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1. SO and SiS Emission Tracing an Embedded Planet and Compact ¹² CO and ¹³ CO Counterparts in the HD 169142 Disk

   https://doi.org/10.3847/2041-8213/acdfd0  

   Law, Charles J. ; Booth, Alice S. ; Öberg, Karin I. ( August 2023 , The Astrophysical Journal Letters)

   Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify compact SOJ= 8₈− 7₇and SiSJ= 19 − 18 emission coincident with the position of a ∼ 2M_Jupplanet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS emission is located along an azimuthal arc and has a morphology similar to that of a known¹²CO kinematic excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of compact¹²CO and¹³COJ= 3 − 2 emission coincident with the planet location. Taken together, a planet-driven outflow provides the best explanation for the properties of the observed chemical asymmetries. We also resolve a bright, azimuthallymore »asymmetric SO ring at ≈24 au. While most of this SO emission originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations driven by a misaligned inner disk or planet–disk interactions. Overall, the HD 169142 disk shows several distinct chemical signatures related to giant planet formation and presents a powerful template for future searches of planet-related chemical asymmetries in protoplanetary disks.

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2. Near-infrared Polarization from Unresolved Disks around Brown Dwarfs and Young Stellar Objects

   https://doi.org/10.3847/1538-4357/ac415c  

   Clemens, Dan P. ; Pillai, Thushara G. S. ; Rilinger, Anneliese M. ; Espaillat, Catherine C. ( February 2022 , The Astrophysical Journal)

   Wide-field near-infrared (NIR) polarimetry was used to examine disk systems around two brown dwarfs (BDs) and two young stellar objects (YSOs) embedded in the Heiles Cloud 2 (HCl2) dark molecular cloud in Taurus as well as numerous stars located behind HCl2. Inclined disks exhibit intrinsic NIR polarization due to scattering of photospheric light, which is detectable even for unresolved systems. After removing polarization contributions from magnetically aligned dust in HCl2 determined from the background star information, significant intrinsic polarization was detected from the disk systems of one BD (ITG 17) and both YSOs (ITG 15, ITG 25), but not from the other BD (2M0444). The ITG 17 BD shows good agreement of the disk orientation inferred from the NIR and from published Atacama Large Millimeter/submillieter Array dust continuum imaging. ITG 17 was also found to reside in a 5200 au wide binary (or hierarchical quad star system) with the ITG 15 YSO disk system. The inferred disk orientations from the NIR for ITG 15 and ITG 17 are parallel to each other and perpendicular to the local magnetic field direction. The multiplicity of the system and the large BD disk nature could have resulted from formation in an environmentmore »characterized by misalignment of the magnetic field and the protostellar disks.

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3. Demographics of disks around young very low-mass stars and brown dwarfs in Lupus

   https://doi.org/10.1051/0004-6361/201936913  

   Sanchis, E. ; Testi, L. ; Natta, A. ; Manara, C. F. ; Ercolano, B. ; Preibisch, T. ; Henning, T. ; Facchini, S. ; Miotello, A. ; de Gregorio-Monsalvo, I. ; et al ( January 2020 , Astronomy & Astrophysics)

   We present new 890 μ m continuum ALMA observations of five brown dwarfs (BDs) with infrared excess in Lupus I and III, which in combination with four previously observed BDs allowed us to study the millimeter properties of the full known BD disk population of one star-forming region. Emission is detected in five out of the nine BD disks. Dust disk mass, brightness profiles, and characteristic sizes of the BD population are inferred from continuum flux and modeling of the observations. Only one source is marginally resolved, allowing for the determination of its disk characteristic size. We conduct a demographic comparison between the properties of disks around BDs and stars in Lupus. Due to the small sample size, we cannot confirm or disprove a drop in the disk mass over stellar mass ratio for BDs, as suggested for Ophiuchus. Nevertheless, we find that all detected BD disks have an estimated dust mass between 0.2 and 3.2 M ⊙ ; these results suggest that the measured solid masses in BD disks cannot explain the observed exoplanet population, analogous to earlier findings on disks around more massive stars. Combined with the low estimated accretion rates, and assuming that the mm-continuum emission ismore »a reliable proxy for the total disk mass, we derive ratios of Ṁ acc ∕ M disk that are significantly lower than in disks around more massive stars. If confirmed with more accurate measurements of disk gas masses, this result could imply a qualitatively different relationship between disk masses and inward gas transport in BD disks.« less
4. Signatures of r-process Enrichment in Supernovae from Collapsars

   https://doi.org/10.3847/2041-8213/ac9b41  

   Barnes, Jennifer ; Metzger, Brian D. ( November 2022 , The Astrophysical Journal Letters)

