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TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
Name
Dai_2021_AJ_162_62.pdf
Description
Published version
Size
4.28 MB
Format
Adobe PDF
Checksum (MD5)
754b20455b6483af0476d98256ea03f2
Date Issued
August 1, 2021
Journal
The Astronomical Journal
Publisher
American Astronomical Society
Version
Final published version
Abstract
We report the discovery of TOI-1444b, a 1.4-$R_\oplus$ super-Earth on a
0.47-day orbit around a Sun-like star discovered by {\it TESS}. Precise radial
velocities from Keck/HIRES confirmed the planet and constrained the mass to be
$3.87 \pm 0.71 M_\oplus$. The RV dataset also indicates a possible
non-transiting, 16-day planet ($11.8\pm2.9M_\oplus$). We report a tentative
detection of phase curve variation and secondary eclipse of TOI-1444b in the
{\it TESS} bandpass. TOI-1444b joins the growing sample of 17
ultra-short-period planets with well-measured masses and sizes, most of which
are compatible with an Earth-like composition. We take this opportunity to
examine the expanding sample of ultra-short-period planets ($<2R_\oplus$) and
contrast them with the newly discovered sub-day ultra-hot Neptunes
($>3R_\oplus$, $>2000F_\oplus$ TOI-849 b, LTT9779 b and K2-100). We find that
1) USPs have predominately Earth-like compositions with inferred iron core mass
fractions of 0.32$\pm$0.04; and have masses below the threshold of runaway
accretion ($\sim 10M_\oplus$), while ultra-hot Neptunes are above the threshold
and have H/He or other volatile envelope. 2) USPs are almost always found in
multi-planet system consistent with a secular interaction formation scenario;
ultra-hot Neptunes ($P_{\rm orb} \lesssim$1 day) tend to be ``lonely' similar
to longer-period hot Neptunes($P_{\rm orb}$1-10 days) and hot Jupiters. 3) USPs
occur around solar-metallicity stars while hot Neptunes prefer higher
metallicity hosts. 4) In all these respects, the ultra-hot Neptunes show more
resemblance to hot Jupiters than the smaller USP planets, although ultra-hot
Neptunes are rarer than both USP and hot Jupiters by 1-2 orders of magnitude.
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DOI of Published Version
10.3847/1538-3881/ac02bd
