arXiv subjects

Mark S. Marley

Publications and source records attributed to Mark S. Marley.

At least 109 records · Page 6Linked to original sources

arXiv2019

First Resolved Scattered-Light Images of Four Debris Disks in Scorpius-Centaurus with the Gemini Planet Imager

We present the first spatially resolved scattered-light images of four debris disks around members of the Scorpius-Centaurus (Sco-Cen) OB Association with high-contrast imaging and polarimetry using the Gemini Planet Imager (GPI). All four disks are resolved for the first time in polarized light and one disk is also detected in total intensity. The three disks imaged around HD 111161, HD 143675, and HD 145560 are symmetric in both morphology and brightness distribution. The three systems span a range of inclinations and radial extents. The disk imaged around HD 98363 shows indications of asymmetries in morphology and brightness distribution, with some structural similarities to the HD 106906 planet-disk system. Uniquely, HD 98363 has a wide co-moving stellar companion Wray 15-788 with a recently resolved disk with very different morphological properties. HD 98363 A/B is the first binary debris disk system with two spatially resolved disks. All four targets have been observed with ALMA, and their continuum fluxes range from one non-detection to one of the brightest disks in the region. With the new results, a total of 15 A/F-stars in Sco-Cen have resolved scattered light debris disks, and approximately half of these systems exhibit some form of asymmetry. Combining the GPI disk structure results with information from the literature on millimeter fluxes and imaged planets reveals a diversity of disk properties in this young population. Overall, the four newly resolved disks contribute to the census of disk structures measured around A/F-stars at this important stage in the development of planetary systems.

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arXiv2019

Detecting and Characterizing Water Vapor in the Atmospheres of Earth Analogs through Observation of the 0.94 Micron Feature in Reflected Light

The characterization of rocky, Earth-like planets is an important goal for future large ground- and space-based telescopes. In support of developing an efficient observational strategy, we have applied Bayesian statistical inference to interpret the albedo spectrum of cloudy true-Earth analogs that include a diverse spread in their atmospheric water vapor mixing ratios. We focus on detecting water-bearing worlds by characterizing their atmospheric water vapor content via the strong 0.94$\,μ$m H$_2$O absorption feature, with several observational configurations. Water vapor is an essential signpost when assessing planetary habitability, and determining its presence is important in vetting whether planets are suitable for hosting life. We find that R=140 spectroscopy of the absorption feature combined with a same-phase green optical photometric point at $0.525-0.575\,μ$m is capable of distinguishing worlds with less than $0.1\times$ Earth-like water vapor levels from worlds with $1\times$ Earth-like levels or greater at a signal-to-noise ratio of 5 or better with $2σ$ confidence. This configuration can differentiate between $0.01\times$ and $0.1\times$ Earth-like levels when the signal-to-noise ratio is 10 or better at the same confidence. However, strong constraints on the water vapor mixing ratio remained elusive with this configuration even at signal-to-noise of 15. We find that adding the same-phase optical photometric point does not significantly help characterize the H$_2$O mixing ratio, but does enable an upper limit on atmospheric ozone levels. Finally, we find that a 0.94$\,μ$m photometric point, instead of spectroscopy, combined with the green-optical point, fails to produce meaningful information about atmospheric water content.

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arXiv2019

Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 $μ$m

As part of the PanCET program, we have conducted a spectroscopic study of WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a period of 3.66 days. Building on the original WASP and TRAPPIST photometry of Smalley et al (2012), we examine HST/WFC3 (1.125 - 1.650 $μ$m), Magellan/LDSS-3C (0.6 - 1 $μ$m) data, and Spitzer data (3.6 and 4.5 $μ$m). Using data from all three instruments, we constrain the water abundance to be --2.20 $\leq$ log(H$_2$O) $\leq$ --1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and H$^-$ in the atmospheric model. We also provide an updated ephemeris based on the Smalley, HST/WFC3, LDSS-3C, Spitzer, and TESS transit times. With the detectable water feature and its occupation of the clear/cloudy transition region of the temperature/gravity phase space, WASP-79b is a target of interest for the approved JWST Director's Discretionary Early Release Science (DD ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets have been approved for 78.1 hours of data collection, and with the delay in the JWST launch, WASP-79b is now a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hours in 4 different instrument modes, providing substantially more data by which to investigate this hot Jupiter.

