Abstract
Planetary rings produce a distinct shape distortion in transit
lightcurves. However, to accurately model such lightcurves the
observations need to cover the entire transit, especially ingress and
egress, as well as an out-of-transit baseline. Such observations can be
challenging for long period planets, where the transits may last for
over a day. Planetary rings will also impact the shape of absorption
lines in the stellar spectrum, as the planet and rings cover different
parts of the rotating star (the Rossiter-McLaughlin effect). These
line-profile distortions depend on the size, structure, opacity,
obliquity and sky projected angle of the ring system. For slow rotating
stars, this mainly impacts the amplitude of the induced velocity shift,
however, for fast rotating stars the large velocity gradient across the
star allows the line distortion to be resolved, enabling direct
determination of the ring parameters. We demonstrate that by modeling
these distortions we can recover ring system parameters (sky-projected
angle, obliquity and size) using only a small part of the transit.
Substructure in the rings, e.g. gaps, can be recovered if the width of
the features ($\delta W$) relative to the size of the star is similar to
the intrinsic velocity resolution (set by the width of the local stellar
profile, $\gamma$) relative to the stellar rotation velocity ($v$
sin$i$, i.e. $\delta W / R_* \gtrsim v$sin$i$/$\gamma$). This opens up a
new way to study the ring systems around planets with long orbital
periods, where observations of the full transit, covering the ingress
and egress, are not always feasible.
Original language | English |
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Pages (from-to) | 2713–2721 |
Number of pages | 9 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 472 |
Early online date | 18 Aug 2017 |
DOIs | |
Publication status | Published - 11 Dec 2017 |
Keywords
- Astrophysics - Earth and Planetary Astrophysics
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Ernst de Mooij
- School of Mathematics and Physics - Senior Lecturer
- Astrophysics Research Centre (ARC)
Person: Academic