Kevin K. Hardegree-Ullman

The Transiting Exoplanet Survey Satellite (TESS) has transformed the study of nearby exoplanetary systems; however, its nominal observing strategy limits sensitivity to planets with orbital periods shorter than ∼10 days for most parts of the sky. The two TESS Continuous Viewing Zones (CVZs) provide extended temporal baselines that help overcome this limitation, enabling the detection of longer-period (>10 days) transiting planets around nearby stars. Here, we present COUNTESS , a transit-search pipeline optimized for long-baseline TESS observations that combines multisector light curves with heterogeneous cadences, and implements fast-folding box least-squares period detection, vetting, and statistical validation. As a first application of the pipeline, we conducted a search on the primary and first extended mission photometry in the TESS northern CVZ. For this analysis, we used Gaia Data Release 3 and Two Micron All Sky Survey photometry to homogeneously derive a stellar catalog of FGKM stars for the TESS northern CVZ, resulting in a sample of 391,059 stars. We used COUNTESS to search for transiting planets around 26,114 of these stars with TESS-SPOC light curves and assessed its performance, recovering 115 out of 159 known TESS Objects of Interest (TOIs; 0.85 < P < 124.72 days; 1.03 < R _p < 16.35 R _⊕ ). Additionally, we identified 10 new exoplanet candidates (1.20 < P < 34.62 days; 1.73 < R _p < 4.19 R _⊕ ) that passed vetting tests, including two new statistically validated sub-Neptunes, TIC 219893931 b and TIC 237254473 b. COUNTESS enables extended-baseline TESS analyses and identification of longer-period planets, establishing a foundation for future exoplanet demographic studies, including comparisons with the Kepler Space Telescope and K2.

We present the results of a Spitzer Space Telescope Exploration Science Program to search for and characterize variability in Y dwarfs. We observed 14 Y dwarfs over a 24 hr period at [3.6] and [4.5] and then repeated the observations a few months later. We add two Y dwarfs, WD 0806−661B and WISE J085510.83−071442.5, that were also observed with Spitzer so that our sample includes all Y dwarfs observed for variability with Spitzer. We infer variability fractions of 59% ± 15% and 64 − 13 % + 10 % for [3.6] and [4.5] in the first epoch, and 35% − 11 % + 17 % and 75% − 15 % + 8 % in the second epoch. We also find that Y dwarf Spitzer light curves are generally stable over timescales of months, but in some cases can show clear changes in amplitude. Combining our results with a similar Spitzer survey of L and T dwarfs by S. A. Metchev et al., we find the mid-infrared variability fraction of L, T, and Y dwarfs weakly supports the hypothesis that brown dwarf variability is caused by variations in the horizonal and/or vertical structure of condensate clouds.

The TESS Input Catalog (TIC) was built on Gaia Data Release 2 (DR2). To date, there has not been an update to the TIC to incorporate Gaia Data Release 3 (DR3) IDs. In this Research Note, we outline how we cross-matched the TIC with Gaia DR3 IDs, its immediate applications to exoplanet research, and lessons learned when dealing with such large datasets. A full TIC/Gaia DR3 cross-match table is available for download on the Exoplanet Follow-up Observing Program website, and a Jupyter Notebook with instructions to reproduce the table is available on GitHub.

Recent discoveries of transiting giant exoplanets ( R _p ≳ 8 R _⊕ ) around M dwarfs present an opportunity to investigate their atmospheric compositions and explore how such massive planets form around low-mass stars contrary to the prediction from formation models. We present the first transmission spectra of TOI-5205b, a short-period ( P = 1.63 days) Jupiter-like planet ( M _p = 1.08 M _J and R _p = 0.94 R _J ) orbiting an M4 dwarf ( M _⋆ = 0.392 M _⊙ , R _⋆ = 0.394 R _⊙ ). We obtained three transits using the PRISM mode of the JWST Near Infrared Spectrograph spanning 0.6–5.3 μ m. The data reveal significant stellar contamination that is evident in the light curves as spot-crossing events and in the transmission spectra as a larger transit depth at bluer wavelengths. Atmospheric retrievals demonstrate that stellar contamination from unocculted starspots and faculae is the dominant component of the transmission spectrum at wavelengths λ ≲ 3.0 μ m, reducing the sensitivity to the presence of clouds or hazes in our models and preventing detection of H _2O . The wavelength coverage enabled a robust detection of CH ₄ and H ₂ S, which have detectable molecular features between 3.0 and 5.0 μ m. For both clear or cloudy atmospheres, Bayesian retrievals consistently favored an atmosphere with subsolar metallicity (3 σ upper limit of log [ M / H ] ≲ − 1.24 ) and supersolar C/O ratio (3 σ lower limit of log [ C / O ] ≳ 0.09 ), although this may partly be driven by the nondetection of water due to stellar contamination. Planetary interior models predict a bulk metallicity of 10%–20%, which is larger than the atmospheric metallicity and suggests that the interior of TOI-5205b is decoupled from its atmosphere.

