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1. Science Extraction from TESS Observations of Known Exoplanet Hosts

   https://doi.org/10.1088/1538-3873/abc610  

   Kane, Stephen R. ; Bean, Jacob L. ; Campante, Tiago L. ; Dalba, Paul A. ; Fetherolf, Tara ; Mocnik, Teo ; Ostberg, Colby ; Pepper, Joshua ; Simpson, Emilie R. ; Turnbull, Margaret C. ; et al ( January 2021 , Publications of the Astronomical Society of the Pacific)

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2. The PEPSI Exoplanet Transit Survey (PETS). II. A Deep Search for Thermal Inversion Agents in KELT-20 b/MASCARA-2 b with Emission and Transmission Spectroscopy*

   https://doi.org/10.3847/1538-3881/acb7e2  

   Johnson, Marshall C. ; Wang 吉, Ji 王 ; Asnodkar, Anusha Pai ; Bonomo, Aldo S. ; Gaudi, B. Scott ; Henning, Thomas ; Ilyin, Ilya ; Keles, Engin ; Malavolta, Luca ; Mallonn, Matthias ; et al ( March 2023 , The Astronomical Journal)

   Recent observations have shown that the atmospheres of ultrahot Jupiters (UHJs) commonly possess temperature inversions, where the temperature increases with increasing altitude. Nonetheless, which opacity sources are responsible for the presence of these inversions remains largely observationally unconstrained. We used LBT/PEPSI to observe the atmosphere of the UHJ KELT-20 b in both transmission and emission in order to search for molecular agents which could be responsible for the temperature inversion. We validate our methodology by confirming a previous detection of Feiin emission at 16.9σ. Our search for the inversion agents TiO, VO, FeH, and CaH results in non-detections. Using injection-recovery testing we set 4σupper limits upon the volume mixing ratios for these constituents as low as ∼1 × 10⁻⁹for TiO. For TiO, VO, and CaH, our limits are much lower than expectations from an equilibrium chemical model, while we cannot set constraining limits on FeH with our data. We thus rule out TiO and CaH as the source of the temperature inversion in KELT-20 b, and VO only if the line lists are sufficiently accurate.

    

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3. The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High-contrast Imaging of the Exoplanet HIP 65426 b from 2 to 16 μm

   https://doi.org/10.3847/2041-8213/acd93e  

   Carter, Aarynn L. ; Hinkley, Sasha ; Kammerer, Jens ; Skemer, Andrew ; Biller, Beth A. ; Leisenring, Jarron M. ; Millar-Blanchaer, Maxwell A. ; Petrus, Simon ; Stone, Jordan M. ; Ward-Duong, Kimberly ; et al ( July 2023 , The Astrophysical Journal Letters)

   We present JWST Early Release Science coronagraphic observations of the super-Jupiter exoplanet, HIP 65426b, with the Near-Infrared Camera (NIRCam) from 2 to 5μm, and with the Mid-Infrared Instrument (MIRI) from 11 to 16μm. At a separation of ∼0.″82 (87${}_{-31}^{+108}$au), HIP 65426b is clearly detected in all seven of our observational filters, representing the first images of an exoplanet to be obtained by JWST, and the first-ever direct detection of an exoplanet beyond 5μm. These observations demonstrate that JWST is exceeding its nominal predicted performance by up to a factor of 10, depending on separation and subtraction method, with measured 5σcontrast limits of ∼1 × 10⁻⁵and ∼2 × 10⁻⁴at 1″ for NIRCam at 4.4μm and MIRI at 11.3μm, respectively. These contrast limits provide sensitivity to sub-Jupiter companions with masses as low as 0.3M_Jupbeyond separations of ∼100 au. Together with existing ground-based near-infrared data, the JWST photometry are fit well by aBT-SETTLatmospheric model from 1 to 16μm, and they span ∼97% of HIP 65426b's luminous range. Independent of the choice of model atmosphere, we measure an empirical bolometric luminosity that is tightly constrained between$\log \left(L_{\mathrm{bol}}/L_{\odot }\right)$= −4.31 and −4.14, which in turn provides a robust mass constraint of 7.1 ± 1.2M_Jup. In totality, these observations confirm that JWST presents a powerful and exciting opportunity to characterize the population of exoplanets amenable to high-contrast imaging in greater detail.

