Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System
Jordan M. Stone, Andrew J. Skemer, Kaitlin M. Kratter, Trent J. Dupuy, Laird M. Close, Josh A. Eisner, Jonathan J. Fortney, Philip M. Hinz, Jared R. Males, Caro… 展开作者
Jordan M. Stone, Andrew J. Skemer, Kaitlin M. Kratter, Trent J. Dupuy, Laird M. Close, Josh A. Eisner, Jonathan J. Fortney, Philip M. Hinz, Jared R. Males, Caroline V. Morley, Katie M. Morzinski, Kimberly Ward-Duong
Recently, Gauza et al. (2015) reported the discovery of a companion to the late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute photometry suggests its mass and atmosphere are similar to the HR 8799 planets. However, as a wide companion to a late-type star, it is more accessible to spectroscopic characterization. We discovered that the primary of this system is an equal-magnitude binary. For an age $\sim300$ Myr the A and B components each have a mass of $64.6^{+0.8}_{-2.0}~M_{\mathrm{Jup}}$, and the b component has a mass of $11.2^{+9.7}_{-1.8}$, making VHS 1256-1257 only the third brown dwarf triple system. There exists some tension between the spectrophotometric distance of $17.2\pm2.6$ pc and the parallax distance of $12.7\pm1.0$ pc. At 12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are even faint outliers among M8 types. If the larger spectrophotmetric distance is more accurate than the parallax, then the mass of each component increases. In particular, the mass of the b component increases well above the deuterium burning limit to $\sim35~M_{\mathrm{Jup}}$ and the mass of each binary component increases to $73^{+20}_{-17}~M_{\mathrm{Jup}}$. At 17.1 pc, the UVW kinematics of the system are consistent with membership in the AB~Dor moving group. The architecture of the system resembles a hierarchical stellar multiple suggesting it formed via an extension of the star-formation process to low masses. Continued astrometric monitoring will resolve this distance uncertainty and will provide dynamical masses for a new benchmark system.
Rotationally-modulated variability of brown dwarfs and giant planets provides unique information about their surface brightness inhomogeneities, atmospheric circulation, cloud evolution, vertical atmospheric structure, and rotational angular momentum. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared time-series spectroscopic observations of three companions with masses in or near the planetary regime: VHS J125601.92-125723.9 b, GSC 6214-210 B, and ROXs 42 B b. VHS J1256-1257 b exhibits strong total intensity and spectral variability with a brightness difference o…
Photometric and spectral variability of brown dwarfs probes heterogeneous temperature and cloud distribution and traces the atmospheric circulation patterns. We present a new 42-hr Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectral time series of VHS 1256$-$1257 b, a late L-type planetary-mass companion that has been shown to have one of the highest variability amplitudes among substellar objects. The light curve is rapidly evolving and best-fit by a combination of three sine waves with different periods and a linear trend. The amplitudes of the sine waves and the linear slope vary…
We present new parallax measurements from the CFHT Infrared Parallax Program and the Pan-STARRS 3$π$ Steradian Survey for the young ($\approx150-300$ Myr) triple system VHS J125601.92$-$125723.9. This system is composed of a nearly equal-flux binary ("AB") and a wide, possibly planetary-mass companion ("b"). The system's published parallactic distance ($12.7\pm1.0$ pc) implies absolute magnitudes unusually faint compared to known young objects and is in tension with the spectrophotometric distance for the central binary ($17.2\pm2.6$ pc). Our CFHT and Pan-STARRS parallaxes are consistent, and …
Multi-wavelength time-resolved observations of rotationally modulated variability from brown dwarfs and giant exoplanets are the most effective method for constraining their heterogeneous atmospheric structures. In a companion paper (Bowler et al. 2020), we reported the discovery of strong near-infrared variability in HST/WFC3/G141 light curves of the very red L-dwarf companion VHS J1256-1257b. In this paper, we present a follow-up 36-hr Spitzer/IRAC Channel 2 light curve together with an in-depth analysis of the HST and the Spitzer data. The combined dataset provides time-resolved light curve…
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
The discovery of 9 new brown-dwarf candidates orbiting stars in the CORALIE and HARPS radial-velocity surveys is reported. New CORALIE radial velocities yielding accurate orbits of 6 previously-known hosts of potential brown-dwarf companions are presented. Including targets selected from the literature, 33 hosts of potential brown-dwarf companions are examined. Employing innovative methods, we use the new reduction of the Hipparcos data to fully characterise the astrometric orbits of 6 objects, revealing M-dwarf companions with masses between 90 M_Jup and 0.52 M_Sun. Additionally, the masses o…