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arXiv2019

An updated visual orbit of the directly-imaged exoplanet 51 Eridani b and prospects for a dynamical mass measurement with Gaia

We present a revision to the visual orbit of the young, directly-imaged exoplanet 51 Eridani b using four years of observations with the Gemini Planet Imager. The relative astrometry is consistent with an eccentric ($e=0.53_{-0.13}^{+0.09}$) orbit at an intermediate inclination ($i=136_{-11}^{+10}$\,deg), although circular orbits cannot be excluded due to the complex shape of the multidimensional posterior distribution. We find a semi-major axis of $11.1_{-1.3}^{+4.2}$\,au and a period of $28.1_{-4.9}^{+17.2}$\,yr, assuming a mass of 1.75\,M$_{\odot}$ for the host star. We find consistent values with a recent analysis of VLT/SPHERE data covering a similar baseline. We investigated the potential of using absolute astrometry of the host star to obtain a dynamical mass constraint for the planet. The astrometric acceleration of 51~Eri derived from a comparison of the {\it Hipparcos} and {\it Gaia} catalogues was found to be inconsistent at the 2--3$σ$ level with the predicted reflex motion induced by the orbiting planet. Potential sources of this inconsistency include a combination of random and systematic errors between the two astrometric catalogs or the signature of an additional companion within the system interior to current detection limits. We also explored the potential of using {\it Gaia} astrometry alone for a dynamical mass measurement of the planet by simulating {\it Gaia} measurements of the motion of the photocenter of the system over the course of the extended eight-year mission. We find that such a measurement is only possible ($>98$\% probability) given the most optimistic predictions for the {\it Gaia} scan astrometric uncertainties for bright stars, and a high mass for the planet ($\gtrsim3.6$\,M$_{\rm Jup}$).

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arXiv2019

Detection of a low-mass stellar companion to the accelerating A2IV star HR 1645

The $\sim500$\, Myr A2IV star HR 1645 has one of the most significant low-amplitude accelerations of nearby early-type stars measured from a comparison of the {\it Hipparcos} and {\it Gaia} astrometric catalogues. This signal is consistent with either a stellar companion with a moderate mass ratio ($q\sim0.5$) on a short period ($P<1$\,yr), or a substellar companion at a separation wide enough to be resolved with ground-based high contrast imaging instruments; long-period equal mass ratio stellar companions that are also consistent with the measured acceleration are excluded with previous imaging observations. The small but significant amplitude of the acceleration made HR 1645 a promising candidate for targeted searches for brown dwarf and planetary-mass companions around nearby, young stars. In this paper we explore the origin of the astrometric acceleration by modelling the signal induced by a wide-orbit M8 companion discovered with the Gemini Planet Imager, as well as the effects of an inner short-period spectroscopic companion discovered a century ago but not since followed-up. We present the first constraints on the orbit of the inner companion, and demonstrate that it is a plausible cause of the astrometric acceleration. This result demonstrates the importance of vetting of targets with measured astrometric acceleration for short-period stellar companions prior to conducting targeted direct imaging surveys for wide-orbit substellar companions.

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arXiv2019

Measuring the D/H Ratios of Exoplanets and Brown Dwarfs

The relative abundance of deuterium and hydrogen is a potent tracer of planet formation and evolution. Jupiter and Saturn have protosolar atmospheric D/H ratios, a relic of substantial gas accretion from the nebula, while the atmospheres of Neptune and Uranus are enhanced in D by accretion of ices into their envelopes. For terrestrial planets, D/H ratios are used to determine the mechanisms of volatile delivery and subsequent atmosphere loss over the lifetime of the planet. Planets and brown dwarfs more massive than 13 M_J quickly fuse their initial D reservoir. Here, we simulate spectra for giant exoplanets and brown dwarfs (2 M_Neptune to ~10 M_Jupiter) from Teff=200--1800 K including both CH3D and HDO to determine the observability of these dominant deuterium isotopologues in mid-infrared thermal emission spectra. Colder objects have stronger molecular features in their spectra, due to the temperature-dependence of molecular cross sections. CH3D is easier to observe than HDO at all temperatures considered, due to the strength of its absorption bands and locations of features at wavelengths with few other strong absorption features. We predict that for nearby cool brown dwarfs, the CH3D abundance can be measured at high signal-to-noise with the James Webb Space Telescope; for objects from 200--800 K closer than 10 pc, a protosolar D/H ratio would be readily observable in 2.5 hours. Moderately young Jupiter-mass planets (100--300 Myr) and young Neptunes (10 Myr) may be discovered with JWST and provide the best targets for detecting deuterium on an exoplanet in the coming decade. Future telescope designs should consider the importance of isotopes for understanding the formation and evolution of planetary atmospheres.

