Comet 240P/NEAT is Stirring. (arXiv:1911.02383v1 [astro-ph.EP])

Comet 240P/NEAT is Stirring. (arXiv:1911.02383v1 [astro-ph.EP])
<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:+Ye_Q/0/1/0/all/0/1">Quanzhi Ye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farnham_T/0/1/0/all/0/1">Tony L. Farnham</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:+Helou_G/0/1/0/all/0/1">George Helou</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:+Laher_R/0/1/0/all/0/1">Russ R. Laher</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:+Rusholme_B/0/1/0/all/0/1">Ben Rusholme</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shupe_D/0/1/0/all/0/1">David L. Shupe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Soumagnac_M/0/1/0/all/0/1">Maayane T. Soumagnac</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zolkower_J/0/1/0/all/0/1">Jeffry Zolkower</a>

Comets are primitive objects that formed in the protoplanetary disk, and have
been largely preserved over the history of the Solar System. However, they are
not pristine, and surfaces of cometary nuclei do evolve. In order to understand
the extent of their primitive nature, we must define the mechanisms that affect
their surfaces and comae. We examine the lightcurve of comet 240P/NEAT over
three consecutive orbits, and investigate three events of significant
brightening ($Delta m sim -2$ mag). Unlike typical cometary outbursts, each
of the three events are long-lived, with enhanced activity for at least 3 to 6
months. The third event, observed by the Zwicky Transient Facility, occurred in
at least two stages. The anomalous behavior appears to have started after the
comet was perturbed by Jupiter in 2007, reducing its perihelion distance from
2.53 to 2.12 au. We suggest that the brightening events are temporary
transitions to a higher baseline activity level, brought on by the increased
insolation, which has warmed previously insulated sub-surface layers. The new
activity is isolated to one or two locations on the nucleus, indicating that
the surface or immediate sub-surface is heterogeneous. Further study of this
phenomenon may provide insight into cometary outbursts, the structure of the
near-surface nucleus, and cometary nucleus mantling.

Comets are primitive objects that formed in the protoplanetary disk, and have
been largely preserved over the history of the Solar System. However, they are
not pristine, and surfaces of cometary nuclei do evolve. In order to understand
the extent of their primitive nature, we must define the mechanisms that affect
their surfaces and comae. We examine the lightcurve of comet 240P/NEAT over
three consecutive orbits, and investigate three events of significant
brightening ($Delta m sim -2$ mag). Unlike typical cometary outbursts, each
of the three events are long-lived, with enhanced activity for at least 3 to 6
months. The third event, observed by the Zwicky Transient Facility, occurred in
at least two stages. The anomalous behavior appears to have started after the
comet was perturbed by Jupiter in 2007, reducing its perihelion distance from
2.53 to 2.12 au. We suggest that the brightening events are temporary
transitions to a higher baseline activity level, brought on by the increased
insolation, which has warmed previously insulated sub-surface layers. The new
activity is isolated to one or two locations on the nucleus, indicating that
the surface or immediate sub-surface is heterogeneous. Further study of this
phenomenon may provide insight into cometary outbursts, the structure of the
near-surface nucleus, and cometary nucleus mantling.

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