Myriam Benisty

We report the updated orbital solution for the spectroscopic binary WISPIT 2 based on 17 spectra collected with VLT/X-Shooter and the MPG/ESO 2.2 m FEROS spectrograph. The addition of ten new FEROS epochs extends the observational baseline to 144 days. Our new orbital parameters yield a period of P = 4.8026 ± 0.0001 days, a radial velocity (RV) semiamplitude of K ₁ = 26.665 ± 0.014 km s ⁻¹ , a systemic velocity of V ₀ = 5.81 ± 0.01 km s ⁻¹ , and a non-zero eccentricity of e = 0.0079 ± 0.0004 with argument of periastron ω = 9 . ° 81 ± 1 . ° 65 . Adopting a total disk dynamical mass range between 1.30 and 1.39 M _⊙ at an inclination of i = 45 . ° 66 , these results resolve the individual components to M ₁ = 0.95–1.02 M _⊙ and M ₂ = 0.35–0.37 M _⊙ ( q = 0.36–0.37), providing better estimates for the evolutionary stage of the system, ongoing accretion line studies, and circumbinary disk modeling.

Water and methanol are the fundamental constituents of interstellar and cometary ices; understanding their abundances in disks is therefore of high importance to reveal how this ice reservoir evolves across the timeline of star and planet formation. We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 5 line emission observations of water and methanol in the warm Herbig disks of HD 100546 and IRS 48. While the IRS 48 disk is methanol-rich, water vapor is not detected, implying a high methanol-to-water column density ratio of >0.2, possibly reflecting a distinct ice composition. Methanol and water are both detected in the HD 100546 disk, leading to a CH ₃ OH/H ₂ O ratio of ∼0.02, consistent with the median of the cometary distribution and with the lower edge of the distribution of young stellar objects (YSOs). We suggest that the gas-phase methanol-to-water ratio in the HD 100546 disk directly reveals the ice reservoir subsequently sublimated in the warm disk stage. Moreover, we report a methyl formate-to-methanol ratio in the IRS 48 disk of ∼0.2, consistent with the upper edge of the distribution of YSOs. The methyl formate-to-methanol ratio in the HD 100546 disk is ∼2, much higher than in younger and older sources, possibly reflecting a chemical enhancement of gas-phase methyl formate. We additionally constrain non-LTE conditions, optical depths, and emitting regions of the methanol lines in both disks. These results offer a new opportunity to probe the chemical trail of molecular complexity in the intermediate-disk stage, bridging early and late phases of the star and planet formation history.

Context . Herbig stars are intermediate mass pre-main sequence stars of 1.5 to ∼15 M _⊙ and are between low- and high-mass star formation. Despite the giant exoplanet occurrence rate peaking at intermediate mass stars, a systematic analysis of the complete known Herbig star and protoplanetary disk population is lacking. Aims . This work provides a catalog of all 243 known bona fide Herbig stars with clear infrared excess and in many cases accretion signatures within 1 kpc. It contains archival, recalibrated, and newly derived stellar parameters, accretion rate properties, and disk dust mass measurements. With these, we aim to examine the Herbig star relationship between the accretion rate and the stellar and disk dust mass, get an estimate for the completeness of our catalog, and obtain an estimate of the lifetime of a Herbig star. These relationships and disk dust masses are put into the context of T Tauri stars and the giant exoplanet population. Methods . We revised the stellar masses, radii, and ages using a Hertzsprung-Russell diagram, and computed new accretion rates for part of our sample. We derived dust masses for all targets using a combination of newly obtained millimeter photometry (60% of the targets) and literature values, from a combination of ALMA, ACA, SMA, and NOEMA data. Results . We find that 50% of Herbig dust disks are more massive than 10 M _⊕ , while this is only true for 20% and 5% of the T Tauri disks in Lupus and Upper Scorpius, respectively. Furthermore, the Herbig disk dust mass distribution is bimodal; it consists of a high and low disk mass population with a mean dust mass of 21 M _⊕ and 0.45 M _⊕ , respectively. We find that the catalog is near complete for within 300 pc, however, this decreases to 24% out to 1 kpc. We also find a decreasing Herbig lifetime with increasing stellar mass of the form t = 12 × M _⋆ ^−1.4 Myr. The bulk of the Herbig disks are above the T Tauri accretion rate-disk mass relationship, and we observe a flat relation for Herbig disks due to objects with short disk lifetimes, caused by a combination of low disk masses and high accretion rates. Furthermore, we find the peak of the occurrence rate of massive (>10 M _⊕ ) disks to occur at ∼1–2 M _⊙ stars, which coincides with the peak in occurrence rate of giant exoplanets. For higher stellar masses, the disk dust mass decreases again. Conclusions . This catalog characterizes intermediate mass star formation, and links massive disks to the occurrence rate of giant exoplanets. The scarcity of Herbig stars with low accretion rates (−8 M _⊙ yr ⁻¹ ) or disk masses (≲1 M _⊕ ), combined with the lack of disk dust mass age dependence, suggests that the observed Herbig star population represents the surviving disk-hosting phase in late intermediate mass star formation. We attribute this survival to deep dust traps, late-infall replenishment, or a combination of the two.

