We present the results of a survey program with JWST's MIRI LRS that obtained 5-14 μm R 100 spectra of twenty-three L0-T6 dwarfs. This spectral type range spans the formation, growth, and sedimentation of silicate condensate clouds, as well as the appearance of methane and ammonia in the atmospheres of brown dwarfs. The initial onset of silicate absorption at spectral type L0 as well as the evolution of this feature with spectral type are both examined in unprecedented detail. We detect 7.5-9.5 μm gas-phase SiO absorption for the first time in dwarf stars, with detections in M5.5-L2.5 dwarfs from combined Spitzer IRS and JWST spectra. This feature has previously been detected in K and M giants, with stronger absorption in these giants than in higher-gravity M dwarfs. In contrast, low-gravity L dwarfs show weaker SiO absorption than field-gravity L dwarfs. We also confirm water, ammonia, and methane absorption trends with spectral type previously seen in Spitzer IRS observations. We report the possible detection of CS2 in a T3.5 dwarf, although confirmation would require higher-dispersion spectroscopy. We find two newly resolved binaries, confirm two near-equal flux unresolved candidate binaries, and identify two additional possible non-equal flux binaries. After accounting for contamination by resolved and candidate binaries, we find that single field dwarfs are 0.15-0.20 mag underluminous compared to existing empirical relations. The presented spectral library offers a spectrophotometrically calibrated basis for future interpretation of JWST MIRI spectra of brown dwarfs or of directly imaged or transiting exoplanets.

We examine the positions of substellar objects in mid-infrared color-magnitude and color-color diagrams to distinguish between cloudy and cloud-free atmospheres. Using Spitzer mid-infrared spectra of 113 M5-T9 ultracool dwarfs, we derive synthetic photometry for the JWST Mid-Infrared Instrument (MIRI) F560W, F770W, F1000W, and F1280W filters, which cover key absorption features including the similar to 9 mu m silicate signature. We find that diagrams involving F770W and F1000W best separate L-type objects with silicate clouds in their photospheres. L dwarfs with m(F770W) - m(F1000W) < 0.03 mag are 7 times more likely to host cloudy atmospheres. Diagrams using F1000W and F1280W are less informative due to the lower signal of the spectra at long wavelengths. Current model predictions struggle to reproduce the positions of cloudy, warm brown dwarfs, likely because atmospheric models underestimate the similar to 9 mu m silicate feature. Cloudy Sonora Diamondback models better match the observed trends, although this may reflect improvements in capturing the indirect effects of clouds on the 6.25 mu m water absorption feature rather than accurately modeling the silicate feature itself. Our analysis indicates that JWST MIRI imaging can efficiently identify new cloudy extrasolar atmospheres for targeted spectroscopic follow-up, optimizing the use of telescope time.

JWST defines a new era for the data-driven approach of retrieval modelling, which has become a cornerstone tool for the statistical inference of exoplanetary and brown dwarf properties. The Early Release Science program #1386 observations of VHS 1256 b represent a huge jump in data quality, data quantity and spectral coverage for such objects. VHS 1256 b is a young, planetary mass and extremely variable companion that populates the enigmatic L/T cohort of substellar atmospheres. In this first retrieval analysis of the full 1 - 18 micron dataset, we apply the Brewster retrieval framework to the NIRSpec and MIRI spectroscopic observations of VHS 1256 b, exploring a variety of cloud species and structures. Using Delta(BIC) we find that the data is best described by a forsterite (Mg_2SiO_4) and enstatite (MgSiO_3) cloud combination. Our analysis shows a strong preference for patchy silicate cloud coverage, which aligns with VHS 1256 b's extensive and well documented spectral variability. Our retrieval is able to place constraints on the abundances of H_2O, CO, CO_2, CH_4 as well as NH_3. We also show that the retrieved parameters are sensitive to the data used and the relative signal-to-noise ratios between data from different instruments. We conclude with the next steps for the wider retrieval community to better understand young and cloudy exoplanetary atmospheres.

