Logan A. Pearce

Rings are ubiquitous among the giant planets in the solar system, yet their presence around exoplanets remains observationally unconstrained. As direct imaging missions such as the Nancy Grace Roman Space Telescope approach first light, understanding the influence of circumplanetary rings on reflected light photometry is critical for the accurate interpretation and follow-up of direct imaging observations. We present a hybrid forward model for reflected light phase curves of ringed exoplanets, coupling a ray-casting framework for computing mutual planet–ring shadowing with empirical reflectance spectra from Cassini observations of Saturn’s rings. We model Jupiter-like planets with opaque, icy rings spanning 1–10× the radial extent of Saturn’s A, B, and C rings across a grid of inclinations and ring obliquities. Our simulations show that rings enhance the flux ratios at favorable ring geometries. Saturn-equivalent rings increase peak flux by a factor of 3.1 in the visible, while more extended rings produce enhanced contrasts exceeding an order of magnitude. The flux contribution of a ring is highly sensitive to obliquity and orbital location. At certain geometries, rings can suppress total system brightness below that of a ringless planet. We highlight multiband observations as a complementary route for diagnosing the presence of an exoring. We also apply the model to υ Andromedae d as an observational test case and discuss the implications for exoring detectability with the Roman Coronagraph. Exorings have the potential to bias inferred planetary properties from direct images and must be properly accounted for in observation preparation and interpretation.

We report the direct imaging detection of a stellar companion to HD 101452 (HIP 56925; Gaia DR3 5384905720847544192), an A star historically used as an infrared flux calibrator. The companion was identified from an asymmetry in the stellar point-spread function (PSF) using short-integration (μ m that was obtained as part of the absolute flux calibration program CAL 4496. We detect the stellar companion in four MIRI imaging filters at a projected separation of 1 . ″ 3 with a mid-infrared flux ratio of approximately 27×, warranting its removal from the ensemble of JWST flux calibrator systems. This detection also demonstrates that noncoronagraphic MIRI imaging can recover companions at separations below 3 λ / D when a reference star with a closely matched flux level to the science target is available. Using the measured contrast curves from the calibration data, we evaluate the predicted sensitivity achievable with similar short MIRI observations for nearby stars (<30 pc) that are of interest to the direct imaging community with comparable brightness to HD 101452 (W4 ∼ 6.8 mag). We find that integrations of only 17–42 s are capable of detecting sub-Jupiter-mass planets at solar system–like separations around a subset of neighboring systems if the PSF subtraction is conducted with closely flux-matched references. These results demonstrate that minutes-length, noncoronagraphic MIRI observations can provide a powerful and efficient new avenue for exploring the cold giant planet population around nearby stars.

Modeling circumstellar disks in the traditional sense carries the assumption that the dust density distribution can be accurately described with a fixed parametric form. Furthermore, commonly used algorithms for subtracting the stellar point-spread function (PSF) distort the true morphology of the faint underlying disk structure, especially dusty features that are located at small angular separations. These phenomena often lead to significant residuals with parametric disk models and make it difficult to measure the full realizable range of the scattering function of the dust. We address these challenges with ffortissimo , a novel, pixel-based freeform forward modeling pipeline designed to characterize extended objects in images reduced using the Karhunen–Loéve Image Projection algorithm. We built this pipeline within the framework of Jax , which is a machine learning library in Python that enables efficient optimization through automatic differentiation (“autodiff”) and graphics processing unit–accelerated array computations. Using visible light images of the disk around HR 4796A taken by the “extreme” Magellan Adaptive Optics instrument (MagAO-X), we show that our data-driven freeform models excel at fitting a complex dust distribution and can infer the dust scattering properties even through PSF subtraction artifacts. Additionally, we demonstrate the potential for retrieving spatial dust features beyond the diffraction limit of the telescope. We note that there are remaining challenges to address before precision photometry using these freeform models is advised. These include a better background, wind-driven halo, and speckle characterization, as preventing the freeform models from learning these noise artifacts is currently difficult.

Most stars, including our Sun, will one day evolve into red giants and, subsequently, white dwarfs. Several planet candidates have recently been identified orbiting white dwarfs ^1–4 , demonstrating that planets can survive the stellar post-main-sequence stage intact. Little is known about the atmospheric composition of post-main-sequence planets, with the most evolved transiting planets with atmospheric detections so far orbiting subgiants ^5,6 . Here we report an atmospheric detection for the white dwarf planet WD 1856 b, achieved through transmission spectroscopy with the James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSpec) PRISM. Our 0.5–5.0-μm spectrum reveals the presence of hydrocarbons (odds ratio of 167:1–5,377:1, with CH ₄ preferred at 17:1–30:1), aerosols (2 × 10 ⁵ :1–2 × 10 ⁶ :1) and thermal emission from the planetary nightside (2 × 10 ⁶³ :1–2 × 10 ⁷³ :1). Our spectral analysis constrains the mass of WD 1856 b to 4.3–10.9 M _J , finds a carbon-enriched atmosphere (with a CH ₄ abundance of approximately 7%) and an effective temperature exceeding the expected planetary equilibrium temperature (390–412 K versus 160 K). On the basis of cooling models, these results indicate that WD 1856 b underwent a migration-related reheating event 3.0–5.5 Gyr into the white dwarf phase, consistent with post-main-sequence tidal evolution to the present-day 0.02- au circular orbit. Our results provide a window into the ultimate fate of giant planets orbiting stars with masses similar to our Sun.

