We investigate angular momentum transport and accretion properties in a sample of protoplanetary discs with dynamical measurements of stellar masses, disc masses, and scale radii. From these data we infer effective alpha-viscosities, finding a remarkably broad range spanning over three orders of magnitude. This spread correlates with the stellar rotation period: systems with shorter periods exhibit significantly lower accretion rates, suggesting that they are undergoing at least temporary episodes of accretion bottleneck. We interpret this behaviour within the framework of magnetospheric accretion models, where the transition between steady accretion and the propeller regime is set by the relative locations of the co-rotation and magnetospheric radii. Our results indicate that stellar spin is a key parameter in regulating mass transfer from the disc to the star, and provide new evidence that the observed dispersion in alpha reflects transitions between distinct accretion states rather than differences in global disc properties.

The last decade has witnessed remarkable advances in the characterization of the (sub-)millimeter emission from planet-forming disks. Conversely, the study of (sub-)centimeter emission has made more limited progress, to the point that only a few exceptional disk-bearing objects have been characterized in the centimeter regime. This work takes a broad view of the centimeter emission from a large sample with Karl G. Jansky Very Large Array (VLA) observations that is selected from previous Atacama Large (sub-)Millimeter Array (ALMA) surveys of more representative disks in brightness and extent . We report on the detection and characterization of flux at centimeter wavelengths from 21 sources in the Taurus star-forming region. Complemented by literature and archival data, the entire photometry from 0.85 mm to 6 cm is fit by a two-component model that determines the ubiquitous presence of free-free emission entangled with the dust emission. The flux density of the free-free emission is found to scale with the accretion rate but is independent of the outer-disk morphology depicted by ALMA. The dust emission at 2 cm is still appreciable and offers the possibility to extract an unprecedented large set of dust spectral indices in the centimeter regime. A pronounced change between the median millimeter indices (2.3) and centimeter indices (2.8) suggests that a large portion of the disk emission is optically thick up to 3 mm. The comparison of both indices and fluxes with the ALMA disk extent indicates that this portion can be as large as 40 au and suggests that the grain population within this disk region that emits the observed centimeter emission is similar in disks with different sizes and morphologies. All these results await confirmation and dedicated dust modeling once facilities such as next generation VLA (ngVLA) or Square Kilometre Array (SKA)-mid are able to resolve the centimeter emission from planet-forming disks and disentangle the various components.

(Abridged) We present high angular resolution and sensitivity ALMA 3.1 mm and VLA 9.1 mm observations of the disc around CI Tau. These new data were combined with similar-resolution archival ALMA 0.9 and 1.3 mm observations and new and archival VLA 7.1 mm, 2.0, 3.0, and 6.0 cm photometry to study the properties of dust in this system. At wavelengths <3.1 mm, CI Tau's continuum emission is very extended and highly substructured (with three gaps, four rings, and two additional gap-ring pairs identified by non-parametric visibility modelling). Instead, the VLA 9.1 mm data are dominated by a bright central component, only partially (< 50

The European Space Agency has selected PLATO (PLAnetary Transits and Oscillations of stars) for its M3 launch which is scheduled for 2026. With its extremely large field of view, PLATO is designed to obtain photometric measurements over an extended period for bright stars in order to detect and characterise (primarily) rocky planets in the habitable zones of solar type stars. The PLATO measurements will have sufficient sensitivity to determine the mass, radius and age of the host stars with unprecedented accuracy. The PLATO planet database will provide the first large-scale catalogue of accurately and homogeneously characterised small planets at intermediate orbital periods, which will can be used to severely constraint planet formation theories. This would facilitate large scale comparative exo-planetology. In addition the bright PLATO host stars will be ideal targets for atmospheric study with next generation facilities such as the ELT. The PLATO sensitivity will be sufficient to detect pulsations from stars across the HR diagram allowing a deep understanding of stellar structure and evolution to be developed using parameters determined from asteroseismology.

Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.

