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Highly irradiated planets in the hot Neptune desert are usually either small (R < 2 Rearth) and rocky or they are gas giants with radii of >1 Rjup. Here, we report on the intermediate-sized planet TOI-2196 on a 1.2 day orbit around a G-type star discovered by TESS in sector 27. We collected 42 radial velocity measurements with the HARPS spectrograph to determine the mass. The radius of TOI-2196 b is 3.51 +/- 0.15 Rearth, which, combined with the mass of 26.0 +/- 1.3 Mearth, results in a bulk density of 3.31+0.51-0.43 g/cm3. Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocities points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 Mjup, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 +/- 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of > 1800 K: a hot sub-Neptune desert devoid of planets with radii of 1.8-3 Rearth and a sub-Jovian desert for radii of 5-12 Rearth. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4 % and 3 %, with a mean value of 0.7 % on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age, and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet, and it remains one at present., 17 pages, 15 figures, 7 tables, accepted 11 July 2022 for publication in Astronomy & Astrophysics

After the detection of numerous planetary systems outside of our own Solar System which tend to be extremely diverse and which show a wide range of evolutionary states, the focus is now shifting to a characterization of their formation and evolution, as well as to the architecture of planetary systems and planet habitability. One of the astonishing discoveries in exoplanet research has been the detection of Jupiter-like planets (in size and mass) that orbit their host star within 10 days. These so-called hot Jupiters are rarely accompanied by smaller close-in companions. TOI-1130 is one of very these rare systems. It hosts two transiting planets: a hot Jupiter and an inner low-mass planet that are near to the 2:1 period commensurability. Planetary systems with transiting planets are markedly well-suited for a detailed characterization, since they allow the measurement of the planetary radius, which is essential to constrain the planet’s evolution and migration history, as well as to characterize the internal structure of the planet. The second fundamental parameter for the characterization is the planetary mass, that together with the radius allows the bulk density of a planet to be estimated, thereby constraining its composition. In order to find out the history and future evolution of exoplanet systems, a complete knowledge of all orbital and planetary parameters with a high accuracy is crucial. However, precise measurements of the planetary mass are difficult to obtain, in particular for small planets. If there are multiple planets in a system close to a period commensurability, as is the case for TOI-1130, the planetary masses can be determined using the gravitational interactions leading to measurable transit timing variations. TOI-1130 is a known planetary system consisting of a hot Jupiter, TOI-1130 c, on an 8.4-day orbit accompanied by an inner Neptune-sized planet, TOI-1130 b, with an orbital period of 4.1 days around a K-dwarf. As part of the ongoing radial velocity (RV) follow-up program carried out by our team with the HARPS spectrograph, we collected precise radial velocity measurements of TOI-1130. We perform a photodynamical modeling of the RVs, and the transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program. We find that the two planets orbit with small eccentricities in a 2:1 resonant configuration. This is the first system where a hot Jupiter accompanied by an inner lower mass planet is locked in a mean-motion-resonance. We discuss possible formation scenarios.

Full list of authors: Turtelboom, Emma V.; Weiss, Lauren M.; Dressing, Courtney D.; Nowak, Grzegorz; Pallé, Enric; Beard, Corey; Blunt, Sarah; Brinkman, Casey; Chontos, Ashley; Claytor, Zachary R.; Dai, Fei; Dalba, Paul A.; Giacalone, Steven; Gonzales, Erica; Harada, Caleb K.; Hill, Michelle L.; Holcomb, Rae; Korth, Judith; Lubin, Jack; Masseron, Thomas; MacDougall, Mason; Mayo, Andrew W.; Močnik, Teo; Akana Murphy, Joseph M.; Polanski, Alex S.; Rice, Malena; Rubenzahl, Ryan A.; Scarsdale, Nicholas; Stassun, Keivan G.; Tyler, Dakotah B.; Zandt, Judah Van; Crossfield, Ian J. M.; Deeg, Hans J.; Fulton, Benjamin; Gandolfi, Davide; Howard, Andrew W.; Huber, Dan; Isaacson, Howard; Kane, Stephen R.; Lam, Kristine W. F.; Luque, Rafael; Martín, Eduardo L.; Morello, Giuseppe; Orell-Miquel, Jaume; Petigura, Erik A.; Robertson, Paul; Roy, Arpita; Van Eylen, Vincent; Baker, David; Belinski, Alexander A.; Bieryla, Allyson; Ciardi, David R.; Collins, Karen A.; Cutting, Neil; Della-Rose, Devin J.; Ellingsen, Taylor B.; Furlan, E.; Gan, Tianjun; Gnilka, Crystal L.; Guerra, Pere; Howell, Steve B.; Jimenez, Mary; Latham, David W.; Larivière, Maude; Lester, Kathryn V.; Lillo-Box, Jorge; Luker, Lindy; Mann, Christopher R.; Plavchan, Peter P.; Safonov, Boris; Skinner, Brett; Strakhov, Ivan A.; Wittrock, Justin M.; Caldwell, Douglas A.; Essack, Zahra; Jenkins, Jon M.; Quintana, Elisa V.; Ricker, George R.; Vanderspek, Roland; Seager, S.; Winn, Joshua N.-- This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., Multiplanet systems are valuable arenas for investigating exoplanet architectures and comparing planetary siblings. TOI-1246 is one such system, with a moderately bright K dwarf (V = 11.6, K = 9.9) and four transiting sub-Neptunes identified by TESS with orbital periods of 4.31, 5.90, 18.66, and 37.92 days. We collected 130 radial velocity observations with Keck/HIRES and TNG/HARPS-N to measure planet masses. We refit the 14 sectors of TESS photometry to refine planet radii (2.97 ± 0.06 R⊕, 2.47 ± 0.08 R⊕, 3.46 ± 0.09 R⊕, and 3.72 ± 0.16 R⊕) and confirm the four planets. We find that TOI-1246 e is substantially more massive than the three inner planets (8.1 ± 1.1 M⊕, 8.8 ± 1.2 M⊕, 5.3 ± 1.7 M⊕, and 14.8 ± 2.3 M⊕). The two outer planets, TOI-1246 d and TOI-1246 e, lie near to the 2:1 resonance (Pe/Pd = 2.03) and exhibit transit-timing variations. TOI-1246 is one of the brightest four-planet systems, making it amenable for continued observations. It is one of only five systems with measured masses and radii for all four transiting planets. The planet densities range from 0.70 ± 0.24 to 3.21 ± 0.44 g cm−3, implying a range of bulk and atmospheric compositions. We also report a fifth planet candidate found in the RV data with a minimum mass of 25.6 ± 3.6 M⊕. This planet candidate is exterior to TOI-1246 e, with a candidate period of 93.8 days, and we discuss the implications if it is confirmed to be planetary in nature. © 2022. The Author(s). Published by the American Astronomical Society., We thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawaii for supporting the TESS-Keck Survey with observing time at Keck Observatory. We thank NASA for funding associated with our Key Strategic Mission Support project. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. We thank Ken and Gloria Levy, who supported the construction of the Levy Spectrometer on the Automated Planet Finder. We thank the University of California and Google for supporting Lick Observatory, and the UCO staff for their dedicated work scheduling and operating the telescopes of Lick Observatory. This paper is based on data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. C.D. gratefully acknowledges support from the David & Lucile Packard Foundation and the Alfred P. Sloan Foundation. A.A.B., B.S.S., and I.A.S. acknowledge the support of the Ministry of Science and Higher Education of the Russian Federation under the grant 075-15-2020-780(N13.1902.21.0039). J.K. gratefully acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). A.W.M. is supported by the NSF Graduate Research Fellowship grant No. DGE 1752814. J.M.A.M. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1842400. J.M.A.M. acknowledges 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. C.K.H. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant No. DGE 2146752. M.R. is supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1752134. R.A.R. is supported by an NSF Graduate Research Fellowship, grant No. DGE 1745301. P.D. is supported by a National Science Foundation (NSF) Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. R.L. acknowledges financial support from the Centre of Excellence "Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). D.H. acknowledges support from the Alfred P. Sloan Foundation and the National Aeronautics and Space Administration (80NSSC20K0593, 80NSSC21K0652). 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). K.W.F.L. acknowledges support by DFG grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, "Exploring the Diversity of Extrasolar Planets."

