Spinning and color properties of the active asteroid (6478) Gault

Albino Carbognani; Alberto Buzzoni

doi:10.1093/mnras/staa208

paper

Spinning and color properties of the active asteroid (6478) Gault

arXiv:2001.05748 · doi:10.1093/mnras/staa208

Abstract

We report on accurate $B V R_{c}$ observations of (6478) Gault, a 5-6 km diameter inner main-belt asteroid in the Phocaea family, notable for its sporadic, comet-like ejection of dust. This curious behavior has been mainly interpreted as reconfigurations after YORP spin-up, although merging of a contact binary system cannot be fully excluded. We collected optical observations along the 2019 March-April period, at orbital phase angles between $1 2^{\circ} - 2 1^{\circ}$ , to search for direct evidence of asteroid quick spinning rotation. A prevailing period value of $3.34 \pm 0.02$ hours is supported by our and other photometric observations. In the YORP spin-up hypothesis, this period points to a bulk density $ρ \approx 1$ $g / cm^{3}$ . The mean colors are $B - V = + 0.8 2_{\pm 0.3}$ , $V - R_{c} = + 0.2 8_{\pm 0.06}$ and $B - R_{c} = + 1.1 1_{\pm 0.4}$ , but we have observed a strong bluer color during the April session, with about $Δ (B - V) \sim 0.35 \pm 0.09$ ~mag. This color change can be due to asteroid rotation and support the hypothesis that there is a bluer surface under the Gault's dust, as indicated by spectroscopic observations made on 2019 March 31 and April 8 by Marsset et al. (2019).

arXiv comment8 pages, 12 figures, submitted to Mon. Not. R. Astron. Soc

Spinning and color properties of the active asteroid (6478) Gault

Abstract

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