   Despite recent progress, the astrophysical channels responsible for rapid neutron capture (r-process) nucleosynthesis remain an unsettled question. Observations of the kilonova following the gravitational-wave-detected neutron star merger GW170817 established mergers as one site of ther-process, but additional sources may be needed to fully explainr-process enrichment in the universe. One intriguing possibility is that rapidly rotating massive stars undergoing core collapse launchr-process-rich outflows off the accretion disks formed from their infalling matter. In this scenario,r-process winds are one component of the supernova (SN) ejecta produced by “collapsar” explosions. We present the first systematic study of the effects ofr-process enrichment on the emission from collapsar-generated SNe. We semianalytically modelr-process SN emission from explosion out to late times and determine its distinguishing features. The ease with whichr-process SNe can be identified depends on how effectively wind material mixes into the initiallyr-process-free outer layers of the ejecta. In many cases, enrichment produces a near-infrared (NIR) excess that can be detected within ∼75 days of explosion. We also discuss optimal targets and observing strategies for testing ther-process collapsar theory, and find that frequent monitoring of optical and NIR emission from high-velocity SNe in the first few months after explosion offers a reasonable chance ofmore »success while respecting finite observing resources. Such early identification ofr-process collapsar candidates also lays the foundation for nebular-phase spectroscopic follow-up in the NIR and mid-infrared, for example, with the James Webb Space Telescope.

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5. Dusty disk winds at the sublimation rim of the highly inclined, low mass young stellar object SU Aurigae

   https://doi.org/10.1051/0004-6361/201935331  

   Labdon, Aaron ; Kraus, Stefan ; Davies, Claire L. ; Kreplin, Alexander ; Kluska, Jacques ; Harries, Tim J. ; Monnier, John D. ; ten Brummelaar, Theo ; Baron, Fabien ; Millan-Gabet, Rafael ; et al ( July 2019 , Astronomy & Astrophysics)

   Context. T Tauri stars are low-mass young stars whose disks provide the setting for planet formation. Despite this, their structure is poorly understood. We present new infrared interferometric observations of the SU Aurigae circumstellar environment that offer resolution that is three times higher and a better baseline position angle coverage than previous observations. Aims. We aim to investigate the characteristics of the circumstellar material around SU Aur, constrain the disk geometry, composition and inner dust rim structure. Methods. The CHARA array offers unique opportunities for long baseline observations, with baselines up to 331 m. Using the CLIMB three-telescope combiner in the K -band allows us to measure visibilities as well as closure phase. We undertook image reconstruction for model-independent analysis, and fitted geometric models such as Gaussian and ring distributions. Additionally, the fitting of radiative transfer models constrain the physical parameters of the disk. For the first time, a dusty disk wind is introduced to the radiative transfer code TORUS to model protoplanetary disks. Our implementation is motivated by theoretical models of dusty disk winds, where magnetic field lines drive dust above the disk plane close to the sublimation zone. Results. Image reconstruction reveals an inclined disk with slight asymmetrymore »along its minor-axis, likely due to inclination effects obscuring the inner disk rim through absorption of incident star light on the near-side and thermal re-emission and scattering of the far-side. Geometric modelling of a skewed ring finds the inner rim at 0.17 ± 0.02 au with an inclination of 50.9 ± 1.0° and minor axis position angle 60.8 ± 1.2°. Radiative transfer modelling shows a flared disk with an inner radius at 0.18 au which implies a grain size of 0.4 μ m assuming astronomical silicates and a scale height of 15.0 at 100 au. Among the tested radiative transfer models, only the dusty disk wind successfully accounts for the K -band excess by introducing dust above the mid-plane.« less