TOI-1235 b: a keystone super-Earth for testing radius valley emergence models around early M dwarfs

Creators: 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; 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; Matson, Rachel A.; 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; Howell, Steve B.; Hill, Michelle L.; Harutyunyan, Avet; Gonzales, Erica J.; 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; Furlan, Elise

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_p=1.738^(+0.087)_(−0.076) 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 R⊙, M_s = 0.640 ± 0.016 M⊙). 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^(+0.75)_(−0.85) M⊕, which implies an iron core mass fraction of 20⁺¹⁵₋₁₂% 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)_(−0.8) days, m_p sin i=13.0^(+3.8)_(−5.3) M⊕) that cannot be firmly ruled out by our data.

Additional Information

© 2020 The American Astronomical Society. Received 2020 April 13; Accepted 2020 May 19; Published 2020 June 12. R.C. is supported by a grant from the National Aeronautics and Space Administration in support of the TESS science mission. We thank Andrew Vanderburg for enlightening discussions regarding the TESS light curves. M.P. gratefully acknowledges the support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 313014 (ETAEARTH). J.M.A.M. gratefully acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1842400. J.M.A.M. also thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. This work has been partially supported by the National Aeronautics and Space Administration under grant No. NNX17AB59G issued through the Exoplanets Research Program. We acknowledge the use of public TESS Alert data from the pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. The MEarth Team gratefully acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering (awarded to D.C.). This material is based on work supported by the National Science Foundation under grants AST-0807690, AST-1109468, AST-1004488 (Alan T. Waterman Award), and AST-1616624. This work is made possible by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This material is based on work supported by the National Aeronautics and Space Administration under grant No. 80NSSC18K0476 issued through the XRP Program. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work makes use of observations from the LCOGT network. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated by the Fundación Galileo Galilei (FGG) of the Istituto Nazionale di Astrofisica (INAF) at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain). The HARPS-N project has been funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard University Origins of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), the Italian National Astrophysical Institute (INAF), the University of St Andrews, Queens University Belfast, and the University of Edinburgh. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. Based on observations obtained at the international Gemini Observatory under the program GN-2019B-LP-101, a program of NSF's OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Some of the observations in the paper made use of the High-Resolution Imaging instrument 'Alopeke. Facilities: TESS - , MEarth-North - , TRES - , LCOGT - , Gemini/NIRI - , TNG/HARPS-N - , Keck/HIRES. - Software: AstroImageJ (Collins et al. 2017), astropy (Astropy Collaboration et al. 2013, 2018), BANZAI (McCully et al. 2018), batman (Kreidberg 2015), BGLS (Mortier et al. 2015), celerite (Foreman-Mackey et al. 2017), emcee (Foreman-Mackey et al. 2013), EvapMass (Owen & Campos Estrada 2020), EXOFAST (Eastman et al. 2013), EXOFASTv2 (Eastman et al. 2019), exoplanet (Foreman-Mackey et al. 2019), PyMC3 (Salvatier et al. 2016), scipy (Virtanen et al. 2020), SpecMatch-Emp (Yee et al. 2017), STARRY (Luger et al. 2019), Tapir (Jensen 2013), TERRA (Anglada-Escudé & Butler 2012), triceratops (Giacalone & Dressing 2020), vespa (Morton 2012).

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