Search

The radial structure of debris discs can encode important information about their dynamical and collisional history. In this paper we present a 3-phase analytical model to analyse the collisional evolution of solids in debris discs, focusing on their joint radial and temporal dependence. Consistent with previous models, we find that as the largest planetesimals reach collisional equilibrium in the inner regions, the surface density of dust and solids becomes proportional to $\sim r^{2}$ within a certain critical radius. We present simple equations to estimate the critical radius and surface density of dust as a function of the maximum planetesimal size and initial surface density in solids (and vice versa). We apply this model to ALMA observations of 7 wide debris discs. We use both parametric and non-parametric modelling to test if their inner edges are shallow and consistent with collisional evolution. We find that 4 out of 7 have inner edges consistent with collisional evolution. Three of these would require small maximum planetesimal sizes below 10 km, with HR 8799's disc potentially lacking solids larger than a few centimeters. The remaining systems have inner edges that are much sharper, which requires maximum planetesimal sizes $\gtrsim10$ km. Their sharp inner edges suggest they could have been truncated by planets, which JWST could detect. In the context of our model, we find that the 7 discs require surface densities below a Minimum Mass Solar Nebula, avoiding the so-called disc mass problem. Finally, during the modelling of HD 107146 we discover that its wide gap is split into two narrower ones, which could be due to two low-mass planets formed within the disc., Accepted for publication in MNRAS, 21 pages, 11 figures

The Solar System is dominated by giant planets slightly out of the ice-line (Jupiter-like planets). Radial velocity surveys suggest that the Solar System may be unusual and that Jupiter-like planets have a frequency < 20% around solar type stars. However, Jupiter-like planets may be much more common in one of the closest association in the solar neighbourhood. Indeed, four massive Jupiter-like planets have been already discovered in the nearby young (age ∼ 20 Myr) β Pic Moving Group (BPMG) from high contrast imaging and the presence of at least four others is suggested by high precision astrometry by the ESA Gaia satellite. There are 20 stars in the BPMG in the mass range 1-2.5 M⊙ but four of them have stellar companions at separations that make the orbits of Jupiter-like planets unstable. In addition a large fraction of the Jupiter-like planets are expected to be undetectable with the available data because of their low mass. We conclude that Jupiter-like planets are common wherever their orbits would be stable (best estimate is close to 100% and it is > 58% at 95% level of confidence) in the BPMG. We briefly discuss how the conundrum with the low frequency found by radial velocity surveys can be reconciled.

The nearby V4046 Sgr spectroscopic binary hosts a gas-rich disc known for its wide cavity and dusty ring. We present high resolution ($\sim$20 mas or 1.4 au) ALMA observations of the 1.3mm continuum of V4046 Sgr which, combined with SPHERE--IRDIS polarised images and a well-sampled spectral energy distribution (SED), allow us to propose a physical model using radiative transfer (RT) predictions. The ALMA data reveal a thin ring at a radius of 13.15$\pm$0.42 au (Ring13), with a radial width of 2.46$\pm$0.56 au. Ring13 is surrounded by a $\sim$10 au-wide gap, and it is flanked by a mm-bright outer ring (Ring24) with a sharp inner edge at 24 au. Between 25 and $\sim$35 au the brightness of Ring24 is relatively flat and then breaks into a steep tail that reaches out to $\sim$60 au. In addition, central emission is detected close to the star which we interpret as a tight circumbinary ring made of dust grains with a lower size limit of 0.8 mm at 1.1 au. In order to reproduce the SED, the model also requires an inner ring at $\sim$5 au (Ring5) composed mainly of small dust grains, hiding under the IRDIS coronagraph, and surrounding the inner circumbinary disc. The surprisingly thin Ring13 is nonetheless roughly 10 times wider than its expected vertical extent. The strong near-far disc asymmetry at 1.65 $\mu$m points at a very forward-scattering phase function and requires grain radii of no less than 0.4 $\mu$m., Comment: 11 pages, 7 figures

