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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, P.A., Benner, Lance A.M., Fitzsimmons, A., Zegmott, T.J., Weissman, P.R., Green, Simon F, Rozitis, B., and others. (2019) Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations. Astronomy and Astrophysics, 631 . Article Number 149. ISSN 0004-6361. (doi:10.1051/0004-6361/201936302) (KAR id:77234)


Context. The potentially hazardous asteroid (85990) 1999 JV6 has been a target of previously published thermal-infrared observations and optical photometry. It has been identified as a promising candidate for possible Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect detection. Aims. The YORP effect is a small thermal-radiation torque considered to be a key factor in spin-state evolution of small Solar System bodies. In order to detect YORP on 1999 JV6 we developed a detailed shape model and analysed the spin-state using both optical and radar observations. Methods. For 1999 JV6, we collected optical photometry between 2007 and 2016. Additionally, we obtained radar echo-power spectra and imaging observations with Arecibo and Goldstone planetary radar facilities in 2015, 2016, and 2017. We combined our data with published optical photometry to develop a robust physical model. Results. We determine that the rotation pole resides at negative latitudes in an area with a 5◦ radius close to the south ecliptic pole. The refined sidereal rotation period is 6.536787 ± 0.000007 h. The radar images are best reproduced with a bilobed shape model. Both lobes of 1999 JV6 can be represented as oblate ellipsoids with a smaller, more spherical component resting at the end of a larger, more elongated component. While contact binaries appear to be abundant in the near-Earth population, there are only a few published shape models for asteroids in this particular configuration. By combining the radar-derived shape model with optical light curves we determine a constant-period solution that fits all available data well. Using light-curve data alone we determine an upper limit for YORP of 8.5 × 10−8 rad day−2. Conclusions. The bifurcated shape of 1999 JV6 might be a result of two ellipsoidal components gently merging with each other, or a deformation of a rubble pile with a weak-tensile-strength core due to spin-up. The physical model of 1999 JV6 presented here will enable future studies of contact binary asteroid formation and evolution.

Item Type: Article
DOI/Identification number: 10.1051/0004-6361/201936302
Uncontrolled keywords: minor planets, asteroids: individual: (85990) 1999 JV6 – methods: observational – methods: data analysis – techniques: photometric – techniques: radar astronomy – radiation mechanisms: thermal
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Funders: Science and Technology Facilities Council (
Depositing User: Agata Makiela
Date Deposited: 10 Oct 2019 13:21 UTC
Last Modified: 04 Mar 2024 17:55 UTC
Resource URI: (The current URI for this page, for reference purposes)

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