arXiv subjects

Audrey Thirouin

Publications and source records attributed to Audrey Thirouin.

At least 19 recordsLinked to original sources

arXiv2026

The Non-Principal-Axis Rotation and Convex Shape Model of Earth Quasi-Satellite and the Target of China's Tianwen-2 Mission (469219) Kamo`oalewa

(469219) Kamo`oalewa is the most stable Earth quasi-satellite and the target of China's Tianwen-2 asteroid sample return mission. Due to its small size, fast rotation, and the limited observing geometry accessible from the ground, many physical properties of Kamo`oalewa remain poorly constrained, including the rotational state and shape. We obtained three epochs of high-cadence, high signal-to-noise photometric lightcurves of Kamo`oalewa with the Gemini North Telescope from 2026 April to May, supplemented by one lightcurve from the Lowell Discovery Telescope in 2026 May. Our analysis suggests that Kamo`oalewa is in a non-principal-axis rotation with an elongated shape. Four possible solutions exist, including a long-axis mode (LAM) solution and a short-axis mode (SAM) solution, as well as their corresponding mirrored angular momentum directions. The most preferable solution has a LAM model with a precession period $P_ϕ=27.65\pm0.03~\text{min}$ and a rotational period $P_ψ=50.49\pm0.08~\text{min}$, and the angular momentum points to ecliptic coordinates $(λ, β) = (226^\mathrm{o}\pm20^\mathrm{o}, -39^\mathrm{o}\pm20\mathrm{o})$, although we cannot rule out other solutions or other close-by periods due to aliasing. We also derived a convex shape inversion for the LAM models with consistent rotational parameters but could not find a satisfactory inversion for the SAM models. The corresponding angular momentum points to $(λ, β)=(225^\mathrm{o}, -43^\mathrm{o})$, and the periods are $P_ϕ=27.90~\text{min}$ and $P_ψ=49.66~\text{min}$. The non-principal-axis rotation provides additional constraints on the dynamic history or the internal structure of Kamo`oalewa.

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arXiv2026

Rotation and Mutual Eclipse Events Season in the Kuiper Belt: (524366) 2001 XR$_{254}$

(524366) 2001 XR$_{254}$ is a dynamically Cold Classical Kuiper Belt Object that is a nearly equal-sized wide binary whose upcoming mutual events season makes it a particularly valuable target for physical characterization. In advance of the mutual eclipse events, we conducted a ground-based photometric observing campaign between 2021 and 2026 using the \textit{Lowell Discovery Telescope} to investigate the rotational and physical properties of the system, to refine predictions for its future mutual events, as well as provide a lightcurve we can use as a baseline to identify eclipse events superimposed with the rotation. We derive a double-peaked asymmetric rotational lightcurve with a period of 11.17$\pm$0.04 h and a lightcurve amplitude of 0.42$\pm$0.04 mag. The lightcurve presents a sharp V-shaped minimum consistent with the primary being a close/contact binary, possibly making this a triple system. Using the Keplerian mutual orbit solution, we model the upcoming mutual event season expected between $\sim$2031 and $\sim$2040 and present some individual events for future campaigns. 2001 XR$_{254}$ is one of the few wide binary Kuiper belt systems with a well-determined mutual orbit and a soon observable mutual eclipse event season. Mutual event observations of this possible triple system will provide a rare opportunity to improve component sizes, shapes, densities, and surface properties, offering insights into the formation of the Kuiper Belt.

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arXiv2026

Photometry of Kuiper belt objects in inner and outer mean motion resonances with Neptune

We present a time-resolved photometric survey of Kuiper Belt Objects (KBOs) trapped in the inner and outer Neptune resonances. Lightcurves and rotational properties provide constraints on the shapes, internal structures, collisional histories, and formation environments of these primitive bodies. Our survey was conducted using the Magellan-Baade telescope and the Lowell Discovery Telescope, allowing us to go fainter than past works and yielding lightcurve studies for 41 KBOs in the 1:1, 5:4, 4:3, 11:5, 7:3, 12:5, and 5:2 resonances. We obtained complete lightcurves for objects displaying large amplitudes, with two KBOs in the 5:2 resonance (2001 XQ$_{254}$, 2013 RZ$_{108}$), one object in the 7:3 (2013 TJ$_{159}$), and one object in the 12:5 (2015 AR$_{293}$). Their lightcurve amplitudes range from 0.26 to 0.46mag, with rotational periods between 5.35 and 11.63 h. 2013 TJ$_{159}$ has the fastest rotation, largest amplitude, and most asymmetric lightcurve in our sample. Combining our results with published studies, we find that inner and outer resonant KBOs generally display lower lightcurve amplitudes than the dynamically Cold Classical population and the 5:3 and 7:4 resonances. The absence of the amplitude--period trends observed in those populations, and their surface color distributions, further suggests that inner and outer resonances do not share the same origin or evolutionary history as the Cold Classicals and overlapping resonances. Based on the literature and our survey, only one nearly equal-sized contact binary, 2004 TT$_{357}$, is currently known among the surveyed populations, implying a lower limit to the contact binary fraction of $\sim$12-15% in the 5:2 resonance.

