Simultaneous Spectroscopic and Photometric Observations of Binary Asteroids

TL;DR

This study combines spectroscopic and photometric observations of binary asteroids (90) Antiope and (1509) Esclangona to analyze surface composition, color variations, and eclipse events, revealing insights into their surface features and possible shared origins.

Contribution

First simultaneous spectroscopic and photometric analysis of binary asteroids, identifying surface color variations and eclipse phenomena with implications for their composition and history.

Findings

(90) Antiope showed an eclipse event with no significant spectral slope change.

(1509) Esclangona exhibited surface color variations correlated with lightcurve features.

Surface compositions of the two components of Antiope are similar, suggesting a common origin.

Abstract

We present results of visible wavelengths spectroscopic measurements (0.45 to 0.72 microns) of two binary asteroids, obtained with the 1-m telescope at the Wise Observatory on January 2008. The asteroids (90) Antiope and (1509) Esclangona were observed to search for spectroscopic variations correlated with their rotation while presenting different regions of their surface to the viewer. Simultaneous photometric observations were performed with the Wise Observatory's 0.46-m telescope, to investigate the rotational phase behavior and possible eclipse events. (90) Antiope displayed an eclipse event during our observations. We could not measure any slope change of the spectroscopic albedo within the error range of 3%, except for a steady decrease in the total light flux while the eclipse took place. We conclude that the surface compositions of the two components do not differ dramatically, implying a common origin and history. (1509) Esclangona did not show an eclipse, but rather a unique lightcurve with three peaks and a wide and flat minimum, repeating with a period of 3.2524 hours. Careful measurements of the spectral albedo slopes reveal a color variation of 7 to 10 percent on the surface of (1509) Esclangona, which correlates with a specific region in the photometric lightcurve. This result suggests that the different features on the lightcurve are at least partially produced by color variations and could perhaps be explained by the existence of an exposed fresh surface on (1509) Esclangona.