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arXiv2019

The Possible Astrometric Signature of a Planetary-mass Companion to the Nearby Young Star TW Piscis Austrini (Fomalhaut B): Constraints from Astrometry, Radial Velocities, and Direct Imaging

We present constraints on the presence of substellar companions to the nearby ($d\sim7.6$ pc), young ($440\pm40$ Myr) K4Ve star TW Piscis Austrini, the wide ($\sim$0.3 pc) companion to the A4V star Fomalhaut. We combined absolute astrometry from Hipparcos and Gaia with literature radial velocity measurements and dedicated high-contrast imaging observations obtained with Keck/NIRC2 to achieve sensitivity to brown dwarf and planetary-mass companions ($\gtrsim2$ M$_{\rm Jup}$) over many decades of orbital period ($\lesssim 10^3$ yr). The significant astrometric acceleration measured between the Hipparcos and Gaia catalogues, reported previously in the literature, cannot be explained by the orbital motion of TW PsA around the barycenter of the Fomalhaut triple system. Instead, we find that it is consistent with the reflex motion induced by an orbiting substellar companion. The combination of astrometry, radial velocities, and a deep $L^{\prime}$ imaging dataset leads to a constraint on the companion mass of $1.2_{-0.6}^{+0.7}$ M$_{\rm Jup}$. However, the period of the companion is poorly constrained, with a highly multi-modal period posterior distribution due to aliasing with the 24.25 year baseline between Hipparcos and Gaia. If confirmed through continued astrometric or spectroscopic monitoring, or via direct detection, the companion to TW PsA would represent a choice target for detailed atmospheric characterization with high-contrast instruments on the upcoming James Webb Space Telescope and Wide Field Infrared Survey Telescope.

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arXiv2019

Asymmetries in adaptive optics point spread functions

An explanation for the origin of asymmetry along the preferential axis of the PSF of an AO system is developed. When phase errors from high altitude turbulence scintillate due to Fresnel propagation, wavefront amplitude errors may be spatially offset from residual phase errors. These correlated errors appear as asymmetry in the image plane under the Fraunhofer condition. In an analytic model with an open-loop AO system, the strength of the asymmetry is calculated for a single mode of phase aberration, which generalizes to two dimensions under a Fourier decomposition of the complex illumination. Other parameters included are the spatial offset of the AO correction, which is the wind velocity in the frozen flow regime multiplied by the effective AO time delay, and propagation distance or altitude of the turbulent layer. In this model, the asymmetry is strongest when the wind is slow and nearest to the coronagraphic mask when the turbulent layer is far away, such as when the telescope is pointing low towards the horizon. A great emphasis is made about the fact that the brighter asymmetric lobe of the PSF points in the opposite direction as the wind, which is consistent analytically with the clarification that the image plane electric field distribution is actually the inverse Fourier transform of the aperture plane. Validation of this understanding is made with observations taken from the Gemini Planet Imager, as well as being reproducible in end-to-end AO simulations.

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arXiv2019

An Empirical Mass-Radius Relation for Cool Giant Planets

Probabilistic relationships between the mass and radius of planets are useful for a variety of purposes, including estimating the yields of planet discovery efforts and the radii of discovered planets given their masses. Previous work on giant planets often do not make the important distinction between cool and (inflated) hot giants. This can lead to needlessly large uncertainties and overestimated radii for the cooler objects. Using hierarchical bayesian modeling and the AIC model selection criterion, we identify an empirical mass-radius relationship for cool giant planets above 15 Earth masses. It takes the form of a quadratic function in log mass, with a power-law dispersion. Parametric uncertainties from MCMC are provided, and we compare our results with the outputs of interior structure models and the radii of the solar system giant planets, which fit comfortably within our relation.

