arXiv subjects

Timothy R. Holt

Publications and source records attributed to Timothy R. Holt.

12 recordsLinked to original sources

arXiv2025

Optimising Radial Velocity Detection Limits for Southern Habitable Worlds Observatory Targets

The planned NASA Habitable Worlds Observatory (HWO) flagship mission aims to image and spectroscopically characterise 25 Earth-size planets in the habitable zones of their stars. However, one giant planet in the habitable zone can ruin your whole day. Recent work has examined the current state of our knowledge on the presence or absence of such objects in samples of likely HWO targets, and that knowledge has been found wanting; even Saturn-mass planets remain undetectable in many of these systems. In this work, we present simulations assessing the degree to which new campaigns of high-cadence radial velocity observations can ameliorate this woeful state of affairs. In particular, we highlight the value of moderate-precision but highly flexibly-scheduled RV facilities in aiding this necessary HWO precursor science. We find that for a subset of Southern HWO stars, 6 years of new RVs from the Minerva-Australis telescope array in Australia can improve the median detection sensitivity in the habitable zones of 13 likely HWO targets to $\sim$50 Earth masses, an improvement of $\sim$44%.

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arXiv2024

The Search for the Inbetweeners: How packed are TESS planetary systems?

In this work, we examine seven systems discovered by TESS, to see whether there is any room in those systems for an additional planet (or several) to lurk unseen between the two planets already confirmed therein. In five of those systems (namely HD 15337; HD 21749; HD 63433; HD 73583 and LTT 3780) we find that there is ample room for an undiscovered planet to move between those that have already been discovered. In other words, as they currently stand, those systems are not tightly packed. In stark contrast, the perturbative influence of the two known TOI-1670 planets is such that additional planets in between are ruled out. The final system, TOI 421, is more challenging. In the vast majority of cases, adding an Earth-mass planet to that system between the orbits of the known planets caused catastrophic instability. Just ~1.1% of our simulations of the modified system proved dynamically stable on a timescale of one million years. As a result, it seems that there is very little room between the two known planets in the TOI 421 system for an addition unseen world to exist, but the existence of such a planet can not be definitely ruled out on dynamical grounds alone.

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arXiv2024

Candidate Distant Trans-Neptunian Objects Detected by the New Horizons Subaru TNO Survey

We report the detection of 239 trans-Neptunian Objects discovered through the on-going New Horizons survey for distant minor bodies being performed with the Hyper Suprime-Cam mosaic imager on the Subaru Telescope. These objects were discovered in images acquired with either the r2 or the recently commissioned EB-gri filter using shift and stack routines. Due to the extremely high stellar density of the search region down stream of the spacecraft, new machine learning techniques had to be developed to manage the extremely high false positive rate of bogus candidates produced from the shift and stack routines. We report discoveries as faint as r2$\sim26.5$. We highlight an overabundance of objects found at heliocentric distances $R\gtrsim70$~au compared to expectations from modelling of the known outer Solar System. If confirmed, these objects betray the presence of a heretofore unrecognized abundance of distant objects that can help explain a number of other observations that otherwise remain at odds with the known Kuiper Belt, including detections of serendipitous stellar occultations, and recent results from the Student Dust Counter on-board the New Horizons spacecraft.

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arXiv2022

HD 83443c: A highly eccentric giant planet on a 22-year orbit

We report the discovery of a highly eccentric long-period Jovian planet orbiting the hot-Jupiter host HD\,83443. By combining radial velocity data from four instruments (AAT/UCLES, Keck/HIRES, HARPS, Minerva-Australis) spanning more than two decades, we find evidence for a planet with m~sin~$i=1.35^{+0.07}_{-0.06}$\,\mj, moving on an orbit with $a=8.0\pm$0.8\,au and eccentricity $e=0.76\pm$0.05. We combine our radial velocity analysis with \textit{Gaia} eDR3 /\textit{Hipparcos} proper motion anomalies and derive a dynamical mass of $1.5^{+0.5}_{-0.2} M_{\rm Jup}$. We perform a detailed dynamical simulation that reveals locations of stability within the system that may harbor additional planets, including stable regions within the habitable zone of the host star. HD\,83443 is a rare example of a system hosting a hot Jupiter and an exterior planetary companion. The high eccentricity of HD\,83443c suggests that a scattering event may have sent the hot Jupiter to its close orbit while leaving the outer planet on a wide and eccentric path.

