A Fireball and Potentially Hazardous Binary Near-Earth Asteroid (164121) 2003 YT${}_1$

Abstract

We present a fireball detected in the night sky over Kyoto, Japan on UT 2017 April 28 at $15^{\mathrm{h}}58^{\mathrm{m}}19^{\mathrm{s}}$ by the SonotaCo Network. The absolute visual magnitude is $M_{\mathrm{v}}$=$-$4.10$\pm$0.42mag. Luminous light curves obtain a meteoroid mass $m$=29$\pm$1g, corresponding to the size $a_{\mathrm{s}}$=2.7$\pm$0.1cm. Orbital similarity assessed by D-criterions (cf. $D_{\mathrm{SH}}$=0.0079) has identified a likely parent, the binary near-Earth asteroid (164121) 2003 YT${}_1$. The suggested binary formation process is a YORP-driven rotational disintegration (Pravec & Harris 2007). The asynchronous state indicates the age of $<$10${}^4$yr, near or shorter than the upper limit to meteoroid stream lifetime. We examine potential dust production mechanisms for the asteroid, including rotational instability, resurfacing, impact, photoionization, radiation pressure sweeping, thermal fracture and sublimation of ice. We find some of them capable of producing the meteoroid-scale particles. Rotational instability is presumed to cause mass shedding, in consideration of the recent precedents (e.g. asteroid (6478) Gault), possibly releasing mm-cm scale dust particles. Impacts by micrometeorites with size $\simeq$1mm could be a trigger for ejecting the cm-sized particles. Radiation pressure can sweep out the mm-sized dust particles, while not sufficient for the cm-sized. For the other mechanisms, unprovable or unidentified. The feasibility in the parental aspect of 2003 YT${}_1$ is somewhat reconciled with the fireball observation, yielding an insight into how we approach potentially hazardous objects.

36 pages, AJ, in press

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