We have combined multi-epoch images from the Infrared Side Port Imager on the CTIO 4-meter telescope to derive a 3-sigma limit of J=21.7 for the ultra cool brown dwarf companion to WD 0806-661 (GJ 3483). We find that J-[4.5]>4.95, redder than any other brown dwarf known to date. With theoretical evolutionary models and ages 1.5-2.7 Gyr, we estimate the brown dwarf companion to have mass <10-13 Jupiter masses and temperature <400 K, providing evidence that this is among the coolest brown dwarfs currently known. The range of masses for this object is consistent with that anticipated from Jeans-m…
Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~ 0.05M* secondary, and new observations of GD 1400 which show that it too is a close, post-comon envelope system. We also present the lat- est results in a near-infrared photometric search for unresolved ultracool companions and to white dwarfs with UKIDSS. Twenty five DA white dwarfs were identified as having photometric excesses indicative of a low mass compani…
The orbital eccentricities of directly imaged exoplanets and brown dwarf companions provide clues about their formation and dynamical histories. We combine new high-contrast imaging observations of substellar companions obtained primarily with Keck/NIRC2 together with astrometry from the literature to test for differences in the population-level eccentricity distributions of 27 long-period giant planets and brown dwarf companions between 5-100 AU using hierarchical Bayesian modeling. Orbit fits are performed in a uniform manner for companions with short orbital arcs; this typically results in …
We present simultaneous 0.65-2.5 microns medium resolution (3300 < R < 8100) VLT/X-Shooter spectra of the young low-mass (19+/-5MJup) L-T transition object VHS 1256-1257 b, a known spectroscopic analogue of HR8799d. The companion is a prime target for the JWST Early Release Science (ERS) and one of the highest-amplitude variable brown-dwarf known to date. We compare the spectrum to the custom grids of cloudless ATMO models exploring different atmospheric composition with the Bayesian inference tool ForMoSA. We also re-analyze low-resolution HST/WFC3 1.10-1.67 microns spectra at minimum and max…
In this paper, we determine the detectability of eclipsing binary star companions from eclipse timing variations using the Kepler mission dataset. Extensive and precise stellar time-series photometry from space-based missions enable searches for binary star companions. However, due to the large datasets and computational resources involved, these searches would benefit from guidance from detection simulations. Our simulations start with and benefit from the use of empirical Kepler mission data, into which we inject third bodies to predict the resulting timing of binary star eclipses. We find t…
We report the discovery of a transiting brown dwarf companion to KOI-205, a K0 main-sequence star, in a 11.720125-day period orbit. The transits were detected by the Kepler space telescope, and the reflex motion of the star was measured using radial velocity observations obtained with the SOPHIE spectrograph. The atmospheric parameters of the host stars were determined from the analysis of high-resolution, high signal-to-noise ratio ESPaDOns spectra obtained for this purpose. Together with spectrophotometric measurements recovered from the literature, these spectra indicate that the star is a …
Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ~5 AU in the mass range of ~10 - 80 M$_{\text{Jup}}$. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help asses the reality of the desert and provide insight to the formation and evolution of these objects. Here we present 10 new brown dwarf and two low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digit…
We present a high-contrast imaging survey of intermediate-mass (1.75--4.5 $M_\odot$) stars to search for the most extreme stellar binaries, i.e., for the lowest mass stellar companions. Using adaptive optics at the Lick and Gemini observatories, we observed 169 stars and detected 24 candidates companions, 16 of which are newly discovered and all but three are likely or confirmed physical companions. Despite obtaining sensitivity down to the substellar limit for 75\% of our sample, we do not detect any companion below 0.3 $M_\odot$, strongly suggesting that the distribution of stellar companion…
The last decade of direct imaging (DI) searches for sub-stellar companions has uncovered a widely diverse sample that challenges the current formation models, while highlighting the intrinsically low occurrence rate of wide companions, especially at the lower end of the mass distribution. These results clearly show how blind surveys, crucial to constrain the underlying planet and sub-stellar companion population, are not an efficient way to increase the sample of DI companions. It is therefore becoming clear that efficient target selection methods are essential to ensure a larger number of det…
We study the evolution of the orbit of a planetary companion as the primary star evolves during the red giant branch phase. Our aim is to determine a prescription for the capture radius and capture timescales for companions in a wide range of masses, from planet to star, including the effect of a non constant f parameter. Our initial results reproduce past findings. According to our study the mass-loss during the red giant branch does not significantly affect the semi major axis of the planet and for a 1.5 M star the capture radius is approximately 300 R or 1.4 AU.
Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-year radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass orbiting solar-type stars with periods longer than ten years. An upper ma…
The formation of hot subdwarf stars (sdBs), which are core helium-burning stars located on the extended horizontal branch, is still not understood. Many of the known hot subdwarf stars reside in close binary systems with short orbital periods between a few hours and a few days with either M star or white dwarf companions. Common envelope ejection is the most probable formation channel. Among these, eclipsing systems are of special importance because it is possible to constrain the parameters of both components tightly by combining spectroscopic and light curve analyses. We report the discovery…
We used the Magellan adaptive optics (MagAO) system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and Ys. With our new photometry and Teff~2500 K derived from the shape its K-band spectrum, we find that CT Cha B has Av = 3.4+/-1.1 mag, and a mass of 14-24 Mj according to the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r' detection indicates that the companion has significant Halpha emission and a mass accretion rate ~6*10^-10 Msun/yr, similar to so…
The mass domain where massive extrasolar planets and brown dwarfs overlap is still poorly understood due to the paucity of brown dwarfs orbiting close to solar-type stars, the so-called brown dwarf desert. In this paper we collect all of available data about close brown dwarfs around solar type stars and their host stars from literature and study the demographics of the brown dwarf desert. The data clearly show a short period and a medium mass gap in the brown dwarf period-mass distribution diagram ($ 35<m\sin i<55 M_{\rm Jup}$ and $P<100$ days), representing the "driest land" in the brown dwa…
We present the discovery of a substellar companion to the primary host lens in the microlensing event MOA-2012-BLG-006. The companion-to-host mass ratio is 0.016, corresponding to a companion mass of $\approx8~M_{\rm Jup} (M_*/0.5M_\odot)$. Thus, the companion is either a high-mass giant planet or a low-mass brown dwarf, depending on the mass of the primary $M_*$. The companion signal was separated from the peak of the primary event by a time that was as much as four times longer than the event timescale. We therefore infer a relatively large projected separation of the companion from its host…
In recent years there have been many attempts to characterize the occurrence of stellar, BD and planetary-mass companions to solar-type stars, with the aim of constraining formation mechanisms. From RV observations a dearth of companions with masses between 10-40 MJup has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range. We present a model for the substellar companion mass function (CMF). It consists of the superposition of the planet and BD companion mass distributions, assuming that we can extrapolate the R…
We present the discovery and spectroscopy of HIP 75056Ab, a companion directly imaged at a very small separation of 0.125 arcsec to an A2V star in the Scorpius-Centaurus OB2 association. Our observations utilized VLT/SPHERE between 2015$-$2019, enabling low-resolution spectroscopy (0.95$-$1.65 $μm$), dual-band imaging (2.1$-$2.25 $μm$), and relative astrometry over a four-year baseline. HIP 75056Ab is consistent with spectral types in the range of M6$-$L2 and $T_{\rm eff}\sim$ 2000$-$2600 K. A comparison of the companion's brightness to evolutionary tracks suggests a mass of $\sim$20$-$30 M$_{…
We report the discovery of a substellar companion around the giant star HIP67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP67537$\,b$: m$_b$sin$i$ = 11.1$^{+0.4}_{-1.1}$ M$_{\rm {\tiny jup}}$, $a$ = 4.9$^{+0.14}_{-0.13}$ AU and $e$ = 0.59$^{+0.05}_{-0.02}$. Considering random inclination angles, this object has $\gtrsim$ 65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf transition region. In add…
Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
Northwestern University（西北大学）；California Institute of Technology（加州理工学院）；University of California, Los Angeles（加州大学洛杉矶分校）；University of California, San Diego（加州大学圣地亚哥分校）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
The determination of the fundamental properties (mass, separation, age, gravity and atmospheric properties) of brown dwarf companions allows us to infer crucial informations on their formation and evolution mechanisms. Spectroscopy of substellar companions is available to date only for a limited number of objects (and mostly at very low resolution, R<50) because of technical limitations, i.e., contrast and angular resolution. We present medium resolution (R=350), coronagraphic long-slit spectroscopic observations with SPHERE of two substellar companions, HD 1160 B and HD 19467 B. We found that…
We present the discovery of a substellar companion on a wide orbit around the ~2.5 Msun star HIP 78530, which is a member of the 5 Myr-old Upper Scorpius association. We have obtained follow-up imaging over two years and show that the companion and primary share common proper motion. We have also obtained JHK spectroscopy of the companion and confirm its low surface gravity, in accordance with the young age of the system. A comparison with Drift-Phoenix synthetic spectra indicates an effective temperature of 2800+/-200 K and a comparison with template spectra of young and old dwarfs indicates …
