arXiv subjects

Darin Ragozzine

Publications and source records attributed to Darin Ragozzine.

At least 19 recordsLinked to original sources

arXiv2026

Beyond Point Masses. VI. Spin-Orbit Evolution of the Centaur Binary Typhon-Echidna

Only three binaries have been identified among the Centaur population. Because their perihelia are significantly closer than those of other trans-Neptunian binaries (TNBs), these systems allow a detailed look at tight binaries in the broader TNO population and provide critical insight into the disruption of binaries as they enter the Centaur population. Using recent and archival \textit{Hubble Space Telescope} (HST) observations, along with Keck data, we present a spin-orbit study of Typhon-Echidna. We find that the binary's mutual orbit is inconsistent with a Keplerian orbit; more detailed non-Keplerian fits show that the mutual orbit is rapidly precessing. We measure Typhon's dynamical oblateness, $J_2$, at $\sim10σ$ confidence and find that Typhon's rotation pole is $\gtrsim20^\circ$ misaligned with the binary's mutual orbit. Assuming Typhon has a triaxial shape, our results, combined with rotational light curves and thermal measurements from the literature, suggest ellipsoidal semi-axes of $a=93^{+8}_{-6}$ km, $b=84^{+6}_{-6}$ km, and $c=65^{+9}_{-8}$ km. We further investigate the observational consequences of the complex spin-orbit dynamics, including light curve alteration by axial precession of Typhon and substantial changes to the system's mutual event season. Based on the system's dynamically excited state, we suggest a recent encounter with a giant planet may have substantially altered the system, potentially consistent with a binary in an early stage of disruption. This hypothesis can be tested with resolved photometric observations of the system. Our investigation highlights how non-Keplerian dynamics enhances our understanding of TNB systems and motivates ongoing observations of TNBs with astrometry, photometry, and stellar occultations.

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arXiv2026

Triaxial shapes and densities of G!kún||'hòmdímà, Haumea, and Varda from stellar occultations

The shapes and densities of mid-sized and large trans-Neptunian objects (TNOs) are pivotal for understanding a variety of important aspects of planet formation. In this work, we present a Bayesian shape modeling method which combines constraints from rotational light curves and satellite orbits to construct three-dimensional shape models of TNOs. We use it to reanalyze three stellar occultations of the TNOs (229762) G!kún||'hòmdímà (2007 UK$_{126}$), (136108) Haumea, and (174567) Varda. By assuming that their satellites (or ring) orbit in their respective equatorial planes, we are able to derive unique shape models for both G!kún||'hòmdímà and Haumea. Our derived shape for G!kún||'hòmdímà is spheroidal with $a = b = 329^{+4}_{-3}$ km and $c = 294^{+11}_{-10}$ km, with a system density $ρ= 1007^{+50}_{-49}$ kg m$^{-3}$. For Haumea, we find $a = 1061^{+87}_{-71}$ km, $b = 844^{+5}_{-7}$ km, and $c = 514^{+18}_{-19}$ km, providing $ρ= 2050^{+157}_{-152}$ kg m$^{-3}$. For Varda, after updating its mutual orbit with its satellite Ilmarë, we find that currently published data are unable to fully constrain its three-dimensional shape. Intriguingly, Varda's elongated limb appears to point towards its satellite at the time of the occultation. With a $\sim$2\% chance of such an alignment happening randomly, this may be suggestive of a frozen-in tidal and/or rotational bulge. Our work emphasizes the importance of how external constraints can improve occultation analyses. With continued observations of rotational light curves, stellar occultations, and satellite orbits, these and other TNOs can have their shapes and densities further refined.

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arXiv2026

You Only Stack Once (YOSO): A Motion-Filtered, Deep-Learning Framework for Detecting Faint Moving Sources

We present You Only Stack Once (YOSO), an automated pipeline designed to detect faint, slow-moving Solar System objects in wide-field astronomical surveys. The pipeline integrates a novel Gaussian Motion Filter (GMoF) that operates at the pixel level to enhance signal-to-noise for objects exhibiting a range of apparent rates of motion. Unlike conventional shift-and-stack methods, which rely on discrete velocity trials, GMoF amplifies trails while suppressing random noise and static background features. Applied to a subset of DEEP observations from the Dark Energy Camera, YOSO recovered 45 out of 73 previously detected objects, as well as 11 new TNOs. It also discovered 216 objects in the near Solar System. Although alternative shift-and-stack methods are sensitive to objects about 0.88 magnitudes fainter, YOSO's false positive rate is extremely low, since it detects only sources that exhibit a trail and are consistent with a point source when shifted at the right rate. We show how this method can be deployed on large surveys like LSST, and adapted for other domains that require motion-based signal enhancement, including exoplanet imaging through Angular Differential Imaging (ADI), and near-Earth object (NEO) detection for missions like NEO Surveyor. YOSO thus provides a versatile, scalable approach for extracting faint, motion-dependent signals in the era of data-intensive astronomy.

