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TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs
- Cloutier, Ryan;
- Rodriguez, Joseph E;
- Irwin, Jonathan;
- Charbonneau, David;
- Stassun, Keivan G;
- Mortier, Annelies;
- Latham, David W;
- Isaacson, Howard;
- Howard, Andrew W;
- Udry, Stéphane;
- Wilson, Thomas G;
- Watson, Christopher A;
- Pinamonti, Matteo;
- Lienhard, Florian;
- Giacobbe, Paolo;
- Guerra, Pere;
- Collins, Karen A;
- Beiryla, Allyson;
- Esquerdo, Gilbert A;
- Matthews, Elisabeth;
- Matson, Rachel A;
- Howell, Steve B;
- Furlan, Elise;
- Crossfield, Ian JM;
- Winters, Jennifer G;
- Nava, Chantanelle;
- Ment, Kristo;
- Lopez, Eric D;
- Ricker, George;
- Vanderspek, Roland;
- Seager, Sara;
- Jenkins, Jon M;
- Ting, Eric B;
- Tenenbaum, Peter;
- Sozzetti, Alessandro;
- Sha, Lizhou;
- Ségransan, Damien;
- Schlieder, Joshua E;
- Sasselov, Dimitar;
- Roy, Arpita;
- Robertson, Paul;
- Rice, Ken;
- Poretti, Ennio;
- Piotto, Giampaolo;
- Phillips, David;
- Pepper, Joshua;
- Pepe, Francesco;
- Molinari, Emilio;
- Mocnik, Teo;
- Micela, Giuseppina;
- Mayor, Michel;
- Fiorenzano, Aldo F Martinez;
- Mallia, Franco;
- Lubin, Jack;
- Lovis, Christophe;
- López-Morales, Mercedes;
- Kosiarek, Molly R;
- Kielkopf, John F;
- Kane, Stephen R;
- Jensen, Eric LN;
- Isopi, Giovanni;
- Huber, Daniel;
- Hill, Michelle L;
- Harutyunyan, Avet;
- Gonzales, Erica;
- Giacalone, Steven;
- Ghedina, Adriano;
- Ercolino, Andrea;
- Dumusque, Xavier;
- Dressing, Courtney D;
- Damasso, Mario;
- Dalba, Paul A;
- Cosentino, Rosario;
- Conti, Dennis M;
- Colón, Knicole D;
- Collins, Kevin I;
- Cameron, Andrew Collier;
- Ciardi, David;
- Christiansen, Jessie;
- Chontos, Ashley;
- Cecconi, Massimo;
- Caldwell, Douglas A;
- Burke, Christopher;
- Buchhave, Lars;
- Beichman, Charles;
- Behmard, Aida;
- Beard, Corey;
- Murphy, Joseph M Akana
- et al.
Abstract
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, rp1.738-0.076+0.087 R⊕), 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 (R s = 0.630± 0.015 ⊕, M s = 0.640 ± 0.016 ⊙. 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+0.75M⊕ 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+0.9-0.8days,mp sin =13.0+ 3.8-5.3M⊕) that cannot be firmly ruled out by our data.
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