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

   https://doi.org/10.3847/PSJ/ac7ab8  

   Thirouin, Audrey ; Sheppard, Scott S. ( July 2022 , The Planetary Science Journal)

   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 that 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 VD₁₃₀and (531074) 2012 DX₉₈. The full lightcurve of 2012 DX₉₈infers a periodicity of 20.80 ± 0.06 hr and amplitude of 0.56 ± 0.03 mag, whereas 2002 VD₁₃₀rotates in 9.85 ± 0.07 hr with a 0.31 ± 0.04 mag lightcurve amplitude. Based on lightcurve morphology, we classify (531074) 2012 DX₉₈as a likely contact binary but 2002 VD₁₃₀as 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 TNOs. 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 Sloang′,r′, andi′ surface colors of 2002 VD₁₃₀, which is an ultra-red TNO whereas 2012 DX₉₈is a very red object based on published surface colors.

    

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2. A Search of the Full Six Years of the Dark Energy Survey for Outer Solar System Objects

   https://doi.org/10.3847/1538-4365/ac3914  

   Bernardinelli, Pedro H. ; Bernstein, Gary M. ; Sako, Masao ; Yanny, Brian ; Aguena, M. ; Allam, S. ; Andrade-Oliveira, F. ; Bertin, E. ; Brooks, D. ; Buckley-Geer, E. ; et al ( February 2022 , The Astrophysical Journal Supplement Series)

   Abstract We present a search for outer solar system objects in the 6 yr of data from the Dark Energy Survey (DES). The DES covered a contiguous 5000 deg 2 of the southern sky with ≈80,000 3 deg 2 exposures in the grizY filters between 2013 and 2019. This search yielded 812 trans-Neptunian objects (TNOs), one Centaur and one Oort cloud comet, 458 reported here for the first time. We present methodology that builds upon our previous search on the first 4 yr of data. All images were reprocessed with an optimized detection pipeline that leads to an average completeness gain of 0.47 mag per exposure, as well as improved transient catalog production and algorithms for linkage of detections into orbits. All objects were verified by visual inspection and by the “sub-threshold significance,” the signal-to-noise ratio in the stack of images in which its presence is indicated by the orbit, but no detection was reported. This yields a pure catalog complete to r ≈ 23.8 mag and distances 29 < d < 2500 au. The TNOs have minimum (median) of 7 (12) nights’ detections and arcs of 1.1 (4.2) yr, and will have grizY magnitudes available in a further publication. We present software for simulating our observational biases for comparisons of models to our detections. Initial inferences demonstrating the catalog’s statistical power are: the data are inconsistent with the CFEPS-L7 model for the classical Kuiper Belt; the 16 “extreme” TNOs ( a > 150 au, q > 30 au) are consistent with the null hypothesis of azimuthal isotropy; and nonresonant TNOs with q > 38 au, a > 50 au show a significant tendency to be sunward of major mean-motion resonances. 

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3. The DECam Ecliptic Exploration Project (DEEP). IV. Constraints on the Shape Distribution of Bright Trans-Neptunian Objects

   https://doi.org/10.3847/1538-3881/ad1526  

   Strauss, Ryder ; Trilling, David E. ; Bernardinelli, Pedro H. ; Beach, Christiano ; Oldroyd, William J. ; Sheppard, Scott S. ; Schlichting, Hilke E. ; Gerdes, David W. ; Fuentes, Cesar ; Holman, Matthew J. ; et al ( February 2024 , The Astronomical Journal)

   We present the methods and results from the discovery and photometric measurement of 26 bright VR > 24 trans-Neptunian objects (TNOs) during the first year (2019–20) of the DECam Ecliptic Exploration Project (DEEP). The DEEP survey is an observational TNO survey with wide sky coverage, high sensitivity, and a fast photometric cadence. We apply a computer vision technique known as a progressive probabilistic Hough transform to identify linearly moving transient sources within DEEP photometric catalogs. After subsequent visual vetting, we provide a photometric and astrometric catalog of our TNOs. By modeling the partial lightcurve amplitude distribution of the DEEP TNOs using Monte Carlo techniques, we find our data to be most consistent with an average TNO axis ratiob/a< 0.5, implying a population dominated by non-spherical objects. Based on ellipsoidal gravitational stability arguments, we find our data to be consistent with a TNO population containing a high fraction of contact binaries or other extremely non-spherical objects. We also discuss our data as evidence that the expected binarity fraction of TNOs may be size-dependent.

