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1. ALMA Discovery of a Disk around the Planetary-mass Companion SR 12 c

   https://doi.org/10.3847/2041-8213/ac6420  

   Wu, Ya-Lin; Bowler, Brendan P.; Sheehan, Patrick D.; Close, Laird M.; Eisner, Joshua A.; Best, William M.; Ward-Duong, Kimberly; Zhu, Zhaohuan; Kraus, Adam L. (April 2022, The Astrophysical Journal Letters)

   Abstract We report an Atacama Large Millimeter/submillimeter Array 0.88 mm (Band 7) continuum detection of the accretion disk around SR 12 c, an ∼11 M Jup planetary-mass companion (PMC) orbiting its host binary at 980 au. This is the first submillimeter detection of a circumplanetary disk around a wide PMC. The disk has a flux density of 127 ± 14 μ Jy and is not resolved by the ∼0.″1 beam, so the dust disk radius is likely less than 5 au and can be much smaller if the dust continuum is optically thick. If, however, the dust emission is optically thin, then the SR 12 c disk has a comparable dust mass to the circumplanetary disk around PDS 70 c but is about five times lower than that of the ∼12 M Jup free-floating OTS 44. This suggests that disks around bound and unbound planetary-mass objects can span a wide range of masses. The gas mass estimated with an accretion rate of 10 −11 M ☉ yr −1 implies a gas-to-dust ratio higher than 100. If cloud absorption is not significant, a nondetection of 12 CO(3–2) implies a compact gas disk around SR 12 c. Future sensitive observations may detect more PMC disks at 0.88 mm flux densities of ≲100 μ Jy. 

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2. Hints of Planet Formation Signatures in a Large-cavity Disk Studied in the AGE-PRO ALMA Large Program

   https://doi.org/10.3847/1538-4357/ad6e73  

   Sierra, Anibal; Pérez, Laura M; Agurto-Gangas, Carolina; Miley, James; Zhang, Ke; Pinilla, Paola; Pascucci, Ilaria; Trapman, Leon; Kurtovic, Nicolas; Vioque, Miguel; et al (October 2024, The Astrophysical Journal)

   Abstract Detecting planet signatures in protoplanetary disks is fundamental to understanding how and where planets form. In this work, we report dust and gas observational hints of planet formation in the disk around 2MASS J16120668-301027, as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program “AGE-PRO: ALMA survey of Gas Evolution in Protoplanetary disks.” The disk was imaged with the ALMA at Band 6 (1.3 mm) in dust continuum emission and four molecular lines:¹²CO(J= 2–1),¹³CO(J= 2–1), C¹⁸O(J= 2–1), and H₂CO(J= 3_(3,0)–2_(2,0)). Resolved observations of the dust continuum emission (angular resolution of ∼150 mas, 20 au) show a ring-like structure with a peak at 0.″57 (75 au), a deep gap with a minimum at 0.″24 (31 au), an inner disk, a bridge connecting the inner disk and the outer ring, along with a spiral arm structure, and a tentative detection (to 3σ) of a compact emission at the center of the disk gap, with an estimated dust mass of ∼2.7−12.9 Lunar masses. We also detected a kinematic kink (not coincident with any dust substructure) through several¹²CO channel maps (angular resolution ∼200 mas, 30 au), located at a radius of ∼0.″875 (115.6 au). After modeling the¹²CO velocity rotation around the protostar, we identified a purple tentative rotating-like structure at the kink location with a geometry similar to that of the disk. We discuss potential explanations for the dust and gas substructures observed in the disk and their potential connection to signatures of planet formation. 

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3. Detection of Near-infrared Water Ice at the Surface of the (Pre)Transitional Disk of AB Aur: Informing Icy Grain Abundance, Composition, and Size

   https://doi.org/10.3847/1538-3881/ac4d9b  

   Betti, S. K.; Follette, K.; Jorquera, S.; Duchêne, G.; Mazoyer, J.; Bonnefoy, M.; Chauvin, G.; Pérez, L. M.; Boccaletti, A.; Pinte, C.; et al (March 2022, The Astronomical Journal)