Context . Planets form through the growth and accumulation of dust grains in protoplanetary disks. The observational characterization of dust properties such as dust size, surface density, and temperature is key to understanding the planet formation process. Aims . We characterized the dust properties of the protoplanetary disk around HD 163296 by performing spectral energy distribution (SED) fitting of multiwavelength high-resolution observations. Methods . We present new high-resolution ALMA Band 9 (0.45 mm) observations, which are sensitive to the temperature. We performed SED fitting at a common resolution of 0.″066 using these new Band 9 observations along with archival ALMA Band 3, 4, 6, and 7 observations. We also compared the fitted results with VLA observations. We explored multiple dust models with different optical constants and porosities. Results . The Band 9 image shows the central disk, two rings at 0.″67 and 1.″00, and outer extended emission previously seen at other wavelengths. At higher frequencies, the rings appear wider, the gaps appear shallower, and the extended emission appears brighter, which can be explained by optical-depth effects and/or size segregation. We characterized the dust properties, including temperature, surface density, and dust size, for each dust model. However, the inferred dust properties are dependent on the dust model, and the ALMA data alone do not allow us to determine which dust model is preferred. We identified DSHARP Zubko (porous) as the preferred model based on a comparison with the VLA profiles and its consistency with other physical and observational constraints. The estimated temperature in the outer ring is lower than predicted by a passively irradiated disk model, suggesting shadowing by the inner ring. Although the estimated surface density and dust size are dependent on the dust model, the preferred model indicates that the central disk, both major rings, and the extended disk each contains more than a few Earth masses of dust.

Kinematic perturbations observed with the Atacama Large Millimeter/submillimeter Array in CO line emission provide evidence for a population of embedded giant protoplanets shaping the structure of protoplanetary disks. We present JWST/MIRI F1140C ( λ = 11.3 μ m) coronagraphic observations of five protoplanetary disks—HD 163296, RXJ 1615.3–3255, RXJ 1842.9–3532, SY Cha, and LkCa 15—with the goal of directly detecting candidate protoplanets orbiting at ≳70 au that were previously inferred from gas kinematics. The data were analyzed using a bespoke methodology that combines subtraction of a reference point-spread function with forward modeling of partially resolved inner disk emission, which otherwise dominates the diffraction pattern in the images. This approach improves the sensitivity to young companions at small separations. No point source consistent with an embedded protoplanet is detected in any of the systems. Instead, in three systems we detect extended emission at 11.3 μ m tracing the outer disk out to radii comparable to those probed by CO. Injection tests indicate upper mass limits of roughly 3–20 M _J at separations of a few hundred astronomical units, assuming no additional thermal contribution from the circumplanetary environment. Even with space-based observations, these limits remain mostly above the ∼1–5 M _J masses inferred from disk kinematics, largely due to the limitations imposed by emission (and/or scattered light) contributions from both the inner disk and outer disk. These observations highlight the challenges of observing protoplanets embedded in their forming environment at large separation with JWST/MIRI. Lessons learned can inform future studies with the Extremely Large Telescope, which will probe separations where the occurrence rate of gas giants is expected to be higher.