We present ALMA observations of the $^{12}$CO, $^{13}$CO, C$^{18}$O J=2-1 transitions and the 1.3\,mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of $\approx$\,0\farcs3. We observe multiple spiral structures in intensity, velocity and velocity dispersion for the $^{12}$CO and $^{13}$CO gas tracers. A newly detected $^{12}$CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the inter-spiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning > 360$^\circ$. A spatial offset of ~30 au is observed between the $^{12}$CO and $^{13}$CO spirals, to which we hypothesize that the gas layers are propagating at different speeds (``surfing'') due to a non-zero vertical temperature gradient. Leveraging the varying optical depths between the CO isotopologues, we reconstruct temperature and column density maps of the outer disc. Gas surface density peaks at r\,$\approx$\,180\,au, coincident with the peak of continuum emission. Here the dust grains have a Stokes number of $\approx$\,1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of $\approx$\,100\,au, and a cavity eccentricity between 0.3 and 0.45.

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 $$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 $\sim$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 $\sim5\%$ 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., Comment: 21 pages, 10 figures. Appendix with 3 additional figures. Version 2, identical to previous one, but now accepted for publication (in MNRAS)

Class III stars are those in star forming regions without large non-photospheric infrared emission, suggesting recent dispersal of their protoplanetary disks. We observed 30 class III stars in the 1-3 Myr Lupus region with ALMA at ${\sim}856��$m, resulting in 4 detections that we attribute to circumstellar dust. Inferred dust masses are $0.036{-}0.093M_\oplus$, ${\sim}1$ order of magnitude lower than any previous measurements; one disk is resolved with radius ${\sim}80$ au. Two class II sources in the field of view were also detected, and 11 other sources, consistent with sub-mm galaxy number counts. Stacking non-detections yields a marginal detection with mean dust mass ${\sim}0.0048M_\oplus$. We searched for gas emission from the CO J=3-2 line, and present its detection to NO Lup inferring a gas mass ($4.9 {\pm} 1.1$) ${\times}10^{-5} M_\oplus$ and gas-to-dust ratio $1.0{\pm}0.4$. Combining our survey with class II sources shows a gap in the disk mass distribution from $0.09{-}2M_\oplus$ for ${>}0.7M_\odot$ Lupus stars, evidence of rapid dispersal of mm-sized dust from protoplanetary disks. The class III disk mass distribution is consistent with a population model of planetesimal belts that go on to replenish the debris disks seen around main sequence stars. This suggests that planetesimal belt formation does not require long-lived protoplanetary disks, i.e., planetesimals form within ${\sim}$2 Myr. While all 4 class III disks are consistent with collisional replenishment, for two the gas and/or mid-IR emission could indicate primordial circumstellar material in the final stages of protoplanetary disk dispersal. Two class III stars without sub-mm detections exhibit hot emission that could arise from ongoing planet formation processes inside ${\sim}1$ au., 30 pages, 20 figures. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review

