Multiple Outbursts of Asteroid (6478) Gault. (arXiv:1903.05320v1 [astro-ph.EP])

Multiple Outbursts of Asteroid (6478) Gault. (arXiv:1903.05320v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ye_Q/0/1/0/all/0/1">Quanzhi Ye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kelley_M/0/1/0/all/0/1">Michael S. P. Kelley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bodewits_D/0/1/0/all/0/1">Dennis Bodewits</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bolin_B/0/1/0/all/0/1">Bryce Bolin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lin_Z/0/1/0/all/0/1">Zhong-Yi Lin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bellm_E/0/1/0/all/0/1">Eric C. Bellm</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dekany_R/0/1/0/all/0/1">Richard Dekany</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duev_D/0/1/0/all/0/1">Dmitry A. Duev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Groom_S/0/1/0/all/0/1">Steven Groom</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Helou_G/0/1/0/all/0/1">George Helou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kulkarni_S/0/1/0/all/0/1">Shrinivas R. Kulkarni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kupfer_T/0/1/0/all/0/1">Thomas Kupfer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masci_F/0/1/0/all/0/1">Frank J. Masci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prince_T/0/1/0/all/0/1">Thomas A. Prince</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Soumagnac_M/0/1/0/all/0/1">Maayane T. Soumagnac</a>

Main-belt asteroid (6478) Gault unexpectedly sprouted two tails in late 2018
and early 2019, identifying it as a new active asteroid. Here we present
observations obtained by the 1.2-m Zwicky Transient Facility survey telescope
that provide detailed time-series coverage of the onset and evolution of
Gault’s activity. Gault exhibited two brightening events, with the first one
starting on 2018 Oct. 18$pm5$ days and a second one starting on 2018 Dec.
24$pm1$ days. The amounts of mass released are $2times10^7$ kg and
$1times10^6$ kg, respectively. Based on photometric measurements, each event
persisted for about a month. Gault’s color has not changed appreciably over
time, with a pre-outburst color of $g_mathrm{PS1}-r_mathrm{PS1}=0.50pm0.04$
and $g_mathrm{PS1}-r_mathrm{PS1}=0.46pm0.04$ during the two outbursts.
Simulations of dust dynamics shows that the ejecta consists of dust grains of
up to 10 $mu$m in size that are ejected at low velocities below
$1~mathrm{m~s^{-1}}$ regardless of particle sizes. This is consistent with
non-sublimation-driven ejection events. The size distribution of the dust
exhibits a broken power-law, with particles at 10–20 $mu$m following a
power-law of $-2.5$ to $-3.0$, while larger particles follow a steeper slope of
$-4.0$. The derived properties can be explained by either rotational excitation
of the nucleus or a merger of a near-contact binary, with the latter scenario
to be statistically more likely.

Main-belt asteroid (6478) Gault unexpectedly sprouted two tails in late 2018
and early 2019, identifying it as a new active asteroid. Here we present
observations obtained by the 1.2-m Zwicky Transient Facility survey telescope
that provide detailed time-series coverage of the onset and evolution of
Gault’s activity. Gault exhibited two brightening events, with the first one
starting on 2018 Oct. 18$pm5$ days and a second one starting on 2018 Dec.
24$pm1$ days. The amounts of mass released are $2times10^7$ kg and
$1times10^6$ kg, respectively. Based on photometric measurements, each event
persisted for about a month. Gault’s color has not changed appreciably over
time, with a pre-outburst color of $g_mathrm{PS1}-r_mathrm{PS1}=0.50pm0.04$
and $g_mathrm{PS1}-r_mathrm{PS1}=0.46pm0.04$ during the two outbursts.
Simulations of dust dynamics shows that the ejecta consists of dust grains of
up to 10 $mu$m in size that are ejected at low velocities below
$1~mathrm{m~s^{-1}}$ regardless of particle sizes. This is consistent with
non-sublimation-driven ejection events. The size distribution of the dust
exhibits a broken power-law, with particles at 10–20 $mu$m following a
power-law of $-2.5$ to $-3.0$, while larger particles follow a steeper slope of
$-4.0$. The derived properties can be explained by either rotational excitation
of the nucleus or a merger of a near-contact binary, with the latter scenario
to be statistically more likely.

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