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arXiv2026

Emerging Diversity Among the Main-Belt Comets: Insights from JWST and Ground-Based Observations of 457P/Lemmon-PANSTARRS

We present JWST NIRSpec and NIRCam observations of 457P/Lemmon-PANSTARRS, a main-belt comet that displayed activity around its 2020 perihelion and that was observed to regain activity during its 2024 perihelion by a ground-based observing campaign. The previous successful measurements of water production from two main-belt comets by the JWST NIRSpec instrument confirmed the hypothesis that H2O reservoirs are responsible for activity in dynamically stable main-belt comets. However, the main-belt comets observed with JWST thus far, 238P/Read and 358P/PANSTARRS, occupy orbits in the outer main-belt, with main-belt comets with smaller semi-major axes not yet sensitively tested for H2O. We find that despite clearly displaying dust activity in both ground-based and JWST imaging over a broad period, there were no corresponding H2O, CO, CO2, or CH3OH emissions within sensitive upper limits; notable given 457P is the first main-belt comet with a semi-major axis within the 5:2 mean-motion resonance with Jupiter. We show that we were sensitive to production rates of gas predicted by the dust/gas ratios of 238P and 358P, and hypothesize that 457P may be more depleted than its companions; Q(H2O) must be less than 2x10^24 molecules/s, or 0.035 kg/s. Further surveying of main-belt comets across the parameter space of semi-major axis and eccentricity will shed light on whether 457P represents an edge member of a spectrum or a distinct subclass of main-belt comets.

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arXiv2026

Characterization of the Volatile Properties of 133P/Elst-Pizarro and Other Main-Belt Comets with JWST and Ground-Based Observations

We report results from an analysis of the volatile composition and evolution of main-belt comet (MBC) 133P/Elst-Pizarro using JWST NIRSpec and NIRCam observations and ground-based observations during its 2024 active apparition, and also assess the body of JWST MBC observations acquired to date. Using NIRSpec, we measure water vapor outgassing rates at two points in 133P's orbit, finding Q(H2O)=(1.9+/-0.6)x10^25 molecules/s on UT 2024 June 12 (at a true anomaly of nu=8 deg and heliocentric distance of rh=2.674 au), and Q(H2O)=(1.4+/-0.4)x10^25 molecules/s on UT 2024 October 14 (at nu=37.4 deg and rh=2.747 au). These measurements nominally represent a decline of ~25% in Q(H2O) between the visits, although they are also consistent with no change within uncertainties. We do not detect CO, CO2, or CH3OH, placing 133P's hypervolatile depletion (Q(CO2)/Q(H_2O)<0.009) at a similar level found for previously observed MBCs. We find log(Afrho/Q(H2O)) values for the three MBCs for which water vapor outgassing has been successfully detected that are consistent within uncertainties with an average value of log(Afrho/Q(H2O))=-24.6+/-0.2. Lastly, we find no clear correlations of water production rates with nucleus size, semimajor axis, or heliocentric distance among MBCs observed by JWST so far, but would particularly encourage future JWST observations of additional MBCs interior to the 5A:2J MMR with Jupiter and at high inclinations, as well as multiple observations of MBCs during single active apparitions to further investigate areas of interest identified from the current sample of JWST-observed MBCs.