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arXiv2026

Small Body Dynamics with SBDynT: Proper Elements and Chaos Analysis

The Small Body Dynamics Tool (SBDynT) is software written for the community of Solar System small body researchers to perform dynamical classification, characterization, and investigation. SBDynT provides advanced simulation analysis capabilities that make it straightforward to determine mean motion resonance occupation, proper orbital elements, and a variety of stability indicators. These calculations can be performed for small bodies that are known, newly discovered, or simulated; observational uncertainties can be incorporated through the use of dynamical clones. In this paper, we describe the methods for producing proper orbital elements and stability indicators, which serve as essential tools for characterizing dynamical stability and long-term evolution. Through extensive validation, we demonstrate that this code offers a robust open-source framework for investigating the dynamics of Solar System small bodies with high accuracy. We also aim for computational efficiency allowing SBDynT to provide dynamical information for the several-fold increases in small bodies expected in the LSST era.

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arXiv2026

Trans-Neptunian Binary Mutual Events in the 2020s and 2030s

Mutual events of trans-Neptunian binaries (TNBs) provide rare opportunities to measure the physical and orbital properties of small bodies in the outer solar system. However, successful observations of these events have been limited by uncertain predictions. Here, we present probabilistic predictions of TNB mutual events occurring through the 2030s, using high-precision non-Keplerian orbit solutions from the Beyond Point Masses project combined with a Bayesian framework that propagates orbital and size uncertainties. Our methods generate distributions of event timing, duration, depth, and probability of occurrence, enabling direct assessment of observability. We provide predictions for five systems with ongoing or imminent mutual event seasons, including (38628) Huya, (58534) Logos-Zoe, (148780) Altjira, (469705) Kágára and !Hãunu, and (524366) 2001 XR$_{254}$. Preparing for upcoming events with long-baseline light curve monitoring is vital, as events may be difficult to distinguish from a regular rotational light curve. Rapid dissemination of event detections will benefit the entire community, allowing predictions to be updated, ensuring that these rare mutual event opportunities can be fully exploited.

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arXiv2025

Beyond Point Masses. V. Weywot's Non-Keplerian Orbit

We present a detailed dynamical analysis of the Quaoar-Weywot system based on nearly 20 years of high-precision astrometric data, including new HST observations and stellar occultations. Our study reveals that Weywot's orbit deviates significantly from a purely Keplerian model, requiring the inclusion of Quaoar's non-spherical gravitational field and center-of-body-center-of-light (COB-COL) offsets in our orbit models. We place a robust upper limit on Weywot's orbital eccentricity ($e<0.02$), substantially lower than previous estimates, which has important implications for the strength of mean motion resonances (MMRs) acting on Quaoar's ring system. Under the assumption that Quaoar's rings lie in its equatorial plane, we detect Quaoar's dynamical oblateness, $J_2$, at $\sim$2$σ$ confidence. The low $J_2$ value found under that assumption implies Quaoar is differentiated, with a total bulk density of $1751\pm13$ (stat.) kg m$^{-3}$. Additionally, we detect significant COB-COL offsets likely arising from latitudinal albedo variations across Quaoar's surface. These offsets are necessary to achieve a statistically robust orbit fit and highlight the importance of accounting for surface heterogeneity when modeling the orbits of dwarf planet moons. These findings improve our understanding of Quaoar's interior and surface while providing key insights into the stability and confinement mechanisms of its rings.