Full list of authors: Hinkley, Sasha; Carter, Aarynn L.; Ray, Shrishmoy; Skemer, Andrew; Biller, Beth; Choquet, Elodie; Millar-Blanchaer, Maxwell A.; Sallum, Stephanie; Miles, Brittany; Whiteford, Niall; Patapis, Polychronis; Perrin, Marshall; Pueyo, Laurent; Schneider, Glenn; Stapelfeldt, Karl; Wang, Jason; Ward-Duong, Kimberly; Bowler, Brendan P.; Boccaletti, Anthony; Girard, Julien H.; Hines, Dean; Kalas, Paul; Kammerer, Jens; Kervella, Pierre; Leisenring, Jarron; Pantin, Eric; Zhou, Yifan; Meyer, Michael; Liu, Michael C.; Bonnefoy, Mickael; Currie, Thayne; McElwain, Michael; Metchev, Stanimir; Wyatt, Mark; Absil, Olivier; Adams, Jea; Barman, Travis; Baraffe, Isabelle; Bonavita, Mariangela; Booth, Mark; Bryan, Marta; Chauvin, Gael; Chen, Christine; Danielski, Camilla; De Furio, Matthew; Factor, Samuel M.; Fitzgerald, Michael P.; Fortney, Jonathan J.; Grady, Carol; Greenbaum, Alexandra; Henning, Thomas; Hoch, Kielan K. W.; Janson, Markus; Kennedy, Grant; Kenworthy, Matthew; Kraus, Adam; Kuzuhara, Masayuki; Lagage, Pierre-Olivier; Lagrange, Anne-Marie; Launhardt, Ralf; Lazzoni, Cecilia; Lloyd, James; Marino, Sebastian; Marley, Mark; Martinez, Raquel; Marois, Christian; Matthews, Brenda; Matthews, Elisabeth C.; Mawet, Dimitri; Mazoyer, Johan; Phillips, Mark; Petrus, Simon; Quanz, Sascha P.; Quirrenbach, Andreas; Rameau, Julien; Rebollido, Isabel; Rickman, Emily; Samland, Matthias; Sargent, B.; Schlieder, Joshua E.; Sivaramakrishnan, Anand; Stone, Jordan M.; Tamura, Motohide; Tremblin, Pascal; Uyama, Taichi; Vasist, Malavika; Vigan, Arthur; Wagner, Kevin; Ygouf, Marie.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/3.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles. © 2022. The Author(s). Published by IOP Publishing Ltd on behalf of the Astronomical Society of the Pacific (ASP). All rights reserved., This project was supported by a grant from STScI (JWST-ERS-01386) under NASA contract NAS5-03127. M.T.is supported by JSPS KAKENHI Grant No.18H05442. M.B. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG) through grant Kr 2164/13–2. K.W. acknowledges support from NASA through the NASA Hubble Fellowship grant HST-HF2-51472.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a $, Comment: Accepted ApJL Iterations of spectra reduced by the ERS team are hosted at this link: https://github.com/bemiles/JWST_VHS1256b_Reduction/tree/main/reduced_spectra

Ionic liquid crystals (ILCs), that is, ionic liquids exhibiting mesomorphism, liquid crystalline phases, and anisotropic properties, have received intense attention in the past years. Among others, this is due to their special properties arising from the combination of properties stemming from ionic liquids and from liquid crystalline arrangements. Besides interesting fundamental aspects, ILCs have been claimed to have tremendous application potential that again arises from the combination of properties and architectures that are not accessible otherwise, or at least not accessible easily by other strategies. The current review highlights recent developments in ILC research, starting with some key fundamental aspects. Further subjects covered include the synthesis and variations of modern ILCs, including the specific tuning of their mesomorphic behavior. The review concludes with reflections on some applications that may be within reach for ILCs and finally highlights a few key challenges that must be overcome prior and during true commercialization of ILCs.

The question of what determines the width of Kuiper belt analogues (exoKuiper belts) is an open one. If solved, this understanding would provide valuable insights into the architecture, dynamics, and formation of exoplanetary systems. Recent observations by ALMA have revealed an apparent paradox in this field, the presence of radially narrow belts in protoplanetary discs that are likely the birthplaces of planetesimals, and exoKuiper belts nearly four times as wide in mature systems. If the parent planetesimals of this type of debris disc indeed form in these narrow protoplanetary rings via streaming instability where dust is trapped, we propose that this width dichotomy could naturally arise if these dust traps form planetesimals whilst migrating radially, e.g. as caused by a migrating planet. Using the dust evolution software DustPy, we find that if the initial protoplanetary disc and trap conditions favour planetesimal formation, dust can still effectively accumulate and form planetesimals as the trap moves. This leads to a positive correlation between the inward radial speed and final planetesimal belt width, forming belts up to $\sim$100 au over 10 Myr of evolution. We show that although planetesimal formation is most efficient in low viscosity ($\alpha = 10^{-4}$) discs with steep dust traps to trigger the streaming instability, the large widths of most observed planetesimal belts constrain $\alpha$ to values $\geq4\times 10^{-4}$ at tens of au, otherwise the traps cannot migrate far enough. Additionally, the large spread in the widths and radii of exoKuiper belts could be due to different trap migration speeds (or protoplanetary disc lifetimes) and different starting locations, respectively. Our work serves as a first step to link exoKuiper belts and rings in protoplanetary discs., Comment: Accepted for publication in MNRAS. 15 pages,12 figures

The Solar System gas giants are each surrounded by many moons, with at least 50 prograde satellites thought to have formed from circumplanetary material. Just like the Sun is not the only star surrounded by planets, extrasolar gas giants are likely surrounded by satellite systems. Here, we report on ALMA observations of four, 6 pages, 3 figures, accepted for publication in MNRAS

