Outcomes of Sub-Neptune Collisions. (arXiv:2312.07648v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ghosh_T/0/1/0/all/0/1">Tuhin Ghosh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chatterjee_S/0/1/0/all/0/1">Sourav Chatterjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lombardi_J/0/1/0/all/0/1">James C. Lombardi</a>
Observed high multiplicity planetary systems are often tightly packed.
Numerical studies indicate that such systems are susceptible to dynamical
instabilities. Dynamical instabilities in close-in tightly packed systems,
similar to those found in abundance by Kepler, often lead to planet-planet
collisions. For sub-Neptunes, the dominant type of observed exoplanets, the
planetary mass is concentrated in a rocky core, but the volume is dominated by
a low-density gaseous envelope. For these, using the traditional
`sticky-sphere’ assumption is questionable. Using both N-body integration and
smoothed-particle hydrodynamics, we have simulated sub-Neptune collisions for a
wide range in realistic kinematic properties such as impact parameters
($b^{prime}$) and impact velocities ($v_{rm{im}}$) to study the possible
outcomes in detail. We find that the majority ($sim 76%$) of the collisions
with kinematic properties similar to what is expected from dynamical
instabilities in multiplanet systems may not lead to mergers of sub-Neptunes.
Instead, the sub-Neptunes separate from each other, often with significant
atmosphere loss. When mergers do occur, they can involve significant mass loss
even from the core and can sometimes lead to complete disruption of one or both
planets. Sub-Neptunes merge or disrupt if $b^{prime}<b_{rm{c}}$, a critical
value dependent on $ v_{rm{im}}/v_{rm{esc}}$, where $v_{rm{esc}}$ is the
escape velocity from the surface of the hypothetical merged planet assuming
sticky-sphere. For $ v_{rm{im}}/v_{rm{esc}}lesssim2.5$, $b_{rm{c}}propto
(v_{rm{im}}/v_{rm{esc}})^{-2}$, and collisions with $b^{prime}<b_{rm{c}}$
typically leads to mergers. On the other hand, for $
v_{rm{im}}/v_{rm{esc}}gtrsim2.5$, $b_{rm{c}}propto
v_{rm{im}}/v_{rm{esc}}$, and the collisions with $b^{prime}<b_{rm{c}}$ can
result in complete destruction of one or both sub-Neptunes.
Observed high multiplicity planetary systems are often tightly packed.
Numerical studies indicate that such systems are susceptible to dynamical
instabilities. Dynamical instabilities in close-in tightly packed systems,
similar to those found in abundance by Kepler, often lead to planet-planet
collisions. For sub-Neptunes, the dominant type of observed exoplanets, the
planetary mass is concentrated in a rocky core, but the volume is dominated by
a low-density gaseous envelope. For these, using the traditional
`sticky-sphere’ assumption is questionable. Using both N-body integration and
smoothed-particle hydrodynamics, we have simulated sub-Neptune collisions for a
wide range in realistic kinematic properties such as impact parameters
($b^{prime}$) and impact velocities ($v_{rm{im}}$) to study the possible
outcomes in detail. We find that the majority ($sim 76%$) of the collisions
with kinematic properties similar to what is expected from dynamical
instabilities in multiplanet systems may not lead to mergers of sub-Neptunes.
Instead, the sub-Neptunes separate from each other, often with significant
atmosphere loss. When mergers do occur, they can involve significant mass loss
even from the core and can sometimes lead to complete disruption of one or both
planets. Sub-Neptunes merge or disrupt if $b^{prime}<b_{rm{c}}$, a critical
value dependent on $ v_{rm{im}}/v_{rm{esc}}$, where $v_{rm{esc}}$ is the
escape velocity from the surface of the hypothetical merged planet assuming
sticky-sphere. For $ v_{rm{im}}/v_{rm{esc}}lesssim2.5$, $b_{rm{c}}propto
(v_{rm{im}}/v_{rm{esc}})^{-2}$, and collisions with $b^{prime}<b_{rm{c}}$
typically leads to mergers. On the other hand, for $
v_{rm{im}}/v_{rm{esc}}gtrsim2.5$, $b_{rm{c}}propto
v_{rm{im}}/v_{rm{esc}}$, and the collisions with $b^{prime}<b_{rm{c}}$ can
result in complete destruction of one or both sub-Neptunes.
http://arxiv.org/icons/sfx.gif