Young protoplanetary discs are expected to be gravitationally unstable, which can drive angular momentum transport as well as be a potential mechanism for planet formation. Gravitational instability is most prevalent in the outer disc where cooling timescales are short. At large radii, stellar irradiation makes a significant contribution to disc heating and is expected to suppress instability. In this study, we compare two models of implementing irradiation in 2D hydrodynamic simulations of self-gravitating discs: supplying a constant heating rate per unit mass and per unit area of the disc. In the former case, instability is quenched once the stellar irradiation becomes the dominant heating source. In the latter case, we find instability persists under high levels of irradiation, despite large values of the Toomre Q parameter, in agreement with analytic predictions. Fragmentation was able to occur in this regime with the critical cooling timescale required decreasing as irradiation is increased, corresponding to a maximum threshold for the viscosity parameter: $\alpha\sim0.03-0.09$.

The variation in hot Jupiter (HJ) occurrence across stellar environments holds clues as to the dominant formation channels of these extreme planets. Recent studies suggest HJ hosts preferentially reside in regions of high-phase space density, possibly reflecting natal environmental conditions. These regions are kinematically cold (|v| < 40kms(-1)), prompting the alternative hypothesis that the correlation reflects an age bias: planetary systems in overdensities are systematically younger and therefore less likely to have undergone tidal inspiral and destruction. We test whether the apparent excess of HJs in phase space overdensities arises from differences in intrinsic host properties-mass, metallicity, and age-which may correlate with phase space density or whether there is evidence for an additional environmental effect. We derive homogeneous estimates for the mass, metallicity, and age of planet-hosting stars using Two Micron All-Sky Survey (2MASS) and Gaia DR3 photometry, parallaxes, and self-consistent spectroscopic and spectrophotometric observables. In a sample of 2265 confirmed exoplanet hosts, we find a significant relative excess of HJs orbiting stars in overdense regions. However, we also find that overdensities preferentially host younger, more massive, and more metal-rich stars compared to underdensities. After correcting for these differences, either by detrending the phase space density against age or by matching host properties across subsamples, we find no significant differences in the HJ populations between over-and underdense regions. Our results suggest that the previously reported correlation between HJ occurrence and phase space density is driven by underlying differences in host star demographics rather than an intrinsic environmental effect.

The detection of planets in protoplanetary disks has proven to be extremely challenging. By contrast, rings and gaps, usually attributed to planet-disk interactions, have been found in virtually every large protoplanetary (Class II) disk observed at 0.9-1.3 mm with sufficient spatial resolution (5 au). The nearby disk around MP Mus (PDS 66) stands as an exception to this rule, and its advanced age (7-10 Myr) is particularly difficult to reconcile with its apparent lack of substructures. Despite the disk's smooth appearance, Gaia data of MP Mus show a significant proper motion anomaly, signalling the presence of a companion. Here we present ALMA 3-mm observations of the system with high spatial resolution comparable to previous 1.3-mm data. The new observations pierce deeper into the disk midplane and reveal an inner cavity (<3 au) and a ring at 10 au. The disk structure inferred from ALMA observations narrows down the properties of the companion to a gas giant orbiting at 1-3 au, and hydrodynamic simulations further confirm that such a planet can produce the observed cavity. These independent pieces of evidence constitute an indirect but compelling detection of an exoplanet within a protoplanetary disk using Gaia astrometry. The detection of dust substructures in MP Mus, thanks to the lower optical depths at longer wavelengths, suggests that rings and gaps are even more abundant than previously thought.

The size, density, and chemical characteristics of solar system bodies have been shaped by material transport during the protoplanetary disk stage. This includes transport from the inner to outer solar system of refractory dust grains that carry nucleosynthetic anomalies. Here, we show that rare earth element (REE) isotopes in fine-grained calcium-aluminum-rich inclusions (CAIs) display anomalies stemming from incomplete mixing of r-, s-, and p-process nucleosynthesis. The data points define two correlations, which are best explained by mixing between three isotopic reservoirs in two successive stages, one of which involved a variable admixture of a p-process component. We propose that CAI precursors formed in the inner solar system and were subsequently transported by FU Orionis outbursts from the disk to the envelope where they mixed with an isotopically distinct reservoir before settling on the midplane.

