Warm Saturns: Rings Around Exoplanets that Reside

Inside the Ice Line

Extreme Solar Systems IISeptember. 14th 2011

Schlichting & Chang (2011), ApJ 734, 117

Hilke E. Schlichting (UCLA)Hubble Postdoctoral Fellow

Obvious Obstacles:

• Best ring candidates have a > 0.1 AU• Ring lifetimes due to Poynting-Robertson drag 106-109 years

Rings must be rocky!Poynting-Robertson drag timescale

Rings vs. Moons

RRoche

RP

ρice ~ 1g/cm3

ρrock ~ 2-5g/cm3

Roche Radius

For Saturn:RRoche/RP~2.2

(ice:1g/cm3)RRoche/RP~1.5

(rock:3g/cm3)

(Schlichting & Chang, 2011)

ρ =3g/cm3

ρ =5g/cm3

Laplace Plane

RL > RRoche

RL < RRoche

J2: Quadrupole Gravitational Harmonic

Warped Rings

(Schlichting & Chang, 2011)

For Reference:

J2 of Uranus & Neptune ~ 0.003

J2 of Jupiter & Saturn ~ 0.01

Ring Light Curves

Quadratic Limb Darkening as in Mandel & Agol (2001), for Ring light curves see also Barnes & Fortney (2004)

RP=1 RJ

RR1=2.0 RP

RP2=2.5 RP

RP=1 RJ

RR1=1.5 RP

RP2=2.5 RP

RP=1 RJ

RR1=2.0 RP

RP2=2.5 RP

RP=1.8 RJ

Transit duration ~ 6 hours

Time in ingress/egress ~ 2

hours

Ring Properties &Possibility for Detection

• Rings may be common• Rings must consist of rocky

material• Some Rings maybe warped

J2

• Best candidates for ring detection have a > 0.1 AU

• Obliquity damping, temperature, ideally want short cadence