The discovery of the first methane brown dwarf provides a framework for describing the important advances in both fundamental physics and astrophysics that are due to the study of companions of stars. I present a few highlights of the history of this subject along with details of the discovery of the brown dwarf Gliese 229B. The nature of companions of stars is discussed with an attempt to avoid biases induced by anthropocentric nomenclature. With the newer types of remote reconnaissance of nearby stars and their systems of companions, an exciting and perhaps even more profound set of contribu…
Time-resolved observations of brown dwarfs' rotational modulations provide powerful insights into the properties of condensate clouds in ultra-cool atmospheres. Multi-wavelength light curves reveal cloud vertical structures, condensate particle sizes, and cloud morphology, which directly constrain condensate cloud and atmospheric circulation models. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared G141 taken in six consecutive orbits observations of HN Peg B, an L/T transition brown dwarf companion to a G0V type star. The best-fit sine wave to the $1.1-1.7μ$m bro…
Benchmark Brown Dwarf Systems I: Chemical Abundance Analysis of FGK Stars with Wide-Separation Brown Dwarf Companions Using PEPSI
University of California, Santa Cruz（加州大学圣克鲁兹分校）；Flatiron Institute（平顿研究所）；University of Utah（犹他大学）；The Ohio State University（俄亥俄州立大学）；California Institute of Technology（加州理工学院）；University of Colorado（科罗拉多大学）；American Museum of Natural History（美国自然历史博物馆）；City University of New York（纽约市立大学）；Hunter College, City University of New York（纽约市立大学亨特学院）
Aims. The project aims to understand better the role of wide brown dwarf companions on planetary systems. Methods. We obtained high-resolution spectra of six bright stars with co-moving wide substellar companions with the SONG, CARMENES, and STELLA high-resolution spectrographs. We used these spectra to derive radial velocities together with a complete set of stellar physical parameters. We then investigated radial velocities signals and discussed the fraction of planets in such systems. We also re-analyzed the ages of our targets, which were used to derive the physical parameters of wide brow…
Host-star metallicities and kinematics of directly imaged brown-dwarf companions
Università degli Studi di Milano（米兰大学）；Indian Institute of Astrophysics（印度天体物理研究所）；Visvesvaraya Technological University（维斯瓦纳塔亚理工大学）；Vikram Sarabhai Space Centre, ISRO（印度空间研究组织维克拉姆·萨拉巴伊太空中心）；St. Albert’s College（圣阿尔伯特学院）；European Southern Observatory（欧洲南方天文台）；Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology, Dhanbad（印度理工学院丹巴德分校）；Pontificia Universidad Católica de Chile（智利天主教 Pontificia 大学）
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 target…
HD 81817 is known as a hybrid star. Hybrid stars have both cool stellar wind properties and Ultraviolet (UV) or even X-ray emission features of highly ionized atoms in their spectra. A white dwarf companion has been suggested as the source of UV or X-ray features. HD 81817 has been observed since 2004 as a part of a radial velocity (RV) survey program to search for exoplanets around K giant stars using the Bohyunsan Observatory Echelle Spectrograph at the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained 85 RV measurements between 2004 and 2019 for HD 81817 and f…
We report the discovery of a low-mass companion to HR3549, an A0V star surrounded by a debris disk with a warm excess detected by WISE at 22 $μ$m ($10σ$ significance). We imaged HR3549 B in the L-band with NAOS-CONICA, the adaptive optics infrared camera of the Very Large Telescope, in January 2013 and confirmed its common proper motion in January 2015. The companion is at a projected separation of $\simeq 80$ AU and position angle of $\simeq 157^\circ$, so it is orbiting well beyond the warm disk inner edge of $r > 10$ AU. Our age estimate for this system corresponds to a companion mass in th…
We analyse FORS2/VLT $I$-band imaging data to monitor the motions of both components in the nearest known binary brown dwarf WISE J104915.57-531906.1AB (LUH16) over one year. The astrometry is dominated by parallax and proper motion, but with a precision of $\sim$0.2 milli-arcsecond per epoch we accurately measure the relative position change caused by the orbital motion of the pair. This allows us to directly measure a mass ratio of $q=0.78\pm0.10$ for this system. We also search for the signature of a planetary-mass companion around either of the A and B component and exclude at 3-$σ$ the pr…
The Companions to B and A Stars Snapshot (C-BASS) Survey: I. Discovery of a Young Brown Dwarf Companion to HIP 17453
University of Notre Dame（圣母大学）；Arizona State University（亚利桑那州立大学）；New Mexico State University（新墨西哥州立大学）；European Southern Observatory（欧洲南方天文台）；Northern Arizona University（北亚利桑那大学）；University of California San Diego（加州大学圣地亚哥分校）
Context: We studied numerically the formation of giant planet (GP) and brown dwarf (BD) embryos in gravitationally unstable protostellar disks and compared our findings with directly-imaged, wide-orbit (>= 50 AU) companions known to-date. The viability of the disk fragmentation scenario for the formation of wide-orbit companions in protostellar disks around (sub-)solar mass stars was investigated. Methods: We used numerical hydrodynamics simulations of disk formation and evolution with an accurate treatment of disk thermodynamics. The use of the thin-disk limit allowed us to probe the long-ter…
We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of ~100 Myr, not with the 1 Gyr age proposed from astroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the astroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs.