Unresolved stellar companions can cause both underestimations in the radii of transiting planets and overestimations of their detectability, affecting our ability to reliably measure planet occurrence rates. To quantify the latter, we identified a control sample of 198 Kepler stars with sensitivity to Earth-like planets if they were single stars, and imaged them with adaptive optics. In 20% of systems, we detected stellar companions that were close enough to go unresolved in Kepler observations. We calculated the distribution of planet radius correction factors needed to adjust for these observed companions, along with simulations of undetected companions to which our observations were not sensitive. We then used these correction factors to optimize an occurrence rate model for small, close-in planets while correcting Kepler’s detection efficiency for the presence of unresolved companions, and quantified how this correction affects occurrence estimates. Median occurrence rates for small planets between 2 and 100 days increased by an average factor of 1.08–1.19 (depending on statistical treatments), with the largest differences found for smaller planets at larger orbital periods. We found that the frequency of Earth-sized planets in the habitable zone ( η _⊕ ) increased by a factor of 1.18 − 0.66 + 0.43 – 1.46 − 0.83 + 0.53 when accounting for the effect of unresolved companions on Kepler’s detection sensitivity.

Understanding how giant planet occurrence rates vary with stellar mass and orbital distance provides key insights into planet formation and evolution. However, most surveys are limited in sample size and stellar mass coverage, inhibiting demographic studies. Using an integrated demographics approach, we combine transit (Kepler, K2) and radial-velocity (CLS) surveys to measure the occurrence of 0.1–10 M _J planets around M-K (0.4–0.8 M _⊙ ) stars and compare with population-synthesis models. We find no evidence for a turnover inside 3 au, unlike observations around Sun-like stars. We interpret the implications of this result and use our forward model to predict exoplanet occurrence at semimajor axes relevant for Gaia and direct imaging, which will provide critical constraints at wide separations and test the existence of a turnover.

Will future direct imaging missions such as NASA’s upcoming Habitable Worlds Observatory (HWO) be able to understand Earth-sized planets as a population? In this study, we simulate the ability of space-based coronagraphy missions to uncover trends in planetary albedo as a function of instellation, and potentially constrain the boundaries of the habitable zone (HZ). We adapt the Bioverse statistical comparative planetology framework to simulate the scientific output of possible designs for HWO. With this tool, we generate a synthetic planetary population with injected population-level trends in albedo and simulate the observability of planets. We then determine the statistical power to which these trends can be recovered as a function of the strength of the injected trend and the sample size of Earth-sized planets in the habitable zone (exoEarths). The strongest trends in albedo require a sample size of roughly 25–30 exoEarths to recover with high confidence. However, for weaker albedo trends, the required number of planets increases rapidly. If a mission is designed to meet the Decadal Survey’s requirement of 25 exoEarths, it would be able to recover very strong trends in albedo associated with the HZ, but would struggle to confidently detect weaker trends. We explore multiple strategies to increase one’s ability to recover weak trends, such as reducing the uncertainties in observables, incorporating additional observables such as planet colors, and obtaining direct constraints on planetary albedo from full spectral retrievals.

We uniformly combined data from the NASA Kepler and K2 missions to compute planet occurrence rates across the entire FGK and M-dwarf stellar range. The K2 mission, driven by targets selected by guest observers, monitored nine times more M dwarfs than the Kepler mission. Combined, Kepler and K2 observed 130 short-period (P = 1–40 days) Earth to Neptune-sized candidate planets orbiting M dwarfs. K2 observed 3.5 times more of these planets than Kepler for host stars below 3700 K. Our planet occurrence rates show that short-period sub-Neptunes peak at 375 0 − 97 + 153 K and drop for cooler M dwarfs. A peak near this location was predicted by pebble accretion planet formation models and confirmed here by observations for the first time. Super-Earths continue to increase in occurrence toward cooler stars and show no clear evidence of a peak in the host star range considered here (3200–6900 K). Our observations provide critical input to further refine planet formation models. We strongly recommend further study of mid-to-late M dwarfs with TESS and soon the Nancy Grace Roman Space Telescope and PLATO to identify additional small planet trends.

The NASA Exoplanet Archive (NEA) and the Exoplanet Follow-up Observing Program service are two widely used resources for the exoplanet community. The NEA provides a complete and accurate accounting of exoplanetary systems published by NASA missions and by the community in the refereed literature. In anticipation of continued exponential growth in the number of exoplanetary systems and the increasing complexity in our characterization of these systems, the NEA has restructured its primary tables and interfaces, as well as extending and standardizing their modes of access. The Exoplanet Follow-up Observing Program service provides the exoplanet community with a venue for coordinating and sharing follow-up and precursor data for exoplanets, their host stars, and stars that might eventually be targets for future planet searches and recently reached 1 million files uploaded by the community. In this paper, we describe the updates to our data holdings, functionality, accessibility, and tools, as well as future priorities for these two services.