Understanding when and how circumstellar disks disperse is crucial to constrain planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (~3-6 km/s) blue-shifts in [Ne II] 12.81 um lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (~30 au in radius) and blue-shifted [Ne II] emission. We detect four forbidden noble gas lines, [Ar II], [Ar III], [Ne II], and [Ne III], of which [Ar III] is the first detection in any protoplanetary disk. We use line flux ratios to constrain the energy of the ionizing photons and find that Argon is ionized by EUV whereas Neon is most likely ionized by X-rays. After performing continuum and Point Spread Function (PSF) subtraction on the IFU cube, we discover a spatial extension in the [Ne II] emission off the disk continuum emission. This is the first spatially resolved [Ne II] disk wind emission. The mostly ionic spectrum of T Cha, in combination with the extended [Ne II] emission, points to an evolved stage for any inner MHD wind and is consistent with the existence of an outer thermal wind ionized and driven by high-energy stellar photons. This work acts as a pathfinder for future observations aiming at investigating disk dispersal using JWST.

Vertical gas and dust flows in protoplanetary discs waft material above the mid-plane region in the presence of a protoplanet. This motion may alter the delivery of dust to the planet and its circumplanetary disc, as well as through a planetary-induced gap region and hence the inner disc chemistry. Here, we investigate the impact of a massive embedded planet on this material transport through the gap region. We use 3D global hydrodynamic simulations run using FARGO3D with gas and dust species to investigate the dust filtration and the origin of material that can make it through the gap. We find small dust particles can pass through the gap as expected from results in 2D and that this can be considered in two parts - filtering due to the planetary-induced pressure maximum and filtering due to accretion on to the planet. When gas accretion on to the planet is included, we find that the larger dust grains that cross the gap (i.e. those with $\mathrm{St} \sim 10<^>{-4}$) originate from regions near the mid-plane. We also find that dust and gas that enter the planet-carved gap region pass through the Hill sphere of the planet, where the temperature is likely to be strongly enhanced compared with the mid-plane regions from which this material originated. Considering the application of our simulations to a Jupiter-mass planet at $\sim 100\ \mathrm{au}$, this suggests that CO ice is very likely to desorb from grains in the close proximity of the planet, without requiring any fine-tuning of the planet's location with respect to the CO snowline.

Context. With a mass exceeding several 10^4 solar masses and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions among stars. Aims. In this paper we present the "Extended Westerlund 1 and 2 Open Clusters Survey" (EWOCS) project, which aims to investigate the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars. The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun. Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically, the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec. Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation were carried out using the ACIS-Extract software. Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a photon flux threshold of approximately 2x10^-8 photons/cm^2/s. The X-ray sources exhibit a highly concentrated spatial distribution, with 1075 sources located within the central 1 arcminute. We have successfully detected X-ray emissions from 126 out of the 166 known massive stars of the cluster, and we have collected over 71000 photons from the magnetar CXO J164710.20-455217

Gravitational instability is thought to be one of the main drivers of angular momentum transport in young protoplanetary discs. The disc around Elias 2-27 offers a unique example of gravitational instability at work. It is young and massive, displaying two prominent spiral arms in dust continuum emission and global non-axisymmetric kinematic signatures in molecular line data. In this work, we used archival ALMA observations of (CO)-C-13 line emission to measure the efficiency of angular momentum transport in the Elias 2-27 system through the kinematic signatures generated by gravitational instability, known as "GI wiggles". Assuming the angular momentum is transported by the observed spiral structure and leveraging previously-derived dynamical disc mass measurements, the amount of angular momentum transport we found corresponds to an alpha-viscosity of alpha = 0.038 +/- 0.018. This value implies an accretion rate onto the central star of log(10) (M) over dot(star) = -6.99 +/- 0.17 M-circle dot yr(-1), which reproduces the one observed value of log(10) (M) over dot(star,obs) = -7.2 +/- 0.5 M-circle dot yr(-1) very well. The excellent agreement we have found serves as further proof that gravitational instability is the main driver of angular momentum transport acting in this system.

