Issue |
A&A
Volume 631, November 2019
|
|
---|---|---|
Article Number | A149 | |
Number of page(s) | 28 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/201936302 | |
Published online | 13 November 2019 |
Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations★,★★
1
Centre for Astrophysics and Planetary Science, University of Kent,
Canterbury, UK
e-mail: a.rozek@kent.ac.uk
2
Lunar and Planetary Laboratory, University of Arizona,
Tucson,
Arizona, USA
3
Lunar and Planetary Institute, Universities Space Research Association,
Houston,
Texas, USA
4
Planetary Science Section, Jet Propulsion Laboratory/Caltech,
Pasadena,
California, USA
5
Astrophysics Research Centre, Queens University Belfast,
Belfast, UK
6
Planetary Sciences Institute,
Tucson,
Arizona, USA
7
Planetary and Space Sciences, School of Physical Sciences, The Open University,
Milton Keynes, UK
8
Institute for Astronomy, University of Edinburgh,
Royal Observatory, Edinburgh, UK
9
Arecibo Observatory, University of Central Florida,
Arecibo,
Porto Rico, USA
10
National Radio Astronomy Observatory,
Green Bank,
West Virginia, USA
Received:
12
July
2019
Accepted:
1
October
2019
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.
Key words: minor planets, asteroids: individual: (85990) 1999 JV6 / methods: observational / methods: data analysis / techniques: photometric / techniques: radar astronomy / radiation mechanisms: thermal
Table A.2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/631/A149
© ESO 2019
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