    

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4. Can Neptune’s Distant Mean Motion Resonances Constrain Undiscovered Planets in the Solar System? Lessons from a Case Study of the 9:1 Resonance

   https://doi.org/10.3847/PSJ/ad2201  

   Porter, Matthew W. ; Gerdes, David W. ; Napier, Kevin J. ; Lin 林, Hsing Wen 省文 ; Adams, Fred C. ( March 2024 , The Planetary Science Journal)

   Recent observational surveys of the outer solar system provide evidence that Neptune's distantn:1 mean motion resonances may harbor relatively large reservoirs of trans-Neptunian objects (TNOs). In particular, the discovery of two securely classified 9:1 resonators, 2015 KE₁₇₂and 2007 TC₄₃₄, by the Outer Solar System Origins Survey is consistent with a population of order 10⁴such objects in the 9:1 resonance with absolute magnitudeH_r< 8.66. This work investigates whether the long-term stability of such populations in Neptune’sn:1 resonances can be used to constrain the existence of distant 5–10M_⊕planets orbiting at hundreds of au. The existence of such a planet has been proposed to explain a reported clustering in the orbits of highly eccentric “extreme” trans-Neptunian objects (or eTNOs), although this hypothesis remains controversial. We engage in a focused computational case study of the 9:1 resonance, generating synthetic populations and integrating them for 1 Gyr in the presence of 81 different test planets with various masses, perihelion distances, eccentricities, and inclinations. While none of the tested planets are incompatible with the existence of 9:1 resonators, our integrations shed light on the character of the interaction between such planets and nearbyn:1 resonances, and we use this knowledge to construct a simple heuristic method for determining whether or not a given planet could destabilize a given resonant population. We apply this method to the currently estimated properties of Planet 9, and find that a large primordial population in the 15:1 resonance (or beyond), if discovered in the future, could potentially constrain the existence of this planet.

    

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5. Photometry of Outer Solar System Objects from the Dark Energy Survey. I. Photometric Methods, Light-curve Distributions, and Trans-Neptunian Binaries

   https://doi.org/10.3847/1538-4365/acf6bf  

   Bernardinelli, Pedro H. ; Bernstein, Gary M. ; Jindal, Nicholas ; Abbott, T. M. C. ; Aguena, M. ; Alves, O. ; Andrade-Oliveira, F. ; Annis, J. ; Bacon, D. ; Bertin, E. ; et al ( October 2023 , The Astrophysical Journal Supplement Series)

   We report the methods of and initial scientific inferences from the extraction of precision photometric information for the >800 trans-Neptunian objects (TNOs) discovered in the images of the Dark Energy Survey (DES). Scene-modeling photometry is used to obtain shot-noise-limited flux measures for each exposure of each TNO, with background sources subtracted. Comparison of double-source fits to the pixel data with single-source fits are used to identify and characterize two binary TNO systems. A Markov Chain Monte Carlo method samples the joint likelihood of the intrinsic colors of each source as well as the amplitude of its flux variation, given the time series of multiband flux measurements and their uncertainties. A catalog of these colors and light-curve amplitudesAis included with this publication. We show how to assign a likelihood to the distributionq(A) of light-curve amplitudes in any subpopulation. Using this method, we find decisive evidence (i.e., evidence ratio <0.01) that cold classical (CC) TNOs with absolute magnitude 6 <H_r< 8.2 are more variable than the hot classical (HC) population of the sameH_r, reinforcing theories that the former form in situ and the latter arise from a different physical population. Resonant and scattering TNOs in thisH_rrange have variability consistent with either the HCs or CCs. DES TNOs withH_r< 6 are seen to be decisively less variable than higher-H_rmembers of any dynamical group, as expected. More surprising is that detached TNOs are decisively less variable than scattering TNOs, which requires them to have distinct source regions or some subsequent differential processing.

    

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