Jorge Llop-Sayson

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.

ϵ Eridani b, the nearest known Jupiter analog, has its orbit and mass constrained from radial velocity (RV) and absolute astrometry, and its atmosphere from JWST/NIRCam imaging upper limits in A. Sanghi et al. Here we follow up that work with a self-consistent model of ϵ Eridani b that treats all available data within a single Bayesian framework. We extend the RV data with new measurements, update the treatment of the astrometry data with a new model, and include the NIRCam observations with a grid of evolutionary and atmospheric models. We find a mass of 0.91 ± 0.04 M _Jup and an orbit consistent with previous work. The imaging data helps constrain planet effective temperature, atmospheric metallicity, and surface gravity. The constraints are dependent on model assumptions: for an atmosphere in chemical equilibrium, an otherwise low statistically significant feature in one of the epochs is recovered as the planet at high confidence. When assuming chemical disequilibrium, the posteriors exhibit a bimodal distribution, with one mode consistent with zero flux and the other coinciding with the flux of the tentative feature. Consistent with previous work, the clear atmosphere models are found to be viable at very enhanced metallicity, whereas the cloudy models yield more moderate values. Applying these models to the Roman Coronagraph, we find that the predicted reflected-light fluxes place every cloudy atmosphere our fit allows within the instrument’s expected sensitivity. A nondetection would be very constraining: a final contrast sensitivity of 2 × 10 ⁻⁹ would rule out all cloudy atmospheres under our model assumptions.

Altair ( α Aql) is one of the nearest stars to the Sun at 5.13 pc and its age has recently been revised to 88 ± 10 Myr, making it one of the youngest stars in the solar neighborhood. This makes Altair a compelling target for high-contrast direct imaging searches for giant planets. We present two epochs of simultaneous F444W and F200W MASK430R JWST/NIRCam coronagraphic imaging observations. After postprocessing, these data achieve F444W contrast levels of 2 × 10 ⁻⁶ at 1″ (5.1 au), 1.5 × 10 ⁻⁷ at 2″ (10.3 au), and a few ×10 ⁻⁸ beyond 4″(20 au). Using the Sonora Flame Skimmer models, this corresponds to sub-Jupiter mass sensitivity beyond 5 au and sub-Saturn mass sensitivity beyond 10 au. We identified several candidate point sources in the field in the first epoch data. Second epoch observations confirmed that none of the candidates were co-moving with Altair and their colors are consistent with background stars. Altair has no known companions, no detected debris disk, and is not associated with any stellar association. Despite this, its youth and proximity ensure it will remain a high-priority target for future high-contrast imaging observations. We additionally discuss Altair as a potential reference star for future observations, presenting measurements of background sources in the field and showing that Altair will remain at least a few arcsec from background stars over the next 10–20 yr, making it a reliable reference target for upcoming imaging campaigns including the Roman Space Telescope Coronagraph Instrument.

Debris disks, composed of rocks, boulders, planetesimals, and the dust produced in their collisions, present the most readily observable components of mature planetary systems. They also serve as valuable diagnostic tools, enabling studies of planetary dynamical interactions and mineral compositions. Observed from optical to radio wavelengths, each band reveals unique information about the dust populations. Optical and near-infrared observations are specifically sensitive to light scattered off the surfaces of the micron-sized particles. Here, we present results from the JWST/NIRCam Guaranteed Time Observing program 2780, designed to observe five disk systems previously identified to be exceptionally bright at optical wavelengths (HD 10647, HD 32297, HD 61005, HD 107146, and HD 181327) with six filters using the NIRCam coronagraphs. The NIRCam data complement previous shorter-wavelength images of these same systems. They reveal scattered light from the disks and from the extended halos of tiny grains under the influence of radiative forces, at high resolution and signal-to-noise ratio. All the systems show evidence for water ice, although it can have differing radial distributions and tends to show stronger signatures in the halos. In the two cases we could analyze, the scattering phase function in the disks resembles the behavior of dust in the solar system, with evidence for enhanced forward scattering in the halos, consistent with the latter being composed of tiny grains. MIRI images for two systems are more centrally concentrated than the shorter-wavelength ones, suggesting a role for dragged-in larger grains.

