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Transiting exoplanets orbiting young nearby stars are ideal laboratories for testing theories of planet formation and evolution. However, to date only a handful of stars with age, submitted to MNRAS

We report the discovery of a hot ($T_{\rm eq}$ $\approx$ 1055 K) planet in the small planet radius valley transiting the Sun-like star TOI-733, as part of the KESPRINT follow-up program of TESS planets carried out with the HARPS spectrograph. TESS photometry from sectors 9 and 36 yields an orbital period of $P_{\rm orb}$ = $4.884765 _{ - 2.4e-5 } ^ { + 1.9e-5 }$ days and a radius of $R_{\mathrm{p}}$ = $1.992 _{ - 0.090 } ^ { + 0.085 }$ $R_{\oplus}$. Multi-dimensional Gaussian process modelling of the radial velocity measurements from HARPS and activity indicators, gives a semi-amplitude of $K$ = $2.23 \pm 0.26 $ m s$^{-1}$, translating into a planet mass of $M_{\mathrm{p}}$ = $5.72 _{ - 0.68 } ^ { + 0.70 }$ $M_{\oplus}$. These parameters imply that the planet is of moderate density ($\rho_\mathrm{p}$ = $3.98 _{ - 0.66 } ^ { + 0.77 }$ g cm$^{-3}$) and place it in the transition region between rocky and volatile-rich planets with H/He-dominated envelopes on the mass-radius diagram. Combining these with stellar parameters and abundances, we calculate planet interior and atmosphere models, which in turn suggest that TOI-733 b has a volatile-enriched, most likely secondary outer envelope, and may represent a highly irradiated ocean world - one of only a few such planets around G-type stars that are well-characterised., Comment: Accepted for publication in A&A

Funding: TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1. We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data-sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82 day orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60 day orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 minutes for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet. Publisher PDF

Full list of authors: Murgas, F.; Nowak, G.; Masseron, T.; Parviainen, H.; Luque, R.; Pallé, E.; Korth, J.; Carleo, I.; Csizmadia, S.; Esparza-Borges, E.; Alqasim, A.; Cochran, W. D.; Dai, F.; Deeg, H. J.; Gandolfi, D.; Goffo, E.; Kabáth, P.; Lam, K. W. F.; Livingston, J.; Muresan, A.; Osborne, H. L. M.; Persson, C. M.; Serrano, L. M.; Smith, A. M. S.; Van Eylen, V.; Orell-Miquel, J.; Hinkel, N. R.; Galán, D.; Puig-Subirà, M.; Stangret, M.; Fukui, A.; Kagetani, T.; Narita, N.; Ciardi, D.R.; Boyle, A.W.; Ziegler, C.; Briceño, C.; Law, N.; Mann, A.W.; Jenkins, J.M.; Latham, D.W.; Quinn, S.N.; Ricker, G.; Seager, S.; Shporer, A.; Ting, E. B.; Vanderspek, R.; Winn, J. N.-- This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Context. Ultra-short-period (USP) planets are defined as planets with orbital periods shorter than one day. This type of planets is rare, highly irradiated, and interesting because their formation history is unknown. Aims. We aim to obtain precise mass and radius measurements to confirm the planetary nature of a USP candidate found by the Transiting Exoplanet Survey Satellite (TESS). These parameters can provide insights into the bulk composition of the planet candidate and help to place constraints on its formation history. Methods. We used TESS light curves and HARPS-N spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate found around the star HD 20329 (TOI-4524). We performed a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. Results. We confirm and characterize HD 20329b, a USP planet transiting a solar-type star. The host star (HD 20329, V = 8.74 mag, J = 7.5 mag) is characterized by its G5 spectral type with M∗ = 0.90 ± 0.05 M⊙, R∗ = 1.13 ± 0.02 R⊙, and Teff = 5596 ± 50 K; it is located at a distance d = 63.68 ± 0.29 pc. By jointly fitting the available