Context. Dynamical and turbulent motions of gas in a protoplanetary disk are crucial for their evolution and affect planet formation. Recent observations suggest weak turbulence in the disk's outer regions. However, the physical mechanism of turbulence in these outer regions remains uncertain. The vertical shear instability (VSI) is a promising mechanism to produce turbulence in disks. Aims. Our aim is to study the observability of the gas velocity structure produced by the VSI via CO kinematics with ALMA. Methods. We perform global 3D hydrodynamical simulations of a VSI-unstable disk. We post-process the simulation results with radiative transfer calculations, and produce synthetic predictions of CO rotational emission lines. Following, we compute the line of sight velocity map, and its deviations from a sub-Keplerian equilibrium solution. We explore the detectability of the VSI by identifying kinematic signatures using realistic simulated observations. Results. Our 3D simulations of the VSI show the steady state dynamics of the gas in great detail. From the velocity structure we infer a turbulent stress value of $\alpha_{r\phi}=1.4 \times 10^{-4}$. On large scales, we observe velocity deviations of 50 m s$^{-1}$ as axisymmetric rings. We find optimal conditions at $i \lesssim 20^{\circ}$ to trace for the kinematic structures of the VSI. We found that current diagnostics to constrain gas turbulence from non-thermal broadening of the line emission are not applicable to anisotropic VSI turbulence. Conclusions. The detection of kinematic signatures produced by the VSI is possible with ALMA. Observations including an extended antenna configuration combined with the highest spectral resolution available are needed for robust detection. The characterization of the large-scale velocity perturbations is required to constrain the turbulence level produced by the VSI from gas observations., Comment: Accepted for publication in A&A. 17 pages with 10 figures and 1 table

Recent observations of resolved cold debris disks at tens of au have revealed that gaps could be a common feature in these Kuiper belt analogues. Such gaps could be evidence for the presence of planets within the gaps or closer-in near the edges of the disk. We present SPHERE observations of HD 92945 and HD 107146, two systems with detected gaps. We constrained the mass of possible companions responsible for the gap to 1-2 M Jup for planets located inside the gap and to less than 5 M Jup for separations down to 20 au from the host star. These limits allow us to exclude some of the possible configurations of the planetary systems proposed to explain the shape of the disks around these two stars. In order to put tighter limits on the mass at very short separations from the star, where direct imaging data are less effective, we also combined our data with astrometric measurements from Hipparcos and Gaia and radial velocity measurements. We were able to limit the separation and the mass of the companion potentially responsible for the proper motion anomaly of HD 107146 to values of 2-7 au and 2-5 M Jup , respectively., Comment: 17 pages, 14 Figures, accepted for publication on MNRAS

Self-assembly is one of the crucial mechanisms allowing to design multifunctional materials. Soft hybrid materials contain components of different nature and exhibit competitive interactions which drive self-organisation into structures of a particular function. Here we demonstrate a novel type of a magnetic hybrid material where the molecular tilt can be manipulated through a delicate balance between the topologically-assisted colloidal self-assembly of \rev{magnetic nanoparticles} and the anisotropic molecular interactions in a liquid crystal matrix.

Debris disks are tenuous, dusty belts surrounding main sequence stars generated by collisions between planetesimals. HD 206893 is one of only two stars known to host a directly imaged brown dwarf orbiting interior to its debris ring, in this case at a projected separation of 10.4 au. Here we resolve structure in the debris disk around HD 206893 at an angular resolution of 0.6" (24 au) and wavelength of 1.3 mm with the Atacama Large Millimeter/submillimeter Array (ALMA). We observe a broad disk extending from a radius of, 24 pages, 12 figures, Accepted for publication in ApJ