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arXiv2025

Are We There Yet? Challenges in Quantifying the Frequency of Earth Analogs in the Habitable Zone

Searching for life elsewhere in the universe is one of the most highly prioritized pursuits in astronomy today. However, the ability to observe evidence of Earth-like life through biosignatures is limited by the number of planets in the solar neighborhood with conditions similar to Earth. The occurrence rate of Earth-like planets in the habitable zones of Sun-like stars, $η_{\oplus}$, is therefore crucial for addressing the apparent lack of consensus on its value in the literature. Here we present a review of the current understanding of $η_{\oplus}$. We first provide definitions for parameters that contribute to $η_{\oplus}$. Then, we discuss the previous and current estimated parameter values and the context of the limitations on the analyses that produced these estimates. We compile an extensive list of the factors that go into any calculation of $η_{\oplus}$, and how detection techniques and surveys differ in their sensitivity and ability to accurately constrain $η_{\oplus}$. Understanding and refining the value of $η_{\oplus}$ is crucial for upcoming missions and telescopes, such as the planned Habitable Worlds Observatory and the Large Interferometer for Exoplanets, which aim to search for biosignatures on exoplanets in the solar neighborhood.

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arXiv2025

Synchronous Rotation in the (120347) Salacia-Actaea System

We report on roughly 16 years of photometric monitoring of the transneptunian binary system (120347) Salacia-Actaea which provides significant evidence that Salacia and Actaea are tidally locked to the mutual orbital period in a fully synchronous configuration. The orbit of Actaea is updated, followed by a Lomb-Scargle periodogram analysis of the ground-based photometry which reveals a synodic period similar to the orbital period and a peak-to-peak lightcurve amplitude of δm = 0.0900 {\pm} 0.0036 mag (1σ uncertainty). Incorporating archival HST photometry that resolves each component, we argue that the periodicity in the unresolved data is driven by a longitudinally varying surface morphology on Salacia, and derive a sidereal rotation period that is within 1σ of the mutual orbital period. A rudimentary tidal evolution model is invoked that suggests synchronization occurred within 1.1 Gyr after Actaea was captured/formed.

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arXiv2025

Characterization of the Deep, Extended Kuiper Belt in the Galactic Disk

We propose a Roman Space Telescope survey to investigate fundamental properties of the distant solar system in the region of the Kuiper Belt where object characteristics and the size distribution are inaccessible from any other telescope. Our pointing is coincident with the search space accessible to NASA's New Horizons spacecraft meaning, that a discovered object sufficiently near the orbit of New Horizons would potentially be investigated by a close flyby. In addition, numerous objects expected to be discovered by this search can be observed in the distance by New Horizons allowing their surface properties and satellite systems to both be probed. As designed, this survey will discover and determine orbits for as many as 900 Kuiper Belt objects (KBOs), providing a unique opportunity for ground-breaking Kuiper Belt science. It will simultaneously: (1) Probe and characterize the deep Kuiper Belt by identifying objects as small as a few km and taking our understanding of the size distribution to a new level. This has implications for understanding the the standard model (the Streaming Instability) of KBO formation and elucidating crater formation physics on these icy bodies. (2) Open KBO rotation studies, in particular of those objects with long rotation periods,(3) Discover and characterize KBO binaries at large distances, important because their duplicity offers information about object densities at these distant locations from the Sun. (4) Shed light on the cratering history of KBOs and improving the dating of the surfaces of Arrokoth, Pluto and Charon in addition to helping to place the 32 distant KBOs New Horizons has observed in context. This project also has synergies with transiting exoplanet studies due to the stellar density of our search fields. Coupled with our timing requirements it is sensitive to discovery of hot Jupiters and hot Neptunes.

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arXiv2024

Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods

We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multi-planet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly-derived for use in occurrence rates studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multi-decadal timescales as predicted by the small formal errors (typically 1 part in $10^6$ and rarely $ > 10^{-5}$) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anti-correlated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen non-transiting planets that have been identified around stars that host transiting planets discovered by Kepler.

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arXiv2024

Beyond Point Masses. I. New Non-Keplerian Modeling Tools Applied to Trans-Neptunian Triple (47171) Lempo

Many details of the formation and evolution of the solar system are best inferred by understanding the orbital and physical properties of small bodies in the solar system. For example, small body binaries are particularly valuable for measuring masses. By extending the models of small body binaries beyond point masses, new information about the shape and spin orientation becomes available. This is particularly informative for Trans-Neptunian multiples (two or more components) where shapes and spin orientations are poorly understood. Going beyond point masses requires modeling tools that no longer assume fixed Keplerian orbits. To this end, we have developed a new n-quadrupole integrator SPINNY (SPIN+N-bodY) and pair it with a Bayesian parameter inference tool MultiMoon, both of which are publicly available. We describe these tools and how they can be used to learn more about solar system small body multiple systems. We then apply them to the unique Trans-Neptunian hierarchical triple system (47171) Lempo, finding a three-point-mass solution for the first time. This solution has two surprises: unequal densities of the inner components and a dynamical configuration apparently unstable on the age of the solar system.

