Kepler-78 and the Ultra-Short-Period Planets. (arXiv:1803.03303v3 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Winn_J/0/1/0/all/0/1">Joshua N. Winn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchis_Ojeda_R/0/1/0/all/0/1">Roberto Sanchis-Ojeda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rappaport_S/0/1/0/all/0/1">Saul Rappaport</a>
Compared to the Earth, the exoplanet Kepler-78b has a similar size (1.2
$R_oplus$) and an orbital period a thousand times shorter (8.5 hours). It is
currently the smallest planet for which the mass, radius, and dayside
brightness have all been measured. Kepler-78b is an exemplar of the
ultra-short-period (USP) planets, a category defined by the simple criterion
$P_{rm orb} < 1$ day. We describe our Fourier-based search of the Kepler data
that led to the discovery of Kepler-78b, and review what has since been learned
about the population of USP planets. They are about as common as hot Jupiters,
and they are almost always smaller than 2 $R_oplus$. They are often members of
compact multi-planet systems, although they tend to have relatively large
period ratios and mutual inclinations. They might be the exposed rocky cores of
"gas dwarfs," the planets between 2-4 $R_oplus$ in size that are commonly
found in somewhat wider orbits.
Compared to the Earth, the exoplanet Kepler-78b has a similar size (1.2
$R_oplus$) and an orbital period a thousand times shorter (8.5 hours). It is
currently the smallest planet for which the mass, radius, and dayside
brightness have all been measured. Kepler-78b is an exemplar of the
ultra-short-period (USP) planets, a category defined by the simple criterion
$P_{rm orb} < 1$ day. We describe our Fourier-based search of the Kepler data
that led to the discovery of Kepler-78b, and review what has since been learned
about the population of USP planets. They are about as common as hot Jupiters,
and they are almost always smaller than 2 $R_oplus$. They are often members of
compact multi-planet systems, although they tend to have relatively large
period ratios and mutual inclinations. They might be the exposed rocky cores of
“gas dwarfs,” the planets between 2-4 $R_oplus$ in size that are commonly
found in somewhat wider orbits.
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