Context . Direct imaging enables the characterisation of substellar companions on wide orbits. These objects provide a testbed for our formation theories; therefore, it is important to obtain accurate physical parameters for them. One of these objects is YSES 1 b. Aims . Our objective is to improve the spectral energy distribution (SED) modelling of YSES 1 b and determine the bulk and atmospheric parameters. Methods . We obtained observations in the r ′, i ′, and z ′ bands using MagAO-X on the 6.5 metre Magellan Clay telescope at Las Campanas Observatory. We combined this data with archival VLT/SPHERE and VLT/NACO data and used a forward-modelling approach to estimate the physical parameters. We tested models both without and with a circumplanetary disc (CPD) model. We represented the CPD by including a dust extinction model and a blackbody radiation component. Using the derived bolometric luminosity, we estimated the mass of YSES 1 by fitting evolutionary models. Results . Including the CPD model provides a significantly better fit to the photometric data, yielding an object that is considerably warmer (2854 ₋₉₄ ⁺¹¹⁰ K vs 1727 ₋₁₂₇ ⁺¹⁷² K) and smaller (1.58 _−0.07 ^+0.06 R _J vs 3.0 _−0.7 ^+0.2 R _J ) than previous estimates. The newly determined radius suggests that the addition of dust extinction could resolve the large radius anomaly identified previously. Depending on the age of the system, the estimated mass increases from 14 ± 3 M _J (17 Myr) to either 25.7 _−3.6 ^+4.1 (17 Myr) or 41.6 _−3.4 ^+3.6 M _J (27 Myr). Conclusions . Dust extinction and blackbody radiation from a CPD can substantially change the estimated physical parameters of an object. For YSES 1 b, this moves it into the brown dwarf regime.

Epsilon Indi A b (hereafter Eps Ind A b) is a directly imaged ∼6 M _Jup exoplanet orbiting a nearby (3.6 pc) K dwarf at ∼30 au. We analyze archival JWST/MIRI 15 μ m coronagraphic imaging of this planet to search for directly imaged satellites orbiting Eps Ind A b. Within the planet’s Hill sphere (radius R _H ≈ 2.3 au or 1.3 λ / D ), we compare single and double point-spread-function (PSF) models using Bayesian evidence. We find that a double-PSF (binary planet) fit is preferred. This apparent preference can most plausibly be explained by systematics, although follow-up observations would be required to fully rule out a binary planet interpretation. We construct a contrast curve of the exoplanet after removing this feature, demonstrating sensitivity to companions as faint as 0.03× the F1550C flux of Eps Ind A b (equivalent to T = 130 K, 1.3 M _Jup ) at large separations (> 2 au). We also demonstrate sensitivity to brighter companions 0.2× the F1550C flux of Eps Ind A b (equivalent to T = 180 K, 2.5 M _Jup ) down to separations of 0.52 au (1.3 pixels; 0.29 λ / D ; 144 mas). This study demonstrates that JWST/MIRI can directly detect exomoons or binary planets inside the Hill sphere of directly imaged exoplanets orbiting neighboring stars.

We present total intensity images of the debris disk around HR 4796A from observations spanning 2023 to 2025 with the Magellan extreme adaptive optics instrument (MagAO-X). We detected the disk at high signal-to-noise ratios at g ′ ( 527 nm), r ′ ( 615 nm), i ′ ( 762 nm), and z ′ ( 909 nm). Additionally, we present images collected using the “star-hopping” technique that show the entirety of the disk, including the dramatic forward-scattering at the minor axis. We subjected our images to a battery of modeling techniques to constrain the geometry and photometry of the disk. Leveraging our clear detections of the disk’s minor axis, we modeled the scattering phase function (SPF) using a basis of the Legendre polynomials. To mitigate self-subtraction artifacts in our angular differential imaging, we implemented a forward-modeling pipeline that generates a pixel-based freeform disk forward model leading to a deconvolved image of the disk. Our best-fit disk models reveal (1) highly forward-scattering SPFs with a minimum at the ∼65 ^∘ scattering angle, (2) a faint halo of dust just exterior to the spine of the disk that is not well-described by a broken power-law density profile, (3) a red spectral slope for the dust, and finally (4) a compact, clump-like feature in the freeform disk models. Our empirically measured SPFs suggest that the scattering is dominated by large, highly absorptive grains. However, we emphasize the need for testing advanced irregular grain models using our SPFs to learn more about the physical and chemical properties of this complex system.