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arXiv2024

Beyond Point Masses. IV. TNO Altjira is Likely a Hierarchical Triple Discovered Through Non-Keplerian Motion

Dynamically studying Trans-Neptunian Object (TNO) binaries allows us to measure masses and orbits. Most of the known objects appear to have only two components, except (47171) Lempo which is the single known hierarchical triple system with three similar-mass components. Though hundreds of TNOs have been imaged with high-resolution telescopes, no other hierarchical triples (or trinaries) have been found among solar system small bodies, even though they are predicted in planetesimal formation models such as gravitational collapse after the streaming instability. By going beyond the point-mass assumption and modeling TNO orbits as non-Keplerian, we open a new window into the shapes and spins of the components, including the possible presence of unresolved ``inner'' binaries. Here we present evidence for a new hierarchical triple, (148780) Altjira (2001 UQ$_{18}$), based on non-Keplerian dynamical modeling of the two observed components. We incorporate two recent Hubble Space Telescope (HST) observations, leading to a 17 year observational baseline. We present a new open-source Bayesian Point Spread Function (PSF) fitting code called nPSF that provides precise relative astrometry and uncertainties for single images. Our non-Keplerian analysis measures a statistically-significant ($\sim$2.5-$σ$) non-spherical shape for Altjira. The measured $J_2$ is best explained as an unresolved inner binary and an example hierarchical triple model gives the best fit to the observed astrometry. Using an updated non-Keplerian ephemeris (which is significantly different from the Keplerian predictions), we show that the predicted mutual event season for Altjira has already begun with several excellent opportunities for observations through $\sim$2030.

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arXiv2023

The DECam Ecliptic Exploration Project (DEEP) II. Observational Strategy and Design

We present the DECam Ecliptic Exploration Project (DEEP) survey strategy including observing cadence for orbit determination, exposure times, field pointings and filter choices. The overall goal of the survey is to discover and characterize the orbits of a few thousand Trans-Neptunian Objects (TNOs) using the Dark Energy Camera (DECam) on the Cerro Tololo Inter-American Observatory (CTIO) Blanco 4 meter telescope. The experiment is designed to collect a very deep series of exposures totaling a few hours on sky for each of several 2.7 square degree DECam fields-of-view to achieve a magnitude of about 26.2 using a wide VR filter which encompasses both the V and R bandpasses. In the first year, several nights were combined to achieve a sky area of about 34 square degrees. In subsequent years, the fields have been re-visited to allow TNOs to be tracked for orbit determination. When complete, DEEP will be the largest survey of the outer solar system ever undertaken in terms of newly discovered object numbers, and the most prolific at producing multi-year orbital information for the population of minor planets beyond Neptune at 30 au.

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arXiv2023

A Possible Third Body in the X-Ray System GRS 1747-312 and Models with Higher-Order Multiplicity

GRS 1747-312 is a bright Low-Mass X-ray Binary in the globular cluster Terzan 6, located at a distance of 9.5 kpc from the Earth. It exhibits regular outbursts approximately every 4.5 months, during which periodic eclipses are known to occur. These eclipses have only been observed in the outburst phase, and are not clearly seen when the source is quiescent. Recent Chandra observations of the source were performed in June 2019 and April, June, and August of 2021. Two of these observations captured the source during its outburst, and showed clear flux decreases at the expected time of eclipse. The other two observations occurred when the source was quiescent. We present the discovery of a dip that occurred during the quiescent state. The dip is of longer duration and its time of occurrence does not fit the ephemeris of the shorter eclipses. We study the physical characteristics of the dip and determine that it has all the properties of an eclipse by an object with a well defined surface. We find that there are several possibilities for the nature of the object causing the 5.3 ks eclipse. First, GRS 1747-312 may be an X-ray triple, with an LMXB orbited by an outer third object, which could be an M-dwarf, brown dwarf, or planet. Second, there could be two LMXBs in close proximity to each other, likely bound together. Whatever the true nature of the eclipser, its presence suggests that the GRS 1747-312 system is unique.

