TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs

July 2020 • 2020AJ....160...22C

Authors • 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 J. M. • 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 • Martinez Fiorenzano, Aldo F. • Mallia, Franco • Lubin, Jack • Lovis, Christophe • López-Morales, Mercedes • Kosiarek, Molly R. • Kielkopf, John F. • Kane, Stephen R. • Jensen, Eric L. N. • 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 • Akana Murphy, Joseph M.

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, ${r}_{{\rm{p}}}={1.738}_{-0.076}^{+0.087}$ ${R}_{\oplus }$ ), 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.


IPAC Authors


Jessie Christiansen

Associate Scientist


David Ciardi

Senior Scientist