Models of terrestrial planet formation predict that the final stages of planetary assembly, lasting tens of millions of years beyond the dispersal of young protoplanetary disks, are dominated by planetary collisions. It is through these giant impacts that planets like the young Earth grow to their final mass and achieve long-term stable orbital configurations. A key prediction is that these impacts produce debris. To date, the most compelling observational evidence for post-impact debris comes from the planetary system around the nearby 23 Myr-old A star HD 172555. This system shows large amounts of fine dust with an unusually steep size distribution and atypical dust composition, previously attributed to either a hypervelocity impact or a massive asteroid belt. Here, we report the spectrally resolved detection of a CO gas ring co-orbiting with dusty debris between ~6-9 au - a region analogous to the outer terrestrial planet region of our Solar System. Taken together, the dust and CO detections favor a giant impact between large, volatile-rich bodies. This suggests that planetary-scale collisions, analogous to the Moon-forming impact, can release large amounts of gas as well as debris, and that this gas is observable, providing a window into the composition of young planets., Comment: 21 pages (double spaced, including references and figures), 3 figures, 1 table, published in Nature 20/10/2021, published version available online through SharedIt initiative at https://rdcu.be/cAlEy

Young giant planets and brown dwarf companions emit near-infrared radiation that can be linearly polarized up to several percent. This polarization can reveal the presence of a circumsubstellar accretion disk, rotation-induced oblateness of the atmosphere, or an inhomogeneous distribution of atmospheric dust clouds. We measured the near-infrared linear polarization of 20 known directly imaged exoplanets and brown dwarf companions with the high-contrast imager SPHERE-IRDIS at the VLT. We reduced the data using the IRDAP pipeline to correct for the instrumental polarization and crosstalk with an absolute polarimetric accuracy, Accepted for publication in A&A. Shortened abstract. 29 pages, 22 figures

Context. Planetary systems and debris discs are natural by-products of the star formation process, and they affect each other. The direct imaging technique allows simultaneous imaging of both a companion and the circumstellar disc it resides in, and is thus a valuable tool to study companion-disc interactions. However, the number of systems in which a companion and a disc have been detected at the same time remains low. Aims. Our aim is to increase this sample, and to continue detecting and studying the population of giant planets in wide orbits. Methods. We carry out the L′ band Imaging Survey for Exoplanets in the North (LIStEN), which targeted 28 nearby stars: 24 are known to harbour a debris disc (DD) and the remaining 4 are protoplanetary disc-hosting stars. We aim to detect possible new companions, and study the interactions between the companion and their discs. Angular differential imaging observations were carried out in the L′ band at 3.8 μm using the LMIRCam instrument at the LBT, between October 2017 and April 2019. Results. No new companions were detected. We combined the derived mass detection limits with information on the disc, and on the proper motion of the host star, to constrain the presence of unseen planetary and low-mass stellar companion around the 24 disc-hosting stars in our survey. We find that 2 have an uncertain DD status and the remaining 22 have disc sizes compatible with self-stirring. Three targets show a proper motion anomaly (PMa) compatible with the presence of an unseen companion. Conclusions. Our achieved mass limits combined with the PMa analysis for HD 113337 support the presence of a second companion around the star, as suggested in previous RV studies. Our mass limits also help to tighten the constraints on the mass and semi-major axis of the unseen companions around HD 161868 and HD 8907.

Context. The detection and characterization of planets and debris disks is a very active field in current research. The F5V star HD 206893 hosts a ~25 M Jup brown dwarf detected at ~10 au in VLT/SPHERE high-contrast images. This system is also known to host a debris disk, which is inferred from its high infrared excess. This disk was recently resolved in thermal submillimeter imaging with ALMA and extends from 30 to 180 au, with a ~27 au wide gap at ~74 au.Aims. Our goal is to search for the scattered light emission of the disk using the largest amount of SPHERE imaging data available to date. We also want to bring tighter constraints on the presence of additional low-mass companions based on the available multi-epoch high-contrast imaging data.Methods. We analyzed six epochs of SPHERE near-infrared data, processed with angular, polarimetric, and reference differential imaging, in order to detect the disk around HD 206893.Results. We do not detect the debris disk. Based on recent constraints on the disk morphology from ALMA data, this non-detection is compatible with a maximum albedo of 0.55 in the H band and 0.96 in the K band. Furthermore, we do not detect additional low-mass companions in the system. A low-mass companion is expected from radial velocity and astrometric measurements between 1.4 and 2.6 au, and we estimate our probability of detection higher than 90% for brown dwarfs more massive than 55 M Jup in this separation range. At 74 au, where a gap is detected in the disk in thermal imaging, this probability of detection corresponds to planets above 2.5 M Jup .Conclusions. The non-detection of the disk through the methods used in this study should not exclude an attempt with other techniques, such as advanced reference-star differential imaging using machine-learning-based libraries or star hopping. Furthermore, the future JWST instrument NIRCam might offer the possibility of detecting the disk in scattered light thanks to its increased sensitivity.

