The unexpected narrowness of eccentric debris rings: a sign of eccentricity during the protoplanetary disc phase. (arXiv:2005.14200v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kennedy_G/0/1/0/all/0/1">Grant M. Kennedy</a>
This paper shows that the eccentric debris rings seen around the stars
Fomalhaut and HD 202628 are narrower than expected in the standard eccentric
planet perturbation scenario (sometimes referred to as “pericenter glow”). The
standard scenario posits an initially circular and narrow belt of planetesimals
at semi-major axis $a$, whose eccentricity is increased to $e_f$ after the gas
disc has dispersed by secular perturbations from an eccentric planet, resulting
in a belt of width $2ae_f$. In a minor modification of this scenario, narrower
belts can arise if the planetesimals are initially eccentric, which could
result from earlier planet perturbations during the gas-rich protoplanetary
disc phase. However, a primordial eccentricity could alternatively be caused by
instabilities that increase the disc eccentricity, without the need for any
planets. Whether these scenarios produce detectable eccentric rings within
protoplanetary discs is unclear, but they nevertheless predict that narrow
eccentric planetesimal rings should exist before the gas in protoplanetary
discs is dispersed. PDS 70 is noted as a system hosting an asymmetric
protoplanetary disc that may be a progenitor of eccentric debris ring systems.
This paper shows that the eccentric debris rings seen around the stars
Fomalhaut and HD 202628 are narrower than expected in the standard eccentric
planet perturbation scenario (sometimes referred to as “pericenter glow”). The
standard scenario posits an initially circular and narrow belt of planetesimals
at semi-major axis $a$, whose eccentricity is increased to $e_f$ after the gas
disc has dispersed by secular perturbations from an eccentric planet, resulting
in a belt of width $2ae_f$. In a minor modification of this scenario, narrower
belts can arise if the planetesimals are initially eccentric, which could
result from earlier planet perturbations during the gas-rich protoplanetary
disc phase. However, a primordial eccentricity could alternatively be caused by
instabilities that increase the disc eccentricity, without the need for any
planets. Whether these scenarios produce detectable eccentric rings within
protoplanetary discs is unclear, but they nevertheless predict that narrow
eccentric planetesimal rings should exist before the gas in protoplanetary
discs is dispersed. PDS 70 is noted as a system hosting an asymmetric
protoplanetary disc that may be a progenitor of eccentric debris ring systems.
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