Extreme asteroids in the Pan-STARRS 1 Survey

Abstract

Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude $A_{obs}\ge 1.0$ mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for 'high-amplitude' had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the 'high-amplitude asteroids' identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes $\lambda =218\pm 10^{\circ },\beta =-82\pm 5^{\circ }$ and asteroid 206167 was found to have best fit spin pole axes $\lambda =57\pm 5^{\circ }$, $\beta =-67\pm 5^{\circ }$. An additional object not initially measured with $A_{obs}>1.0$ mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values $\lambda =112\pm 6^{\circ },\beta =6\pm 5^{\circ }$. In the course of this project to date no large super-fast rotators ($P_{rot}<2.2$ h) have been identified.

arXiv comment31 pages; accepted by AJ

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