TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes
Creators: name: Dai, Fei
name: Howard, Andrew W.
name: Batalha, Natalie M.
name: Beard, Corey
name: Behmard, Aida
name: Blunt, Sarah
name: Brinkman, Casey L.
name: Chontos, Ashley
name: Crossfield, Ian J. M.
name: Dalba, Paul A.
name: Dressing, Courtney
name: Fulton, Benjamin
name: Giacalone, Steven
name: Hill, Michelle L.
name: Huber, Daniel
name: Isaacson, Howard
name: Kane, Stephen R.
name: Lubin, Jack
name: Mayo, Andrew
name: Mocnik, Teo
name: Murphy, Joseph M. Akana
name: Petigura, Erik A.
name: Rice, Malena
name: Robertson, Paul
name: Rosenthal, Lee
name: Roy, Arpita
name: Rubenzahl, Ryan A.
name: Weiss, Lauren M.
name: Van Zandt, Judah
name: Beichman, Charles
name: Ciardi, David
name: Collins, Karen A.
name: Gonzales, Erica
name: Howell, Steve B.
name: Matson, Rachel A.
name: Matthews, Elisabeth C.
name: Schlieder, Joshua E.
name: Schwarz, Richard P.
name: Ricker, George R.
name: Vanderspek, Roland
name: Latham, David W.
name: Seager, Sara
name: Winn, Joshua N.
name: Jenkins, Jon M.
name: Caldwell, Douglas A.
name: Colon, Knicole D.
name: Dragomir, Diana
name: Lund, Michael B.
name: McLean, Brian
name: Rudat, Alexander
name: Shporer, Avi
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 ($&lt;2R_\oplus$) and contrast them with the newly discovered sub-day ultra-hot Neptunes ($&gt;3R_\oplus$, $&gt;2000F_\oplus$ 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.
description: Accepted too AJ. 12 Figures, 4 tables