It is commonly accepted that exoplanets with orbital periods shorter than 1 day, also known as ultra-short period (USP) planets, formed further out within their natal protoplanetary disk, before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here, we present the discovery of a four planet system orbiting the bright (V=10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of $\sim$ 13 hours, a mass of 1.42 $\pm$ 0.18 M$_{\oplus}$, a radius of $1.166^{0.061}_{-0.058}$ R$_{\oplus}$, and a mean density of 4.89$^{+1.03}_{-0.88}$ gcm$^{-3}$. Via Doppler spectroscopy, we discovered that the system hosts three outer planets on nearly circular orbits with periods of 6.6, 26.2, and 61.3d and minimum masses of 5.03 $\pm$ 0.41 M$_{\oplus}$, 33.12 $\pm$ 0.88 M$_{\oplus}$ and 15.05$^{+1.12}_{-1.11}$ M$_{\oplus}$, respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits, then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyrs, starting from an initial orbit of 0.02au. TOI-500 is the first four planet system known to host a USP Earth analog whose current architecture can be explained via a non-violent migration scenario., Published on Nature Astronomy (April 28th, 2022)

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.--Full lis of authors: Fukui, Akihiko; Kimura, Tadahiro; Hirano, Teruyuki; Narita, Norio; Kodama, Takanori; Hori, Yasunori; Ikoma, Masahiro; Palle, Enric; Murgas, Felipe; Parviainen, Hannu; Kawauchi, Kiyoe; Mori, Mayuko; Esparza-Borges, Emma; Bieryla, Allyson; Irwin, Jonathan; Safonov, Boris S.; Stassun, Keivan G.; Alvarez-Hernandez, Leticia; Bejar, Victor J. S.; Casasayas-Barris, Nuria; Chen, Guo; Crouzet, Nicolas; de Leon, Jerome P.; Isogai, Keisuke; Kagetani, Taiki; Klagyivik, Peter; Korth, Judith; Kurita, Seiya; Kusakabe, Nobuhiko; Livingston, John; Luque, Rafael; Madrigal-Aguado, Alberto; Morello, Giuseppe; Nishiumi, Taku; Orell-Miquel, Jaume; Oshagh, Mahmoudreza; Sanchez-Benavente, Manuel; Stangret, Monika; Terada, Yuka; Watanabe, Noriharu; Zou, Yujie; Tamura, Motohide; Kurokawa, Takashi; Kuzuhara, Masayuki; Nishikawa, Jun; Omiya, Masashi; Vievard, Sebastien; Ueda, Akitoshi; Latham, David W.; Quinn, Samuel N.; Strakhov, Ivan S.; Belinski, Alexandr A.; Jenkins, Jon M.; Ricker, George R.; Seager, Sara; Vanderspek, Roland; Winn, Joshua N.; Charbonneau, David; Ciardi, David R.; Collins, Karen A.; Doty, John P.; Bachelet, Etienne; Harbeck, Daniel., We report the discovery of TOI-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 d. We identified the transit signal from the Transiting Exoplanet Survey Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high-resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high-resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of 1.74±0.08R⊕⁠, a mass of, Funding for the TESS mission is provided by NASA’s Science Mission Directorate. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS SPOC. 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. This paper includes data that are publicly available from the MAST. 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 NASA under the Exoplanet Exploration Program. This work makes use of observations from the LCO global telescope network. This paper is based on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center (ABC) and under financial supports by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at FTN on Maui, HI, operated by the LCO, and observations made with the MuSCAT2 instrument, developed by ABC, at TCS operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This paper is partially based on observations made at the CMO SAI MSU with the support by M.V. Lomonosov Moscow State University Program of Development. This work is partly supported by JSPS KAKENHI Grant Numbers 22000005, JP15H02063, JP17H04574, JP18H05439, JP18H05442, JP20K14518, Grant-in-Aid for JSPS Fellows Grant Number JP20J21872, JST PRESTO Grant Number JPMJPR1775, and the ABC of National Institutes of Natural Sciences (Grant Number AB031010). This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grants PGC2018-098153-B-C31 and PID2019-109522GB-C53. A.A.B., B.S.S., and I.A.S. acknowledge the support of Ministry of Science and Higher Education of the Russian Federation under the grant 075-15-2020-780 (N13.1902.21.0039). N.C.B. and G.M. acknowledge the funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program under grant agreement No. 694513 and under the Marie Skłodowska-Curie grant agreement No. 895525, respectively. J.K. acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). R.L. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, through project PID2019-109522GB-C52/AEI/10.13039/501100011033, and the Centre of Excellence “Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).