We report the direct imaging discovery of a third exoplanet in the β Pictoris system. We detect β Pictoris d in non-coronagraphic observations obtained with VLT/ERIS as well as multi-epoch archival datasets from JWST/NIRCam and VLT/SPHERE. Astrometric measurements over an 11-year baseline demonstrate that it is consistent with a gravitationally-bound source with orbital motion. Joint multi-planet orbit fits of all three planets in the system yield a semi-major axis of 26.0^+2.2_-6.1 au and inclination 89.0^+0.7_-0.6 deg for planet d. β Pictoris d has a larger orbital semi-major axis than the other known planets in the system, but is coplanar with the inner two planets, and its orbit is consistent with sculpting the inner edge of the debris disk. β Pictoris d has a contrast of ΔL^'=12.11±0.15 mag, with colors and luminosity that closely match those of 51 Eri b, another exoplanet in the β Pictoris moving group. Its VLT/ERIS and JWST/NIRCam colors are distinct from those of free-floating planetary-mass objects of a similar age and temperature. Its red F410M-F444W color indicates strong CO_2 absorption in its atmosphere and suggests significant enhancement in metals compared to free-floating objects. From the ATMO hot-start evolutionary models, we estimate an effective temperature of 600^+45_-60 K and mass of 2.4±0.6 M_ Jup, which also closely matches similar estimates for 51 Eri b. β Pictoris d is among the lowest-mass exoplanets imaged from the ground. This discovery highlights the deep sensitivity achievable with ground-based imaging in the mid-infrared and the discovery potential of future high-contrast observations with the Extremely Large Telescope.

We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of 6 4 − 14 + 32 au and eccentricity 0.23 − 0.16 + 0.24 . Spectral analysis of the GPI H -band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of 104 2 − 132 + 178 K for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 M Jup assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.

We present a high signal-to-noise (SNR similar to 450), high-dispersion (R equivalent to lambda/Delta lambda similar to 28 000) H- and K-band spectroscopic atlas of the L7.5 and T0.5 components of the Luhman 16AB binary (WISE J104915.57-531906.1AB): the closest pair of brown dwarfs, and one of the best substellar benchmarks. The spectra were combined from a 70-d spectroscopic monitoring campaign of the binary with IGRINS on Gemini South. We fit model photospheres to the combined high-quality spectra to estimate atmospheric parameters. The model is based on the Sonora model atmosphere further incorporating the effects of clouds and disequilibrium. We detect ammonia (NH3) lines in both binary components, making Luhman 16A the warmest object where individual NH3 lines were identified. We discover hydrogen (H-2), hydrogen sulfide (H2S), and hydrogen fluoride (HF) lines in both components, following recent reports of these species in either cooler (H-2, H2S in a T6 dwarf) or warmer (HF in young late-M or mid-L dwarfs) objects. Methane (CH4) shows a small contribution, with lines sensitive to the slight temperature difference spanning the L/T transition. Against model expectations, we do not detect FeH lines, implying more efficient iron rainout than incorporated in the models. We find various unidentified features in water-dominated regions, likely the result of residual inaccuracies in the water line lists. We searched for planetary-mass companions by periodogram analysis of radial velocities over 70 d but detected no significant signal. The upper limits of projected planetary mass are M sin i = 0.2 M-J and 0.3 M-J at P similar to 1 d, and 0.4 M-J and 0.7 M-J at P similar to 10 d for Luhman 16A and B, respectively.

HD 143811 AB is the host star to the directly imaged planet HD 143811 AB b, which was recently discovered using data from the Gemini Planet Imager and Keck NIRC2. A member of the Sco-Cen star-forming region with an age of 13 ± 4 Myr, HD 143811 AB is somewhat rare among hosts of directly imaged planets, as it is a close stellar binary, with an ∼18-day period. Accurate values for the orbital and stellar parameters of this binary are needed to understand the formation and evolutionary history of the planet in orbit. We utilize archival high-resolution spectroscopy from FEROS on the MPG/ESO 2.2 m telescope to fit the orbit of the binary, and we combine with unresolved photometry to derive the basic stellar properties of the system. From the orbit, we derive precise values of orbital period of 18.59090 ± 0.00007 days and mass ratio of 0.886 ± 0.003. When combined with stellar evolutionary models, we find masses of both components of M A = 1.3 0 − 0.05 + 0.03 M ⊙ and M B = 1.1 5 − 0.04 + 0.03 M ⊙ . While the current data are consistent with the planet and stellar orbits being coplanar, the 3D orientations of both systems are currently poorly constrained, with additional observations required to more rigorously test for coplanarity.

