The Reactivation of Main-Belt Comet 259P/Garradd (P/2008 R1). (arXiv:2102.06290v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hsieh_H/0/1/0/all/0/1">Henry H. Hsieh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ishiguro_M/0/1/0/all/0/1">Masateru Ishiguro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Knight_M/0/1/0/all/0/1">Matthew M. Knight</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moskovitz_N/0/1/0/all/0/1">Nicholas A. Moskovitz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sheppard_S/0/1/0/all/0/1">Scott S. Sheppard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trujillo_C/0/1/0/all/0/1">Chadwick A. Trujillo</a>
We present observations of main-belt comet 259P/Garradd from four months
prior to its 2017 perihelion passage to five months after perihelion using the
Gemini North and South telescopes. The object was confirmed to be active during
this period, placing it among seven MBCs confirmed to have recurrent activity.
We find an average net pre-perihelion dust production rate for 259P in 2017 of
dM/dt = 4.6+/-0.2 kg/s (assuming grain densities of rho = 2500 kg/m^3 and a
mean effective particle size of a_d = 2 mm) and a best-fit start date of
detectable activity of 2017 April 22+/-1, when the object was at a heliocentric
distance of r_h = 1.96-/+0.03 au and a true anomaly of nu = 313.9+/-0.4 deg. We
estimate the effective active fraction of 259P’s surface area to be from f_act
~ 7×10^-3 to f_act ~ 6×10^-2 (corresponding to effective active areas of A_act
~ 8×10^3 m^2 to A_act ~ 7×10^4 m^2) at the start of its 2017 active period. A
comparison of estimated total dust masses measured for 259P in 2008 and 2017
shows no evidence of changes in activity strength between the two active
apparitions. The heliocentric distance of 259P’s activity onset point is much
smaller than those of other MBCs, suggesting that its ice reservoirs may be
located at greater depths than on MBCs farther from the Sun, increasing the
time needed for a solar irradiation-driven thermal wave to reach subsurface
ice. We suggest that deeper ice on 259P could be a result of more rapid ice
depletion caused by the object’s closer proximity to the Sun compared to other
MBCs.
We present observations of main-belt comet 259P/Garradd from four months
prior to its 2017 perihelion passage to five months after perihelion using the
Gemini North and South telescopes. The object was confirmed to be active during
this period, placing it among seven MBCs confirmed to have recurrent activity.
We find an average net pre-perihelion dust production rate for 259P in 2017 of
dM/dt = 4.6+/-0.2 kg/s (assuming grain densities of rho = 2500 kg/m^3 and a
mean effective particle size of a_d = 2 mm) and a best-fit start date of
detectable activity of 2017 April 22+/-1, when the object was at a heliocentric
distance of r_h = 1.96-/+0.03 au and a true anomaly of nu = 313.9+/-0.4 deg. We
estimate the effective active fraction of 259P’s surface area to be from f_act
~ 7×10^-3 to f_act ~ 6×10^-2 (corresponding to effective active areas of A_act
~ 8×10^3 m^2 to A_act ~ 7×10^4 m^2) at the start of its 2017 active period. A
comparison of estimated total dust masses measured for 259P in 2008 and 2017
shows no evidence of changes in activity strength between the two active
apparitions. The heliocentric distance of 259P’s activity onset point is much
smaller than those of other MBCs, suggesting that its ice reservoirs may be
located at greater depths than on MBCs farther from the Sun, increasing the
time needed for a solar irradiation-driven thermal wave to reach subsurface
ice. We suggest that deeper ice on 259P could be a result of more rapid ice
depletion caused by the object’s closer proximity to the Sun compared to other
MBCs.
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