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Abstract Variability of millimeter wavelength continuum emission from Class II protoplanetary disks is extremely rare, and when detected, it is usually interpreted as originating from nonthermal emission mechanisms that relate to the host star itself rather than its disk. During observations made as part of the AGE-PRO Large Program, significant variability in the brightness of the 2MASS J16202863-2442087 system was detected between individual executions. We report the observed properties of the variability detected at millimeter wavelengths and investigate potential driving mechanisms. To investigate the nature of the variability, we construct a light curve from the continuum observations and analyze images constructed from both flaring and quiescent emission. We characterize the dust disk around the star through analysis in the image and visibility plane, and carry out kinematic analysis of CO (2–1) emission from the gas disk. The continuum flux decays by a factor of 8 in less than an hour, and by a factor of 13 within 8 days. The peak brightness coincides with an expected brightness maximum extrapolated from the periodicity of previously observed optical variability. The flare is most likely the product of synchrotron emission in the close vicinity of the star. The nature of the millimeter flare closely resembles those detected in very close binary systems, and may be due to the interaction of magnetic fields in an as-yet undetected binary. Alternatively, if the central host is a single-star object, the flare may be due to the interaction of magnetic field loops at the stellar surface or a strong accretion burst. 

Abstract The ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program aims to trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks by using the Atacama Large Millimeter/submillimeter Array (ALMA). This paper presents Band-6 ALMA observations of 10 embedded (Class I and Flat Spectrum) sources in the Ophiuchus molecular cloud, with spectral types ranging from M3 to K6 stars, which serve as the evolutionary starting point in the AGE-PRO sample. While we find four nearly edge-on disks (≥70°), and three highly inclined disks (≥60°) in our sample, we show that, as a population, embedded disks in Ophiuchus are not significantly contaminated by more-evolved, but highly inclined sources. We derived dust disk masses from the Band-6 continuum and estimated gas disk masses from the C¹⁸OJ= 2−1 and C¹⁷OJ= 2−1 lines. The mass estimates from the C¹⁷O line are slightly higher, suggesting C¹⁸O emission might be partially optically thick. While the¹²CO and¹³CO lines are severely contaminated by extended emission and self-absorption, the C¹⁸O and C¹⁷O lines are allowed to trace the radial extent of the gaseous disks. From these measurements, we found that the C¹⁸OJ= 2−1 and C¹⁷OJ= 2−1 fluxes correlate well with each other and with the continuum fluxes. Furthermore, the C¹⁸O and C¹⁷O lines present a larger radial extension than disk dust sizes by factors ranging from ∼1.5 to ∼2.5, as is found for Class II disks using the radial extension of the¹²CO. In addition, we have detected outflows in three disks from¹²CO observations. 

Abstract Protoplanetary disk evolution can be deeply influenced by the UV radiation emitted by neighboring massive stars (mainly of spectral types O and B). We show that the process ofexternal photoevaporation, which causes an outside-in depletion of disk material due to environmental UV radiation, can lead to a significant decrease in disk size, disk mass, and lifetime even at moderate irradiation levels (1–10 G₀). In this work, we investigate the role of external photoevaporation in shaping the masses and sizes of the 10 AGE-PRO disks in the Upper Scorpius (Upper Sco) region, which we estimate to be subject to far-ultraviolet (FUV) fluxes ranging between ∼2 and ∼12 G₀, on average. We compare the disk masses and sizes resulting from 1D numerical viscous evolution simulations, in which the effect of external photoevaporation is included, to the values retrieved from the AGE-PRO observations. While the pure viscous framework fails in adequately explaining the observed disk properties in Upper Sco, with the inclusion of external photoevaporation, we can successfully reproduce gas disk sizes for seven out of 10 sources within a factor <2, when the initial disk mass is 1%–10% of the stellar mass. We emphasize the importance of accounting for the environmental irradiation when comparing star-forming regions of different ages, even when moderate FUV irradiation fields are experienced, as in the case of Upper Sco. 

Abstract The Atacama Large Millimeter/submillimeter Array (ALMA) large program AGE-PRO explores protoplanetary disk evolution by studying gas and dust across various ages. This work focuses on 10 evolved disks in Upper Scorpius, observed in dust continuum emission, CO and its isotopologues, and N₂H⁺with ALMA Bands 6 and 7. Disk radii, from the radial location enclosing 68% of the flux, are comparable to those in the younger Lupus region for both gas and dust tracers. However, solid masses are about an order of magnitude below those in Lupus and Ophiuchus, while the dust spectral index suggests some level of dust evolution. These empirical findings align with a combination of radial drift, dust trapping, and grain growth into larger bodies. A moderate correlation between CO and continuum fluxes suggests a link between gas and dust content, through the increased scatter compared to younger regions, possibly due to age variations, gas-to-dust ratio differences, or CO depletion. Additionally, the correlation between C¹⁸O and N₂H⁺fluxes observed in Lupus persists in Upper Scorpius, indicating a relatively stable CO gas abundance over the Class II stage of disk evolution. In conclusion, the AGE-PRO survey of Upper Scorpius disks reveals intriguing trends in disk evolution. The findings point toward potential gas evolution and the presence of dust traps in these older disks. Future high-resolution observations are needed to confirm these possibilities and further refine our understanding of disk evolution and planet formation in older environments. 

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. 

Abstract We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1.″4 from the star at a position angle of 161°), isolated via 13 CO J = 2−1 emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a 117 × 82 mas beam and manifests as a point source in 13 CO, indicating that its diameter is ≲14 au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using 12 CO and near-infrared scattered-light observations and is associated with localized velocity perturbations in 12 CO. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the 13 CO intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is ≳35 K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is ≳0.095 M Jup ≃ 30 M ⊕ adopting a standard 13 CO abundance. From the nondetection of millimeter continuum emission at the location of the CPD (3 σ flux density ≲26.4 μ Jy), we infer that the CPD dust mass is ≲0.027 M ⊕ ≃ 2.2 lunar masses, indicating a low dust-to-gas mass ratio of ≲9 × 10 −4 . We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion. 

ABSTRACT We present 1.3 mm continuum ALMA long-baseline observations at 3–5 au resolution of 10 of the brightest discs from the Ophiuchus DIsc Survey Employing ALMA (ODISEA) project. We identify a total of 26 narrow rings and gaps distributed in 8 sources and 3 discs with small dust cavities (r <10 au). We find that two discs around embedded protostars lack the clear gaps and rings that are ubiquitous in more evolved sources with Class II SEDs. Our sample includes five objects with previously known large dust cavities (r >20 au). We find that the 1.3 mm radial profiles of these objects are in good agreement with those produced by numerical simulations of dust evolution and planet–disc interactions, which predict the accumulation of mm-sized grains at the edges of planet-induced cavities. Our long-baseline observations resulted in the largest sample of discs observed at ∼3–5 au resolution in any given star-forming region (15 objects when combined with Ophiuchus objects in the DSHARP Large Program) and allow for a demographic study of the brightest $$\sim\! 5{{\ \rm per\ cent}}$$ of the discs in Ophiuchus (i.e. the most likely formation sites of giant planets in the cloud). We use this unique sample to propose an evolutionary sequence and discuss a scenario in which the substructures observed in massive protoplanetary discs are mainly the result of planet formation and dust evolution. If this scenario is correct, the detailed study of disc substructures might provide a window to investigate a population of planets that remains mostly undetectable by other techniques.