   Abstract We present near-infrared Large Binocular Telescope LMIRCam imagery of the disk around the Herbig Ae/Be star AB Aurigae. A comparison of the surface brightness at K s (2.16 μ m), H 2 O narrowband (3.08 μ m), and L ′ (3.7 μ m) allows us to probe the presence of icy grains in this (pre)transitional disk environment. By applying reference differential imaging point-spread function subtraction, we detect the disk at high signal-to-noise ratios in all three bands. We find strong morphological differences between the bands, including asymmetries consistent with the observed spiral arms within 100 au in L ′ . An apparent deficit of scattered light at 3.08 μ m relative to the bracketing wavelengths ( K s and L ′ ) is evocative of ice absorption at the disk surface layer. However, the Δ( K s − H 2 O) color is consistent with grains with little to no ice (0%–5% by mass). The Δ ( H 2 O − L ′ ) color, conversely, suggests grains with a much higher ice mass fraction (∼0.68), and the two colors cannot be reconciled under a single grain population model. Additionally, we find that the extremely red Δ ( K s − L ′ ) disk color cannot be reproduced under conventional scattered light modeling with any combination of grain parameters or reasonable local extinction values. We hypothesize that the scattering surfaces at the three wavelengths are not colocated, and that the optical depth effects in each wavelength result from probing the grain population at different disk surface depths. The morphological similarity between K s and H 2 O suggests that their scattering surfaces are near one another, lending credence to the Δ( K s − H 2 O) disk color constraint of <5% ice mass fraction for the outermost scattering disk layer. 

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4. A Radially Broad Collisional Cascade in the Debris Disk of γ Ophiuchi Observed by JWST

   https://doi.org/10.3847/1538-4357/ae6ef7  

   Han, Yinuo; Wyatt, Mark; Su, Kate_Y L; Sefilian, Antranik A; Lovell, Joshua B; del_Burgo, Carlos; Marshall, Jonathan P; Marino, Sebastian; Wilner, David J; Matthews, Brenda C; et al (June 2026, The Astrophysical Journal)

   Abstract The A1V starγ Oph, at a distance of 29.7 pc, is known from Spitzer imaging to host a debris disk with a large radial extent and from its spectral energy distribution to host inner warm dust. We imagedγ Oph with the James Webb Space Telescope (JWST)/Mid-InfraRed Instrument at 15 and 25.5μm, revealing smooth and radially broad emission that extends to a radius of at least 250 au at 25.5μm. In contrast to JWST findings of an inner small-grain component with distinct ringed structures in Fomalhaut and Vega, the mid-infrared radial profile combined with prior Atacama Large Millimeter/submillimeter Array imaging suggests a radially broad steady-state collisional cascade with the same grain size distribution throughout the disk. This further suggests that the system is populated by a radially broad planetesimal belt from tens of astronomical units or less to well over 200 au, rather than a narrow planetesimal belt from which the observed dust is displaced to appear broad. The disk is also found to be asymmetric, which could be modeled by a stellocentric offset corresponding to a small eccentricity of ∼0.03. Such a disk eccentricity could be induced by a mildly eccentric <10M_Jupgiant planet outside 10 au, or a more eccentric companion up to stellar mass at a few astronomical units, without producing a resolvable radial gap in the disk. 

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5. Annular substructures in the transition disks around LkCa 15 and J1610

   https://doi.org/10.1051/0004-6361/202038027  

   Facchini, S.; Benisty, M.; Bae, J.; Loomis, R.; Perez, L.; Ansdell, M.; Mayama, S.; Pinilla, P.; Teague, R.; Isella, A.; et al (July 2020, Astronomy & Astrophysics)

   We present high-resolution millimeter continuum ALMA observations of the disks around the T Tauri stars LkCa 15 and 2MASS J16100501-2132318 (hereafter, J1610). These transition disks host dust-depleted inner regions, which have possibly been carved by massive planets, and they are of prime interest to the study of the imprints of planet-disk interactions. While at moderate angular resolution, they appear as a broad ring surrounding a cavity, the continuum emission resolves into multiple rings at a resolution of ~60 × 40 mas (~7.5 au for LkCa 15, ~6 au for J1610) and ~7 μ Jy beam −1 rms at 1.3 mm. In addition to a broad extended component, LkCa 15 and J1610 host three and two narrow rings, respectively, with two bright rings in LkCa 15 being radially resolved. LkCa 15 possibly hosts another faint ring close to the outer edge of the mm emission. The rings look marginally optically thick, with peak optical depths of ~0.5 (neglecting scattering), in agreement with high angular resolution observations of full disks. We performed hydrodynamical simulations with an embedded, sub-Jovian-mass planet and show that the observed multi-ringed substructure can be qualitatively explained as the outcome of the planet-disk interaction. We note, however, that the choice of the disk cooling timescale alone can significantly impact the resulting gas and dust distributions around the planet, leading to different numbers of rings and gaps and different spacings between them. We propose that the massive outer disk regions of transition disks are favorable places for planetesimals, and possibly second-generation planet formation of objects with a lower mass than the planets carving the inner cavity (typically few M Jup ), and that the annular substructures observed in LkCa 15 and J1610 may be indicative of planetary core formation within dust-rich pressure traps. Current observations are compatible with other mechanisms contributing to the origin of the observed substructures, in particular with regard to narrow rings generated (or facilitated) at the edge of the CO and N 2 snowlines. 

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