, respectively, as part of the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey. These were detected by NASA’s Transiting Exoplanet Survey Satellite and then confirmed via ground-based photometry and radial velocity observations with the Habitable-zone Planet Finder. TOI-6303b has a mass of 7.84 ± 0.31M_J, a radius of 1.03 ± 0.06R_J, and an orbital period of 9.485 days. TOI-6330b has a mass of 10.00 ± 0.31M_J, a radius of 0.97 ± 0.03R_J, and an orbital period of 6.850 days. We put these planets in the context of super-Jupiters around M dwarfs discovered from radial-velocity surveys, as well as recent discoveries from astrometry. These planets have masses that can be attributed to two dominant planet formation mechanisms—gravitational instability and core accretion. Their masses necessitate massive protoplanetary disks that should either be gravitationally unstable, i.e., forming through gravitational instability, or be among the most massive protoplanetary disks known to date to form objects through core accretion. We also discuss their possible migration mechanisms via their eccentricity distribution. 

Abstract Brown dwarfs bridge the gap between stars and planets, providing valuable insight into both planetary and stellar-formation mechanisms. Yet the census of transiting brown-dwarf companions, in particular around M-dwarf stars, remains incomplete. We report the discovery of two transiting brown dwarfs around low-mass hosts using a combination of space- and ground-based photometry along with near-infrared radial velocities. We characterize TOI-5389Ab ( $68.0_{-2.2}^{+2.2}{M}_{\mathrm{J}}$) and TOI-5610b ( $40.4_{-1.0}^{+1.0}{M}_{\mathrm{J}}$), two moderately massive brown dwarfs orbiting early M-dwarf hosts (T_eff = 3569 ± 59 K and 3618 ± 59 K, respectively). For TOI-5389Ab, the best fitting parameters are periodP = 10.40046 ± 0.00002 days, radius $R_{\mathrm{BD}}=0.824_{-0.031}^{+0.033}$R_J, and low eccentricity $e=0.0962_{-0.0046}^{+0.0027}$. In particular, this constitutes one of the most extreme substellar-stellar companion-to-host mass ratios ofq= 0.150. For TOI-5610b, the best-fitting parameters are periodP = 7.95346 ± 0.00002 days, radius $R_{\mathrm{BD}}=0.887_{-0.031}^{+0.031}$R_J, and moderate eccentricity $e=0.354_{-0.012}^{+0.011}$. Both targets are expected to have shallow, but potentially observable, occultations: ≲500 ppm in the JohnsonKband. A statistical analysis of M-dwarf/BD systems reveals for the first time that those at short orbital periods (P < 13 days) exhibit a dearth of 13M_J < M_BD < 40M_Jcompanions (q < 0.1) compared to those at slightly wider separations. 

Abstract We present the confirmation of TOI-5573 b, a Saturn-sized exoplanet on an 8.79 days orbit around an early M dwarf (3790 K, 0.59R_⊙, 0.61M_⊙, 12.30 Jmag). TOI-5573 b has a mass of $112_{-19}^{+18}$M_⊕(0.35 ± 0.06M_Jup) and a radius of 9.75 ± 0.47R_⊕(0.87 ± 0.04R_Jup), resulting in a density of $0.66_{-0.13}^{+0.16}$g cm⁻³, akin to that of Saturn. The planet was initially discovered by the Transiting Exoplanet Survey Satellite (TESS) and confirmed using a combination of 11 transits from four TESS Sectors (20, 21, 47, and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder and NN-EXPLORE Exoplanet Investigations with Doppler spectrographs, achieving a 5σprecision on the planet’s mass. TOI-5573 b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of only 528 ± 10 K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star’s supersolar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573 b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with supersolar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573 b. 

Abstract We present the discovery of a low-density planet orbiting the high-metallicity early M-dwarf TOI-5688 A b. This planet was characterized as part of the search for transiting giant planets (R ≳ 8R_⊕) through the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey. The planet was discovered with the Transiting Exoplanet Survey Satellite, and characterized with ground-based transits from Red Buttes Observatory, the Table Mountain Observatory of Pomona College, and radial velocity (RV) measurements with the Habitable-Zone Planet Finder on the 10 m Hobby Eberly Telescope and NEID on the WIYN 3.5 m telescope. From the joint fit of transit and RV data, we measure a planetary mass and radius of 124 ± 24M_⊕(0.39 ± 0.07M_J) and 10.4 ± 0.7R_⊕(0.92 ± 0.06R_J), respectively. The spectroscopic and photometric analysis of the host star TOI-5688 A shows that it is a metal-rich ([Fe/H] = 0.47 ± 0.16 dex) M2V star, favoring the core-accretion formation pathway as the likely formation scenario for this planet. Additionally, Gaia astrometry suggests the presence of a wide-separation binary companion, TOI-5688 B, which has a projected separation of ~5″ (1110 au) and is an M4V, making TOI-5688 A b part of the growing number of GEMS in wide-separation binary systems. 