TESS transit light curves and follow-up radial velocity measurements, we find an orbital period of 0.9261 ± (0.5 ×10-4) days, a planetary radius of 1.72 ± 0.07 R∗, and a mass of 7.42 ± 1.09 M∗, implying a mean density of ρp = 8.06 ± 1.53 g cm-3. HD 20329b joins the ~30 currently known USP planets with radius and Doppler mass measurements. © F. Murgas et al. 2022., T.M. acknowledges financial support from the Spanish Ministry of Science and Innovation (MICINN) through the Spanish State Research Agency, under the Severo Ochoa Program 2020-2023 (CEX2019-000920-S) as well as support from the ACIISI, Consejería de Economía, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference PROID2021010128. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26 under the EU Next Generation funds and financial support from the Spanish Ministerio de Ciencia e Innovación, through project PID2019-109522GB-C52, and the Centre of Excellence “Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). PK acknolwedges the support from grant LTT-20015. K.W.F.L. was supported by Deutsche Forschungsgemeinschaft grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. HJD acknowledges support from the Spanish Research Agency of the Ministry of Science and Innovation (AEI-MICINN) under the grant PID2019-107061GB-C66, DOI: 10.13039/501100011033. C.M.P. and J.K. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19 2020-00104). This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA’s Science Mission directorate. 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. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This publication makes use of data products from the AAVSO Photometric All Sky Survey (APASS). Funded by the Robert Martin Ayers Sciences Fund 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 made use of tpfplotter by J. Lillo-Box (publicly available in www.github.com/jlillo/tpfplotter), which also made use of the python packages astropy, lightkurve, matplotlib and numpy. This work is partly supported by JSPS KAKENHI Grant Numbers JP17H04574, JP18H05442, JST CREST Grant Number JPMJCR1761, and the Astrobiology Center of National Institutes of Natural Sciences (NINS) (Grant Number AB031010). This paper is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide.

Full list of authors: Kabath, Petr; Chaturvedi, Priyanka; MacQueen, Phillip J.; Skarka, Marek; Subjak, Jan; Esposito, Massimilliano; Cochran, William D.; Bellomo, Salvatore E.; Karjalainen, Raine; Guenther, Eike W.; Endl, Michael; Csizmadia, Szilard; Karjalainen, Marie; Hatzes, Artie; Zak, Jiri; Gandolfi, Davide; Boffin, Henri M. J.; Vines, Jose, I; Livingston, John H.; Garcia, Rafael A.; Mathur, Savita; Gonzalez-Cuesta, Lucia; Blazek, Martin; Caldwell, Douglas A.; Colon, Knicole D.; Deeg, Hans; Erikson, Anders; Van Eylen, Vincent; Fong, William; Fridlund, Malcolm; Fukui, Akihiko; Furesz, Gabor; Goeke, Robert F.; Goffo, Elisa; Howell, Steve; Jenkins, Jon M.; Klagyivik, Peter; Korth, Judith; Latham, David W.; Luque, Rafael; Moldovan, Dan; Murgas, Felipe; Narita, Norio; Orell-Miquel, Jaume; Palle, Enric; Parviainen, Hannu; Persson, Carina M.; Reed, Phillip A.; Redfield, Seth; Ricker, George R.; Seager, Sara; Serrano, Luisa Maria; Shporer, Avi; Smith, Alexis M. S.; Watanabe, Noriharu; Winn, Joshua N.; KESPRINT Team., We present the confirmation and characterization of three hot Jupiters, TOI-1181b, TOI-1516b, and TOI-2046b, discovered by the TESS space mission. The reported hot Jupiters have orbital periods between 1.4 and 2.05 d. The masses of the three planets are 1.18 ± 0.14 MJ, 3.16 ± 0.12 MJ, and 2.30 ± 0.28 MJ, for TOI-1181b, TOI-1516b, and TOI-2046b, respectively. The stellar host of TOI-1181b is a F9IV star, whereas TOI-1516b and TOI-2046b orbit F main sequence host stars. The ages of the first two systems are in the