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arXiv2019

Cloud Atlas: Variability in and out of the Water Band in the Planetary-mass HD 203030B Points to Cloud Sedimentation in Low-gravity L Dwarfs

We use the Wide Field Camera 3 on the {\sl Hubble Space Telescope} to spectrophotometrically monitor the young L7.5 companion HD~203030B. Our time series reveal photometric variability at 1.27\,$μ$m and 1.39\,$μ$m on time scales compatible with rotation. We find a rotation period of $7.5^{+0.6}_{-0.5}$ h: comparable to those observed in other brown dwarfs and planetary-mass companions younger than 300 Myr. We measure variability amplitudes of $1.1\pm0.3\%$ (1.27\,$μ$m) and $1.7\pm0.4\%$ (1.39\,$μ$m), and a phase lag of 56$^\circ\pm$28$^\circ$ between the two light curves. We attribute the difference in photometric amplitudes and phases to a patchy cloud layer that is sinking below the level where water vapor becomes opaque. HD 203030B and the few other known variable young late-L dwarfs are unlike warmer (earlier-type and/or older) L dwarfs, for which variability is much less wavelength-dependent across the 1.1--1.7$μ$m region. We further suggest that a sinking of the top-most cloud deck below the level where water or carbon monoxide gas become opaque may also explain the often enhanced variability amplitudes of even earlier-type low-gravity L dwarfs. Because these condensate and gas opacity levels are already well-differentiated in T dwarfs, we do not expect the same variability amplitude enhancement in young vs.\ old T dwarfs.

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arXiv2019

3.8um Imaging of 400-600K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB

Half of the energy emitted by late-T- and Y-type brown dwarfs emerges at 3.5 < lambda um < 5.5. We present new L' (3.43 < lambda um < 4.11) photometry obtained at the Gemini North telescope for nine late-T and Y dwarfs, and synthesize L' from spectra for an additional two dwarfs. The targets include two binary systems which were imaged at a resolution of 0.25". One of these, WISEP J045853.90+643452.6AB, shows significant motion, and we present an astrometric analysis of the binary using Hubble Space Telescope, Keck Adaptive Optics, and Gemini images. We compare lambda ~4um observations to models, and find that the model fluxes are too low for brown dwarfs cooler than ~700K. The discrepancy increases with decreasing temperature, and is a factor of ~2 at T_eff=500K and ~4 at T_eff=400K. Warming the upper layers of a model atmosphere generates a spectrum closer to what is observed. The thermal structure of cool brown dwarf atmospheres above the radiative-convective boundary may not be adequately modelled using pure radiative equilibrium; instead heat may be introduced by thermochemical instabilities (previously suggested for the L- to T-type transition) or by breaking gravity waves (previously suggested for the solar system giant planets). One-dimensional models may not capture these atmospheres, which likely have both horizontal and vertical pressure/temperature variations.

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arXiv2019

Spitzer Phase Curves of KELT-1b and the Signatures of Nightside Clouds in Thermal Phase Observations

We observed two full orbital phase curves of the transiting brown dwarf KELT-1b, at 3.6um and 4.5um, using the Spitzer Space Telescope. Combined with previous eclipse data from Beatty et al. (2014), we strongly detect KELT-1b's phase variation as a single sinusoid in both bands, with amplitudes of $964\pm36$ ppm at 3.6um and $979\pm54$ ppm at 4.5um, and confirm the secondary eclipse depths measured by Beatty et al. (2014). We also measure noticeable Eastward hotspot offsets of $28.4\pm3.5$ degrees at 3.6um and $18.6\pm5.2$ degrees at 4.5um. Both the day-night temperature contrasts and the hotspot offsets we measure are in line with the trends seen in hot Jupiters (e.g., Crossfield 2015), though we disagree with the recent suggestion of an offset trend by Zhang et al. (2018). Using an ensemble analysis of Spitzer phase curves, we argue that nightside clouds are playing a noticeable role in modulating the thermal emission from these objects, based on: 1) the lack of a clear trend in phase offsets with equilibrium temperature, 2) the sharp day-night transitions required to have non-negative intensity maps, which also resolves the inversion issues raised by Keating & Cowan (2017), 3) the fact that all the nightsides of these objects appear to be at roughly the same temperature of 1000K, while the dayside temperatures increase linearly with equilibrium temperature, and 4) the trajectories of these objects on a Spitzer color-magnitude diagram, which suggest colors only explainable via nightside clouds.

