Rotation Periods of Binary Asteroids with Large Separations - Confronting the Escaping Ejecta Binaries Model with Observations

Abstract

Durda et al. (2004), using numerical models, suggested that binary asteroids with large separation, called Escaping Ejecta Binaries (EEBs), can be created by fragments ejected from a disruptive impact event. It is thought that six binary asteroids recently discovered might be EEBs because of the high separation between their components (~100 > a/Rp > ~20). However, the rotation periods of four out of the six objects measured by our group and others and presented here show that these suspected EEBs have fast rotation rates of 2.5 to 4 hours. Because of the small size of the components of these binary asteroids, linked with this fast spinning, we conclude that the rotational-fission mechanism, which is a result of the thermal YORP effect, is the most likely formation scenario. Moreover, scaling the YORP effect for these objects shows that its timescale is shorter than the estimated ages of the three relevant Hirayama families hosting these binary asteroids. Therefore, only the largest (D~19 km) suspected asteroid, (317) Roxane, could be, in fact, the only known EEB. In addition, our results confirm the triple nature of (3749) Balam by measuring mutual events on its lightcurve that match the orbital period of a nearby satellite in addition to its distant companion. Measurements of (1509) Esclangona at different apparitions show a unique shape of the lightcurve that might be explained by color variations.

23 pages, 7 figures, 3 tables. accepted for publication in Icarus

References in corpus (7)

• Formation of asteroid pairs by rotational fission
• Extreme Kuiper Belt Object 2001 QG298 and the Fraction of Contact Binaries
• Main Belt Binary Asteroidal Systems With Eccentric Mutual Orbits
• New determination of the size and bulk density of the binary asteroid 22 Kalliope from observations of mutual eclipses
• The Centurion 18 telescope of the Wise Observatory
• Photometry and Spin Rate Distribution of Small-Sized Main Belt Asteroids
• Simultaneous Spectroscopic and Photometric Observations of Binary Asteroids

Cited by in corpus (15)

• Asteroid Systems: Binaries, Triples, and Pairs
• Multiple Asteroid Systems: Dimensions and Thermal Properties from Spitzer Space Telescope and Ground-Based Observations
• Observations of "Fresh" and Weathered Surfaces on Asteroid Pairs and Their Implications on the Rotational-Fission Mechanism
• The Formation of the Wide Asynchronous Binary Asteroid Population
• Asteroid rotation periods from the Palomar Transient Factory survey
• Colors of Dynamically Associated Asteroid Pairs
• Direct $N$-body simulations of satellite formation around small asteroids: insights from DART's encounter with the Didymos system
• Spin Axes and Shape Models of Asteroid Pairs: Fingerprints of YORP and a Path to the Density of Rubble Piles
• Characteristics and Large Bulk Density of the C-type Main-Belt Triple Asteroid (93) Minerva
• The Large Array Survey Telescope -- Science Goals
• Rotationally Resolved Spectroscopy of Asteroid Pairs: No Spectral Variation Suggests Fission is followed by Settling of Dust
• Photometric Observations of 107P/Wilson-Harrington
• Deficit of primitive compositions in binary asteroids and pairs
• Surface slopes of asteroid pairs as indicators of mechanical properties and cohesion
• Orbits of very distant asteroid satellites