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arXiv2026

NEO Colors from The Mission Accessible Near-Earth Object Survey (MANOS)

We present spectro-photometric griz colors for 189 near-Earth objects (NEOs) collected by the Mission Accessible Near-Earth Object Survey (MANOS). Data acquisition involved non-simultaneous multi-band exposures, thus particular attention was given to the influence of rotational lightcurves on the derived colors. We show that colors measured without accounting for lightcurve variations can significantly influence results for individual objects and potentially have systematic offsets for ensemble studies. Color-based taxonomic classifications were used to investigate the distribution of spectral types. Our results were combined with other visible wavelength surveys to highlight a previously reported change in the observed taxonomic distribution of NEOs as a function of size, namely a decrease in S complex and an increase in X complex objects with increasing absolute magnitude. Plausibility arguments are given to suggest that Main Belt source region, thermal modification, discovery bias, tidal resurfacing, regolith grain size, and impact shock darkening are unlikely explanations for this size-dependent trend. Consistent with recent NEO population models and work on the connection between meteorites and young asteroid families in the Main Belt, this trend is best explained by a compositional gradient in the NEO population. In particular, the observed abundance of S complex or ordinary chondrite-like NEOs decreases by a factor of two from ~65% of the population at km-scales down to a third at sizes <50m. This result has implications for understanding the initial pre-impact population of meteorite parent bodies prior to atmospheric filtering. Furthermore, this will have implications for probabilistic impact risk assessment models.

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arXiv2025

Colors and Dynamics of a Near-Sun Orbital Asteroid Family: 2021 PH27 and 2025 GN1

We observed the dynamically similar near-Sun asteroids 2021 PH27 and 2025 GN1 for their optical colors. These objects have the lowest known semi-major axes of any asteroids. 2021 PH27 has the largest general relativistic effects of any known solar system object. The small semi-major axis and very close passage to the Sun suggests the extreme thermal and gravitational environment should highly modify these asteroids' surfaces. From g', r', i' and z'-band imaging, we find the colors of 2021 PH27 to be between the two major asteroid types the S and C classes (g'-r'= 0.58 +- 0.02, r'-i'=0.12 +- 0.02 and i'-z'=-0.08 +- 0.05 mags). With a spectral slope of 6.8 +-0.03 percent per 100nm, 2021 PH27 is a X-type asteroid and requires albedo or spectral features to further identify its composition. We find the dynamically similar 2025 GN1 also has very similar colors (g'-r'=0.55 +-0.06 and r'-i'=0.14 +-0.04) as 2021 PH27, suggesting these objects are fragments from a once larger parent asteroid or 2021 PH27 is shedding material. The colors are not blue like some other near-Sun asteroids such as 3200 Phaethon that have been interpreted to be from the loss of reddening substances from the extreme temperatures. There is no evidence of activity or a large amplitude period for 2021 PH27, whereas 2025 GN1 might have a more significant rotational light curve. 2025 GN1 may have a very close encounter or hit Venus in about 2155 years and likely separated from 2021 PH27 in about the last 10 kyrs.

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arXiv2025

Logos-Zoe: A contact binary triple system in the trans-neptunian belt

The trans-neptunian object (58534) 1997 CQ$_{29}$ (a.k.a. Logos) is a resolved wide binary in the dynamically Cold Classical population. With Hubble Space Telescope resolved observations where the primary Logos is well separated from its secondary Zoe it can be established that Logos has a time-variable brightness. Logos' brightness varied by several tenths of a magnitude over a short timescale of hours while the brightness variability of Zoe was on a longer timescale. New unresolved ground-based observations obtained with the Lowell Discovery Telescope and the Magellan-Baade telescope confirm at least one highly variable component in this system. With our ground-based observations and photometric constraints from space-based observations, we suggest that the primary Logos is likely a close/contact binary whose rotational period is 17.43$\pm$0.06 h for a lightcurve amplitude of 0.70$\pm$0.07 mag while Zoe is potentially a (very) slow rotator with an unknown shape. Using the Candela software, we model the Logos-Zoe system and predict its upcoming mutual events season using rotational, physical, and mutual orbit parameters derived in this work or already published. Zoe's shape and rotational period are still uncertain, so we consider various options to better understand Zoe. The upcoming mutual event season for Logos-Zoe starts in 2026 and will last for four years with up to two events per year. Observations of these mutual events will allow us to significantly improve the physical and rotational properties of both Logos and Zoe.

