Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations

Rożek, A.; Lowry, S. C.; Nolan, M. C.; Taylor, Patrick A.; Benner, L. A. M.; Fitzsimmons, A.; Zegmott, Tarik; Weissman, P. R.; Green, Simon; Rozitis, B.; Snodgrass, C.; Smythe, W. D.; Hicks, Michael; Howell, E. S.; Virkki, Anne; Aponte-Hernández, Betzaida; Rivera-Valentín, E. G.; Rodriguez-Ford, Linda A.; Zambrano-Marín, Luisa F.; Brozović, M.; Naidu, Shantanu P.; Giorgini, Jon D.; Snedeker, L. G.; Jao, Joseph S.; Ghigo, F. D.

doi:10.1051/0004-6361/201936302

Cited by 10 publications

(5 citation statements)

References 48 publications

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“…Five pre-2015 cases have been summarized in the review chapter by Vokrouhlický et al (2015). Since then, the YORP detection has been reported for (161989) Cacus by Ďurech et al (2018b), (101955) Bennu by Hergenrother et al (2019), (68346) 2001KZ66 by Zegmott et al (2021), and Rożek et al (2019 discussed a plausible YORP determination in the case of (85990) 1999 JV6 (though here its significance is only marginal because of a still short arclength covered by the observations). In this paper, we added a robust YORP detection for (10115) 1992 SK and argue for a weak, but very plausible YORP signal in the case of ( 1685) Toro (see also Ďurech et al 2018b).…”

Section: Discussionmentioning

confidence: 99%

“…So eventually, observations may help to set this asymmetry degree. Given this perspective, we might interpret the YORP detections achieved thus far -not counting the result of Rożek et al (2019) for (85990) 1999 JV6 -as evidence for a >10 : 1 favor in YORP making the rotation accelerated over decelerated for kilometer-sized near-Earth objects.…”

Section: Discussionmentioning

confidence: 99%

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Rotation acceleration of asteroids (10115) 1992 SK, (1685) Toro, and (1620) Geographos due to the YORP effect

Ďurech

Vokrouhlický

Pravec

et al. 2021

A&A

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Context. The rotation state of small asteroids is affected by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, which is a net torque caused by solar radiation directly reflected and thermally reemitted from the surface. Due to this effect, the rotation period slowly changes, which can be most easily measured in light curves because the shift in the rotation phase accumulates over time quadratically. Aims. By new photometric observations of selected near-Earth asteroids, we want to enlarge the sample of asteroids with a detected YORP effect. Methods. We collected archived light curves and carried out new photometric observations for asteroids (10115) 1992 SK, (1620) Geographos, and (1685) Toro. We applied the method of light curve inversion to fit observations with a convex shape model. The YORP effect was modeled as a linear change of the rotation frequency υ ≡ dω∕dt and optimized together with other spin and shape parameters. Results. We detected the acceleration υ = (8.3 ± 0.6) × 10−8 rad d−2 of the rotation for asteroid (10115) 1992 SK. This observed value agrees well with the theoretical value of YORP-induced spin-up computed for our shape and spin model. For (1685) Toro, we obtained υ = (3.3 ± 0.3) × 10−9 rad d−2, which confirms an earlier tentative YORP detection. For (1620) Geographos, we confirmed the previously detected YORP acceleration and derived an updated value of υ with a smaller uncertainty. We also included the effect of solar precession into our inversion algorithm, and we show that there are hints of this effect in Geographos’ data. Conclusions. The detected change of the spin rate of (10115) 1992 SK has increased the total number of asteroids with YORP detection to ten. In all ten cases, the dω∕dt value is positive, so the rotation of these asteroids is accelerated. It is unlikely to be just a statistical fluke, but it is probably a real feature that needs to be explained.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Rotation acceleration of asteroids (10115) 1992 SK, (1685) Toro, and (1620) Geographos due to the YORP effect

Ďurech

Vokrouhlický

Pravec

et al. 2021

A&A

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“…rotational period of 2.2 h for rubble pile asteroids), leading to resurfacing (Sánchez & Scheeres 2020) and rotation disruption (Scheeres 2007;Fatka et al 2020;Veras & Scheeres 2020). YORP-induced rotational disruption is supported by the observed asteroid pairs Polishook 2014) and binary asteroids (Jacobson & Scheeres 2011;Delbo et al 2011;Jacobson et al 2013Jacobson et al , 2016, including contact-binary asteroids (Rożek et al 2019;Zegmott et al 2021) and binary comets (Agarwal et al 2020), which evolve under tidal effects and the binary YORP (BYORP) effect after the binary system is formed ( Ćuk & Burns 2005;Steinberg & Sari 2011). Further potential observational evidence is the abnormal spin distribution and the obliquity distribution of near-Earth asteroids (Vokrouhlickỳ et al 2003;Pravec et al 2008;Rozitis & Green 2013b;Lupishko & Tielieusova 2014) and main belt asteroids (Lupishko et al 2019), although a recent study points out that collisions might reproduce the observed distribution without the involvement of the YORP effect (Holsapple 2022).…”