range of 2–5 Gyrs. However, TOI-2046 is among the few youngest known planetary systems hosting a hot Jupiter, with an age estimate of 100–400 Myrs. The main instruments used for the radial velocity follow-up of these three planets are located at Ondřejov, Tautenburg, and McDonald Observatory, and all three are mounted on 2–3 m aperture telescopes, demonstrating that mid-aperture telescope networks can play a substantial role in the follow-up of gas giants discovered by TESS and in the future by PLATO. © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society, This work is done under the framework of the KESPRINT collaboration (http://www.kesprint.science). KESPRINT is an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions. This work is based on data sets obtained with the Perek 2-m telescope. PK, JS, MS, RK, and MB are acknowledging the support by Inter-transfer grant no LTT-20015. MK acknowledges the support from ESA-PRODEX PEA4000127913. PK and JS acknowledge a travel budget from ERASMUS + grant 2020-1-CZ01-KA203-078200. HB’s mobility was funded under: MŠMT – CZ.02.2.69/0.0/0.0/18_053/0016972 Podpora mezinárodní spolupráce v astronomii. PC acknowledges the generous support from Deutsche Forschungsgemeinschaft (DFG) of the grant CH 2636/1-1. PR acknowledges support from National Science Foundations (NSF) grant No. 1952545. This work was generously supported by the Thüringer Ministerium für Wirtschaft, Wissenschaft und Digitale Gesellschaft. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. 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. JIV acknowledges support of CONICYT-PFCHA/Doctorado Nacional-21191829. This work is partly supported by JSPS KAKENHI Grant Number JP20K14518. JK gratefully acknowledge the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). HD acknowledges support from the Spanish Research Agency of the Ministry of Science and Innovation (AEI-MICINN) under grant PID2019-107061GB-C66, DOI: 10.13039/501100011033. RL acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, through project PID2019-109522GB-C52, and the Centre of Excellence ’Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). 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 is University of Texas Center for Planetary Systems Habitability contribution #0054. LGC acknowledges support from grant FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO) (research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610). SM acknowledges support by the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and the grant number PID2019-107187GB-I00. RAG acknowledges the support from PLATO and GOLF CNES grants. This paper includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Observations in the paper made use of the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI). NESSI was funded by the NASA Exoplanet Exploration Program and the NASA Ames Research Center. NESSI was built at the Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. The authors are honored to be permitted to conduct observations on Iolkam Du’ag (Kitt Peak), a mountain within the Tohono O’odham Nation with particular significance to the Tohono O’odham people. This work is partly supported by JSPS KAKENHI Grant Number JP17H04574 and JP18H05439, JST PRESTO Grant Number JPMJPR1775, the Astrobiology Center of National Institutes of Natural Sciences (NINS; Grant Number AB031010). This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. Observations in the paper made use of the High-Resolution Imaging instrument ‘Alopeke. ‘Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. ‘Alopeke was mounted on the Gemini North telescope of the international Gemini Observatory, a program of NSF’s NOIRLab, 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 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).

