I report updates to the substellar mass-radius diagram for 11 transiting brown dwarfs (BDs) and low-mass stars published before the third data release from the Gaia mission (Gaia DR3). I reanalyse ...these transiting BD systems whose physical parameters were published between 2008 and 2019 and find that when using the parallax measurements from Gaia DR3, 7 BDs show significant differences in their radius estimate or an improvement in the radius uncertainty. This has important implications for how these BDs are used to test substellar evolutionary models in the mass-radius diagram. The remaining 4 BDs show mass-radius estimates that are consistent with their previous pre-Gaia DR3 measurements. The 7 BDs that show significant deviation from the original mass-radius measurements are AD 3116b, CoRoT-3b, CoRoT-15b, EPIC 201702477b, Kepler-39b, KOI-205b, and KOI-415b. Of these, AD 3116b is a known member of the Praesepe cluster at an age of 600 Myr. Additionally, some of the previously smallest known transiting BDs, KOI-205b and KOI-415b, are not as small as once thought, leaving the mass-radius region for the very oldest BDs relatively sparse as a result of this work.
We present the discoveries of a brown dwarf and a low mass star from the Kepler and K2 missions. The newly discovered brown dwarf is EPIC 212036875b and the low mass star is KOI-607b. EPIC 212036875b ...has a mass of \( M_{b}=52.3\pm 1.9M_J\), a radius of \( R_{b}=0.874\pm 0.017R_J\), and orbits its host star in \( P=5.169885 \pm 0.000027\) days. Its host star is a late F-type star with \( M_\star=1.288\pm 0.065M_\odot\), \( R_\star=1.498\pm 0.025R_\odot\), and \( T_{\rm eff}=6238 \pm 60\)K. KOI-607b has a mass of \( M_{b}=95.1\pm 3.4M_J\), a radius of \( R_{b}=1.089\pm 0.089R_J\), and an orbital period of \( P=5.89399148 \pm 0.00000060\) days. The primary star in the KOI-607 system is a G dwarf with \( M_\star=0.993\pm 0.052M_\odot\), \( R_\star=0.915\pm 0.031R_\odot\), and \( T_{\rm eff} = 5418\pm 87\)K. We also revisit a brown dwarf, CWW 89Ab, that was previously published by Nowak et al. 2017 (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting brown dwarfs associated with a star cluster, which illustrates the need for more brown dwarfs with accurate masses and radii and reliable age determinations to test theoretical models. We find that the newly discovered brown dwarf, EPIC 212036875b, falls in the middle of the so-called "brown dwarf desert", indicating that EPIC 212036875b is either a particularly rare object, or the brown dwarf desert may not be so dry after all.
We introduce the OATMEAL survey, an effort to measure the obliquities of stars with transiting brown dwarf companions. We observed a transit of the close-in (\(P_{\rm orb} = 1.74 \,\) days) brown ...dwarf GPX-1 b using the Keck Planet Finder (KPF) spectrograph to measure the sky-projected angle between its orbital axis and the spin axis of its early F-type host star (\(\lambda\)). We measured \(\lambda = 6.88 \pm 1.72 ^\circ\) (with additional unquantified systematic uncertainty), suggesting an orbit that is prograde and well aligned with the stellar equator. Hot Jupiters around early F stars are frequently found to have highly misaligned orbits, with polar and retrograde orbits being commonplace. It has been theorized that these misalignments stem from dynamical interactions, such as von Zeipel-Kozai-Lidov cycles, and are retained over long timescales due to weak tidal dissipation in stars with radiative envelopes. By comparing GPX-1 to similar systems under the frameworks of different tidal evolution theories, we argued that the rate of tidal dissipation is too slow to have re-aligned the system. This suggests that GPX-1 may have arrived at its close-in orbit via coplanar high-eccentricity migration or migration through an aligned protoplanetary disk. Our result for GPX-1 is the fifth measurement of the obliquity of a star with a transiting brown dwarf. By enlarging the number of such measurements and comparing them with hot Jupiter systems, we will more clearly discern the differences between the mechanisms that dictate the formation and evolution of both classes of objects.
Do external galaxies host planetary systems? Many lines of reasoning suggest that the answer must be 'yes'. In the foreseeable future, however, the question cannot be answered by the methods most ...successful in our own Galaxy. We report on a different approach which focuses on bright X-ray sources (XRSs). M51-ULS-1b is the first planet candidate to be found because it produces a full, short-lived eclipse of a bright XRS. M51-ULS-1b has a most probable radius slightly smaller than Saturn. It orbits one of the brightest XRSs in the external galaxy M51, the Whirlpool Galaxy, located 8.6 Megaparsecs from Earth. It is the first candidate for a planet in an external galaxy. The binary it orbits, M51-ULS-1, is young and massive. One of the binary components is a stellar remnant, either a neutron star (NS) or black hole (BH), and the other is a massive star. X-ray transits can now be used to discover more planets in external galaxies and also planets orbiting XRSs inside the Milky Way.
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 the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite TESS as TOI-588 b. HIP ...33609 b is a large (R\(_{b}\) = 1.580\(_{-0.070}^{+0.074}\) R\(_{J}\)) brown dwarf on a highly eccentric (e = 0.560\(_{-0.031}^{+0.029}\)) orbit with a 39-day period. The host star is a bright (V = 7.3 mag), T\(_{eff}\) = 10,400\(_{-660}^{+800}\) K star with a mass of M\(_{*}\) = 2.383\(_{-0.095}^{+0.10}\) M\(_{\odot}\) and radius of R\(_{*}\) = 1.863\(_{-0.082}^{+0.087}\) R\(_{\odot}\), making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M\(_{b}\) = 68.0\(_{-7.1}^{+7.4}\) M\(_{J}\) as well as the host star's rotation rate (\(vsini_{*} = 55.6 \pm 1.8\) km/s). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 \(\pm\) 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.