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arXiv2025

JWST sighting of decameter main-belt asteroids and view on meteorite sources

Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors. While large asteroids ($\geq$100 km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population. However, due to the lack of direct observational constraints, their size-frequency distribution--which informs our understanding of the NEOs and the delivery of meteorite samples to Earth--varies significantly among models. Here, we report 138 detections of the smallest asteroids ($\gtrapprox $10 m) ever observed in the main belt, which were enabled by JWST's infrared capabilities covering the asteroids' emission peaks and synthetic tracking techniques. Despite small orbital arcs, we constrain the objects' distances and phase angles using known asteroids as proxies, allowing us to derive sizes via radiometric techniques. Their size-frequency distribution exhibits a break at ${\sim}100$ m (debiased cumulative slopes of $q = -2.66\pm0.60$ and $-0.97\pm0.14$ for diameters smaller and larger than $\sim $100 m, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from multiple asteroid families--most likely Nysa, Polana and Massalia--according to the geometry of pointings considered here. Through additional long-stare infrared observations, JWST is poised to serendipitously detect thousands of decameter-scale asteroids across the sky, probing individual asteroid families and the source regions of meteorites "in-situ".

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arXiv2024

The Volatile Composition and Activity Evolution of Main-Belt Comet 358P/PANSTARRS

We report the detection of water vapor associated with main-belt comet 358P/PANSTARRS on UT 2024 January 8-9 using the NIRSPEC instrument aboard JWST. We derive a water production rate of Q(H2O)=(5.0+/-0.2)x10^25 molecules/s, marking only the second direct detection of sublimation products of any kind from a main-belt comet, after 238P/Read. Similar to 238P, we find a remarkable absence of hypervolatile species, finding Q(CO2)<7.6x10^22 molecules/s, corresponding to Q(CO2)/Q(H2O)<0.2%. Upper limits on CH3OH and CO emission are also estimated. Photometry from ground-based observations show that the dust coma brightened and faded slowly over ~250 days in 2023-2024, consistent with photometric behavior observed in 2012-2013, but also indicate a ~2.5x decline in the dust production rate between these two periods. Dynamical dust modeling shows that the coma's morphology as imaged by JWST's NIRCAM instrument on 2023 November 22 can be reproduced by asymmetric dust emission from a nucleus with a mid-range obliquity (~80 deg) with a steady-state mass loss rate of ~0.8 kg/s. Finally, we find similar Afrho-to-gas ratios of log10(Afrho/Q(H2O))=-24.8+/-0.2 for 358P and log10(Afrho/QH2O)=-24.4+/-0.2 for 238P, suggesting that Afrho could serve as an effective proxy for estimating water production rates in other active main-belt comets. The confirmation of water vapor outgassing in both main-belt comets observed by JWST to date reinforces the use of recurrent activity near perihelion as an indicator of sublimation-driven activity in active asteroids.

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arXiv2024

The population of small near-Earth objects: composition, source regions and rotational properties

The study of small ($<$300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent. Although such collisions cannot produce massive extinction events, they can still produce significant local damage. Here we present the results of a photometric and spectroscopic survey of small NEOs, which include near-infrared (NIR) spectra of 84 objects with a mean diameter of 126 m and photometric data of 59 objects with a mean diameter of 87 m. We found that S-complex asteroids are the most abundant among the NEOs, comprising $\sim$66\% of the sample. Most asteroids in the S-complex were found to have compositions consistent with LL-chondrites. Our study revealed the existence of NEOs with spectral characteristics similar to those in the S-complex, but that could be hidden within the C- or X-complex due to their weak absorption bands. We suggest that the presence of metal or shock-darkening could be responsible for the attenuation of the absorption bands. These objects have been grouped into a new subclass within the S-complex called Sx-types. The dynamical modeling showed that 83\% of the NEOs escaped from the $ν_{6}$ resonance, 16\% from the 3:1 and just 1\% from the 5:2 resonance. Lightcurves and rotational periods were derived from the photometric data. No clear trend between the axis ratio and the absolute magnitude or rotational period of the NEOs was found.

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arXiv2024

Rotational Study of 5:3 and 7:4 Resonant Objects within the Main Classical Trans-Neptunian Belt