We present a high signal-to-noise (SNR $\sim$ 450), high-dispersion ($R \equiv \lambda / \Delta \lambda \sim 28\,000$) H- and K-band spectroscopic atlas of the L7.5 and T0.5 components of the Luhman 16AB binary (WISE J104915.57$-$531906.1AB): the closest pair of brown dwarfs, and one of the best substellar benchmarks. The spectra were combined from a 70-day spectroscopic monitoring campaign of the binary with IGRINS on Gemini South. We fit model photospheres to the combined high-quality spectra to estimate atmospheric parameters. The model is based on the Sonora model atmosphere further incorporating the effects of clouds and disequilibrium. We detect ammonia (NH3) lines in both binary components, making Luhman 16A the warmest object where individual NH3 lines were identified. We discover hydrogen (H2), hydrogen sulfide (H2S), and hydrogen fluoride (HF) lines in both components, following recent reports of these species in either cooler (H2, H2S in a T6 dwarf) or warmer (HF in young late-M or mid-L dwarfs) objects. Methane (CH4) shows a small contribution, with lines sensitive to the slight temperature difference spanning the L/T transition. Against model expectations, we do not detect FeH lines, implying more efficient iron rainout than incorporated in the models. We find various unidentified features in water-dominated regions, likely the result of residual inaccuracies in the water line lists. We searched for planetary-mass companions by periodogram analysis of radial velocities over 70 days but detected no significant signal. The upper limits of projected planetary mass are $M\sin{i}=$ 0.2 $M_{\mathrm{J}}$ and 0.3 $M_{\mathrm{J}}$ at P $\sim$ 1 day, and 0.4 $M_{\mathrm{J}}$ and 0.7 $M_{\mathrm{J}}$ at P $\sim$ 10 days for Luhman 16A and B, respectively.

POET is a proposed Canadian Microsatellite mission to detect new, potentially habitable, rocky planets transiting low-mass stars, and to characterize the atmospheres of known transitioning extrasolar planets. With the support of the Space Technology Development Program (STDP) of the Canadian Space Agency, the all-reflective telescope has been designed and built. The prototype underwent complete integration and high-level optical testing.1 This paper presents the full optical performance results at room temperature and in ambient pressure, including ensquared energy, distortion, and Effective Focal Length (EFL) measurement, and the results from the thermal-vacuum campaign. POET is a collaboration between Bishop's University, Western University, ABB and SFL-UTIAS.

Recent studies suggest that the angular momentum evolution of late-M and brown dwarfs differs from the well-known spin-down evolution of hotter stars. Characterizing the distribution of rotation periods of these objects in the solar neighborhood can help elucidate this evolutionary pathway just above, at, and below the hydrogen-burning limit. In this paper, we examine 399 candidate single late-M dwarfs with G − G _RP ≥ 1.4 mag (≳M6) using Transiting Exoplanet Survey Satellite (TESS) light curves. To determine rotation periods, we employed Lomb–Scargle periodograms to provide a first estimate of the period, then refined them with a Gaussian process approach, requiring multisector confirmation when available. We found 133 rotation periods, ranging from 2 hr to 6 days, and amplitudes between 0.08% and 2.71%. We find that the observed variability fraction in late-M dwarfs rises with the number of available TESS sectors, approaching an apparent ceiling of ∼50%. This likely reflects a detection limit determined by viewing geometry and supports the idea that spot-induced variability is common across the late-M and brown dwarf population. In our comparison with previously published late-M dwarf rotation periods reported, we found consistent results, confirming or updating 31 periods. Our findings expand the number of previously known late-M dwarf periods under 1 day by 76%. Combined with published rotation periods for a broader range of spectral types, we find a lower envelope on the rotation period decreasing from 5 hr at early-M dwarfs to 1 hr at L, T, and Y dwarfs.