We report the discovery of two transiting brown dwarfs (BDs), TOI-811b and TOI-852b, from NASA's Transiting Exoplanet Survey Satellite mission. These two transiting BDs have similar masses, but very ...different radii and ages. Their host stars have similar masses, effective temperatures, and metallicities. The younger and larger transiting BD is TOI-811b at a mass of \(M_b = 55.3 \pm 3.2{\rm M_J}\) and radius of \(R_b = 1.35 \pm 0.09{\rm R_J}\) and it orbits its host star in a period of \(P = 25.16551 \pm 0.00004\) days. Its age of \(93^{+61}_{-29}\) Myr, which we derive from an application of gyrochronology to its host star, is why this BD's radius is relatively large, not heating from its host star since this BD orbits at a longer orbital period than most known transiting BDs. This constraint on the youth of TOI-811b allows us to test substellar mass-radius isochrones where the radius of BDs changes rapidly with age. TOI-852b is a much older (4.0 Gyr from stellar isochrone models of the host star) and smaller transiting BD at a mass of \(M_b = 53.7 \pm 1.3{\rm M_J}\), a radius of \(R_b = 0.75 \pm 0.03{\rm R_J}\), and an orbital period of \(P = 4.94561 \pm 0.00008\) days. TOI-852b joins the likes of other old transiting BDs that trace out the oldest substellar mass-radius isochrones where contraction of the BD's radius asymptotically slows. Both host stars have a mass of \(M_\star = 1.32{\rm M_\odot}\pm0.05\) and differ in their radii, \(T_{\rm eff}\), and Fe/H with TOI-811 having \(R_\star=1.27\pm0.09{\rm R_\odot}\), \(T_{\rm eff} = 6107 \pm 77\)K, and \(\rm Fe/H = +0.40 \pm 0.09\) and TOI-852 having \(R_\star=1.71\pm0.04{\rm R_\odot}\), \(T_{\rm eff} = 5768 \pm 84\)K, and \(\rm Fe/H = +0.33 \pm 0.09\). We take this opportunity to examine how TOI-811b and TOI-852b serve as test points for young and old substellar isochrones, respectively.
We report the discovery of two short-period massive giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), were ...identified from the 30-minute cadence Full Frame Images and confirmed using ground-based photometric and spectroscopic follow-up observations from TESS's Follow-up Observing Program Working Group. We find that TOI-558 b, which transits an F-dwarf (\(M_{*}=1.349^{+0.064}_{-0.065}\ M_{\odot}\), \(R_{*}=1.496^{+0.042}_{-0.040}\ R_{\odot}\), \(T_{eff}=6466^{+95}_{-93}\ K\), age \(1.79^{+0.91}_{-0.73}\ Gyr\)) with an orbital period of 14.574 days, has a mass of \(3.61\pm0.15\ M_{\rm J}\), a radius of \(1.086^{+0.041}_{-0.038}\ R_{\rm J}\), and an eccentric (e=\(0.300^{+0.022}_{-0.020}\)) orbit. TOI-559 b transits a G-dwarf (\(M_{*}=1.026\pm0.057\ M_{\odot}\), \(R_{*}=1.233^{+0.028}_{-0.026}\ R_{\odot}\), \(T_{eff}=5925^{+85}_{-76}\ K\), age \(6.8^{+2.5}_{-2.0}\ Gyr\)) in an eccentric (e=\(0.151\pm0.011\)) 6.984-day orbit with a mass of \(6.01^{+0.24}_{-0.23}\ M_{\rm J}\) and a radius of \(1.091^{+0.028}_{-0.025}\ R_{\rm J}\). Our spectroscopic follow-up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive (\(>3\ M_{\rm J}\)), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited sample of transiting hot Jupiters, allowing for future detailed population studies.
We report the discovery of two intermediate-mass brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of \(P = 6.55604 ...\pm 0.00016\) days, a mass of \(M_b = 64.1 \pm 1.9 M_J\), and a radius of \(R_b = 0.75 \pm 0.02 R_J\). Its host star, TOI-569, has a mass of \(M_\star = 1.21 \pm 0.03 M_\odot\), a radius of \(R_\star = 1.47 \pm 0.03 R_\odot\), \(\rm Fe/H = +0.29 \pm 0.09\) dex, and an effective temperature of \(T_{\rm eff} = 5768 \pm 110K\). TOI-1406b has an orbital period of \(P = 10.57415 \pm 0.00063\) days, a mass of \(M_b =46.0 \pm 2.7 M_J\), and a radius of \(R_b = 0.86 \pm 0.03 R_J\). The host star for this BD has a mass of \(M_\star =1 .18 \pm 0.09 M_\odot\), a radius of \(R_\star = 1.35 \pm 0.03 R_\odot\), \( \rm Fe/H = -0.08 \pm 0.09\) dex and an effective temperature of \(T_{\rm eff} = 6290 \pm 100K\). Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of \(40-50 M_J\) and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b).Both BDs have reliable ages from stellar isochrones in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.
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.