Advancing the technological development of small inner working angle (IWA) coronagraphs is essential to enabling high-contrast imaging of temperate exoplanets with future extremely large telescopes (ELTs). The PIAACMC has been shown to closely approach the theoretical limit for coronagraphic throughput but its performance has not been fully characterised on-sky. This study serves as the first on-sky characterisation of contrast and IWA performance of the PIAACMC. We also performed a technological demonstration of the PIAACMC at sub-micron nearinfrared (NIR) wavelengths approaching the visible. We designed and manufactured phase-shifting focal plane masks for the PIAACMC. These were optimised for two cases, a narrowband 875 filter (875 nm, ∼3% bandwidth) and a broadband z′ filter (908 nm, ∼14% bandwidth). We tested the coronagraphs both with an internal source and on-sky using MagAO-X, the extreme adaptive optics (XAO) instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory, Chile. We show good recovery of the off-axis light’s point spread function (PSF) shape both with the internal source (within ∼92% and ∼97% depending on the separation) and on-sky when aligning the inverse set of PIAA lenses. We demonstrate sub- λ /D IWAs with the instrument’s internal source of about 0.74 λ /D with the 875 filter and 0.76 λ /D with the z’ filter. We reach average raw contrasts within 1 and 5 λ /D with the internal source of about 1.6 × 10 ⁻³ with the 875 filter and 1.3 × 10 ⁻³ with the z’ filter. These are mainly limited by the focal plane mask manufacturing errors, jitter, and residual quasi-static speckles in MagAO-X. We also show on-sky average raw contrasts within 1 and 5 λ /D of about 1.4 × 10 ⁻² with the 875 filter and 7.8 × 10 ⁻³ with the z’ filter. These are likely limited by wavefront control, low-order aberrations, and poor observing conditions. We have successfully characterised PIAACMC’s performance and demonstrated its technology on-sky for the first time at sub-micron wavelengths. Future work will improve the design and manufacturing processes of the focal plane masks to improve robustness and reach deeper contrast, as well as integrate focal plane wavefront control for non-common path aberrations (NCPAs) correction.

Here we present an open-source cloud model for substellar atmospheres, called Virga . The Virga-v0 series has already been widely adopted in the literature. It is written in Python and has heritage from the A. S. Ackerman & M. S. Marley model (often referred to as eddysed ), used to study clouds on both exoplanets and brown dwarfs. In the development of the official Virga-v1 we have retained all the original functionality of eddysed and updated/expanded several components, including the back-end optical constant data, calculations of the Mie properties, available condensate species, saturation vapor pressure curves, and formalism for fall speed calculations. Here we benchmark Virga by reproducing key results in the literature, including the SiO ₂ cloud detection in WASP-17 b and the brown dwarf Sonora Diamondback model series. Development of Virga is ongoing, with future versions already planned and ready for release. We encourage community feedback and collaborations within the GitHub code repository.

2MASS J16120668–3010270 (hereafter 2MJ1612) is a young M0 star that hosts a protoplanetary disk in the Upper Scorpius star-forming region. Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of 2MJ1612 show a mildly inclined disk (i = 37°) with a large dust-depleted gap (R _cav ≈ 0 . ″ 4 or 53 au). We present high-contrast Hα observations from MagAO-X on the 6.5 m Magellan telescope and new high-resolution submillimeter dust continuum observations with ALMA of 2MJ1612. On both 2025 April 13 and 16, we recovered a point source with Hα excess with a signal-to-noise ratio ≳5 within the disk gap in our MagAO-X angular and spectral differential images at a separation of 141.96 ± 2.10 mas (23.45 ± 0.29 au deprojected) from the star and a position angle ​​​​​of 159 . ° 00 ± 0 . ° 55. Furthermore, this Hα source is within close proximity to a K-band point source in the SPHERE/IRDIS observation taken on 2023 July 21. The astrometric offset between the K band and Hα source can be explained by orbital motion of a bound companion. Thus, our observations can be best explained by the discovery of an accreting protoplanet, 2MJ1612 b, with an estimated mass of 4 M _Jup and a Hα line flux ranging from (29.7 ± 7.5) × 10⁻¹⁶ erg s cm² to (8.2 ± 3.4) × 10⁻¹⁶ erg s cm². 2MJ1612 b is likely the third example of an accreting Hα protoplanet responsible for carving the gap in its host disk, joining PDS 70 b and c. Further study is necessary to confirm and characterize this protoplanet candidate and to identify any additional protoplanets that may also play a role in shaping the gap.