The 5:3 and 7:4 mean motion resonances of Neptune are at 42.3 and 43.7 au, respectively, and overlap with objects in the Classical trans-neptunian belt (Kuiper belt). We report the complete/partial lightcurves of 13 and 14 trans-Neptunian objects (TNOs) in the 5:3 and 7:4 resonances, respectively. We report a most likely contact binary in the 7:4 resonance, 2013 FR$_{28}$, with a periodicity of 13.97$\pm$0.04 h and a lightcurve amplitude of 0.94$\pm$0.02 mag. With a V-/U-shaped lightcurve, 2013 FR$_{28}$ has one of the largest well-sampled TNO amplitude observed with ground-based observations, comparable to the well-determined contact binary 2001 QG$_{298}$. 2013 FR$_{28}$ has a mass ratio q$\sim$1 with a density $ρ$$\sim$1 g cm$^{-3}$. We find several objects with large amplitudes and classify 2004 SC$_{60}$, 2006 CJ$_{69}$, and 2013 BN$_{82}$ as likely contact binaries, and 2001 QF$_{331}$, 2003 YW$_{179}$, and 2015 FP$_{345}$ as likely elongated objects. We observe the 17:9 resonant or classical object 2003 SP$_{317}$ that we classify as a likely contact binary. A lower estimate of 10-50% and 20-55% for the fraction of (nearly) equal-sized contact binaries is calculated in the 5:3 and 7:4 resonances, respectively. Surface colors of 2004 SC$_{60}$, 2013 BN$_{82}$, 2014 OL$_{394}$, and 2015 FP$_{345}$ have been obtained. Including these colors with ones from the literature reveals that elongated objects and contact binaries share the same ultra-red surface color, except Manwë-Thorondor and 2004 SC$_{60}$. Not only are the colors of the 7:4 and 5:3 TNOs similar to the Cold Classicals, but we demonstrate that the rotational properties of the 5:3 and 7:4 resonants are similar to those of the Cold Classicals, inferring a clear link between these sub-populations.

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arXiv2023

Photometry of the Didymos system across the DART impact apparition

On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes (Thomas et al. 2023). Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite's orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from July 2022 to February 2023. We focus here on decomposable lightcurves, i.e. those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the post-impact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ~1 day after impact, and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days post-impact. This bulk photometric behavior was not well represented by an HG photometric model. An HG1G2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least March 2023. Its persistence implied ongoing escape of ejecta from the system many months after DART impact.

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arXiv2023

Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science

The Vera C. Rubin Observatory is expected to start the Legacy Survey of Space and Time (LSST) in early to mid-2025. This multi-band wide-field synoptic survey will transform our view of the solar system, with the discovery and monitoring of over 5 million small bodies.The final survey strategy chosen for LSST has direct implications on the discoverability and characterization of solar system minor planets and passing interstellar objects. Creating an inventory of the solar system is one of the four main LSST science drivers. The LSST observing cadence is a complex optimization problem that must balance the priorities and needs of all the key LSST science areas. To design the best LSST survey strategy, a series of operation simulations using the Rubin Observatory scheduler have been generated to explore the various options for tuning observing parameters and prioritizations. We explore the impact of the various simulated LSST observing strategies on studying the solar system's small body reservoirs. We examine what are the best observing scenarios and review what are the important considerations for maximizing LSST solar system science. In general, most of the LSST cadence simulations produce +/-5% or less variations in our chosen key metrics, but a subset of the simulations significantly hinder science returns with much larger losses in the discovery and light curve metrics.

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arXiv2023

Observational Characterization of Main-Belt Comet and Candidate Main-Belt Comet Nuclei

We report observations of nine MBCs or candidate MBCs, most of which were obtained when the targets were apparently inactive. We find effective nucleus radii (assuming albedos of p_V=0.05+/-0.02) of r_n=(0.24+/-0.05) km for 238P/Read, r_n=(0.9+/-0.2) km for 313P/Gibbs, r_n=(0.6+/-0.1) km for 324P/La Sagra, r_n=(1.0+/-0.2) km for 426P/PANSTARRS, r_n=(0.5+/-0.1) km for 427P/ATLAS, r_n<(0.3+/-0.1) km for P/2016 J1-A (PANSTARRS), r_n<(0.17+/-0.04) km for P/2016 J1-B (PANSTARRS), r_n<(0.5+/-0.2) km for P/2017 S9 (PANSTARRS), and r_n=(0.4+/-0.1) km for P/2019 A3 (PANSTARRS). We identify evidence of activity in observations of 238P in 2021, and find similar inferred activity onset times and net initial mass loss rates for 238P during perihelion approaches in 2010, 2016, and 2021. P/2016 J1-A and P/2016 J1-B are also found to be active in 2021 and 2022, making them collectively the tenth MBC confirmed to be recurrently active near perihelion and therefore likely to be exhibiting sublimation-driven activity. The nucleus of 313P is found to have colors of g'-r'=0.52+/-0.05 and r'-i'=0.22+/-0.07, consistent with 313P being a Lixiaohua family member. We also report non-detections of P/2015 X6 (PANSTARRS), where we conclude that its current nucleus size is likely below our detection limits (r_n<0.3 km). Lastly, we find that of 17 MBCs or candidate MBCs for which nucleus sizes (or inferred parent body sizes) have been estimated, >80% have r_n<1.0 km, pointing to an apparent physical preference toward small MBCs, where we suggest that YORP spin-up may play a significant role in triggering and/or facilitating MBC activity.