Abstract We confirm TOI-4201 b as a transiting Jovian-mass planet orbiting an early M dwarf discovered by the Transiting Exoplanet Survey Satellite. Using ground-based photometry and precise radial velocities from NEID and the Planet Finder Spectrograph, we measure a planet mass of ${2.59}_{-0.06}^{+0.07}$M_J, making this one of the most massive planets transiting an M dwarf. The planet is ∼0.4% of the mass of its 0.63M_⊙host and may have a heavy-element mass comparable to the total dust mass contained in a typical class II disk. TOI-4201 b stretches our understanding of core accretion during the protoplanetary phase and the disk mass budget, necessitating giant planet formation to take place either much earlier in the disk lifetime or perhaps through alternative mechanisms like gravitational instability. 

Abstract Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations¹. These ‘hot Jupiter’ planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization^2,3. The discovery of the extremely eccentric (e = 0.93) giant exoplanet HD 80606 b (ref. ⁴) provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway⁵. However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage^6–8. Here we present spectroscopic and photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity ofe = 0.94. The orbit of TIC 241249530 b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity. 

Abstract We confirm the planetary nature of TOI-5344 b as a transiting giant exoplanet around an M0-dwarf star. TOI-5344 b was discovered with the Transiting Exoplanet Survey Satellite photometry and confirmed with ground-based photometry (the Red Buttes Observatory 0.6 m telescope), radial velocity (the Habitable-zone Planet Finder), and speckle imaging (the NN-Explore Exoplanet Stellar Speckle Imager). TOI-5344 b is a Saturn-like giant planet (ρ= 0.80 ${}_{-0.15}^{+0.17}$g cm⁻³) with a planetary radius of 9.7 ± 0.5R_⊕(0.87 ± 0.04R_Jup) and a planetary mass of ${135}_{-18}^{+17}{M}_{\oplus }$(0.42 ${}_{-0.06}^{+0.05}{M}_{\mathrm{Jup}}$). It has an orbital period of ${3.792622}_{-0.000010}^{+0.000010}$days and an orbital eccentricity of ${0.06}_{-0.04}^{+0.07}$. We measure a high metallicity for TOI-5344 of [Fe/H] = 0.48 ± 0.12, where the high metallicity is consistent with expectations from formation through core accretion. We compare the metallicity of the M-dwarf hosts of giant exoplanets to that of M-dwarf hosts of nongiants (≲8R_⊕). While the two populations appear to show different metallicity distributions, quantitative tests are prohibited by various sample caveats. 

Abstract Transiting giant exoplanets around M-dwarf stars (GEMS) are rare, owing to the low-mass host stars. However, the all-sky coverage of TESS has enabled the detection of an increasingly large number of them to enable statistical surveys like the Searching for GEMS survey. As part of this endeavor, we describe the observations of six transiting giant planets, which include precise mass measurements for two GEMS (K2-419Ab, TOI-6034b) and statistical validation for four systems, which includes validation and mass upper limits for three of them (TOI-5218b, TOI-5616b, TOI-5634Ab), while the fourth one—TOI-5414b is classified as a “likely planet.” Our observations include radial velocities from the Habitable-zone Planet Finder on the Hobby–Eberly Telescope, and MAROON-X on Gemini-North, along with photometry and high-contrast imaging from multiple ground-based facilities. In addition to TESS photometry, K2-419Ab was also observed and statistically validated as part of the K2 mission in Campaigns 5 and 18, which provide precise orbital and planetary constraints despite the faint host star and long orbital period of ∼20.4 days. With an equilibrium temperature of only 380 K, K2-419Ab is one of the coolest known well-characterized transiting planets. TOI-6034 has a late F-type companion about 40″ away, making it the first GEMS host star to have an earlier main-sequence binary companion. These confirmations add to the existing small sample of confirmed transiting GEMS.