The apodized vortex coronagraph (AVC) integrates pupil plane apodization to suppress segmentation-induced diffraction and is a leading candidate for high-contrast imaging on future flagship segmented observatories. Selected as the baseline coronagraph for Large Ultraviolet Optical Infrared Surveyor B (LUVOIR-B) and as a pipe-cleaning coronagraph for the Habitable Worlds Observatory (HWO), the AVC achieves ∼5×10−9 raw contrast over a 10% bandwidth in the lab but must be further optimized to meet the stringent ∼1×10−10 contrast requirement of HWO. We present the optimization process for the amplitude apodized vortex coronagraph (AAVC) for HWO’s exploratory analytical cases 1 and 2, along with its performance and sensitivity analyses to various aberrations. In addition, we evaluate the predicted scientific yield of the AAVC across HWO apertures using the Framework for Remote Implementation of Demand-based Altruistic Yields. Our results inform the path toward advancing AVC technology readiness for direct exoplanet imaging.

We observed the HR 8799 planetary system with JWST’s NIRCam instrument using its F356W and F444W filters to search for additional, lower-mass planets that might reside between or exterior to the four previously detected Jovian-mass planets. After blocking out the star with a circular occulting mask with gradual radial opacity, the four known planets (b, c, d, and e) are detected in both filters, even though the innermost planet lies so close to its parent star that the coronagraphic mask nominally blocks ∼86% of the planet’s light. The observed fluxes and positions of the planets are consistent with previous models of the planets’ atmospheres and with predictions of orbital fits. Two background sources are detected interior to and within the outer debris ring, respectively, both of which are visible in ALMA images at submillimeter wavelengths. No new planet candidates ≥1 M _Jup are seen within the region defined by the four known planets. Planets larger than a Saturn mass (∼0.3 M _Jup ) are ruled out within the outer gap between HR 8799 b (at 70 au) and the cold belt of debris (≥120 au), limiting the ability of a potential planet in that region to sculpt the inner edge of the outer disk.

We present the most sensitive direct imaging search for the nearest ( d = 3.2 pc) Jupiter-analog exoplanet, ϵ Eri b, with JWST/NIRCam coronagraphy between 4 and 5 μ m (F444W). We achieve a 5 σ contrast sensitivity ≈3.0 × 10 ⁻⁷ (Δ ≈ 16.3 mag) in the F444W filter at the expected planet separation of ≈1″. This is the deepest 4–5 μ m contrast performance achieved for any JWST/NIRCam observation to date at these separations (and >10× better than ground-based limits). Yet, the planet remains elusive to imaging. We update the star’s age to 1.1 ± 0.1 Gyr, older than previous age estimates, using the latest gyrochronology relations. This significantly impacts ϵ Eri b’s inferred effective temperature ( T _eff ), which is now expected to lie between 150 and 200 K based on evolutionary models for a 1 M _Jup planet. Using cloud-free Sonora Flame Skimmer models and custom PICASO patchy cloud models in the above T _eff range, we find that the F444W nondetection of ϵ Eri b can be explained by a metal-enriched atmosphere and/or an atmosphere containing water ice clouds. Both possibilities suggest that ϵ Eri b’s atmosphere is strikingly similar to that of Jupiter in our solar system. Alternatively, if we do not enforce the dynamical mass (0.98 ± 0.09 M _Jup ), a solar metallicity, cloud-free, ≲0.81 M _Jup planet would be consistent with the NIRCam upper limit based on the Sonora Flame Skimmer evolutionary models. Finally, we place limits on the size of a potential ring system using the NIRCam/F210M data and discuss the opportunity to directly image ϵ Eri b with additional JWST observations, the Roman Coronagraph Instrument, the ExtraSolar Coronagraph on the Lazuli Observatory, and EELT/METIS.

