Repeating gas ejection events from comet 45P/Honda-Mrkos-Pajduv{s}'{a}kov'{a}. (arXiv:2107.10351v2 [astro-ph.EP] UPDATED)

Repeating gas ejection events from comet 45P/Honda-Mrkos-Pajduv{s}'{a}kov'{a}. (arXiv:2107.10351v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Springmann_A/0/1/0/all/0/1">Alessondra Springmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harris_W/0/1/0/all/0/1">Walter M. Harris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ryan_E/0/1/0/all/0/1">Erin L. Ryan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lejoly_C/0/1/0/all/0/1">Cassandra Lejoly</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howell_E/0/1/0/all/0/1">Ellen S. Howell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mueller_B/0/1/0/all/0/1">Beatrice E.A. Mueller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samarasinha_N/0/1/0/all/0/1">Nalin H. Samarasinha</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Woodney_L/0/1/0/all/0/1">Laura M. Woodney</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Steckloff_J/0/1/0/all/0/1">Jordan K. Steckloff</a>

Studying materials released from Jupiter-family comets (JFCs) — as seen in
their inner comae, the envelope of gas and dust that forms as the comet
approaches the Sun — improves the understanding of their origin and
evolutionary history. As part of a coordinated, multi-wavelength observing
campaign, we observed comet 45P/Honda-Mrkos-Pajduv{s}'{a}kov'{a} during its
close approach to Earth in February 2017. Narrowband observations were taken
using the Bok 90” telescope at Kitt Peak National Observatory on February 16
and 17 UT, revealing gas and dust structures. We observed different jet
directions for different volatile species, implying source region
heterogeneity, consistent with other ground-based and textit{in situ}
observations of other comet nuclei. A repeating feature visible in CN and C$_2$
images on February 16 was also observed on February 17 with an interval of
$7.6pm0.1$ hours, consistent with the rotation period of the comet derived
from Arecibo Observatory radar observations. The repeating feature’s projected
gas velocity away from the nucleus is 0.8 km s$^{-1}$, with an expansion
velocity of 0.5 km s$^{-1}$. A bright compact spot adjacent to the nucleus
provides a lower limit of the amount of material released in one cycle of
$sim$totalmass{} kg, depending on composition — a quantity small enough to
be produced by repeated exposure of nucleus ices to sunlight. This repeating CN
jet, forming within 400 km of the nucleus, may be typical of inner coma
behavior in JFCs; however, similar features could be obscured by other
processes and daughter product species when viewed from distances further than
the scale length of CN molecules.

Studying materials released from Jupiter-family comets (JFCs) — as seen in
their inner comae, the envelope of gas and dust that forms as the comet
approaches the Sun — improves the understanding of their origin and
evolutionary history. As part of a coordinated, multi-wavelength observing
campaign, we observed comet 45P/Honda-Mrkos-Pajduv{s}'{a}kov'{a} during its
close approach to Earth in February 2017. Narrowband observations were taken
using the Bok 90” telescope at Kitt Peak National Observatory on February 16
and 17 UT, revealing gas and dust structures. We observed different jet
directions for different volatile species, implying source region
heterogeneity, consistent with other ground-based and textit{in situ}
observations of other comet nuclei. A repeating feature visible in CN and C$_2$
images on February 16 was also observed on February 17 with an interval of
$7.6pm0.1$ hours, consistent with the rotation period of the comet derived
from Arecibo Observatory radar observations. The repeating feature’s projected
gas velocity away from the nucleus is 0.8 km s$^{-1}$, with an expansion
velocity of 0.5 km s$^{-1}$. A bright compact spot adjacent to the nucleus
provides a lower limit of the amount of material released in one cycle of
$sim$totalmass{} kg, depending on composition — a quantity small enough to
be produced by repeated exposure of nucleus ices to sunlight. This repeating CN
jet, forming within 400 km of the nucleus, may be typical of inner coma
behavior in JFCs; however, similar features could be obscured by other
processes and daughter product species when viewed from distances further than
the scale length of CN molecules.

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