We present a high signal-to-noise (SNR ∼ 450), high-dispersion (R ≡λ / Δλ∼ 28 000) H- and K-band spectroscopic atlas of the L7.5 and T0.5 components of the Luhman 16AB binary (WISE J104915.57-531906.1AB): the closest pair of brown dwarfs, and one of the best substellar benchmarks. The spectra were combined from a 70-day spectroscopic monitoring campaign of the binary with IGRINS on Gemini South. We fit model photospheres to the combined high-quality spectra to estimate atmospheric parameters. The model is based on the Sonora model atmosphere further incorporating the effects of clouds and disequilibrium. We detect ammonia (NH3) lines in both binary components, making Luhman 16A the warmest object where individual NH3 lines were identified. We discover hydrogen (H2), hydrogen sulfide (H2S), and hydrogen fluoride (HF) lines in both components, following recent reports of these species in either cooler (H2, H2S in a T6 dwarf) or warmer (HF in young late-M or mid-L dwarfs) objects. Methane (CH4) shows a small contribution, with lines sensitive to the slight temperature difference spanning the L/T transition. Against model expectations, we do not detect FeH lines, implying more efficient iron rainout than incorporated in the models. We find various unidentified features in water-dominated regions, likely the result of residual inaccuracies in the water line lists. We searched for planetary-mass companions by periodogram analysis of radial velocities over 70 days but detected no significant signal. The upper limits of projected planetary mass are Msini= 0.2 M_J and 0.3 M_J at P ∼ 1 day, and 0.4 M_J and 0.7 M_J at P ∼ 10 days for Luhman 16A and B, respectively.

We present aperture masking interferometry (AMI) observations of the star HIP 65426 at 3.8 μ m, as part of the JWST Direct Imaging Early Release Science program, obtained using the Near Infrared Imager and Slitless Spectrograph instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of 0.5 λ / D for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST’s unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a 5 σ contrast of Δ m F380M ∼ 7.62 ± 0.13 mag relative to the host star at separations ​​​​​≳0 . ″ 07 , and the contrast deteriorates steeply at separations ≲0 . ″ 07. However, we detect no additional companions interior to the known companion HIP 65426b (at separation ∼0 . ″ 82 or 8 7 − 31 + 108 au ). Our observations thus rule out companions more massive than 10–12 M Jup at separations ∼10–20 au from HIP 65426, a region out of reach of ground- or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (≳0 . ″ 07), even for thousands of more distant stars at ∼100 pc, in addition to the stars in the nearby young moving groups and associations, as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space.

CASTOR is a proposed wide-field (30 ' x30 '=0.25 deg(2)), high-resolution (FWHM similar to 0.15 ''), 1-m-diameter space telescope that is under development by the Canadian Space Agency and the National Research Council of Canada. Optimized for UV/blue-optical wavelengths, the telescope uses dichroics to enable imaging in three channels (and up to five bands) that cover the 0.15 to 0.55 mu m spectral region, simultaneously. CASTOR will also feature low- and low-medium-resolution spectroscopic capabilities through the use of a deployable grism for low-resolution (R less than or similar to 420) slit-less spectroscopy in its UV and u channels, and low-medium-resolution R similar to 1400 multi-object spectroscopy in a parallel field using a digital micro-mirror device. High-speed, precision photometry will be possible using dedicated CMOS detectors in each of its three channels. We present an overview of the mission, including the optical design, instruments and detectors, payload layout, satellite bus, orbit, and ground segment. We describe the mission's scientific capabilities and expected place within the astronomical landscape in the 2030s. The 5-year lifetime is baselined on a combination of legacy surveys, guest observer programs, and target-of-opportunity science. We summarize scientific plans for the mission in each of eight fields: cosmology, time domain and multi-messenger science, active galactic nuclei, galaxies, near-field cosmology, stellar astrophysics, exoplanets, and solar system studies. We conclude by describing ongoing development efforts, highlighting areas of particular relevance for NASA's Habitable Worlds Observatory.

The Gemini Planet Imager (GPI), an extreme adaptive optics instrument on Gemini South, has been pivotal in the advancement of the debris-disk field. Over the past decade, GPI has observed tens of debris disks at near-infrared wavelengths in both polarized and total intensity as a part of several direct-imaging surveys. Here we discuss the uniform reductions of the J-, H- and K1-band GPI observations, specifically in polarized intensity. This includes 24 debris-disk observations in the H band, 10 debris-disks observations in the J band and 11 disk observations in the K1 band. Additionally, all three reduced data sets have been archived on the digital platform, CANFAR, so that they are available for public use. The purpose of this work is to provide the necessary steps for one to carry out their own data reductions if desired, as well as to create a space where these uniformly reduced data are easily accessible for future analysis and research.

