Photometric BVR Observations of (65803) Didymos after DART

The near-Earth binary asteroid Didymos was observed by robotic telescopes in Australia, Chile, and the United States three to five weeks after its impact with the DART spacecraft. The B − R spectral slope of the Didymos system was 13% ± 1%/100 nm, redder than that of the Sun, active comets, and its previously measured colors. The dust cloud around the Didymos system caused a mean drop of 0.29 ± 0.08 mag and had an optical thickness of 0.27 ± 0.07, based on observations from October 27.743 and 28.740 UT. The mean FWHM of the photometric profile of the Didymos system was 1.1 ± 0.1 larger than that of the unsaturated field stars in the R band during our observing campaign. According to our results, the B − R color index was the best parameter to detect the activity of this asteroid in the visible range.