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arXiv2022

A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus

We are conducting a survey using twilight time on the Dark Energy Camera with the Blanco 4m telescope in Chile to look for objects interior to Earth's and Venus' orbits. To date we have discovered two rare Atira/Apohele asteroids, 2021 LJ4 and 2021 PH27, which have orbits completely interior to Earth's orbit. We also discovered one new Apollo type Near Earth Object (NEO) that crosses Earth's orbit, 2022 AP7. Two of the discoveries likely have diameters greater than 1 km. 2022 AP7 is likely the largest Potentially Hazardous Asteroid (PHA) discovered in about eight years. To date we have covered 624 square degrees of sky near to and interior to the orbit of Venus. The average images go to 21.3 mags in the r-band, with the best images near 22nd mag. Our new discovery 2021 PH27 has the smallest semi-major axis known for an asteroid, 0.4617 au, and the largest general relativistic effects (53 arcseconds/century) known for any body in the Solar System. The survey has detected about 15 percent of all known Atira NEOs. We put strong constraints on any stable population of Venus co-orbital resonance objects existing, as well as the Atira and Vatira asteroid classes. These interior asteroid populations are important to complete the census of asteroids near Earth, including some of the most likely Earth impactors that cannot easily be discovered in other surveys. Comparing the actual population of asteroids found interior to Earth and Venus with those predicted to exist by extrapolating from the known population exterior to Earth is important to better understand the origin, composition and structure of the NEO population.

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arXiv2022

Lightcurves and Rotations of Trans-Neptunian Objects in the 2:1 Mean Motion Resonance with Neptune

We report the rotational lightcurves of 21 trans-Neptunian objects (TNOs) in Neptune's 2:1 mean motion resonance obtained with the 6.5 m Magellan-Baade telescope and the 4.3 m Lowell Discovery Telescope. The main survey's goal is to find objects displaying a large lightcurve amplitude which is indicative of contact binaries or highly elongated objects. In our sample, two 2:1 resonant TNOs showed a significant short-term lightcurve amplitude: 2002 VD$_{130}$ and (531074) 2012 DX$_{98}$. The full lightcurve of 2012 DX$_{98}$ infers a periodicity of 20.80$\pm$0.06h and amplitude of 0.56$\pm$0.03mag whereas 2002 VD$_{130}$ rotates in 9.85$\pm$0.07h with a 0.31$\pm$0.04mag lightcurve amplitude. Based on lightcurve morphology, we classify (531074) 2012 DX$_{98}$ as a likely contact binary, but 2002 VD$_{130}$ as a likely single elongated object. Based on our sample and the lightcurves reported in the literature, we estimate the lower percentage of nearly equal-sized contact binaries at only 7-14$\%$ in the 2:1 resonance, which is comparable to the low fraction reported for the dynamically Cold Classical trans-Neptunian objects. This low contact binary fraction in the 2:1 Neptune resonance is consistent with the lower estimate of the recent numerical modeling. We report the Sloan g', r', i' surface colors of 2002 VD$_{130}$ which is an ultra-red TNO whereas 2012 DX$_{98}$ is a very red object based on published surface colors.

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arXiv2021

Lunar-like silicate material forms the Earth quasisatellite (469219) 2016 HO3 Kamo`oalewa

Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. Here we use the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT) to conduct a comprehensive physical characterization of quasi-satellite (469219) Kamo`oalewa and assess its affinity with other groups of near-Earth objects. We find that (469219) Kamo`oalewa rotates with a period of 28.3 (+1.8/-1.3) minutes and displays a reddened reflectance spectrum from 0.4-2.2 microns. This spectrum is indicative of a silicate-based composition, but with reddening beyond what is typically seen amongst asteroids in the inner solar system. We compare the spectrum to those of several material analogs and conclude that the best match is with lunar-like silicates. This interpretation implies extensive space weathering and raises the prospect that Kamo`oalewa could comprise lunar material.

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