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arXiv2023

The DECam Ecliptic Exploration Project (DEEP) III: Survey characterization and simulation methods

We present a detailed study of the observational biases of the DECam Ecliptic Exploration Project's (DEEP) B1 data release and survey simulation software that enables direct statistical comparisons between models and our data. We inject a synthetic population of objects into the images, and then subsequently recover them in the same processing as our real detections. This enables us to characterize the survey's completeness as a function of apparent magnitudes and on-sky rates of motion. We study the statistically optimal functional form for the magnitude, and develop a methodology that can estimate the magnitude and rate efficiencies for all survey's pointing groups simultaneously. We have determined that our peak completeness is on average 80\% in each pointing group, and our magnitude drops to $25\%$ of this value at $m_{25} = 26.22$. We describe the freely available survey simulation software and its methodology. We conclude by using it to infer that our effective search area for objects at 40 au is $14.8°^2$, and that our lack of dynamically cold distant objects means that there at most $8\times 10^3$ objects with $60 < a < 80$ au and absolute magnitudes $H \leq 8$.

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arXiv2023

The DECam Ecliptic Exploration Project (DEEP) VI: first multi-year observations of trans-Neptunian objects

We present the first set of trans-Neptunian objects (TNOs) observed on multiple nights in data taken from the DECam Ecliptic Exploration Project (DEEP). Of these 110 TNOs, 105 do not coincide with previously known TNOs and appear to be new discoveries. Each individual detection for our objects resulted from a digital tracking search at TNO rates of motion, using two to four hour exposure sets, and the detections were subsequently linked across multiple observing seasons. This procedure allows us to find objects with magnitudes $m_{VR} \approx 26$. The object discovery processing also included a comprehensive population of objects injected into the images, with a recovery and linking rate of at least $94\%$. The final orbits were obtained using a specialized orbit fitting procedure that accounts for the positional errors derived from the digital tracking procedure. Our results include robust orbits and magnitudes for classical TNOs with absolute magnitudes $H \sim 10$, as well as a dynamically detached object found at 76 au (semi-major axis $a\approx 77 \, \mathrm{au}$). We find a disagreement between our population of classical TNOs and the CFEPS-L7 three component model for the Kuiper belt.

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arXiv2023

The DECam Ecliptic Exploration Project (DEEP): I. Survey description, science questions, and technical demonstration

We present here the DECam Ecliptic Exploration Project (DEEP), a three year NOAO/NOIRLab Survey that was allocated 46.5 nights to discover and measure the properties of thousands of trans-Neptunian objects (TNOs) to magnitudes as faint as VR~27, corresponding to sizes as small as 20 km diameter. In this paper we present the science goals of this project, the experimental design of our survey, and a technical demonstration of our approach. The core of our project is "digital tracking," in which all collected images are combined at a range of motion vectors to detect unknown TNOs that are fainter than the single exposure depth of VR~23 mag. Through this approach we reach a depth that is approximately 2.5 magnitudes fainter than the standard LSST "wide fast deep" nominal survey depth of 24.5 mag. DEEP will more than double the number of known TNOs with observational arcs of 24 hours or more, and increase by a factor of 10 or more the number of known small (<50 km) TNOs. We also describe our ancillary science goals, including measuring the mean shape distribution of very small main belt asteroids, and briefly outline a set of forthcoming papers that present further aspects of and preliminary results from the DEEP program.

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arXiv2023

Enabling Exoplanet Demographics Studies with Standardized Exoplanet Survey Meta-Data

Goal 1 of the National Academies of Science, Engineering and Mathematics Exoplanet Science Strategy is "to understand the formation and evolution of planetary systems as products of the process of star formation, and characterize and explain the diversity of planetary system architectures, planetary compositions, and planetary environments produced by these processes", with the finding that "Current knowledge of the demographics and characteristics of planets and their systems is substantially incomplete." One significant roadblock to our ongoing efforts to improve our demographics analyses is the lack of comprehensive meta-data accompanying published exoplanet surveys. The Exoplanet Program Analysis Group (ExoPAG) Science Interest Group 2: Exoplanet Demographics has prepared this document to provide guidance to survey architects, authors, referees and funding agencies as to the most valuable such data products for five different exoplanet detection techniques - transit, radial velocity, direct imaging, microlensing and astrometry. We find that making these additional data easily available would greatly enhance the community's ability to perform robust, reproducible demographics analyses, and make progress on achieving the most important goals identified by the exoplanet and wider astronomical community.

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