Section: Introductionmentioning

confidence: 89%

A semi-analytical thermal model for craters with application to the crater-induced YORP effect

Zhou,

Michel

2024

A&A

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The YORP effect is the thermal torque generated by radiation from the surface of an asteroid. The effect is sensitive to surface topology, including small-scale roughness, boulders, and craters. The aim of this paper is to develop a computationally efficient semi-analytical model for the crater-induced YORP (CYORP) effect that can be used to investigate the functional dependence of this effect. This study linearizes the thermal radiation term as a function of the temperature in the boundary condition of the heat conductivity, and obtains the temperature field in a crater over a rotational period in the form of a Fourier series, accounting for the effects of self-sheltering, self-radiation, and self-scattering. By comparison with a numerical model, we find that this semi-analytical model for the CYORP effect works well for $K>0.1 W/m/K$. This semi-analytical model is computationally three-orders-of-magnitude more efficient than the numerical approach. We obtain the temperature field of a crater, accounting for the thermal inertia, crater shape, and crater location. We then find that the CYORP effect is negligible when the depth-to-diameter ratio is smaller than 0.05. In this case, it is reasonable to assume a convex shape for YORP calculations. Varying the thermal conductivity yields a consistent value of approximately 0.01 for the spin component of the CYORP coefficient, while the obliquity component is inversely related to thermal inertia, declining from 0.004 in basalt to 0.001 in metal. The CYORP spin component peaks at an obliquity of $0^ or $180^ while the obliquity component peaks at an obliquity of around $45^ or $135^ For a z-axis symmetric shape, the CYORP spin component vanishes, while the obliquity component persists. Our model confirms that the total YORP torque is damped by a few tens of percent by uniformly distributed small-scale surface roughness. Furthermore, for the first time, we calculate the change in the YORP torque at each impact on the surface of an asteroid explicitly and compute the resulting stochastic spin evolution more precisely. This study shows that the CYORP effect due to small-scale surface roughness and impact craters is significant during the history of asteroids. The semi-analytical method that we developed, which benefits from fast computation, offers new perspectives for future investigations of the YORP modeling of real asteroids and for the complete rotational and orbital evolution of asteroids accounting for collisions. Future research employing our CYORP model may explore the implications of space-varying roughness distribution, roughness in binary systems, and the development of a comprehensive rotational evolution model for asteroid groups.

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“…For example, Mitchell et al [6] used only the Gaussian law, cosine law [7,8], and a "flat law" [9], for attempts to fit radar scattering by (1) Ceres, (2) Pallas, and (4) Vesta. The cosine law remains the most used scattering law option in the shape modeling of asteroids based on radar data (e.g., [10][11][12][13]); however, the physical interpretation of the fit parameters of the cosine law is not well constrained as will be discussed further below.…”

Section: Introductionmentioning

confidence: 99%

Numerical Evaluation of Planetary Radar Backscatter Models for Self-Affine Fractal Surfaces

Virkki

2024

Remote Sensing

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Numerous analytical radar-scattering laws have been published through the past decades to interpret planetary radar observations, such as Hagfors’ law, which has been commonly used for the Moon, and the cosine law, which is commonly used in the shape modeling of asteroids. Many of the laws have not been numerically validated in terms of their interpretation and limitations. This paper evaluates radar-scattering laws for self-affine fractal surfaces using a numerical approach. Traditionally, the autocorrelation function and, more recently, the Hurst exponent, which describes the self-affinity, have been used to quantify the height correlation. Here, hundreds of three-dimensional synthetic surfaces parameterized using a root-mean-square (rms) height and a Hurst exponent were generated, and their backscattering coefficient functions were computed to evaluate their consistency with selected analytical models. The numerical results were also compared to empirical models for roughness and radar-scattering measurements of Hawaii lava flows and found consistent. The Gaussian law performed best at predicting the rms slope regardless of the Hurst exponent. Consistent with the literature, it was found to be the most reliable radar-scattering law for the inverse modeling of the rms slopes and the Fresnel reflection coefficient from the quasi-specular backscattering peak, when homogeneous statistical properties and a ray-optics approach can be assumed. The contribution of multiple scattering in the backscattered power increases as a function of rms slope up to about 20% of the backscattered power at normal incidence when the rms slope angle is 46∘.

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Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations

Cited by 10 publications

References 48 publications

Rotation acceleration of asteroids (10115) 1992 SK, (1685) Toro, and (1620) Geographos due to the YORP effect

Rotation acceleration of asteroids (10115) 1992 SK, (1685) Toro, and (1620) Geographos due to the YORP effect

A semi-analytical thermal model for craters with application to the crater-induced YORP effect

Numerical Evaluation of Planetary Radar Backscatter Models for Self-Affine Fractal Surfaces

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