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arXiv2019

The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation

We present HST near-ultraviolet (NUV) transits of the hot Jupiter WASP-121b, acquired as part of the PanCET program. Time series spectra during two transit events were used to measure the transmission spectra between 2280 and 3070 Angstroms at a resolution of 30,000. Using HST data from 61 STIS visits, we show that data from HST's Pointing Control System can be used to decorrelate the instrument systematic errors (Jitter Decorrelation), which we used to fit the WASP-121b light curves. The NUV spectrum show very strong absorption features, with the NUV white light curve found to be larger than the average optical and near-infrared value at 6-$σ$ confidence. We identify and spectrally resolve absorption from the Mg ii doublet in the planetary exosphere at a 5.9-$σ$ confidence level. The Mg ii doublet is observed to reach altitudes of $R_{pl}/R_{star}=0.284\pm0.037$ for the 2796 Angstrom line and $0.242\pm0.0431$ in the 2804 Angstrom line, which exceeds the Roche lobe size as viewed in transit geometry ($R_{\rm eqRL}/R_{star}$ = 0.158). We also detect and resolve strong features of the Fe ii UV1 and UV2 multiplets, and observe the lines reaching altitudes of $R_{pl}/R_{star}\approx0.3$. At these high altitudes, the atmospheric Mg ii and Fe ii gas is not gravitationally bound to the planet, and these ionized species may be hydrodynamically escaping or could be magnetically confined. Refractory Mg and Fe atoms at high altitudes also indicates that these species are not trapped into condensate clouds at depth, which places constraints on the deep interior temperature.

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arXiv2019

An emission spectrum for WASP-121b measured across the 0.8-1.1 micron wavelength range using the Hubble Space Telescope

WASP-121b is a transiting gas giant exoplanet orbiting close to its Roche limit, with an inflated radius nearly double that of Jupiter and a dayside temperature comparable to a late M dwarf photosphere. Secondary eclipse observations covering the 1.1-1.6 micron wavelength range have revealed an atmospheric thermal inversion on the dayside hemisphere, likely caused by high altitude absorption at optical wavelengths. Here we present secondary eclipse observations made with the Hubble Space Telescope Wide Field Camera 3 spectrograph that extend the wavelength coverage from 1.1 micron down to 0.8 micron. To determine the atmospheric properties from the measured eclipse spectrum, we performed a retrieval analysis assuming chemical equilibrium, with the effects of thermal dissociation and ionization included. Our best-fit model provides a good fit to the data with reduced chi^2=1.04. The data diverge from a blackbody spectrum and instead exhibit emission due to H- shortward of 1.1 micron. The best-fit model does not reproduce a previously reported bump in the spectrum at 1.25 micron, possibly indicating this feature is a statistical fluctuation in the data rather than a VO emission band as had been tentatively suggested. We estimate an atmospheric metallicity of [M/H]=1.09(-0.69,+0.57), and fit for the carbon and oxygen abundances separately, obtaining [C/H]=-0.29(-0.48,+0.61) and [O/H]=0.18(-0.60,+0.64). The corresponding carbon-to-oxygen ratio is C/O=0.49(-0.37,+0.65), which encompasses the solar value of 0.54, but has a large uncertainty.

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arXiv2019

Exoplanet Reflected Light Spectroscopy with PICASO

Here we present the first open-source radiative transfer model for computing the reflected light of exoplanets at any phase geometry, called PICASO: Planetary Intensity Code for Atmospheric Scattering Observations. This code, written in Python, has heritage from a decades old, well-known Fortran model used for several studies of planetary objects within the Solar System and beyond. We have adopted it to include several methodologies for computing both direct and diffuse scattering phase functions, and have added several updates including the ability to compute Raman scattering spectral features. Here we benchmark PICASO against two independent codes and discuss the degree to which the model is sensitive to a user's specification for various phase functions. Then, we conduct a full information content study of the model across a wide parameter space in temperature, cloud profile, SNR and resolving power.