Late infall episodes, where material from the surrounding environment accretes onto Class II protoplanetary disks, are emerging as a potentially important but poorly quantified driver of disk evolution. Observed as filamentary streamers in molecular lines and scattered light, such late-stage accretion can perturb disk structures through localized shocks, density enhancements, and warps, yet its chemical consequences remain poorly constrained. We present NOEMA 1.2 mm line-survey observations of the AB Aurigae system, a structured young Class II Herbig disk that shows evidence of both ongoing infall and planet formation. We detected strong azimuthal chemical diversity: SO emission is enhanced in the northern disk near the inferred streamer–disk interaction region, while C ₂ H emission peaks on the opposite southern side. In contrast, CS forms a nearly axisymmetric ring, while HCN and HCO ⁺ peak near the dust continuum overdensity at the main millimeter-sized dust ring. Using multi-transition rotational-diagram analyses of SO and CS, we quantified the azimuthal contrast in column density and excitation. The SO-bright sector exhibits higher rotational temperatures and SO column densities, whereas CS remains nearly axisymmetric with substantially lower rotational temperatures, suggesting that the two species probe different disk layers and/or chemical components. For C ₂ H, potential temperature variations contribute to but cannot fully explain the observed asymmetries. The HCO ⁺ /H ¹³ CO ⁺ line ratio further indicates that HCO ⁺ is optically thick across the molecular ring, while the elevated ratio inside the cavity suggests an enhanced gas-phase ¹² C/ ¹³ C, consistent with isotope-selective photodissociation. Comparison with gas-grain chemical models favors gas-phase C/O ratios near or above unity, with a higher effective C/O in the C ₂ H-bright sector. We discuss two plausible, nonexclusive origins for the observed chemical asymmetries: (i) infall-induced heating and desorption of O-bearing ices that enhance SO and lower the local gas-phase C/O near the streamer’s impact site and (ii) planet-driven substructures and localized heating or enhanced UV irradiation that can promote hydrocarbon-rich chemistry on the opposite side. These results highlight that environmental accretion and planet formation can jointly imprint azimuthal variations in disk chemistry, with potential consequences for the compositions of forming planets.

We present new deep, very high-angular-resolution observations of the submillimeter continuum (19 × 13 mas) and ¹² CO J = 3−2 (67 × 52 mas) emission from the disk surrounding the planet host WISPIT 2. Our analysis reveals a clear gas gap carved by WISPIT 2b and an empty cavity within the orbit of WISPIT 2 c. We also find a gaseous and optically thin dusty ring located between the orbits of the two planets. Channel maps show a pronounced change in the emission surface height of the disk, which transitions from flat within the cavity to strongly flared beyond the orbit of planet b, producing clear breaks in the velocity channels. A pronounced thunderbolt-shaped feature, identified as a kinematic planetary signature (KPS), is detected at the location of WISPIT 2b, in agreement with predictions from planet–disk interaction simulations. This constitutes the first system with a confirmed kinematic signature associated with a directly imaged planet. By mirroring opposite velocity-channel maps about the systemic velocity, we further investigate the KPS and identify spatially resolved excess emission in the vicinity of WISPIT 2b. We find that this emission is resolved across the full Hill sphere of the planet, significantly exceeding the expected extent of a circumplanetary disk. We therefore suggest that the observed emission arises from a combination of processes, including prominent planet-driven spiral wakes, localized heating induced by the planet, and a circumplanetary disk. Although higher spectral resolution is required to disentangle these contributions, our observations demonstrate the potential to directly characterize the birth environment of forming massive planets at scales down to sub-Hill radius.