The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose we utilized VLT/NACO to take several well calibrated high resolution images of 6 target systems and analyze them t…
Bayesian atmospheric retrieval tools can place constraints on the properties of brown dwarfs and hot Jupiters atmospheres. To fully exploit these methods, high signal-to-noise spectral libraries with well-understood uncertainties are essential. We present a high signal-to-noise spectral library (1.10-1.69 microns) of the thermal emission of 76 brown dwarfs and hot Jupiters. All our spectra have been acquired with the Hubble Space Telescope's Wide Field Camera 3 instrument and its G141 grism. The near-infrared spectral types of these objects range from L4 to Y1. Eight of our targets have estima…
Observations of rotational modulations of brown dwarfs and giant exoplanets allow the characterization of condensate cloud properties. As of now rotational spectral modulations have only been seen in three L-type brown dwarfs. We report here the discovery of rotational spectral modulations in LP261-75B, an L6-type intermediate surface gravity companion to an M4.5 star. As a part of the Cloud Atlas Treasury program we acquired time-resolved Wide Field Camera 3 grism spectroscopy (1.1--1.69~$μ$m) of LP261-75B. We find gray spectral variations with the relative amplitude displaying only a weak wa…
We present comprehensive orbital analyses and dynamical masses for the substellar companions Gl~229~B, Gl~758~B, HD~13724~B, HD~19467~B, HD~33632~Ab, and HD~72946~B. Our dynamical fits incorporate radial velocities, relative astrometry, and most importantly calibrated Hipparcos-Gaia EDR3 accelerations. For HD~33632~A and HD~72946 we perform three-body fits that account for their outer stellar companions. We present new relative astrometry of Gl~229~B with Keck/NIRC2, extending its observed baseline to 25 years. We obtain a $<$1\% mass measurement of $71.4 \pm 0.6\,M_{\rm Jup}$ for the first T …
Using astrometric measurements obtained with the FORS2/VLT camera, we are searching for low-mass companions around 20 nearby ultracool dwarfs. With a single-measurement precision of 0.1 milli-arcseconds, our survey is sensitive to a wide range of companion masses from planetary companions to binary systems. Here, we report the discovery and orbit characterisation of a new ultracool binary at a distance of 19.5 pc from Earth that is composed of the M8.5-dwarf primary DE0630-18 and a substellar companion. The nearly edge-on orbit is moderately eccentric (e=0.23) with an orbital period of 1120 d,…
We present the discovery of a planetary-mass companion to CFHTWIR-Oph 98, a low-mass brown dwarf member of the young Ophiuchus star-forming region, with a wide 200-au separation (1.46 arcsec). The companion was identified using Hubble Space Telescope images, and confirmed to share common proper motion with the primary using archival and new ground-based observations. Based on the very low probability of the components being unrelated Ophiuchus members, we conclude that Oph 98 AB forms a binary system. From our multi-band photometry, we constrain the primary to be an M9-L1 dwarf, and the faint …
Recent studies have shown that close-in brown dwarfs in the mass range 35-55 M$_{\rm Jup}$ are almost depleted as companions to stars, suggesting that objects with masses above and below this gap might have different formation mechanisms. We determine the fundamental stellar parameters, as well as individual abundances for a large sample of stars known to have a substellar companion in the brown dwarf regime. The sample is divided into stars hosting "massive" and "low-mass" brown dwarfs. Following previous works a threshold of 42.5 M$_{\rm Jup}$ was considered. Our results confirm that stars w…
In its all-sky survey, Gaia will monitor astrometrically and photometrically millions of main-sequence stars with sufficient sensitivity to brown dwarf companions within a few AUs from their host stars and to transiting brown dwarfs on very short periods, respectively. Furthermore, thousands of detected ultra-cool dwarfs in the backyard of the Sun will have direct (absolute) distance estimates from Gaia, and for these Gaia astrometry will be of sufficient precision to reveal any orbiting companions with masses as low as that of Jupiter. Gaia observations thus bear the potential for critical co…