The Coronagraph Instrument on board of the Nancy Grace Roman Space Telescope will demonstrate key technologies that will prepare the ground for the Habitable Worlds Observatory. The current predictions for the Roman Coronagraph's detection limit range from 1e-8 to a few 1e-9, which would allow for groundbreaking science, such as potentially imaging Jupiter-like planets. However, the performance of the instrument depends on many factors. Simulating images with varying optical error sources can help us connect instrument and observatory performance to science yield. Here we present corosims, a tool to simulate observations of astrophysical scenes with the Coronagraph with evolving errors. This tool wraps around the Coronagraph PROPER diffraction model and detector simulator. We use it to investigate the potential degeneracy between jitter-induced speckles and both hot and warm exozodi disk structures. First, we simulate observations of exozodi around Tau Ceti, with varying jitter. We predict that with nominal post-correction pointing jitter performance (~0.3 mas RMS), the Roman Coronagraph should be sensitive to 12x zodis worth of dust, assuming a face-on (worst case scenario) inclination. We further predict that its sensitivity degrades to 35x zodis if jitter on-target is 3x worse than the nominal value. This estimate assumes the best-modeled wavefront control and stability values from the project, including additional model uncertainty factors. We find that, while jitter hinders warm exozodi detection, jitter residuals are unlikely to result in a false positive. However, if a faint hot exozodi falls at small separation, it may not be distinguishable from jitter-induced speckle residuals of comparable brightness. Finally, we discuss the degeneracies induced between flux and separation retrieved near the inner working angle due the sharp edge of the Roman Coronagraph's focal plane mask.

The Coronagraph Instrument on board of the Nancy Grace Roman Space Telescope will demonstrate key technologies that will prepare the ground for the Habitable Worlds Observatory. The current predictions for the Roman Coronagraph’s detection limit range from ∼10−8 to a few 10−9, which would allow for groundbreaking science, such as potentially imaging Jupiter-like exoplanets around mature stars or imaging exozodi disks in scattered light. However, the performance of the instrument depends on many factors. Simulating images with varying optical error sources can help us connect instrument and observatory performance to potential science yield. We present a tool, corosims, to simulate observations of arbitrary astrophysical scenes with the Roman Coronagraph in the presence of evolving wavefront errors. This tool wraps around the Roman Coronagraph PROPER diffraction model and detector simulator. We use corosims to investigate the potential degeneracy between jitter-induced speckles and both hot and warm exozodi disk structures. First, we simulate observations of warm exozodi around τ Ceti, with varying jitter levels. We predict that with nominal post-correction pointing jitter performance (∼0.3 mas RMS), the Roman Coronagraph should be sensitive to 12× zodis worth of dust, assuming a face-on (worst case scenario) inclination. We further predict that its sensitivity degrades to 35× zodis if jitter on-target is 3× worse than the nominal value. This estimate assumes the best-modeled wavefront control and stability values from the Roman project, including additional “model uncertainty factors” on performance. We find that, although jitter hinders warm exozodi detection by increasing the noise, jitter residuals are unlikely to result in a false positive, particularly if two-color imaging is conducted. However, if a faint, hot exozodi disk falls <λ/D projected separation, it may not be distinguishable from jitter-induced speckle residuals of comparable brightness. Finally, we discuss the degeneracies induced between flux and separation retrieved near the inner working angle due to the sharp edge of the Roman Coronagraph’s focal plane mask.

We present JWST/MIRI observations of the debris disk surrounding the nearby solar analog ϵ Eridani obtained as part of the Archetypal Debris Disk Guaranteed Time Observation program. Multiwavelength images from 15, 18, 21, and 25.5 μm show a smooth dust distribution with no evidence of sculpting by massive planets outside of 5 au. Maps of the color temperature and opacity constrain the dust properties, while radiative transfer modeling of a warm dust component traces the interaction between the debris disk and ϵ Eridani b (∼3.5 au). Dynamical and collisional modeling further shows that the disk morphology is dominated by dust produced in the outer planetesimal belt (∼70 au) moving inward via stellar wind drag. We confirm the presence of a disk interior to the ϵ Eri b orbit first detected from mid-IR interferometry. Drag-dominated inner disk regions have also been observed around Vega and Fomalhaut, hinting at the diversity of asteroid belt analogs.