Context: Photoevaporation is an important process for protoplanetary disc dispersal but there has so far been a lack of consensus from simulations over the mass-loss rates and the most important part of the high-energy spectrum for driving the wind. Aims: We aim to isolate the origins of these discrepancies through carefully-benchmarked hydrodynamic simulations of X-ray photoevaporation with time-dependent thermochemistry calculated on the fly. Methods: We conduct hydrodynamic simulations with pluto where the thermochemistry is calculated using prizmo. We explore the contribution of certain key microphysical processes and the impact of using different spectra used previously in literature studies. Results: We find that additional cooling results from the excitation of O by neutral H, which leads to dramatically reduced mass-loss across the disc compared to previous X-ray photoevaporation models, with an integrated rate of 10^-9 Msun/yr. Such rates would allow for longer-lived discs than previously expected from population synthesis. An alternative spectrum with less soft X-ray produces mass-loss rates around a factor of 2-3 times lower. The chemistry is significantly out of equilibrium, with the survival of H2 into the wind aided by advection. This leads to its role as the dominant coolant at 10s au - thus stabilising a larger radial temperature gradient across the wind - as well as providing a possible wind tracer.

While high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations reveal a wealth of substructure in protoplanetary disks, they remain incapable of resolving the types of small-scale dust structures predicted, for example, by numerical simulations of the streaming instability. In this article, we propose a method to find evidence for unresolved, optically thick dusty rings in protoplanetary disks. We demonstrate that, in presence of unresolved rings, the brightness of an inclined disk exhibits a distinctive emission peak at the minor axis. Furthermore, the azimuthal brightness depends on both the geometry of the rings and the dust optical properties; we can therefore use the azimuthal brightness variations to both detect unresolved rings and probe their properties. By analyzing the azimuthal brightness in the test case of ringlike substructures formed by streaming instability, we show that the resulting peak is likely detectable by ALMA for typical disk parameters. Moreover, we present an analytic model that not only qualitatively but also quantitatively reproduces the peak found in the simulations, validating its applicability to infer the presence of unresolved rings in observations and characterize their optical properties and shape. This will contribute to the identification of disk regions where streaming instability (and thus planet formation) is occurring.

Atacama Large Millimetre/submillimetre Array (ALMA) observations of the thermal emission from protoplanetary disc dust have revealed a wealth of substructures that could evidence embedded planets, but planet-driven spirals, one of the more compelling lines of evidence, remain relatively rare. Existing works have focused on detecting these spirals using methods that operate in image space. Here, we explore the planet detection capabilities of fitting planet-driven spirals to disc observations directly in visibility space. We test our method on synthetic ALMA observations of planet-containing model discs for a range of disc/observational parameters, finding it significantly outperforms image residuals in identifying spirals in these observations and is able to identify spirals in regions of the parameter space in which no gaps are detected. These tests suggest that a visibility-space fitting approach warrants further investigation and may be able to find planet-driven spirals in observations that have not yet been found with existing approaches. We also test our method on six discs in the Taurus molecular cloud observed with ALMA at 1.33 mm, but find no evidence for planet-driven spirals. We find that the minimum planet masses necessary to drive detectable spirals range from approximate to 0.03 to 0.5M(Jup) over orbital radii of 10-100 au, with planet masses below these thresholds potentially hiding in such disc observations. Conversely, we suggest that planets greater than or similar to 0.5-1 M-Jup can likely be ruled out over orbital radii of approximate to 20-60au on the grounds that we would have detected them if they were present.