Full list of authors: Tran, Quang H.; Bowler, Brendan P.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Gandolfi, Davide; Persson, Carina M.; Fridlund, Malcolm; Palle, Enric; Nowak, Grzegorz; Deeg, Hans J.; Luque, Rafael; Livingston, John H.; Kabáth, Petr; Skarka, Marek; Šubjak, Ján; Howell, Steve B.; Albrecht, Simon H.; Collins, Karen A.; Esposito, Massimiliano; Van Eylen, Vincent; Grziwa, Sascha; Goffo, Elisa; Huang, Chelsea X.; Jenkins, Jon M.; Karjalainen, Marie; Karjalainen, Raine; Knudstrup, Emil; Korth, Judith; Lam, Kristine W. F.; Latham, David W.; Levine, Alan M.; Osborne, H. L. M.; Quinn, Samuel N.; Redfield, Seth; Ricker, George R.; Seager, S.; Serrano, Luisa Maria; Smith, Alexis M. S.; Twicken, Joseph D.; Winn, Joshua N.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We report the discovery of two transiting planets around the bright (V = 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune (${R}_{{\rm{b}}}={2.06}_{-0.15}^{+0.19}$ R⊕) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter (${R}_{{\rm{c}}}={0.987}_{-0.025}^{+0.025}$ RJup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coudé Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of ${M}_{{\rm{c}}}={0.63}_{-0.08}^{+0.09}$ MJup for the outer warm Jupiter, implying a mean density of ${\rho }_{c}={0.81}_{-0.11}^{+0.13}$ g cm−3. The inner sub-Neptune is undetected in our radial velocity data (Mb < 0.13 MJup at the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit (${e}_{{\rm{c}}}={0.09}_{-0.04}^{+0.05}$) and one or more inner coplanar planets are more consistent with "gentle" formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters. © 2022. The Author(s). Published by the American Astronomical Society., Q.H.T. and B.P.B. acknowledge support from a NASA FINESST grant (80NSSC20K1554). This work benefited from involvement in ExoExplorers, which is sponsored by the Exoplanets Program Analysis Group (ExoPAG) and NASA's Exoplanet Exploration Program Office (ExEP). B.P.B. acknowledges support from National Science Foundation grant AST-1909209 and NASA Exoplanet Research Program grant 20-XRP20_2-0119. C.M.P. and M.F. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19 and 177/19). J.K. gratefully acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). P.K., M.S., J.S., and R.K. acknowledge the financial support of Inter-transfer grant No. LTT-20015. M.K. acknowledges support from ESAs PEA4000127913. M.E. acknowledges the support of the DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (HA 3279/12-1). Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation (grant agreement No. DNRF106). D.G. and L.M.S. gratefully acknowledge financial support from the Cassa di Risparmio di Torino (CRT) foundation under grant No. 2018.2323 "Gaseous or rocky? Unveiling the nature of small worlds." This work is partly supported by JSPS KAKENHI grant No. JP20K14518 and SATELLITE Research from Astrobiology Center (AB022006). Funding for the TESS mission is provided by NASA's Science Mission Directorate. 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. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and 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. This paper includes data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Full list of authors: Hatzes, Artie P.; Gandolfi, Davide; Korth, Judith; Rodler, Florian; Sabotta, Silvia; Esposito, Massimiliano; Barragán, Oscar; Van Eylen, Vincent; Livingston, John H.; Serrano, Luisa Maria; Luque, Rafael; Smith, Alexis M. S.; Redfield, Seth; Persson, Carina M.; Pätzold, Martin; Palle, Enric; Nowak, Grzegorz; Osborne, Hannah L. M.; Narita, Norio; Mathur, Savita; Lam, Kristine W. F.; Kabáth, Petr; Johnson, Marshall C.; Guenther, Eike W.; Grziwa, Sascha; Goffo, Elisa; Fridlund, Malcolm; Endl, Michael; Deeg, Hans J.; Csizmadia, Szilard; Cochran, William D.; Cuesta, Lucía González; Chaturvedi, Priyanka; Carleo, Ilaria; Cabrera, Juan; Beck, Paul G.; Albrecht, Simon.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., π Men hosts a transiting planet detected by the Transiting Exoplanet Survey Satellite space mission and an outer planet in a 5.7 yr orbit discovered by radial velocity (RV) surveys. We studied this system using new RV measurements taken with the HARPS spectrograph on ESO's 3.6 m telescope, as well as archival data. We constrain the stellar RV semiamplitude due to the transiting planet, π Men c, as Kc = 1.21 ± 0.12 m s−1, resulting in a planet mass of Mc = 3.63 ± 0.38 M⊕. A planet radius of Rc = 2.145 ± 0.015 R⊕ yields a bulk density of ρc = 2.03 ± 0.22 g cm−3. The precisely determined density of this planet and the brightness of the host star make π Men c an excellent laboratory for internal structure and atmospheric characterization studies. Our HARPS RV measurements also reveal compelling evidence for a third body, π Men d, with a minimum mass Md sin id = 13.38 ± 1.35 M⊕ orbiting with a period of Porb,d = 125 days on an eccentric orbit (ed = 0.22). A simple dynamical analysis indicates that the orbit of π Men d is stable on timescales of at least 20 Myr. Given the mutual inclination between the outer gaseous giant and the inner rocky planet and the presence of a third body at 125 days, π Men is an important planetary system for dynamical and formation studies. © 2022. The Author(s). Published by the American Astronomical Society., This work was supported by the KESPRINT collaboration, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions (www.kesprint.science). S.G., M.P., S.C., A.P.H., K.W.F.L., M.E., and H.R. acknowledge support by DFG grants PA525/18-1, PA525/19-1, PA525/20-1, HA 3279/12-1, and RA 714/14-1 within the DFG Schwerpunkt SPP 1992, "Exploring the Diversity of Extrasolar Planets." L.M.S. and D.G. gratefully acknowledge financial support from the CRT foundation under grant No. 2018.2323 "Gaseous or rocky? Unveiling the nature of small worlds." J.K. gratefully acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). P.G.B. acknowledges the financial support by NAWI Graz. We thank Matthias Hoeft and Alexander Drabent for use of the computer of the Tautenburg radio group for our dynamical study., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Ultra-short-period (USP) exoplanets have orbital periods shorter than one day. Precise masses and radii of USPs could provide constraints on their unknown formation and evolution processes. We report the detection and characterization of the USP planet GJ 367b using high precision photometry and radial velocity observations. GJ 367b orbits a bright (V-band magnitude = 10.2), nearby, red (M-type) dwarf star every 7.7 hours. GJ 367b has a radius of $0.718 \pm 0.054$ Earth-radii, a mass of $0.546 \pm 0.078$ Earth-masses, making it a sub-Earth. The corresponding bulk density is $8.106 \pm 2.165$ g cm$^-3$, close to that of iron. An interior structure model predicts the planet has an iron core radius fraction of $86 \pm 5\%$, similar to Mercury's interior., Comment: Note: "This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science , (2021-12-03), doi: 10.1126/science.aay3253"

We report on precise Doppler measurements of L231-32 (TOI-270), a nearby M dwarf ($d=22$ pc, $M_\star = 0.39$ M$_\odot$, $R_\star = 0.38$ R$_\odot$), which hosts three transiting planets that were recently discovered using data from the Transiting Exoplanet Survey Satellite (TESS). The three planets are 1.2, 2.4, and 2.1 times the size of Earth and have orbital periods of 3.4, 5.7, and 11.4 days. We obtained 29 high-resolution optical spectra with the newly commissioned Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) and 58 spectra using the High Accuracy Radial velocity Planet Searcher (HARPS). From these observations, we find the masses of the planets to be $1.58 \pm 0.26$, $6.15 \pm 0.37$, and $4.78 \pm 0.43$ M$_\oplus$, respectively. The combination of radius and mass measurements suggests that the innermost planet has a rocky composition similar to that of Earth, while the outer two planets have lower densities. Thus, the inner planet and the outer planets are on opposite sides of the `radius valley' -- a region in the radius-period diagram with relatively few members, which has been interpreted as a consequence of atmospheric photo-evaporation. We place these findings into the context of other small close-in planets orbiting M dwarf stars, and use support vector machines to determine the location and slope of the M dwarf ($T_\mathrm{eff} < 4000$ K) radius valley as a function of orbital period. We compare the location of the M dwarf radius valley to the radius valley observed for FGK stars, and find that its location is a good match to photo-evaporation and core-powered mass loss models. Finally, we show that planets below the M dwarf radius valley have compositions consistent with stripped rocky cores, whereas most planets above have a lower density consistent with the presence of a H-He atmosphere., Accepted for publication in MNRAS

We use TESS, Spitzer, ground-based light curves and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b. We perform a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. We confirm and characterize TOI-674b, a low-density super-Neptune transiting a nearby M dwarf. The host star (TIC 158588995, $V = 14.2$ mag, $J = 10.3$ mag) is characterized by its M2V spectral type with $\mathrm{M}_\star=0.420\pm 0.010$ M$_\odot$, $\mathrm{R}_\star = 0.420\pm 0.013$ R$_\odot$, and $\mathrm{T}_{\mathrm{eff}} = 3514\pm 57$ K, and is located at a distance $d=46.16 \pm 0.03$ pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of $1.977143 \pm 3\times 10^{-6}$ days, a planetary radius of $5.25 \pm 0.17$ $\mathrm{R}_\oplus$, and a mass of $23.6 \pm 3.3$ $\mathrm{M}_\oplus$ implying a mean density of $\rho_\mathrm{p} = 0.91 \pm 0.15$ [g cm$^{-3}$]. A non-circular orbit model fit delivers similar planetary mass and radius values within the uncertainties. Given the measured planetary radius and mass, TOI-674b is one of the largest and most massive super-Neptune class planets discovered around an M type star to date. It is also a resident of the so-called Neptunian desert and a promising candidate for atmospheric characterisation using the James Webb Space Telescope., Comment: 22 pages, 16 figures. Accepted for publication in A&A

In this paper we report the discovery of TOI-220 $b$, a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements we estimate a planetary mass of 13.8 $\pm$ 1.0 M$_{Earth}$ and radius of 3.03 $\pm$ 0.15 R$_{Earth}$, implying a bulk density of 2.73 $\pm$ 0.47 $\textrm{g cm}^{-3}$. TOI-220 $b$ orbits a relative bright (V=10.4) and old (10.1$\pm$1.4 Gyr) K dwarf star with a period of $\sim$10.69 d. Thus, TOI-220 $b$ is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220 $b$ internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative-convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core., Comment: Accepted for publication in MNRAS

Some theories of planet formation and evolution predict that intermediate-mass stars host more hot Jupiters than Sun-like stars, others reach the conclusion that such objects are very rare. By determining the frequencies of those planets we can test those theories. Based on the analysis of Kepler light curves it has been suggested that about 8 per cent of the intermediate-mass stars could have a close-in substellar companion. This would indicate a very high frequency of such objects. Up to now, there was no satisfactory proof or test of this hypothesis. We studied a previously reported sample of 166 planet candidates around main-sequence A-type stars in the Kepler field. We selected six of them for which we obtained extensive long-term radial velocity measurements with the Alfred Jensch 2-m telescope in Tautenburg and the Perek 2-m telescope in Ondřejov. We derive upper limits of the masses of the planet candidates. We show that we are able to detect this kind of planet with our telescopes and their instrumentation using the example of MASCARA-1 b. With the transit finding pipeline Extrans we confirm that there is no single transit event from a Jupiter-like planet in the light curves of those 166 stars. We furthermore determine that the upper limit for the occurrence rate of close-in, massive planets for A-type stars in the Kepler sample is around 0.75 per cent. We argue that there is currently little evidence for a very high frequency of close-in, massive planets of intermediate-mass stars.

TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS Mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). Precise characterization of the planets' masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial velocity measurements using HARPS, FEROS, and PFS break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in the 2:1 resonance with a moderate libration amplitude of 60 +/- 2 degrees; small but significant free eccentricity of 0.0222 +0.0005/-0.0003 for TOI-216b; and small but significant mutual inclination of 1.2-3.9 degrees (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet., Comment: AJ accepted

Context: We report the discovery of TOI-519 b (TIC 218795833), a transiting substellar object (R = 1.07 RJup) orbiting a faint M dwarf (V = 17.35) on a 1.26 d orbit. Brown dwarfs and massive planets orbiting M dwarfs on short-period orbits are rare, but more have already been discovered than expected from planet formation models. TOI-519 is a valuable addition into this group of unlikely systems, and adds towards our understanding of the boundaries of planet formation. Aims: We set out to determine the nature of the Transiting Exoplanet Survey Satellite (TESS ) object of interest TOI-519 b. Methods: Our analysis uses a SPOC-pipeline TESS light curve from Sector 7, multicolour transit photometry observed with MuSCAT2 and MuSCAT, and transit photometry observed with the LCOGT telescopes. We estimate the radius of the transiting object using multicolour transit modelling, and set upper limits for its mass, effective temperature, and Bond albedo using a phase curve model that includes Doppler boosting, ellipsoidal variations, thermal emission, and reflected light components. Results: TOI-519 b is a substellar object with a radius posterior median of 1.07 RJup and 5th and 95th percentiles of 0.66 and 1.20 RJup, respectively, where most of the uncertainty comes from the uncertainty in the stellar radius. The phase curve analysis sets an upper effective temperature limit of 1800 K, an upper Bond albedo limit of 0.49, and a companion mass upper limit of 14 MJup. The companion radius estimate combined with the Teff and mass limits suggests that the companion is more likely a planet than a brown dwarf, but a brown-dwarf scenario is more likely a priori given the lack of known massive planets in 1 day orbits around M dwarfs with Teff < 3800 K, and the existence of some (but few) brown dwarfs., Accepted to A&A

We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54+-0.03 Msun) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velocities, as well as ground-based follow-up transit observations from MEarth and LCOGT telescopes, we measured for the inner planet, TOI-776 b, a period of 8.25 d, a radius of 1.85+-0.13 Re, and a mass of 4.0+-0.9 Me; and for the outer planet, TOI-776 c, a period of 15.66 d, a radius of 2.02+-0.14 Re, and a mass of 5.3+-1.8 Me. The Doppler data shows one additional signal, with a period of 34 d, associated with the rotational period of the star. The analysis of fifteen years of ground-based photometric monitoring data and the inspection of different spectral line indicators confirm this assumption. The bulk densities of TOI-776 b and c allow for a wide range of possible interior and atmospheric compositions. However, both planets have retained a significant atmosphere, with slightly different envelope mass fractions. Thanks to their location near the radius gap for M dwarfs, we can start to explore the mechanism(s) responsible for the radius valley emergence around low-mass stars as compared to solar-like stars. While a larger sample of well-characterized planets in this parameter space is still needed to draw firm conclusions, we tentatively estimate that the stellar mass below which thermally-driven mass loss is no longer the main formation pathway for sculpting the radius valley is between 0.63 and 0.54 Msun. Due to the brightness of the star, the TOI-776 system is also an excellent target for the James Webb Space Telescope, providing a remarkable laboratory to break the degeneracy in planetary interior models and to test formation and evolution theories of small planets around low-mass stars., Comment: 26 pages, 15 figures, 8 tables. Accepted for publication in Astronomy & Astrophysics

The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, steady progress was made in achieving the mission's primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, TESS's observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star TOI-125, a V=11.0 K0 dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TOI-125b, TOI-125c and TOI-125d. TOI-125b has an orbital period of 4.65 days, a radius of $2.726 \pm 0.075 ~\mathrm{R_{\rm E}}$, a mass of $ 9.50 \pm 0.88 ~\mathrm{M_{\rm E}}$ and is near the 2:1 mean motion resonance with TOI-125c at 9.15 days. TOI-125c has a similar radius of $2.759 \pm 0.10 ~\mathrm{R_{\rm E}}$ and a mass of $ 6.63 \pm 0.99 ~\mathrm{M_{\rm E}}$, being the puffiest of the three planets. TOI-125d, has an orbital period of 19.98 days and a radius of $2.93 \pm 0.17~\mathrm{R_{\rm E}}$ and mass $13.6 \pm 1.2 ~\mathrm{M_{\rm E}}$. For TOI-125b and TOI-125d we find unusual high eccentricities of $0.19\pm 0.04$ and $0.17^{+0.08}_{-0.06}$, respectively. Our analysis also provides upper mass limits for the two low-SNR planet candidates in the system; for TOI-125.04 ($R_P=1.36 ~\mathrm{R_{\rm E}}$, $P=$0.53 days) we find a $2\sigma$ upper mass limit of $1.6~\mathrm{M_{\rm E}}$, whereas TOI-125.05 ( $R_P=4.2^{+2.4}_{-1.4} ~\mathrm{R_{\rm E}}$, $P=$ 13.28 days) is unlikely a viable planet candidate with upper mass limit $2.7~\mathrm{M_{\rm E}}$. We discuss the internal structure of the three confirmed planets, as well as dynamical stability and system architecture for this intriguing exoplanet system., Comment: Accepted for publication in MNRAS

A significant fraction of an exoplanet transit model evaluation time is spent calculating projected distances between the planet and its host star. This is a relatively fast operation for a circular orbit, but slower for an eccentric one. However, because the planet's position and its time derivatives are constant for any specific point in orbital phase, the projected distance can be calculated rapidly and accurately in the vicinity of the transit by expanding the planet's $x$ and $y$ positions in the sky plane into a Taylor series at mid-transit. Calculating the projected distance for an elliptical orbit using the four first time derivatives of the position vector (velocity, acceleration, jerk, and snap) is $\sim100$ times faster than calculating it using the Newton's method, and also significantly faster than calculating $z$ for a circular orbit because the approach does not use numerically expensive trigonometric functions. The speed gain in the projected distance calculation leads to 2-25 times faster transit model evaluation speed, depending on the transit model complexity and orbital eccentricity. Calculation of the four position derivatives using numerical differentiation takes $\sim1\,\mu$s with a modern laptop and needs to be done only once for a given orbit, and the maximum error the approximation introduces to a transit light curve is below 1~ppm for the major part of the physically plausible orbital parameter space., Comment: Accepted to MNRAS