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arXiv2021

Astrocladistics of the Jovian Trojan Swarms

The Jovian Trojans are two swarms of small objects that share Jupiter's orbit, clustered around the leading and trailing Lagrange points, L$_4$ and L$_5$. In this work, we investigate the Jovian Trojan population using the technique of astrocladistics, an adaptation of the `tree of life' approach used in biology. We combine colour data from WISE, SDSS, Gaia DR2 and MOVIS surveys with knowledge of the physical and orbital characteristics of the Trojans, to generate a classification tree composed of clans with distinctive characteristics. We identify 48 clans, indicating groups of objects that possibly share a common origin. Amongst these are several that contain members of the known collisional families, though our work identifies subtleties in that classification that bear future investigation. Our clans are often broken into subclans, and most can be grouped into 10 superclans, reflecting the hierarchical nature of the population. Outcomes from this project include the identification of several high priority objects for additional observations and as well as providing context for the objects to be visited by the forthcoming \textit{Lucy} mission. Our results demonstrate the ability of astrocladistics to classify multiple large and heterogeneous composite survey datasets into groupings useful for studies of the origins and evolution of our Solar system.

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arXiv2021

Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), using Hubble, Spitzer, ZTF, Keck, APO and GROWTH Visible & Infrared Imaging and Spectroscopy

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD$_2$ taken with HST/WFC3, Spitzer/IRAC, the GROWTH telescope network, visible spectroscopy from Keck/LRIS and archival ZTF observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD$_2$ has a radius between 0.2-1.8 km assuming a 0.08 albedo and a coma dominated by $\sim$100$μ$ m-scale dust ejected at $\sim$1 m/s speeds with a $\sim$1'' jet pointing in the SW direction. LD$_2$ experienced a total dust mass loss of $\sim$10$^8$ kg at a loss rate of $\sim$6 kg/s with Af$ρ$/cross-section varying between $\sim$85 cm/125 km$^2$ and $\sim$200 cm/310 km$^2$ from 2019 April 9 to 2019 Nov 8. If the increase in Af$ρ$/cross-section remained constant, it implies LD$_2$'s activity began $\sim$2018 November when within 4.8 au of the Sun, implying the onset of H$_2$O sublimation. We measure CO/CO$_2$ gas production of $\lesssim$10$^{27}$ mol/s /$\lesssim$10$^{26}$ mol/s from our 4.5 $μ$m Spitzer observations, $g$-$r$ = 0.59$\pm$0.03, $r$-$i$ = 0.18$\pm$0.05, $i$-$z$ = 0.01$\pm$0.07 from GROWTH observations, H$_2$O gas production of $\lesssim$80 kg/s scaling from our estimated $C_2$ production of $Q_{C_2}\lesssim$7.5$\times10^{24}$ mol/s from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD$_2$ is similar to Jupiter family comets having close encounters with Jupiter within $\sim$0.5 Hill radius in the last $\sim$3 y, within 0.8 Hill radius in $\sim$9 y. Additionally, 78.8$\%$ of our orbital clones are ejected from the Solar System within $1 \times 10^{6}$ years having a dynamical half-life of 3.4 $\times 10^5$ years.

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arXiv2020

Captured Small Solar System Bodies in the Ice Giant Region

This white paper advocates for the inclusion of small, captured Outer Solar system objects, found in the Ice Giant region in the next Decadal Survey. These objects include the Trojans and Irregular satellite populations of Uranus and Neptune. The captured small bodies provide vital clues as to the formation of our Solar system. They have unique dynamical situations, which any model of Solar system formation needs to explain. The major issue is that so few of these objects have been discovered, with very little information known about them. The purpose of this document is to prioritize further discovery and characterization of these objects. This will require the use of NASA and NSF facilities over the 2023 2032 decade, including additional support for analysis. This is in preparation for potential future insitu missions in the following decades.

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arXiv2020

Community Challenges in the Era of Petabyte-Scale Sky Surveys

We outline the challenges faced by the planetary science community in the era of next-generation large-scale astronomical surveys, and highlight needs that must be addressed in order for the community to maximize the quality and quantity of scientific output from archival, existing, and future surveys, while satisfying NASA's and NSF's goals.

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arXiv2020

The Scientific Impact of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) for Solar System Science

Vera C. Rubin Observatory will be a key facility for small body science in planetary astronomy over the next decade. It will carry out the Legacy Survey of Space and Time (LSST), observing the sky repeatedly in u, g, r, i, z, and y over the course of ten years using a 6.5 m effective diameter telescope with a 9.6 square degree field of view, reaching approximately r = 24.5 mag (5-σ depth) per visit. The resulting dataset will provide extraordinary opportunities for both discovery and characterization of large numbers (10--100 times more than currently known) of small solar system bodies, furthering studies of planetary formation and evolution. This white paper summarizes some of the expected science from the ten years of LSST, and emphasizes that the planetary astronomy community should remain invested in the path of Rubin Observatory once the LSST is complete.