We present JWST NIRCam coronagraphic observations of the HD 141569A circumstellar disk, obtained as part of the JWST Early Release Science program. The observations recover the multi-ringed structure seen in previous shorter-wavelength observations, but at filters centered on the ∼3 μ m water ice absorption feature and a complementary continuum region (F300M and F360M, respectively). The observations reveal apparent absorption between the F300M and F360M filters that decreases with radius, with a notable change around 200 au, between the innermost and outermost two rings. These results are consistent whether the data is reduced via deconvolution or through a forward-modeling approach. We demonstrate that these changes suggest a radial decrease in the water ice mass fraction by a factor of ∼3–10 and possibly a change in minimum grain size. We do not detect any point sources within the system and can exclude planetary companions 2 Jupiter masses and greater beyond 1 ″ radius (∼111 au). These observations and the subsequent analysis illustrate a robust pathway for using JWST/NIRCam to characterize the distribution of water ice in other circumstellar disks. We highlight some of the early lessons learned from this work that we hope will be useful for future circumstellar disk observation planning and analysis.

Large-amplitude variations are commonly observed in the atmospheres of directly imaged exoplanets and brown dwarfs. VHS 1256B, the most variable known planet-mass object, exhibits a near-infrared flux change of nearly 40%, with red color and silicate features revealed in recent JWST spectra, challenging current theories. Using a general circulation model, we demonstrate that VHS 1256B's atmosphere is dominated by planetary-scale dust storms persisting for tens of days, with large patchy clouds propagating with equatorial waves. This weather pattern, distinct from the banded structures seen on solar system giants, simultaneously explains the observed spectra and critical features in the rotational light curves, including the large amplitude, irregular evolution, and wavelength dependence, as well as the variability trends observed in near-infrared color-magnitude diagrams of dusty substellar atmospheres.

The Gemini Planet Imager (GPI) has excelled in imaging debris disks in the near-infrared. The GPI Exoplanet Survey (GPIES) imaged twenty-four debris disks in polarized H-band light, while other programs observed half of these disks in polarized J- and/or K1-bands. Using these data, we present a uniform analysis of the morphology of each disk to find asymmetries suggestive of perturbations, particularly those due to planet-disk interactions. The multi-wavelength surface brightness, the disk color and geometry permit identification of any asymmetries such as warps or disk offsets from the central star. We find that nineteen of the disks in this sample exhibit asymmetries in surface brightness, disk color, disk geometry, or a combination of the three, suggesting that for this sample, perturbations, as seen in scattered light, are common. The relationship between these perturbations and potential planets in the system are discussed. We also explore correlations among stellar temperatures, ages, disk properties, and observed perturbations. We find significant trends between the vertical aspect ratio and the stellar temperature, disk radial extent, and the dust grain size distribution power-law, q. We also confirm a trend between the disk color and stellar effective temperature, where the disk becomes increasingly red/neutral with increasing temperature. Such results have important implications on the evolution of debris disk systems around stars of various spectral types.

POET is a proposed Canadian Microsatellite mission to detect new, potentially habitable, rocky planets transiting low-mass stars, and to characterize the atmospheres of known transitioning extrasolar planets. The allreflective telescope offers simultaneous imaging in the u-band (300-400 nm), VNIR (400-900 nm) and SWIR (900-1700 nm) through a 20 cm aperture. The optical telescope assembly (OTA) has been designed and build with support from the Space Technology Development Program (STDP) of the Canadian Space Agency. The prototype underwent complete integration and optical properties testing including ensquared energy, Modulation Transfer Function, distortion, and Effective Focal Length measurement. Results show that the design is compliant with expected performances at ambient temperature. A Thermal-Vacuum Chamber campaign over the range of operation temperature has been designed to verify the OTA's performance from -20 C degrees to 20 degrees C. This enables the investigation of image quality stability in a sub-set of environmental conditions, increasing the OTA's Technology Readiness Level. POET is a collaboration between Bishop's University, Western University, ABB and SFL-UTIAS.