All authors: Bluhm, P.; Luque, R.; Espinoza, N.; Pallé, E.; Caballero, J. A.; Dreizler, S.; Livingston, J. H.; Mathur, S.; Quirrenbach, A.; Stock, S.; Van Eylen, V.; Nowak, G.; López, E. D.; Csizmadia, Sz.; Zapatero Osorio, M. R.; Schöfer, P.; Lillo-Box, J.; Oshagh, M.; González-Álvarez, E.; Amado, P. J.; Barrado, D.; Béjar, V. J. S.; Cale, B.; Chaturvedi, P.; Cifuentes, C.; Cochran, W. D.; Collins, K. A.; Collins, K. I.; Cortés-Contreras, M.; Díez Alonso, E.; El Mufti, M.; Ercolino, A.; Fridlund, M.; Gaidos, E.; García, R. A.; Georgieva, I.; González-Cuesta, L.; Guerra, P.; Hatzes, A. P.; Henning, Th.; Herrero, E.; Hidalgo, D.; Isopi, G.; Jeffers, S. V.; Jenkins, J. M.; Jensen, E. L. N.; Kábath, P.; Kaminski, A.; Kemmer, J.; Korth, J.; Kossakowski, D.; Kürster, M.; Lafarga, M.; Mallia, F.; Montes, D.; Morales, J. C.; Morales-Calderón, M.; Murgas, F.; Narita, N.; Passegger, V. M.; Pedraz, S.; Persson, C. M.; Plavchan, P.; Rauer, H.; Redfield, S.; Reffert, S.; Reiners, A.; Ribas, I.; Ricker, G. R.; Rodríguez-López, C.; Santos, A. R. G.; Seager, S.; Schlecker, M.; Schweitzer, A.; Shan, Y.; Soto, M. G.; Subjak, J.; Tal-Or, L.; Trifonov, T.; Vanaverbeke, S.; Vanderspek, R.; Wittrock, J.; Zechmeister, M.; Zohrabi, F., We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384-1735-1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of Mp = 5.9 ± 0.6 M⊕ and a radius of Rp = 1.69 ± 0.08 R⊕ , which together result in a density of ρp = 6.7- 1.1+ 1.3 g cm-3. When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R⊕ or larger at the insolation levels received by TOI-1235 b (~60 S⊕ ). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution. © ESO 2020., CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. We acknowledge the use of public TESS Alert 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. We acknowledge financial support from the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28, the Deutsche Forschungsgemeinschaft through projects RE 281/32-1, RE 1664/14-1, RE 2694/4-1, and RA714/14-1, PA525/18-1, PA525/19-1 within the Schwerpunkt SPP 1992, the Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades and the European FEDER/ERF funds through projects PGC2018-098153-B-C31, ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, AYA2016-79425-C3-1/2/3P, AYA2015-69350-C3-2-P, RYC-2015-17697, and BES-2017-082610, the Centre of Excellence "Severo Ochoa" and "Maria de Maeztu" awards to the Instituto de Astrofisica de Canarias (SEV-2015-0548), Instituto de Astrofisica de Andalucia (SEV-2017-0709), and Centro de Astrobiologia (MDM-2017-0737), the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant 713673, the Centre national d'etudes spatiales through grants PLATO and GOLF, the Czech Academy of Sciences through grant LTT20015, NASA through grants NNX17AF27G and NNX17AG24G, JSPS KAKENHI through grants JP18H01265 and JP18H05439, JST PRESTO through grant JPMJPR1775, the Fundacion Bancaria "la Caixa" through grant INPhINIT LCF/BQ/IN17/11620033, and the Generalitat de Catalunya/CERCA programme. NESSI was funded by the NASA Exoplanet Exploration Program and the NASA Ames Research Center and built at the Ames Research Center. 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 made use of observations from the LCOGT network and the following software: astrasens, AstroImageJ, Banzai, batman, caracal, emcee, juliet, serval, TESS Transit Finder, tpfplotter, Yabi, and the python packages astropy, lightkurve, matplotlib, and numpy. We thank the SuperWASP team and J. Sanz-Forcada for sharing unpublished information with us. Special thanks to Ismael Pessa for all their support through this work.

We report the discovery of a planetary system orbiting TOI-763 (aka CD-39 7945), a $V=10.2$, high proper motion G-type dwarf star that was photometrically monitored by the TESS space mission in Sector 10. We obtain and model the stellar spectrum and find an object slightly smaller than the Sun, and somewhat older, but with a similar metallicity. Two planet candidates were found in the light curve to be transiting the star. Combining TESS transit photometry with HARPS high-precision radial velocity follow-up measurements confirm the planetary nature of these transit signals. We determine masses, radii, and bulk densities of these two planets. A third planet candidate was discovered serendipitously in the radial velocity data. The inner transiting planet,TOI-763 b, has an orbital period of $P_\mathrm{b}$ = 5.6~days, a mass of $M_\mathrm{b}$ = $9.8\pm0.8$ $M_\oplus$, and a radius of $R_\mathrm{b}$ = $2.37\pm0.10$ $R_\oplus$. The second transiting planet,TOI-763 c, has an orbital period of $P_\mathrm{c}$ = 12.3~days, a mass of $M_\mathrm{c}$ = $9.3\pm1.0$ $M_\oplus$, and a radius of $R_\mathrm{c}$ = $2.87\pm0.11$ $R_\oplus$. We find the outermost planet candidate to orbit the star with a period of $\sim$48~days. If confirmed as a planet it would have a minimum mass of $M_\mathrm{d}$ = $9.5\pm1.6$ $M_\oplus$. We investigated the TESS light curve in order to search for a mono transit by planet~d without success. We discuss the importance and implications of this planetary system in terms of the geometrical arrangements of planets orbiting G-type stars.

Full author list: Grzegorz Nowak, Enric Palle, Davide Gandolfi, Hans J Deeg, Teruyuki Hirano, Oscar Barragán, Masayuki Kuzuhara, Fei Dai, Rafael Luque, Carina M Persson, Malcolm Fridlund, Marshall C Johnson, Judith Korth, John H Livingston, Sascha Grziwa, Savita Mathur, Artie P Hatzes, Jorge Prieto-Arranz, David Nespral, Diego Hidalgo, Maria Hjorth, Simon Albrecht, Vincent Van Eylen, Kristine W F Lam, William D Cochran, Massimiliano Esposito, Szilárd Csizmadia, Eike W Guenther, Petr Kabath, Pere Blay, Rafael Brahm, Andrés Jordán, Néstor Espinoza, Felipe Rojas, Núria Casasayas Barris, Florian Rodler, Roi Alonso Sobrino, Juan Cabrera, Ilaria Carleo, Alexander Chaushev, Jerome de Leon, Philipp Eigmüller, Michael Endl, Anders Erikson, Akihiko Fukui, Iskra Georgieva, Lucía González-Cuesta, Emil Knudstrup, Mikkel N Lund, Pilar Montañes Rodríguez, Felipe Murgas, Norio Narita, Prajwal Niraula, Martin Pätzold, Heike Rauer, Seth Redfield, Ignasi Ribas, Marek Skarka, Alexis M S Smith, Jano Subjak, We present an independent discovery and detailed characterization of K2-280 b, a transiting low density warm sub-Saturn in a 19.9-d moderately eccentric orbit (e = 0.35 -0.04+0.05) from K2 campaign 7. A joint analysis of high precision HARPS, HARPS-N, and FIES radial velocity measurements and K2 photometric data indicates that K2-280 b has a radius of Rb = 7.50 ± 0.44 R⊕ and a mass of Mb = 37.1 ± 5.6 M⊕, yielding a mean density of ρb = 0.48 -0.10+0.13 g cm-3. The host star is a mildly evolved G7 star with an effective temperature of Teff = 5500 ± 100 K, a surface gravity of log g = 4.21 ± 0.05 (cgs), and an iron abundance of [Fe/H] = 0.33 ± 0.08 dex, and with an inferred mass of M∗ = 1.03 ± 0.03 M⊙ and a radius of R∗ = 1.28 ± 0.07 R⊙. We discuss the importance of K2-280 b for testing formation scenarios of sub-Saturn planets and the current sample of this intriguing group of planets that are absent in the Solar system., This work is partly supported by JSPS KAKENHI Grant Numbers JP18H01265, JP18H05439, and JP16K17660, and JST PRESTO Grant Number JPMJPR1775. RB acknowledges support from FONDECYT Postdoctoral Fellowship Project 3180246. AJ acknowledges support from FONDECYT project 1171208.