Full list of authors: Wilson, Thomas G.; Goffo, Elisa; Alibert, Yann; Gandolfi, Davide; Bonfanti, Andrea; Persson, Carina M.; Collier Cameron, Andrew; Fridlund, Malcolm; Fossati, Luca; Korth, Judith; Benz, Willy; Deline, Adrien; Florén, Hans-Gustav; Guterman, Pascal; Adibekyan, Vardan; Hooton, Matthew J.; Hoyer, Sergio; Leleu, Adrien; Mustill, Alexander James; Salmon, Sébastien; Sousa, Sérgio G.; Suarez, Olga; Abe, Lyu; Agabi, Abdelkrim; Alonso, Roi; Anglada, Guillem; Asquier, Joel; Bárczy, Tamas; Barrado Navascues, David; Barros, Susana C. C.; Baumjohann, Wolfgang; Beck, Mathias; Beck, Thomas; Billot, Nicolas; Bonfils, Xavier; Brandeker, Alexis; Broeg, Christopher; Bryant, Edward M.; Burleigh, Matthew R.; Buttu, Marco; Cabrera, Juan; Charnoz, Sébastien; Ciardi, David R.; Cloutier, Ryan; Cochran, William D.; Collins, Karen A.; Colón, Knicole D.; Crouzet, Nicolas; Csizmadia, Szilard; Davies, Melvyn B.; Deleuil, Magali; Delrez, Laetitia; Demangeon, Olivier; Demory, Brice-Olivier; Dragomir, Diana; Dransfield, Georgina; Ehrenreich, David; Erikson, Anders; Fortier, Andrea; Gan, Tianjun; Gill, Samuel; Gillon, Michaël; Gnilka, Crystal L.; Grieves, Nolan; Grziwa, Sascha; Güdel, Manuel; Guillot, Tristan; Haldemann, Jonas; Heng, Kevin; Horne, Keith; Howell, Steve B.; Isaak, Kate G.; Jenkins, Jon M.; Jensen, Eric L. N.; Kiss, Laszlo; Lacedelli, Gaia; Lam, Kristine; Laskar, Jacques; Latham, David W.; Lecavelier des Etangs, Alain; Lendl, Monika; Lester, Kathryn V.; Levine, Alan M.; Livingston, John; Lovis, Christophe; Luque, Rafael; Magrin, Demetrio; Marie-Sainte, Wenceslas; Maxted, Pierre F. L.; Mayo, Andrew W.; McLean, Brian; Mecina, Marko; Mékarnia, Djamel; Nascimbeni, Valerio; Nielsen, Louise D.; Olofsson, Göran; Osborn, Hugh P.; Osborne, Hannah L. M.; Ottensamer, Roland; Pagano, Isabella; Pallé, Enric; Peter, Gisbert; Piotto, Giampaolo; Pollacco, Don; Queloz, Didier; Ragazzoni, Roberto; Rando, Nicola; Rauer, Heike; Redfield, Seth; Ribas, Ignasi; Ricker, George R.; Rieder, Martin; Santos, Nuno C.; Scandariato, Gaetano; Schmider, François-Xavier; Schwarz, Richard P.; Scott, Nicholas J.; Seager, Sara; Ségransan, Damien; Serrano, Luisa Maria; Simon, Attila E.; Smith, Alexis M. S.; Steller, Manfred; Stockdale, Chris; Szabó, Gyula; Thomas, Nicolas; Ting, Eric B.; Triaud, Amaury H. M. J.; Udry, Stéphane; Van Eylen, Vincent; Van Grootel, Valérie; Vanderspek, Roland K.; Viotto, Valentina; Walton, Nicholas; Winn, Joshua N., We report the discovery and characterization of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in the Transiting Exoplanet Survey Satellite (TESS) photometry. To characterize the system, we performed and retrieved the CHaracterising ExOPlanets Satellite (CHEOPS), TESS, and ground-based photometry, the High Accuracy Radial velocity Planet Searcher (HARPS) high-resolution spectroscopy, and Gemini speckle imaging. We characterize the host star and determine Teff,⋆=4734±67K⁠, R⋆=0.726±0.007R⊙⁠, and M⋆=0.748±0.032M⊙⁠. We present a novel detrending method based on point spread function shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of Pb = 6.44387 ± 0.00003 d, a radius of Rb = 2.59 ± 0.04 R⊕, and a mass of Mb=13.5+1.7−1.8 M⊕, whilst TOI-1064 c has an orbital period of Pc=12.22657+0.00005−0.00004 d, a radius of Rc = 2.65 ± 0.04 R⊕, and a 3σ upper mass limit of 8.5 M⊕. From the high-precision photometry we obtain radius uncertainties of ∼1.6 per cent, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterized sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further radial velocities are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of mass–radius space, and it allow us to identify a trend in bulk density–stellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets. © The Author(s) 2022., This study is based on observations made with ESO Telescopes at the La Silla Observatory under program ID 1102.C-0923. CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the UK. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. Funding for the TESS mission is provided by NASA Science Mission Directorate. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. 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. Part of this work was done using data taken by KESPRINT, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions (http://www.kesprint.science/). This work makes use of observations from the LCOGT network. Part of the LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This study is based on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is operated by the consortium institutes with support from the UK Science and Technology Facilities Council (STFC) projects ST/M001962/1 and ST/S002642/1. 