[Ne ii ] 12.81 μ m emission is a well-used tracer of protoplanetary disk winds due to its blueshifted line profile. Mid-Infrared Instrument (MIRI)-Medium Resolution Spectrometer (MRS) recently observed T Cha, detecting this line along with lines of [Ne iii ], [Ar ii ], and [Ar iii ], with the [Ne ii ] and [Ne iii ] lines found to be extended while the [Ar ii ] was not. In this complementary work, we use these lines to address long-debated questions about protoplanetary disk winds regarding their mass-loss rate, the origin of their ionization, and the role of magnetically driven winds as opposed to photoevaporation. To this end, we perform photoionization radiative transfer on simple hydrodynamic wind models to map the line emission. We compare the integrated model luminosities to those observed with MIRI-MRS to identify which models most closely reproduce the data and produce synthetic images from these to understand what information is captured by measurements of the line extents. Along with the low degree of ionization implied by the line ratios, the relative compactness of [Ar ii ] compared to [Ne ii ] is particularly constraining. This requires Ne ii production by hard X-rays and Ar ii production by soft X-rays (and/or EUV) in an extended (≳10 au) wind that is shielded from soft X-rays, necessitating a dense wind with material launched on scales down to ∼1 au. Such conditions could be produced by photoevaporation, whereas an extended magnetohydrodynamic (MHD) wind producing equal shielding would likely underpredict the line fluxes. However, a tenuous inner MHD wind may still contribute to shielding the extended wind. This picture is consistent with constraints from spectrally resolved line profiles.

Crescent-shaped asymmetries are common in millimetre observations of protoplanetary discs and are usually attributed to vortices or dust overdensities. However, they often appear on a single side of the major axis and roughly symmetric about the minor axis, suggesting a geometric origin. In this work, we interpret such asymmetries as emission from the exposed inner cavity walls of inclined discs and use them to characterise their vertical extent. Here we focus on the discs around CIDA 9 and RY Tau, first modelling their observations in visibility space with a simple geometric prescription for the walls, and then exploring more detailed radiative transfer models. Accounting for the wall emission yields significantly better residuals than purely axisymmetric models, and we estimate the dust scale height of these systems to be 0.4 au at 37 au for CIDA 9 and 0.2 au at 12 au for RY Tau. Finally, we identify crescent-shaped asymmetries in twelve discs, nine of which have constraints on their orientation - in all cases, the asymmetry appears on the far-side of the disc, lending support to the hypothesis that they are due to their inner rims. Modelling this effect in larger samples of discs will help to build a statistical view of their vertical structure.

Protoplanetary disks emit radiation across a broad range of wavelengths, requiring a multiwavelength approach to fully understand their physical mechanisms and how they form planets. Observations at sub-millimeter to centimeter wavelengths can provide insights into the thermal emission from dust, free-free emission from ionized gas, and possible gyro-synchrotron emission from the stellar magnetosphere. This work is focused on CX Tau, a ${\sim}0.4\,M_\odot$ star with an extended gas emission and a compact and apparently structureless dust disk, with an average millimeter flux when compared to Class II sources in Taurus. We present observations from the Karl G. Jansky Very Large Array (VLA) across four bands (between 9.0 mm and 6.0 cm) and combine them with archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), the Submillimeter Array (SMA) and the Plateau de Bure Interferometer (PdBI). This multiwavelength approach allows us to separate the dust continuum from other emissions. After isolating the dust thermal emission, we derived an upper limit of the dust disk extent at 1.3 cm which is consistent with theoretical predictions of a radial drift-dominated disk. Centimeter data show a peculiar behavior: deep observations at 6.0 cm did not detect the source, while at 1.3 cm the flux density is anomalously higher than adjacent bands. Intraband spectral indices suggest a dominant contribution from free-free emission, whereas gyro-synchrotron emission is excluded. To explain these observations, we propose a strong variability among the free-free emission with timescales shorter than a month. Another possible interpretation is the presence of anomalous microwave emission from spinning dust grains.