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1. The ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO). XI. Beam-corrected Gas Disk Sizes from Fitting ¹² CO Moment Zero Maps

   https://doi.org/10.3847/1538-4357/adc7af  

   Trapman, Leon; Vioque, Miguel; Kurtovic, Nicolás T; Zhang, Ke; Rosotti, Giovanni P; Pinilla, Paola; Carpenter, John; Cieza, Lucas A; Pascucci, Ilaria; Anania, Rossella; et al (July 2025, The Astrophysical Journal)

   Abstract The inward drift of millimeter–centimeter sized pebbles in protoplanetary disks has become an important part of our current theories of planet formation and, more recently, planet composition as well. The gas-to-dust size ratio of protoplanetary disks can provide an important constraint on how pebbles have drifted inward, provided that observational effects, especially resolution, can be accounted for. Here we present a method for fitting beam-convolved models to integrated intensity maps of line emission using theastropyPython package and use it to fit¹²CO moment zero maps of 10 Lupus and 10 Upper Scorpius protoplanetary disks from the ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO) Program, a sample of disks around M3-K6 stars that cover the  ∼1–6 Myr of gas disk evolution. From the unconvolved best fit models, we measure the gas disk size ( $R_{\mathrm{CO},90\%}^{\mathrm{model}}$), which we combine with the dust disk size ( $R_{\mathrm{dust},90\%}^{\mathrm{FRANK}}$) from continuum visibility fits from M. Vioque et al. to compute beam-corrected gas-to-dust size ratios. In our sample, we find gas-to-dust size ratios between  ∼1 and  ∼5.5, with a median value of $2.78_{-0.32}^{+0.37}$. Contrary to models of dust evolution that predict an increasing size ratio with time, we find that the younger disks in Lupus have similar (or even larger) median ratios $\left(3.02_{-0.33}^{+0.33}\right)$than the older disks in Upper Sco $\left(2.46_{-0.38}^{+0.53}\right)$. A possible explanation for this discrepancy is that pebble drift is halted in dust traps combined with truncation of the gas disk by external photoevaporation in Upper Sco, although survivorship bias could also play a role. 

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2. KMT-2022-BLG-0086: Another Binary-lens Binary-source Microlensing Event

   https://doi.org/10.3847/1538-3881/ade2e7  

   Chung, Sun-Ju; Hwang, Kyu-Ha; Yee, Jennifer C; Gould, Andrew; Bond, Ian A; Yang, Hongjing; Albrow, Michael D; Jung, Youn Kil; Han, Cheongho; Ryu, Yoon-Hyun; et al (July 2025, The Astronomical Journal)

   Abstract We present the analysis of a microlensing event KMT-2022-BLG-0086 of which the overall light curve is not described by a binary-lens single-source (2L1S) model, which suggests the existence of an extra lens or an extra source. We found that the event is best explained by the binary-lens binary-source (2L2S) model, but the 2L2S model is only favored over the triple-lens single-source (3L1S) model by Δχ² ≃ 9. Although the event has noticeable anomalies around the peak of the light curve, they are not enough covered to constrain the angular Einstein radiusθ_E, thus we only measure the minimum angular Einstein radius ${\theta }_{\mathrm{E},\min }$. From the Bayesian analysis, it is found that that the binary lens system is a binary star with masses of $(m_1,m_2)=(0.46_{-0.25}^{+0.35}{M}_{\odot },0.75_{-0.55}^{+0.67}{M}_{\odot })$at a distance of $D_{\mathrm{L}}=5.87_{-1.79}^{+1.21}$kpc, while the triple lens system is a brown dwarf or a massive giant planet in a low-mass binary-star system with masses of $(m_1,m_2,m_3)=(0.43_{-0.35}^{+0.41}{M}_{\odot },0.056_{-0.047}^{+0.055}{M}_{\odot }$, $20.84_{-17.04}^{+20.20}{M}_{\mathrm{J}})$at a distance of $D_{\mathrm{L}}=4.06_{-3.28}^{+1.39}$kpc, indicating a disk lens system. The 2L2S model yields the relative lens-source proper motion ofμ_rel ≥ 4.6 mas yr⁻¹that is consistent with the Bayesian result, whereas the 3L1S model yieldsμ_rel ≥ 18.9 mas yr⁻¹, which is more than three times larger than that of a typical disk object of ∼6 mas yr⁻¹and thus is not consistent with the Bayesian result. This suggests that the event is likely caused by the binary-lens binary-source model. 