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 ASTEP telescope. ASTEP benefited from the support of the French and Italian polar agencies IPEV and PNRA in the framework of the Concordia station program and from Idex UCAJEDI (ANR-15-IDEX-01). Some of the observations in the paper made use of the High-Resolution Imaging instrument Zorro. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Zorro was mounted on the Gemini-South telescope of the international Gemini Observatory, 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 partnership: the National Science Foundation (USA), National Research Council Canada (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). TGW, ACC, and KH acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant ST/R003203/1. YA and MJH acknowledge the support of the Swiss National Fund under grant 200020_172746. DG and LMS gratefully acknowledge financial support from the CRT Foundation under grant no. 2018.2323 ‘Gaseous or rocky? Unveiling the nature of small worlds’. DG, MF, XB, SC, and JL acknowledge their roles as ESA-appointed CHEOPS science team members. CMP, MF, JK, and AJM gratefully acknowledge the support of the Swedish National Space Agency (SNSA; DNR 65/19, 174/18, 2020-00104, and Career grant 120/19C). ADe and DE acknowledge support from the European Research Council (ERC) under the European Union’s Horizon 2020 Framework Programme (project fOURaCES; grant agreement no. 724427). ADe, ALe, and HO acknowledge support from the Swiss National Centre for Competence in Research ‘PlanetS’ and the Swiss National Science Foundation (SNSF). SH gratefully acknowledges CNES funding through the grant 837319. SES have received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Framework Programme (grant agreement no. 833925, project STAREX). SGS acknowledges support from FCT through FCT contract no. CEECIND/00826/2018 and POPH/FSE (EC). We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153-B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiología (INTA-CSIC), and the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract no. 4000124370. SCCB and VA acknowledge support from FCT through FCT contracts no. IF/01312/2014/CP1215/CT0004 and IF/00650/2015/CP1273/CT0001, respectively. ABr was supported by the SNSA. This project was supported by the CNES. LD is an F.R.S.-FNRS Postdoctoral Researcher. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Liège through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. This work was supported by FCT – Fundação para a Ciência e a Tecnologia – through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalizacão by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017, and POCI-01-0145-FEDER-028987, ODSD is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B-OD acknowledges support from the Swiss National Science Foundation (PP00P2-190080). DD acknowledges support from the TESS Guest Investigator Program grant 80NSSC19K1727 and NASA Exoplanet Research Program grant 18-2XRP18_2-0136. MG is an F.R.S.-FNRS Senior Research Associate. KGI is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. GL acknowledges support by CARIPARO Foundation, according to the agreement CARIPARO-Universitá degli Studi di Padova (Pratica no. 2018/0098). This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by the Agence Nationale pour la Recherche. ML acknowledges support from the Swiss National Science Foundation under grant no. PCEFP2_194576. PFLM acknowledges support from STFC research grant number ST/M001040/1. LDN thanks the Swiss National Science Foundation for support under Early Postdoc. Mobility grant P2GEP2_200044. This work was also partially supported by a grant from the Simons Foundation (PI: Queloz, grant number 327127). IR acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. This project has been supported by the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, the MTA-ELTE Lendület Milky Way Research Group, and the City of Szombathely under agreement no. 67.177-21/2016. This research received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Framework Programme (grant agreement no. 803193/BEBOP), and from the Science and Technology Facilities Council (STFC; grant no. ST/S00193X/1). VVG is an F.R.S-FNRS Research Associate., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