We observed the K7 class III star NO Lup in an ALMA survey of the 1-3 Myr Lupus association and detected circumstellar dust and CO gas. Here we show that the J = 3-2 CO emission is both spectrally and spatially resolved, with a broad velocity width ${\sim}19$kms$^{-1}$ for its resolved size ${\sim}1''$ (${\sim}130$ au). We model the gas emission as a Keplerian disc, finding consistency, but only with a central mass of ${\sim}11M_{\odot}$, which is implausible given its spectral type and X-Shooter spectrum. A good fit to the data can also be found by modelling the CO emission as outflowing gas with a radial velocity ${\sim}22$kms$^{-1}$. We interpret NO Lup's CO emission as the first imaged class III circumstellar disc with outflowing gas. We conclude that the CO is continually replenished, but cannot say if this is from the break-up of icy planetesimals or from the last remnants of the protoplanetary disc. We suggest further work to explore the origin of this CO, and its higher than expected velocity in comparison to photoevaporative models., 6 pages, 4 figures. Accepted for publication in MNRAS following peer review (this is a pre-copyedited, author-produced PDF version)

The Vega planetary system hosts the archetype of extrasolar Kuiper belts, and is rich in dust from the sub-au region out to 100's of au, suggesting intense dynamical activity. We present ALMA mm observations that detect and resolve the outer dust belt from the star for the first time. The interferometric visibilities show that the belt can be fit by a Gaussian model or by power-law models with a steep inner edge (at 60-80 au). The belt is very broad, extending out to at least 150-200 au. We strongly detect the star and set a stringent upper limit to warm dust emission previously detected in the infrared. We discuss three scenarios that could explain the architecture of Vega's planetary system, including the new {ALMA} constraints: no outer planets, a chain of low-mass planets, and a single giant planet. The planet-less scenario is only feasible if the outer belt was born with the observed sharp inner edge. If instead the inner edge is currently being truncated by a planet, then the planet must be $\gtrsim$6 M$_{\oplus}$ and at $\lesssim71$ au to have cleared its chaotic zone within the system age. In the planet chain scenario, outward planet migration and inward scattering of planetesimals could produce the hot and warm dust observed in the inner regions of the system. In the single giant planet scenario, an asteroid belt could be responsible for the warm dust, and mean motion resonances with the planet could put asteroids on star-grazing orbits, producing the hot dust., 18 pages, 3 figures, Accepted for publication in ApJ

The presence of CO gas around 10-50 Myr old A stars with debris discs has sparked debate on whether the gas is primordial or secondary. Since secondary gas released from planetesimals is poor in H$_2$, it was thought that CO would quickly photodissociate never reaching the high levels observed around the majority of A stars with bright debris discs. Kral et al. 2019 showed that neutral carbon produced by CO photodissociation can effectively shield CO and potentially explain the high CO masses around 9 A stars with bright debris discs. Here we present a new model that simulates the gas viscous evolution, accounting for carbon shielding and how the gas release rate decreases with time as the planetesimal disc loses mass. We find that the present gas mass in a system is highly dependant on its evolutionary path. Since gas is lost on long timescales, it can retain a memory of the initial disc mass. Moreover, we find that gas levels can be out of equilibrium and quickly evolving from a shielded onto an unshielded state. With this model, we build the first population synthesis of gas around A stars, which we use to constrain the disc viscosity. We find a good match with a high viscosity ($\alpha\sim0.1$), indicating that gas is lost on timescales $\sim1-10$ Myr. Moreover, our model also shows that high CO masses are not expected around FGK stars since their planetesimal discs are born with lower masses, explaining why shielded discs are only found around A stars. Finally, we hypothesise that the observed carbon cavities could be due to radiation pressure or accreting planets., Comment: Accepted for publication in MNRAS, 23 pages, 13 figures

