July
2020
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2020AJ....160...22C
Authors
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Cloutier, Ryan
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Rodriguez, Joseph E.
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Irwin, Jonathan
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Charbonneau, David
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Stassun, Keivan G.
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Mortier, Annelies
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Latham, David W.
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Isaacson, Howard
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Howard, Andrew W.
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Udry, Stéphane
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Wilson, Thomas G.
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Watson, Christopher A.
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Pinamonti, Matteo
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Lienhard, Florian
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Giacobbe, Paolo
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Guerra, Pere
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Collins, Karen A.
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Beiryla, Allyson
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Esquerdo, Gilbert A.
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Matthews, Elisabeth
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Matson, Rachel A.
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Howell, Steve B.
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Furlan, Elise
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Crossfield, Ian J. M.
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Winters, Jennifer G.
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Nava, Chantanelle
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Ment, Kristo
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Lopez, Eric D.
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Ricker, George
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Vanderspek, Roland
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Seager, Sara
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Jenkins, Jon M.
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Ting, Eric B.
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Tenenbaum, Peter
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Sozzetti, Alessandro
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Sha, Lizhou
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Ségransan, Damien
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Schlieder, Joshua E.
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Sasselov, Dimitar
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Roy, Arpita
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Robertson, Paul
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Rice, Ken
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Poretti, Ennio
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Piotto, Giampaolo
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Phillips, David
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Pepper, Joshua
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Pepe, Francesco
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Molinari, Emilio
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Mocnik, Teo
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Micela, Giuseppina
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Mayor, Michel
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Martinez Fiorenzano, Aldo F.
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Mallia, Franco
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Lubin, Jack
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Lovis, Christophe
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López-Morales, Mercedes
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Kosiarek, Molly R.
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Kielkopf, John F.
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Kane, Stephen R.
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Jensen, Eric L. N.
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Isopi, Giovanni
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Huber, Daniel
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Hill, Michelle L.
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Harutyunyan, Avet
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Gonzales, Erica
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Giacalone, Steven
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Ghedina, Adriano
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Ercolino, Andrea
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Dumusque, Xavier
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Dressing, Courtney D.
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Damasso, Mario
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Dalba, Paul A.
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Cosentino, Rosario
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Conti, Dennis M.
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Colón, Knicole D.
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Collins, Kevin I.
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Cameron, Andrew Collier
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Ciardi, David
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Christiansen, Jessie
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Chontos, Ashley
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Cecconi, Massimo
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Caldwell, Douglas A.
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Burke, Christopher
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Buchhave, Lars
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Beichman, Charles
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Behmard, Aida
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Beard, Corey
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Akana Murphy, Joseph M.
Abstract
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Small planets on close-in orbits tend to exhibit envelope mass fractions of either effectively zero or up to a few percent depending on their size and orbital period. Models of thermally driven atmospheric mass loss and of terrestrial planet formation in a gas-poor environment make distinct predictions regarding the location of this rocky/nonrocky transition in period-radius space. Here we present the confirmation of TOI-1235 b (P = 3.44 days, ${r}_{{\rm{p}}}={1.738}_{-0.076}^{+0.087}$ ${R}_{\oplus }$ ), a planet whose size and period are intermediate between the competing model predictions, thus making the system an important test case for emergence models of the rocky/nonrocky transition around early M dwarfs (Rs = 0.630 ± 0.015 ${R}_{\odot }$ , Ms = 0.640 ± 0.016 ${M}_{\odot }$ ). We confirm the TESS planet discovery using reconnaissance spectroscopy, ground-based photometry, high-resolution imaging, and a set of 38 precise radial velocities (RVs) from HARPS-N and HIRES. We measure a planet mass of ${6.91}_{-0.85}^{+0.75}$ ${M}_{\oplus }$ , which implies an iron core mass fraction of ${20}_{-12}^{+15}$ % in the absence of a gaseous envelope. The bulk composition of TOI-1235 b is therefore consistent with being Earth-like, and we constrain an H/He envelope mass fraction to be <0.5% at 90% confidence. Our results are consistent with model predictions from thermally driven atmospheric mass loss but not with gas-poor formation, suggesting that the former class of processes remains efficient at sculpting close-in planets around early M dwarfs. Our RV analysis also reveals a strong periodicity close to the first harmonic of the photometrically determined stellar rotation period that we treat as stellar activity, despite other lines of evidence favoring a planetary origin ( $P={21.8}_{-0.8}^{+0.9}$ days, ${m}_{{\rm{p}}}\sin i={13.0}_{-5.3}^{+3.8}$ ${M}_{\oplus }$ ) that cannot be firmly ruled out by our data.
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