K2-146 is a cool, 0.358 M_sun dwarf that was found to host a mini-Neptune with a 2.67-days period. The planet exhibited strong transit timing variations (TTVs) of greater than 30 minutes, indicative of the presence of a further object in the system. Here we report the discovery of the previously undetected outer planet, K2-146 c, in the system using additional photometric data. K2-146 c was found to have a grazing transit geometry and a 3.97-day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146 b and c were measured using observations spanning a baseline of almost 1200 days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146 b has a radius of 2.25 $\pm$ 0.10 \R_earth and a mass of 5.6 $\pm$ 0.7 M_earth, whereas K2-146 c has a radius of $2.59_{-0.39}^{+1.81}$ R_earth and a mass of 7.1 $\pm$ 0.9 M_earth. The inner and outer planets likely have moderate eccentricities of $e = 0.14 \pm 0.07$ and $0.16 \pm 0.07$, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2 Myr. The evaluation of the resonance angles of the planet pair indicates that K2-146 b and c are likely trapped in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin., Comment: 19 pages with 13 figures and 4 tables; Submitted

Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 RJup) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit. Aims. We setout to determine the nature of the Transiting Exoplanet Survey Satellite (TESS) planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes radial-velocity confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry. Methods. Our analysis combines three transits observed simultaneously in r′, i′, and zs bands usingthe MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g′, r′, and i′ bands, a TESS light curve from Sector 3, and a low-resolution spectrum for stellar characterisation observed with the ALFOSC spectrograph. We modelled the light curves with PYTRANSIT using a transit model that includes a physics-based light contamination component, allowing us to estimate the contamination from unresolved sources from the multicolour photometry. Using this information we were able to derive the true planet-star radius ratio marginalised over the contamination allowed by the photometry.Combining this with the stellar radius, we were able to make a reliable estimate of the absolute radius of the object. Results. The ground-based photometry strongly excludes contamination from unresolved sources with a significant colour difference to TOI 263. Furthermore, contamination from sources of the same stellar type as the host is constrained to levels where the true radius ratio posterior has a median of 0.217 and a 99 percentile of0.286. The median and maximum radius ratios correspond to absolute planet radii of 0.87 and 1.41 RJup, respectively,which confirms the substellar nature of the planet candidate. The object is either a giant planetor a brown dwarf (BD) located deep inside the so-called "brown dwarf desert". Both possibilities offer a challenge to current planet/BD formation models and make TOI 263.01 an object that merits in-depth follow-up studies., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC\,249893012, a G8\,IV-V evolved star ($M_\star$\,=\,1.05\,$\pm$\,0.05\,$M_\odot$, $R_\star$\,=\,1.71\,$\pm$\,0.04\,$R_\odot$, $T_\mathrm{eff}$\,=5430\,$\pm$\,85\,K). The star is just leaving the main sequence. We combined \ktwo \ photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of $3.5949^{+0.0007}_{-0.0007}$ days, a mass of $8.75^{+1.09}_{-1.08}\ M_{\oplus}$ , and a radius of $1.95^{+0.09}_{-0.08}\ R_{\oplus}$, the inner planet b is compatible with nickel-iron core and a silicate mantle ($\rho_b= 6.39^{+1.19}_{-1.04}$ g cm$^{-3}$). Planets c and d with orbital periods of $15.624^{+0.001}_{-0.001}$ and $35.747^{+0.005}_{-0.005}$ days, respectively, have masses and radii of $14.67^{+1,84}_{-1.89}\ M_{\oplus}$ and $3.67^{+0.17}_{-0.14}\ R_{\oplus}$ and $10.18^{+2.46}_{-2.42}\ M_{\oplus}$ and $3.94^{+0.13}_{-0.12}\ R_{\oplus}$, respectively, yielding a mean density of $1.62^{+0.30}_{-0.29}$ and $0.91^{+0.25}_{-0.23}$ g cm$^{-3}$, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view., Comment: Accepted for publication in A\& A

We present a detailed analysis of HARPS-N radial velocity observations of K2-100, a young and active star in the Praesepe cluster, which hosts a transiting planet with a period of 1.7 days. We model the activity-induced radial velocity variations of the host star with a multi-dimensional Gaussian Process framework and detect a planetary signal of $10.6 \pm 3.0 {\rm m\,s^{-1}}$, which matches the transit ephemeris, and translates to a planet mass of $21.8 \pm 6.2 M_\oplus$. We perform a suite of validation tests to confirm that our detected signal is genuine. This is the first mass measurement for a transiting planet in a young open cluster. The relatively low density of the planet, $2.04^{+0.66}_{-0.61} {\rm g\,cm^{-3}}$, implies that K2-100b retains a significant volatile envelope. We estimate that the planet is losing its atmosphere at a rate of $10^{11}-10^{12}\,{\rm g\,s^{-1}}$ due to the high level of radiation it receives from its host star., O.B. and S.Ai. acknowledge support from the UK Science and Technology Facilities Council (STFC) under grants ST/S000488/1 and ST/R004846/1. J.K., S.G. and A.P.H acknowledges support by Deutsche Forschungsgemeinschaft (DFG) grants PA525/18-1 and PA525/19-1 and HPA 3279/12-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extra-solar Planets. L.M. acknowledges support from PLATO ASI-INAF agreement n.2015-019-R.1-2018. S.Al. acknowledges the support from the Danish Council for Independent Research through the DFF Sapere Aude Starting Grant No. 4181-00487B, and the Stellar Astrophysics Centre which funding is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). This work is partly supported by JSPS KAKENHI Grant Numbers JP18H01265, JP18H05439, 15H02063, and 18H05442 and JST PRESTO Grant Number JPMJPR1775. M.C.V.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 174/18).

Our aim is to investigate the nature and formation of brown dwarfs by adding a new well-characterised object to the small sample of less than 20 transiting brown dwarfs. One brown dwarf candidate was found by the KESPRINT consortium when searching for exoplanets in the K2 space mission Campaign 16 field. We combined the K2 photometric data with a series of multi-colour photometric observations, imaging and radial velocity measurements to rule out false positive scenarios and to determine the fundamental properties of the system. We report the discovery and characterisation of a transiting brown dwarf in a 5.17 day eccentric orbit around the slightly evolved F7V star EPIC 212036875. We find a stellar mass of 1.15+/-0.08 M$_\odot$, a stellar radius of 1.41+/-0.05 R$_\odot$, and an age of 5.1+/-0.9 Gyr. The mass and radius of the companion brown dwarf are 51+/-2 MJ and 0.83+/-0.03 RJ, respectively, corresponding to a mean density of 108+15-13 g cm-3. EPIC 212036875 b is a rare object that resides in the brown dwarf desert. In the mass-density diagram for planets, brown dwarfs and stars, we find that all giant planets and brown dwarfs follow the same trend from ~0.3 MJ to the turn-over to hydrogen burning stars at ~73 MJ. EPIC 212036875 b falls close to the theoretical model for mature H/He dominated objects in this diagram as determined by interior structure models, as well as the empirical fit. We argue that EPIC 212036875 b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf's radius was larger. The lack of spin-orbit synchronisation points to a weak stellar dissipation parameter which implies a circularisation timescale of >23 Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf., 14 pages, 12 figures, accepted 13 June 2019 for publication in A&A

