Kavli Affiliate: David Charbonneau
| First 5 Authors: Rena A. Lee, Fei Dai, Andrew W. Howard, Samuel Halverson, Jonathan Gomez Barrientos
| Summary:
We report the confirmation of TOI-6324 b, an Earth-sized (1.059 $pm$ 0.041
R$_oplus$) ultra-short-period (USP) planet orbiting a nearby ($sim$20 pc) M
dwarf. Using the newly commissioned Keck Planet Finder (KPF) spectrograph, we
have measured the mass of TOI-6324 b 1.17 $pm$ 0.22 M$_oplus$. Because of its
extremely short orbit of just $sim$6.7 hours, TOI-6324 b is intensely
irradiated by its M dwarf host, and is expected to be stripped of any thick,
H/He envelope. We were able to constrain its interior composition and found an
iron core mass fraction (CMF = 27$pm$37%) consistent with that of Earth
($sim$33%) and other confirmed USPs. TOI-6324 b is the closest to Earth-sized
USP confirmed to date. TOI-6324 b is a promising target for JWST phase curve
and secondary eclipse observations (Emission Spectroscopy Metric = 25) which
may reveal its surface mineralogy, day-night temperature contrast, and possible
tidal deformation. From 7 sectors of TESS data, we report a tentative detection
of the optical phase curve variation with an amplitude of 42$pm$28 ppm.
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