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arXiv2019

The Need for Laboratory Measurements and Ab Initio Studies to Aid Understanding of Exoplanetary Atmospheres

We are now on a clear trajectory for improvements in exoplanet observations that will revolutionize our ability to characterize their atmospheric structure, composition, and circulation, from gas giants to rocky planets. However, exoplanet atmospheric models capable of interpreting the upcoming observations are often limited by insufficiencies in the laboratory and theoretical data that serve as critical inputs to atmospheric physical and chemical tools. Here we provide an up-to-date and condensed description of areas where laboratory and/or ab initio investigations could fill critical gaps in our ability to model exoplanet atmospheric opacities, clouds, and chemistry, building off a larger 2016 white paper, and endorsed by the NAS Exoplanet Science Strategy report. Now is the ideal time for progress in these areas, but this progress requires better access to, understanding of, and training in the production of spectroscopic data as well as a better insight into chemical reaction kinetics both thermal and radiation-induced at a broad range of temperatures. Given that most published efforts have emphasized relatively Earth-like conditions, we can expect significant and enlightening discoveries as emphasis moves to the exotic atmospheres of exoplanets.

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arXiv2019

Performance of the Gemini Planet Imager Non-Redundant Mask and spectroscopy of two close-separation binaries HR 2690 and HD 142527

The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM), enabling interferometric resolution in complement to its coronagraphic capabilities. The NRM operates both in spectroscopic (integral field spectrograph, henceforth IFS) and polarimetric configurations. NRM observations were taken between 2013 and 2016 to characterize its performance. Most observations were taken in spectroscopic mode with the goal of obtaining precise astrometry and spectroscopy of faint companions to bright stars. We find a clear correlation between residual wavefront error measured by the AO system and the contrast sensitivity by comparing phase errors in observations of the same source, taken on different dates. We find a typical 5-$σ$ contrast sensitivity of $2-3~\times~10^{-3}$ at $\simλ/D$. We explore the accuracy of spectral extraction of secondary components of binary systems by recovering the signal from a simulated source injected into several datasets. We outline data reduction procedures unique to GPI's IFS and describe a newly public data pipeline used for the presented analyses. We demonstrate recovery of astrometry and spectroscopy of two known companions to HR 2690 and HD 142527. NRM+polarimetry observations achieve differential visibility precision of $σ\sim0.4\%$ in the best case. We discuss its limitations on Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects for future upgrades. We summarize lessons learned in observing with NRM in spectroscopic and polarimetric modes.

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arXiv2019

The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU

We present a statistical analysis of the first 300 stars observed by the Gemini Planet Imager Exoplanet Survey (GPIES). This subsample includes six detected planets and three brown dwarfs; from these detections and our contrast curves we infer the underlying distributions of substellar companions with respect to their mass, semi-major axis, and host stellar mass. We uncover a strong correlation between planet occurrence rate and host star mass, with stars M $>$ 1.5 $M_\odot$ more likely to host planets with masses between 2-13 M$_{\rm Jup}$ and semi-major axes of 3-100 au at 99.92% confidence. We fit a double power-law model in planet mass (m) and semi-major axis (a) for planet populations around high-mass stars (M $>$ 1.5M$_\odot$) of the form $\frac{d^2 N}{dm da} \propto m^αa^β$, finding $α$ = -2.4 $\pm$ 0.8 and $β$ = -2.0 $\pm$ 0.5, and an integrated occurrence rate of $9^{+5}_{-4}$% between 5-13 M$_{\rm Jup}$ and 10-100 au. A significantly lower occurrence rate is obtained for brown dwarfs around all stars, with 0.8$^{+0.8}_{-0.5}$% of stars hosting a brown dwarf companion between 13-80 M$_{\rm Jup}$ and 10-100 au. Brown dwarfs also appear to be distributed differently in mass and semi-major axis compared to giant planets; whereas giant planets follow a bottom-heavy mass distribution and favor smaller semi-major axes, brown dwarfs exhibit just the opposite behaviors. Comparing to studies of short-period giant planets from the RV method, our results are consistent with a peak in occurrence of giant planets between ~1-10 au. We discuss how these trends, including the preference of giant planets for high-mass host stars, point to formation of giant planets by core/pebble accretion, and formation of brown dwarfs by gravitational instability.

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