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arXiv2020

A pair of Jovian Trojans at the L4 Lagrange point

Asteroid pairs, two objects that are not gravitationally bound to one another, but share a common origin, have been discovered in the Main belt and Hungaria populations. Such pairs are of major interest, as the study of their evolution under a variety of dynamical influences can indicate the time since the pair was created. To date, no asteroid pairs have been found in the Jovian Trojans, despite the presence of several binaries and collisional families in the population. The search for pairs in the Jovian Trojan population is of particular interest, given the importance of the Trojans as tracers of planetary migration during the Solar system's youth. Here we report a discovery of the first pair, (258656) 2002~ES$_{76}$ and 2013~CC$_{41}$, in the Jovian Trojans. The two objects are approximately the same size and are located very close to the L4 Lagrange point. Using numerical integrations, we find that the pair is at least $360$~Myr old, though its age could be as high as several Gyrs. The existence of the (258656) 2002~ES$_{76}$--2013~CC$_{41}$ pair implies there could be many such pairs scattered through the Trojan population. Our preferred formation mechanism for the newly discovered pair is through the dissociation of an ancient binary system, triggered by a sub-catastrophic impact, but we can not rule out rotation fission of a single object driven by YORP torques. A by-product of our work is an up-to-date catalog of Jovian Trojan proper elements, which we have made available for further studies.

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arXiv2020

Characterization of Temporarily-Captured Minimoon 2020 CD$_3$ by Keck Time-resolved Spectrophotometry

We present time-resolved visible spectrophotometry of minimoon 2020 CD$_3$, the second asteroid known to become temporarily captured by the Earth-Moon system's gravitational field. The spectrophotometry was taken with Keck I/LRIS between wavelengths 434 nm and 912 nm in $B$, $g$, $V$, $R$, $I$ and RG850 filters as it was leaving the Earth-Moon system on 2020 March 23 UTC. The spectrophotometry of 2020 CD$_3$ most closely resembles the spectra of V-type asteroids and some Lunar rock samples with a reddish slope of ~18$\%$/100 nm between 434 nm and 761 nm corresponding to colors of $g$-$r$ = 0.62$\pm$0.08, $r$-$i$ = 0.21 $\pm$ 0.06 and an absorption band at ~900 nm corresponding to $i$-$z$ = -0.54$\pm$0.10. Combining our measured 31.9$\pm$0.1 absolute magnitude with an albedo of 0.35 typical for V-type asteroids, we determine 2020 CD$_3$'s diameter to be ~0.9$\pm$0.1 m making it the first minimoon and one of the smallest asteroids to be spectrally studied. We use our time-series photometry to detect periodic lightcurve variations with a $<$10$^{-4}$ false alarm probability corresponding to a lightcurve period of ~573 s and a lightcurve amplitude of ~1 mag implying 2020 CD$_3$ possesses a $b/a$ axial ratio of ~2.5. In addition, we extend the observational arc of 2020 CD$_3$ to 37 days between 2020 February 15 UTC and 2020 March 23 UTC. From the improved orbital solution for 2020 CD$_3$, we estimate its likely duration of its capture to be ~2 y, and we measure the non-gravitation perturbation on its orbit due to radiation pressure with an area-to-mass ratio of 6.9$\pm$2.4$\times$10$^{-4}$ m$^2$/kg implying a density of 2.3$\pm$0.8 g/cm$^3$, broadly compatible with the densities of other meter-scale asteroids and Lunar rock. We searched for pre-discovery detections of 2020 CD$_3$ in the ZTF archive as far back as 2018 October, but were unable to locate any positive detections.

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arXiv2020

Stability of Jovian Trojans and their collisional families

The Jovian Trojans are two swarms of objects located around the L$_4$ and L$_5$ Lagrange points. The population is thought to have been captured by Jupiter during the Solar system's youth. Within the swarms, six collisional families have been identified in previous work, with four in the L$_4$ swarm, and two in the L$_5$. Our aim is to investigate the stability of the two Trojan swarms, with a particular focus on these collisional families. We find that the members of Trojan swarms escape the population at a linear rate, with the primordial L$_4$ (23.35% escape) and L$_5$ (24.89% escape) population sizes likely 1.31 and 1.35 times larger than today. Given that the escape rates were approximately equal between the two Trojan swarms, our results do not explain the observed asymmetry between the two groups, suggesting that the numerical differences are primordial in nature, supporting previous studies. Upon leaving the Trojan population, the escaped objects move onto orbits that resemble those of the Centaur and short-period comet populations. Within the Trojan collisional families, the 1996 RJ and 2001 UV$_{209}$ families are found to be dynamically stable over the lifetime of the Solar system, whilst the Hektor, Arkesilos and Ennomos families exhibit various degrees of instability. The larger Eurybates family shows 18.81\% of simulated members escaping the Trojan population. Unlike the L4 swarm, the escape rate from the Eurybates family is found to increase as a function of time, allowing an age estimation of approximately $1.045\pm 0.364 \times 10^9$ years.

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