The Thousand Asteroid Light Curve Survey

Abstract

We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada–France–Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids to a limiting magnitude of g ′ ∼ 22.5 corresponding to a diameter range of 0.4 km ⩽ D ⩽ 10 km . Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (∼15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ∼1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis ratio, ( b / a ) 2 , and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2 h with diameters between 400 m and 1.5 km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1–10 km size range.