Context . The wide cavity in the PDS 70 protoplanetary disk harbors two directly imaged confirmed protoplanets. Several studies have proposed the existence of a third inner planet candidate at ~13 au, labeled as PDS 70 d. While its motion is consistent with a Keplerian orbit, its unusually blue spectrum challenges a planetary interpretation. Aims . We investigated the presence and nature of a third inner planet using new SPHERE and GRAVITY observations. Methods . Using the star-hopping strategy, we obtained new coronagraphic SPHERE/IRDIS observations of PDS 70 in dual-polarization imaging mode in the H band, as well as non-coronagraphic observations with SPHERE/IRDIFS covering the YJHK bands. We also searched for a planetary-like signal using GRAVITY+ in astrometric mode with the four-unit-telescope configuration. Results . We consistently detect two inner emission features with SPHERE: one corresponding to the previously proposed planet candidate at ~13 au and another that appears to share the same orbit but leads it by ~120° (clockwise) with a more elongated morphology. Both features exhibit dust-scattered light spectra while displaying different colors, which may indicate differences in dust grain sizes. We show that such a configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a yet undetected planet, distinct from the previously proposed candidate. The analysis of GRAVITY data at the predicted position of this newly proposed planet has resulted in a marginal (3 σ ) detection located between the two clumps along the same orbit ( ρ = 76.2 ± 0.29 mas, and position angle PA = 226.50 ± 0.21°), and consistent with a ~3 M _Jup planet. This planet-like signal aligns with a narrow shadow detected in the outer disk with SPHERE. Additionally, with SPHERE we detect polarized emission very close to the star, which likely arise from the inner disk, with an inclination of 50° and a PA of ~135°. The fact that the two dust clumps appear embedded within this polarized emission motivates an inner disk-related alternative scenario. Conclusions . We conclude that the emission from the previously reported third planet candidate could arise either from a dust clump trailing a yet undetected planet along the same orbit, or from a rotating substructure within the inner disk. Additional observations are required to further test these two proposed scenarios. In particular, confirming the new GRAVITY planet-like signal would support the use of co-orbital substructures as indirect tracers of embedded planets.

Context. While hundreds of protoplanetary discs have been studied in great detail, the detection of protoplanets that are still embedded in their native discs remains rare. WISPIT 2 is only the second laboratory allowing us to directly study planet formation while in progress. The recently discovered system hosts two giant protoplanets in a multi-ringed disc. Aims. We characterise the WISPIT 2 host star spectroscopically to determine its stellar properties, accretion rate, and inner disc diagnostics to provide a more complete picture of the system. Methods. We present optical and near-infrared spectroscopic observations obtained with the ESO VLT/X-shooter and 2.2 m/FEROS instruments. We modelled the stellar spectrum to determine the spectral type and effective temperature, analysed the emission lines to estimate the accretion rate, and searched for evidence of a close stellar companion using radial velocity measurements. Results. Our observations reveal that WISPIT 2 is a spectroscopic binary. The binary has a period of (4.8 ± 0.1) days, which corresponds to a semi-major axis of 0.072 au or 15.54 R _⊙ , assuming co-planarity with the disc and a circular orbit. The binary system consists of a ∼0.97 M _⊙ primary of spectral type K3 ( T _eff ∼ 4700 K) and a ∼0.33 M _⊙ secondary (mass ratio ∼0.34). We detect weak H α emission below the typical chromospheric level, indicating little to no ongoing accretion onto the young stars, consistent with an accretion rate of ≲2 × 10 ⁻¹¹ M _⊙ yr ⁻¹ . Conclusions. This discovery makes the WISPIT 2 disc the first circumbinary system with directly imaged protoplanets and establishes this system as a unique benchmark for studying planet formation and disc evolution around binary stars.

GW Ori is a triple stellar system with a disk featuring three misaligned dust rings. We present Atacama Large Millimeter/submillimeter Array molecular line data of CO isotopologues, revealing a streamer feeding the disk in ¹² CO and ¹³ CO. Through multipointing observations, we find the streamer extends to ∼30″ on-sky (∼12,000 au) and estimate a mass of 1.6 M _Jup using ¹³ CO. Fitting the morphology and kinematics of the streamer, we estimate a mass infall timescale of 0.04 Myr and a mass infall rate of 3.6 × 10 ⁻⁸ M _⊙ yr ⁻¹ , approximately an order of magnitude lower than the stellar accretion rate. Our best-fit trajectory shows that the streamer meets the disk at the outermost dust ring and that the streamer’s angular momentum vector is closely aligned with this outermost ring within ≈3 ^∘ , in contrast to the ≈32 ^∘ misalignment with the innermost ring, suggesting the streamer is the likely cause of the misalignment. However, the total angular momentum of the streamer is smaller than that of GW Ori’s disk; this, together with the low accretion rate, indicates that we are probably witnessing the end stages of infall. Total Power observations reveal bright emission connecting the streamer to the surrounding star-forming region, with the projected distance falling well within the Bondi–Hoyle radius, implying the streamer could have originated through Bondi–Hoyle accretion as GW Ori moves through its natal cloud. Together, these results suggest that GW Ori remains dynamically linked to its parental cloud through ongoing accretion, with the streamer serving as the likely driver of its misaligned disk structure.