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3. Atmospheric Characterization of the Super-Jupiter HIP 99770 b with KPIC

   https://doi.org/10.3847/1538-3881/ad6609  

   Zhang, Yapeng; Xuan, Jerry W; Mawet, Dimitri; Wang, Jason J; Hsu, Chih-Chun; Ruffio, Jean-Bapiste; Knutson, Heather A; Inglis, Julie; Blake, Geoffrey A; Chachan, Yayaati; et al (August 2024, The Astronomical Journal)

   Abstract Young, self-luminous super-Jovian companions discovered by direct imaging provide a challenging test for planet formation and evolution theories. By spectroscopically characterizing the atmospheric compositions of these super-Jupiters, we can constrain their formation histories. Here we present studies of the recently discovered HIP 99770 b, a 16M_Juphigh-contrast companion on a 17 au orbit, using the fiber-fed high-resolution spectrograph KPIC ( $\mathcal{R}$∼ 35,000) on the Keck II telescope. OurK-band observations led to detections of H₂O and CO in the atmosphere of HIP 99770 b. We carried out free retrieval analyses usingpetitRADTRANSto measure its chemical abundances, including the metallicity and C/O ratio, projected rotation velocity ( $v\sin i$), and radial velocity (RV). We found that the companion’s atmosphere has C/O $={0.55}_{-0.04}^{+0.06}$and [M/H] $={0.26}_{-0.23}^{+0.24}$(1σconfidence intervals), values consistent with those of the Sun and with a companion formation via gravitational instability or core accretion. The projected rotation velocity $v\sin \left(i\right)<7.8$km s⁻¹is small relative to other directly imaged companions with similar masses and ages. This may imply a nearly pole-on orientation or effective magnetic braking by a circumplanetary disk. In addition, we added the companion-to-primary relative RV measurement to the orbital fitting and obtained updated constraints on orbital parameters. Detailed characterization of super-Jovian companions within 20 au like HIP 99770 b is critical for understanding the formation histories of this population. 

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4. Detection and Bulk Properties of the HR 8799 Planets with High-resolution Spectroscopy

   https://doi.org/10.3847/1538-3881/ac1349  

   Wang 王, Jason J. 劲飞; Ruffio, Jean-Baptiste; Morris, Evan; Delorme, Jacques-Robert; Jovanovic, Nemanja; Pezzato, Jacklyn; Echeverri, Daniel; Finnerty, Luke; Hood, Callie; Zanazzi, J. J.; et al (September 2021, The Astronomical Journal)

   Abstract Using the Keck Planet Imager and Characterizer, we obtained high-resolution (R∼ 35,000)K-band spectra of the four planets orbiting HR 8799. We clearly detected H₂O and CO in the atmospheres of HR 8799 c, d, and e, and tentatively detected a combination of CO and H₂O in b. These are the most challenging directly imaged exoplanets that have been observed at high spectral resolution to date when considering both their angular separations and flux ratios. We developed a forward-modeling framework that allows us to jointly fit the spectra of the planets and the diffracted starlight simultaneously in a likelihood-based approach and obtained posterior probabilities on their effective temperatures, surface gravities, radial velocities, and spins. We measured $v\sin \left(i\right)$values of ${10.1}_{-2.7}^{+2.8}\mathrm{km}{\mathrm{s}}^{-1}$for HR 8799 d and ${15.0}_{-2.6}^{+2.3}\mathrm{km}{\mathrm{s}}^{-1}$for HR 8799 e, and placed an upper limit of <14 km s⁻¹of HR 8799 c. Under two different assumptions of their obliquities, we found tentative evidence that rotation velocity is anticorrelated with companion mass, which could indicate that magnetic braking with a circumplanetary disk at early times is less efficient at spinning down lower-mass planets. 

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5. Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-velocity Characterization

   https://doi.org/10.3847/1538-3881/ad5203  

   Wu, Zexuan; Dong, Subo; Yi, Tuan; Liu, Zhuokai; El-Badry, Kareem; Gould, Andrew; Wyrzykowski, L; Rybicki, K A; Bachelet, Etienne; Christie, Grant W; et al (July 2024, The Astronomical Journal)

   Abstract We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with $M_{\mathrm{p}}={0.59}_{-0.05}^{+0.15}{M}_{\mathrm{J}}$at a projected orbital separation $r_{\perp }={1.4}_{-0.3}^{+0.8}$au, and the host is a ∼1.1M_⊙turnoff star at ∼1.3 kpc. At $r\prime \approx 14$, the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet’s orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the “inner–outer correlation” inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radiusθ_Ebut also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system. 

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