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1. Molecules with ALMA at Planet-forming Scales (MAPS): Complex Kinematics in the AS 209 Disk Induced by a Forming Planet and Disk Winds

   https://doi.org/10.3847/1538-4357/accae4  

   Galloway-Sprietsma, Maria ; Bae, Jaehan ; Teague, Richard ; Benisty, Myriam ; Facchini, Stefano ; Aikawa, Yuri ; Alarcón, Felipe ; Andrews, Sean M. ; Bergin, Edwin ; Cataldi, Gianni ; et al ( June 2023 , The Astrophysical Journal)

   We study the kinematics of the AS 209 disk using theJ= 2–1 transitions of¹²CO,¹³CO, and C¹⁸O. We derive the radial, azimuthal, and vertical velocity of the gas, taking into account the lowered emission surface near the annular gap at ≃1.″7 (200 au) within which a candidate circumplanetary-disk-hosting planet has been reported previously. In¹²CO and¹³CO, we find a coherent upward flow arising from the gap. The upward gas flow is as fast as 150 m s⁻¹in the regions traced by¹²CO emission, which corresponds to about 50% of the local sound speed or 6% of the local Keplerian speed. Such an upward gas flow is difficult to reconcile with an embedded planet alone. Instead, we propose that magnetically driven winds via ambipolar diffusion are triggered by the low gas density within the planet-carved gap, dominating the kinematics of the gap region. We estimate the ambipolar Elsässer number, Am, using the HCO⁺column density as a proxy for ion density and find that Am is ∼0.1 at the radial location of the upward flow. This value is broadly consistent with the value at which numerical simulations find that ambipolar diffusion drives strong winds. We hypothesize that the activation of magnetically driven winds in a planet-carved gap can control the growth of the embedded planet. We provide a scaling relationship that describes the wind-regulated terminal mass: adopting parameters relevant to 100 au from a solar-mass star, we find that the wind-regulated terminal mass is about one Jupiter mass, which may help explain the dearth of directly imaged super-Jovian-mass planets.

    

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2. The TESS-Keck Survey. VIII. Confirmation of a Transiting Giant Planet on an Eccentric 261 Day Orbit with the Automated Planet Finder Telescope*

   https://doi.org/10.3847/1538-3881/ac415b  

   Dalba, Paul A. ; Kane, Stephen R. ; Dragomir, Diana ; Villanueva, Steven ; Collins, Karen A. ; Jacobs, Thomas Lee ; LaCourse, Daryll M. ; Gagliano, Robert ; Kristiansen, Martti H. ; Omohundro, Mark ; et al ( January 2022 , The Astronomical Journal)

   Abstract We report the discovery of TOI-2180 b, a 2.8 M J giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8 ± 0.6 days, revealed an orbital eccentricity of 0.368 ± 0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method. 

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3. A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder

   https://doi.org/10.3847/1538-3881/abbe19  

   Stefánsson, Guðmundur ; Kopparapu, Ravi ; Lin, Andrea ; Mahadevan, Suvrath ; Cañas, Caleb I. ; Kanodia, Shubham ; Ninan, Joe P. ; Cochran, William D. ; Endl, Michael ; Hebb, Leslie ; et al ( December 2020 , The Astronomical Journal)

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4. Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit

   https://doi.org/10.1093/mnras/staa138  

   Eisner, N L ; Barragán, O ; Aigrain, S ; Lintott, C ; Miller, G ; Zicher, N ; Boyajian, T S ; Briceño, C ; Bryant, E M ; Christiansen, J L ; et al ( May 2020 , Monthly Notices of the Royal Astronomical Society)

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   ABSTRACT We report on the discovery and validation of TOI 813 b (TIC 55525572 b), a transiting exoplanet identified by citizen scientists in data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the first planet discovered by the Planet Hunters TESS project. The host star is a bright (V = 10.3 mag) subgiant ($R_\star =1.94\, R_\odot$, $M_\star =1.32\, M_\odot$). It was observed almost continuously by TESS during its first year of operations, during which time four individual transit events were detected. The candidate passed all the standard light curve-based vetting checks, and ground-based follow-up spectroscopy and speckle imaging enabled us to place an upper limit of $2\, M_{\rm Jup}$ (99 per cent confidence) on the mass of the companion, and to statistically validate its planetary nature. Detailed modelling of the transits yields a period of $83.8911 _{ - 0.0031 } ^ { + 0.0027 }$ d, a planet radius of 6.71 ± 0.38 R⊕ and a semimajor axis of $0.423 _{ - 0.037 } ^ { + 0.031 }$ AU. The planet’s orbital period combined with the evolved nature of the host star places this object in a relatively underexplored region of parameter space. We estimate that TOI 813 b induces a reflex motion in its host star with a semi-amplitude of ∼6 m s−1, making this a promising system to measure the mass of a relatively long-period transiting planet. 

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5. Molecules with ALMA at Planet-forming Scales (MAPS). VII. Substellar O/H and C/H and Superstellar C/O in Planet-feeding Gas

   https://doi.org/10.3847/1538-4365/ac1435  

   Bosman, Arthur D. ; Alarcón, Felipe ; Bergin, Edwin A. ; Zhang, Ke ; van’t Hoff, Merel L. ; Öberg, Karin I. ; Guzmán, Viviana V. ; Walsh, Catherine ; Aikawa, Yuri ; Andrews, Sean M. ; et al ( November 2021 , The Astrophysical Journal Supplement Series)