    

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4. ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS). I. Potential Metal Enrichment of the Exoplanet AF Lep b and a Novel Retrieval Approach for Cloudy Self-luminous Atmospheres

   https://doi.org/10.3847/1538-3881/acf768  

   Zhang 张, Zhoujian 周健 ; Mollière, Paul ; Hawkins, Keith ; Manea, Catherine ; Fortney, Jonathan J. ; Morley, Caroline V. ; Skemer, Andrew ; Marley, Mark S. ; Bowler, Brendan P. ; Carter, Aarynn L. ; et al ( October 2023 , The Astronomical Journal)

   AF Lep A+b is a remarkable planetary system hosting a gas-giant planet that has the lowest dynamical mass among directly imaged exoplanets. We present an in-depth analysis of the atmospheric composition of the star and planet to probe the planet’s formation pathway. Based on new high-resolution spectroscopy of AF Lep A, we measure a uniform set of stellar parameters and elemental abundances (e.g., [Fe/H] = −0.27 ± 0.31 dex). The planet’s dynamical mass (${2.8}_{-0.5}^{+0.6}$M_Jup) and orbit are also refined using published radial velocities, relative astrometry, and absolute astrometry. We usepetitRADTRANSto perform chemically consistent atmospheric retrievals for AF Lep b. The radiative–convective equilibrium temperature profiles are incorporated as parameterized priors on the planet’s thermal structure, leading to a robust characterization for cloudy self-luminous atmospheres. This novel approach is enabled by constraining the temperature–pressure profiles via the temperature gradient$(d\ln T/d\ln P)$, a departure from previous studies that solely modeled the temperature. Through multiple retrievals performed on different portions of the 0.9–4.2μm spectrophotometry, along with different priors on the planet’s mass and radius, we infer that AF Lep b likely possesses a metal-enriched atmosphere ([Fe/H] > 1.0 dex). AF Lep b’s potential metal enrichment may be due to planetesimal accretion, giant impacts, and/or core erosion. The first process coincides with the debris disk in the system, which could be dynamically excited by AF Lep b and lead to planetesimal bombardment. Our analysis also determinesT_eff≈ 800 K,$\log (g)\approx 3.7$dex, and the presence of silicate clouds and disequilibrium chemistry in the atmosphere. Straddling the L/T transition, AF Lep b is thus far the coldest exoplanet with suggested evidence of silicate clouds.

    

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5. Exoplanet Volatile Carbon Content as a Natural Pathway for Haze Formation

   https://doi.org/10.3847/2041-8213/acd377  

   Bergin, Edwin A. ; Kempton, Eliza M.-R. ; Hirschmann, Marc ; Bastelberger, Sandra T. ; Teal, D. J. ; Blake, Geoffrey A. ; Ciesla, Fred J. ; Li, Jie ( May 2023 , The Astrophysical Journal Letters)

   Abstract We explore terrestrial planet formation with a focus on the supply of solid-state organics as the main source of volatile carbon. For the water-poor Earth, the water ice line, or ice sublimation front, within the planet-forming disk has long been a key focal point. We posit that the soot line, the location where solid-state organics are irreversibly destroyed, is also a key location within the disk. The soot line is closer to the host star than the water snow line and overlaps with the location of the majority of detected exoplanets. In this work, we explore the ultimate atmospheric composition of a body that receives a major portion of its materials from the zone between the soot line and water ice line. We model a silicate-rich world with 0.1% and 1% carbon by mass with variable water content. We show that as a result of geochemical equilibrium, the mantle of these planets would be rich in reduced carbon but have relatively low water (hydrogen) content. Outgassing would naturally yield the ingredients for haze production when exposed to stellar UV photons in the upper atmosphere. Obscuring atmospheric hazes appear common in the exoplanetary inventory based on the presence of often featureless transmission spectra. Such hazes may be powered by the high volatile content of the underlying silicate-dominated mantle. Although this type of planet has no solar system counterpart, it should be common in the galaxy with potential impact on habitability. 

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