We report on the confirmation and mass determination of a transiting planet orbiting the old and inactive G7 dwarf star HD219666 (Mstar = 0.92 +/- 0.03 MSun, Rstar = 1.03 +/- 0.03 RSun, tau_star = 10 +/- 2 Gyr). With a mass of Mb = 16.6 +/- 1.3 MEarth, a radius of Rb = 4.71 +/- 0.17 REarth, and an orbital period of P ~ 6 days, HD219666b is a new member of a rare class of exoplanets: the hot-Neptunes. The Transiting Exoplanet Survey Satellite (TESS) observed HD219666 (also known as TOI-118) in its Sector 1 and the light curve shows four transit-like events, equally spaced in time. We confirmed the planetary nature of the candidate by gathering precise radial-velocity measurements with HARPS@ESO3.6m. We used the co-added HARPS spectrum to derive the host star fundamental parameters (Teff = 5527 +/- 65 K, log g = 4.40 +/- 0.11 (cgs), [Fe/H]= 0.04 +/- 0.04 dex, log R'HK = -5.07 +/- 0.03), as well as the abundances of many volatile and refractory elements. The host star brightness (V = 9.9) makes it suitable for further characterisation by means of in-transit spectroscopy. The determination of the planet orbital obliquity, along with the atmospheric metal-to-hydrogen content and thermal structure could provide us with important clues on the formation mechanisms of this class of objects., Comment: Accepted for publication in A&A

Context. The Kepler extended mission, also known as K2, has provided the community with a wealth of planetary candidates that orbit stars typically much brighter than the targets of the original mission. These planet candidates are suitable for further spectroscopic follow-up and precise mass determinations, leading ultimately to the construction of empirical mass-radius diagrams. Particularly interesting is to constrain the properties of planets that are between Earth and Neptune in size, the most abundant type of planet orbiting Sun-like stars with periods of less than a few years. Aims. Among many other K2 candidates, we discovered a multi-planetary system around EPIC 246471491, referred to henceforth as K2-285, which contains four planets, ranging in size from twice the size of Earth to nearly the size of Neptune. We aim here at confirming their planetary nature and characterizing the properties of this system. Methods. We measure the mass of the planets of the K2-285 system by means of precise radial-velocity measurements using the CARMENES spectrograph and the HARPS-N spectrograph. Results. With our data we are able to determine the mass of the two inner planets of the system with a precision better than 15%, and place upper limits on the masses of the two outer planets. Conclusions. We find that K2-285b has a mass of M = 9.68 M and a radius of R = 2.59 R, yielding a mean density of ρ = 3.07 g cm, while K2-285c has a mass of M = 15.68 M, radius of R = 3.53 R, and a mean density of ρ = 1.95 g cm. For K2-285d (R = 2.48 R) and K2-285e (R = 1.95 R), the upper limits for the masses are 6.5 M and 10.7 M, respectively. The system is thus composed of an (almost) Neptune-twin planet (in mass and radius), two sub-Neptunes with very different densities and presumably bulk composition, and a fourth planet in the outermost orbit that resides right in the middle of the super-Earth/sub-Neptune radius gap. Future comparative planetology studies of this system would provide useful insights into planetary formation, and also a good test of atmospheric escape and evolution theories.© 2019 ESO., This work is partly financed by the Spanish MINECO through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R and AYA2016-79425-C3-3-P. This work was also supported by JSPS KAKENHI Grants Numbers JP16K17660 and JP18H01265.

We report the independent discovery and characterization of two K2 planets: K2-180b, a mini-Neptune-size planet in an 8.9-day orbit transiting a V = 12.6 mag, metal-poor ([Fe/H] =$-0.65\pm0.10$) K2V star in K2 campaign 5; K2-140b, a transiting hot Jupiter in a 6.6-day orbit around a V = 12.6 mag G6V ([Fe/H] = $+0.10\pm0.10$) star in K2 campaign 10. Our results are based on K2 time-series photometry combined with high-spatial resolution imaging and high-precision radial velocity measurements. We present the first mass measurement of K2-180b. K2-180b has a mass of $M_\mathrm{p}=11.3\pm1.9$ ${M_{\oplus}}$ and a radius of $R_\mathrm{p}=2.2\pm0.1$ ${R_{\oplus}}$ , yielding a mean density of $\rho_\mathrm{p}=5.6\pm1.9\,g\,cm^{-3}$, suggesting a rock composition. Given its radius, K2-180b is above the region of the so-called `planetary radius gap'. K2-180b is in addition not only one of the densest mini-Neptune-size planets, but also one of the few mini-Neptune-size planets known to transit a metal-poor star. We also constrain the planetary and orbital parameters of K2-140b and show that, given the currently available Doppler measurements, the eccentricity is consistent with zero, contrary to the results of a previous study., Comment: accepted in MNRAS

We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V=9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 3 and 4. We combine the TESS photometry with archival HARPS spectra to confirm the planetary nature of the transit signals and derive the masses of the two transiting planets. With an orbital period of 4.8 days, a mass of 7.51(+1.09)(-1.01) M_Earth, and a radius of 1.64+/-0.06 R_Earth, HD 15337b joins the growing group of short-period super-Earths known to have a rocky terrestrial composition. The sub-Neptune HD 15337c has an orbital period of 17.2 days, a mass of 8.11(+1.82)(-1.69) M_Earth, and a radius of 2.39+/-0.12 R_Earth, suggesting that the planet might be surrounded by a thick atmospheric envelope. The two planets have similar masses and lie on opposite sides of the radius gap, and are thus an excellent testbed for planet formation and evolution theories. Assuming that HD 15337c hosts a hydrogen-dominated envelope, we employ a recently developed planet atmospheric evolution algorithm in a Bayesian framework to estimate the history of the high-energy (extreme ultraviolet and X-ray) emission of the host star. We find that at an age of 150 Myr, the star possessed on average between 3.7 and 127 times the high-energy luminosity of the current Sun., Comment: Published in ApJ Letters

Planet host stars with well-constrained ages provide a rare window to the time domain of planet formation and evolution. The NASA K2 mission has enabled the discovery of the vast majority of known planets transiting stars in clusters, providing a valuable sample of planets with known ages and radii. We present the discovery of two planets transiting K2-264, an M2 dwarf in the intermediate age (600-800 Myr) Praesepe open cluster (also known as the Beehive Cluster, M44, or NGC 2632), which was observed by K2 during Campaign 16. The planets have orbital periods of 5.8 and 19.7 days, and radii of $2.2 \pm 0.2 $ and $2.7 \pm 0.2$ $R_\oplus$, respectively, and their equilibrium temperatures are $496 \pm 10$ and $331 \pm 7$ $K$, making this a system of two warm sub-Neptunes. When placed in the context of known planets orbiting field stars of similar mass to K2-264, these planets do not appear to have significantly inflated radii, as has previously been noted for some cluster planets. As the second known system of multiple planets transiting a star in a cluster, K2-264 should be valuable for testing theories of photoevaporation in systems of multiple planets. Follow-up observations with current near-infrared (NIR) spectrographs could yield planet mass measurements, which would provide information about the mean densities and compositions of small planets soon after photoevaporation is expected to have finished. Follow-up NIR transit observations using Spitzer or large ground-based telescopes could yield improved radius estimates, further enhancing the characterization of these interesting planets., 12 pages, 11 figures, 2 tables, published in MNRAS; see also secular dynamics at https://youtu.be/MSLodufHRes

We report the discovery and characterization of HD 89345b (K2-234b; EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved star. HD 89345 is a bright star ($V = 9.3$ mag) observed by the K2 mission with one-minute time sampling. It exhibits solar-like oscillations. We conducted asteroseismology to determine the parameters of the star, finding the mass and radius to be $1.12^{+0.04}_{-0.01}~M_\odot$ and $1.657^{+0.020}_{-0.004}~R_\odot$, respectively. The star appears to have recently left the main sequence, based on the inferred age, $9.4^{+0.4}_{-1.3}~\mathrm{Gyr}$, and the non-detection of mixed modes. The star hosts a "warm Saturn" ($P = 11.8$~days, $R_p = 6.86 \pm 0.14~R_\oplus$). Radial-velocity follow-up observations performed with the FIES, HARPS, and HARPS-N spectrographs show that the planet has a mass of $35.7 \pm 3.3~M_\oplus$. The data also show that the planet's orbit is eccentric ($e\approx 0.2$). An investigation of the rotational splitting of the oscillation frequencies of the star yields no conclusive evidence on the stellar inclination angle. We further obtained Rossiter-McLaughlin observations, which result in a broad posterior of the stellar obliquity. The planet seems to conform to the same patterns that have been observed for other sub-Saturns regarding planet mass and multiplicity, orbital eccentricity, and stellar metallicity., Comment: Submitted to MNRAS on 23 February 2018, accepted for publication, 4 May 2018