LHS 1140 is a nearby mid-M dwarf known to host a temperate rocky super-Earth (LHS 1140 b) on a 24.737-day orbit. Based on photometric observations by MEarth and Spitzer as well as Doppler spectroscopy from HARPS, we report the discovery of an additional transiting rocky companion (LHS 1140 c) with a mass of $1.81\pm0.39~{\rm M_{Earth}}$ and a radius of $1.282\pm0.024~{\rm R_{Earth}}$ on a tighter, 3.77795-day orbit. We also obtain more precise estimates of the mass and radius of LHS 1140 b to be $6.98\pm0.89~{\rm M_{Earth}}$ and $1.727\pm0.032~{\rm R_{Earth}}$. The mean densities of planets b and c are $7.5\pm1.0~\rm{g/cm^3}$ and $4.7\pm1.1~\rm{g/cm^3}$, respectively, both consistent with the Earth's ratio of iron to magnesium silicate. The orbital eccentricities of LHS 1140 b and c are consistent with circular orbits and constrained to be below 0.06 and 0.31, respectively, with 90% confidence. Because the orbits of the two planets are co-planar and because we know from previous analyses of Kepler data that compact systems of small planets orbiting M dwarfs are commonplace, a search for more transiting planets in the LHS 1140 system could be fruitful. LHS 1140 c is one of the few known nearby terrestrial planets whose atmosphere could be studied with the upcoming James Webb Space Telescope., Comment: 22 pages, 8 figures, accepted by AJ

We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the Minerva-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 M J (43.9 ± 7.3, M⊕), a radius of RP = 0.639 ± 0.013 R J (7.16 ± 0.15, R ⊕), bulk density of 0.65+0.12-0.11 (cgs), and period 18.38818 +0.00085 -0.00084 days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M∗ = 1.390 ± 0.046 rm M sun, R∗ = 1.888 ± 0.033 Rsun, Teff = 6075 ± 90 rm K, and vsin i = 11.3 ± 0.5 km s-1. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems., Daniel Huber acknowledges support by the National Aeronautics and Space Administration through the TESS Guest Investigator Program (80NSSC18K1585) and by the National Science Foundation (AST-1717000). Ashley Chontos acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1842402). William J. Chaplin, Warrick H. Ball, Martin B. Nielsen, and Andrea Miglio. acknowledge support from the Science and Technology Facilities Council and UK Space Agency. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). Rafael Brahm acknowledges support from National Fund for Scientific and Technological Development Post-doctoral Fellowship Project 3180246, and from the Millennium Institute of Astrophysics (MAS). H.Z. Hui Zhang is supported by the Natural Science Foundation of China (NSFC grants 11673011, 11933001). Andres Jordan acknowledges support from FONDECYT project 1171208 and by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS). Aldo M. Serenelli is partially supported by grants ESP2017-82674-R (Spanish Government) and 2017-SGR-1131 (Generalitat de Catalunya). Andrea Miglio acknowledges support from the European Research Council Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, G.A. number 772293). Rafael A. Garcia acknowledges the support of the PLAnetary Transits and Oscillations of stars grant from the Centre National d'Études Spatiales. Savita Mathur acknowledges support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. Tiago L. Campante acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 792848 (PULSATION). This work was supported by Foundation of Science and Technology/Ministry of Science, Technology and Higher Education through national funds (UID/FIS/04434/2019). Enrico Corsaro is funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 664931. L. González-Cuesta thanks the support from grant FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO) (research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610). Sarbani Basu acknowledges NASA grant NNX16AI09G and NSF grant AST-1514676. Ian J. M. Crossfield acknowledges support from the NSF through grant AST-1824644, and from NASA through Caltech/JPL grant RSA-1610091. Tansu Daylan acknowledges support from MIT’s Kavli Institute as a Kavli postdoctoral fellow. Derek L. Buzasi acknowledges support from NASA through the TESS Guest Investigator program (80NSSC19K0385). Cenk Kayhan acknowledges support by Erciyes University Scientific Research Projects Coordination Unit under grant number MAP-2020-9749. Emilie Laychock and Michaela Collins acknowledge support by the National Science Foundation under grant 1559487. Victor Silva Aguirre acknowledges support from the Independent Research Fund Denmark (Research grant 7027-00096B) and the Carlsberg Foundation (grant agreement CF19-0649).