We present the discovery and confirmation of two new transiting giant planets from the Kepler extended mission K2. K2-260 b is a hot Jupiter transiting a $V=12.7$ F6V star in K2 Field 13, with a mass and radius of $M_{\star}=1.39_{-0.06}^{+0.05} M_{\odot}$ and $R_{\star}=1.69 \pm 0.03 R_{\odot}$. The planet has an orbital period of $P=2.627$ days, and a mass and radius of $M_P=1.42^{+0.31}_{-0.32} M_J$ and $R_P=1.552^{+0.048}_{-0.057} R_J$. This is the first K2 hot Jupiter with a detected secondary eclipse in the Kepler bandpass, with a depth of $71 \pm 15$ ppm, which we use to estimate a geometric albedo of $A_g\sim0.2$. We also detected a candidate stellar companion at 0.6" from K2-260; we find that it is very likely physically associated with the system, in which case it would be an M5-6V star at a projected separation of $\sim400$ AU. K2-261 b is a warm Saturn transiting a bright ($V=10.5$) G7IV/V star in K2 Field 14. The host star is a metal-rich ([Fe/H]$=0.36 \pm 0.06$), mildly evolved $1.10_{-0.02}^{+0.01} M_{\odot}$ star with $R_{\star}=1.65 \pm 0.04 R_{\odot}$. Thanks to its location near the main sequence turn-off, we can measure a relatively precise age of $8.8_{-0.3}^{+0.4}$ Gyr. The planet has $P=11.633$ days, $M_P=0.223 \pm 0.031 M_J$, and $R_P=0.850^{+0.026}_{-0.022} R_J$, and its orbit is eccentric ($e=0.39 \pm 0.15$). Its brightness and relatively large transit depth make this one of the best known warm Saturns for follow-up observations to further characterize the planetary system., Published in MNRAS. 18 pages, 10 figures

We report on the discovery of three transiting super-Earths around K2-155 (EPIC 210897587), a relatively bright early M dwarf ($V=12.81$ mag) observed during Campaign 13 of the NASA K2 mission. To characterize the system and validate the planet candidates, we conducted speckle imaging and high-dispersion optical spectroscopy, including radial velocity measurements. Based on the K2 light curve and the spectroscopic characterization of the host star, the planet sizes and orbital periods are $1.55_{-0.17}^{+0.20}\,R_\oplus$ and $6.34365\pm 0.00028$ days for the inner planet; $1.95_{-0.22}^{+0.27}\,R_\oplus$ and $13.85402\pm 0.00088$ days for the middle planet; and $1.64_{-0.17}^{+0.18}\,R_\oplus$ and $40.6835\pm 0.0031$ days for the outer planet. The outer planet (K2-155d) is near the habitable zone, with an insolation $1.67\pm 0.38$ times that of the Earth. The planet's radius falls within the range between that of smaller rocky planets and larger gas-rich planets. To assess the habitability of this planet, we present a series of 3D global climate simulations assuming that K2-155d is tidally locked and has an Earth-like composition and atmosphere. We find that the planet can maintain a moderate surface temperature if the insolation proves to be smaller than $\sim 1.5$ times that of the Earth. Doppler mass measurements, transit spectroscopy, and other follow-up observations should be rewarding, since K2-155 is one of the optically brightest M dwarfs known to harbor transiting planets., 13 pages, 9 figures, Accepted for publication in Astronomical Journal

Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (d = $30.32\pm1.62$ pc) detected by Kepler and K2 . Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Results. We find that GJ 9827 b has a mass of $M_\mathrm{b}=3.74^{+0.50}_{-0.48}$ $M_\oplus$ and a radius of $R_\mathrm{b}=1.62^{+0.17}_{-0.16}$ $R_\oplus$, yielding a mean density of $\rho_\mathrm{b} = 4.81^{+1.97}_{-1.33}$ g cm$^{-3}$. GJ 9827 c has a mass of $M_\mathrm{c}=1.47^{+0.59}_{-0.58}$ $M_\oplus$, radius of $R_\mathrm{c}=1.27^{+0.13}_{-0.13}$ $R_\oplus$, and a mean density of $\rho_\mathrm{c}= 3.87^{+2.38}_{-1.71}$ g cm$^{-3}$. For GJ 9827 d we derive $M_\mathrm{d}=2.38^{+0.71}_{-0.69}$ $M_\oplus$, $R_\mathrm{d}=2.09^{+0.22}_{-0.21}$ $R_\oplus$, and $\rho_\mathrm{d}= 1.42^{+0.75}_{-0.52}$ g cm$^{-3}$. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and mini-Neptunes. We also find that the planetary bulk compositions are compatible with a scenario where all three planets formed with similar core/atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its atmosphere, owing to the much lower stellar irradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmospheric escape can be studied in detail for all planets, helping us to understand how compact systems form and evolve., Comment: 15 pages, 10 Figures, 8 tables

We report on the confirmation and mass determination of Pi Men c, the first transiting planet discovered by NASA's TESS space mission. Pi Men is a naked-eye (V=5.65 mag), quiet G0 V star that was previously known to host a sub-stellar companion (Pi Men b) on a long-period (Porb = 2091 days), eccentric (e = 0.64) orbit. Using TESS time-series photometry, combined with Gaia data, published UCLES@AAT Doppler measurements, and archival HARPS@ESO-3.6m radial velocities, we found that Pi Men c is a close-in planet with an orbital period of Porb = 6.27 days, a mass of Mc = 4.52 +/- 0.81 MEarth, and a radius of Rc = 2.06 +/- 0.03 REarth. Based on the planet's orbital period and size, Pi Men c is a super-Earth located at, or close to, the radius gap, while its mass and bulk density suggest it may have held on to a significant atmosphere. Because of the brightness of the host star, this system is highly suitable for a wide range of further studies to characterize the planetary atmosphere and dynamical properties. We also performed an asteroseismic analysis of the TESS data and detected a hint of power excess consistent with the seismic values expected for this star, although this result depends on the photometric aperture used to extract the light curve. This marginal detection is expected from pre-launch simulations hinting at the asteroseismic potential of the TESS mission for longer, multi-sector observations and/or for more evolved bright stars., Comment: Accepted for publication in A&A. Eleven pages, 5 figures, 5 tables

We present 44 validated planets from the 10$^\mathrm{th}$ observing campaign of the NASA $K2$ mission, as well as high resolution spectroscopy and speckle imaging follow-up observations. These 44 planets come from an initial set of 72 vetted candidates, which we subjected to a validation process incorporating pixel-level analyses, light curve analyses, observational constraints, and statistical false positive probabilities. Our validated planet sample has median values of $R_p$ = 2.2 $R_\oplus$, $P_\mathrm{orb}$ = 6.9 days, $T_{\mathrm{eq}}$ = 890 K, and $J$ = 11.2 mag. Of particular interest are four ultra-short period planets ($P_\mathrm{orb} \lesssim 1$ day), 16 planets smaller than 2 $R_\oplus$, and two planets with large predicted amplitude atmospheric transmission features orbiting infrared-bright stars. We also present 27 planet candidates, most of which are likely to be real and worthy of further observations. Our validated planet sample includes 24 new discoveries, and has enhanced the number of currently known super-Earths ($R_p \approx 1-2 R_\oplus$), sub-Neptunes ($R_p \approx 2-4 R_\oplus$), and sub-Saturns ($R_p \approx 4-8 R_\oplus$) orbiting bright stars ($J = 8-10$ mag) by $\sim$4%, $\sim$17%, and $\sim$11%, respectively., Comment: 25 pages, 6 figures, 12 tables, accepted for publication in AJ