While detecting low mass exoplanets at tens of au is beyond current instrumentation, debris discs provide a unique opportunity to study the outer regions of planetary systems. Here we report new ALMA observations of the 80-200 Myr old Solar analogue HD 107146 that reveal the radial structure of its exo-Kuiper belt at wavelengths of 1.1 and 0.86 mm. We find that the planetesimal disc is broad, extending from 40 to 140 au, and it is characterised by a circular gap extending from 60 to 100 au in which the continuum emission drops by about 50%. We also report the non-detection of the CO J=3-2 emission line, confirming that there is not enough gas to affect the dust distribution. To date, HD 107146 is the only gas-poor system showing multiple rings in the distribution of millimeter sized particles. These rings suggest a similar distribution of the planetesimals producing small dust grains that could be explained invoking the presence of one or more perturbing planets. Because the disk appears axisymmetric, such planets should be on circular orbits. By comparing N-body simulations with the observed visibilities we find that to explain the radial extent and depth of the gap, it would be required the presence of multiple low mass planets or a single planet that migrated through the disc. Interior to HD 107146's exo-Kuiper belt we find extended emission with a peak at ~20 au and consistent with the inner warm belt that was previously predicted based on 22$\mu$m excess as in many other systems. This warm belt is the first to be imaged, although unexpectedly suggesting that it is asymmetric. This could be due to a large belt eccentricity or due to clumpy structure produced by resonant trapping with an additional inner planet., Comment: Accepted for publication in MNRAS, 19 pages, 11 figures

Optical/IR images of transition disks (TDs) have revealed deep intensity decrements in the rings of HAeBes HD142527 and HD100453, that can be interpreted as shadowing from sharply tilted inner disks, such that the outer disks are directly exposed to stellar light. Here we report similar dips in SPHERE+IRDIS differential polarized imaging (DPI) of TTauri DoAr44. With a fairly axially symmetric ring in the submm radio continuum, DoAr44 is likely also a warped system. We constrain the warp geometry by comparing radiative transfer predictions with the DPI data in H band (Q_\phi(H)) and with a re-processing of archival 336GHz ALMA observations. The observed DPI shadows have coincident radio counterparts, but the intensity drops are much deeper in Q_\phi(H) (~88%), compared to the shallow drops at 336GHz (~24%). Radiative transfer predictions with an inner disk tilt of ~30+-5deg approximately account for the observations. ALMA long-baseline observations should allow the observation of the warped gas kinematics inside the cavity of DoAr44., Comment: 11 pages, 10 figures, 3 tables, accepted for publication in MNRAS

Demographic surveys of protoplanetary disks, carried out mainly with ALMA, have provided access to a large range of disk dust masses ($M_{\rm{dust}}$) around stars with different stellar types and in different star-forming regions. These surveys found a power-law relation between $M_{\rm{dust}}$ and $M_{\star}$ that steepens in time, but which is also flatter for transition disks (TDs). We performed dust evolution models, which included perturbations to the gas surface density with different amplitudes to investigate the effect of particle trapping on the $M_{\rm{dust}}-M_{\star}$ relation. These perturbations were aimed at mimicking pressure bumps that originated from planets. We focused on the effect caused by different stellar and disk masses based on exoplanet statistics that demonstrate a dependence of planet mass on stellar mass and metallicity. Models of dust evolution can reproduce the observed $M_{\rm{dust}}-M_{\star}$ relation in different star-forming regions when strong pressure bumps are included and when the disk mass scales with stellar mass (case of $M_{\rm{disk}}=0.05\,M_\star$ in our models). This result arises from dust trapping and dust growth beyond centimeter-sized grains inside pressure bumps. However, the flatter relation of $M_{\rm{dust}}-M_{\star}$ for TDs and disks with substructures cannot be reproduced by the models unless the formation of boulders is inhibited inside pressure bumps. In the context of pressure bumps originating from planets, our results agree with current exoplanet statistics on giant planet occurrence increasing with stellar mass, but we cannot draw a conclusion about the type of planets needed in the case of low-mass stars. This is attributed to the fact that for $M_\star, Accepted for publication in A&A, minor changes after language edition

Radial substructure in the form of rings and gaps has been shown to be ubiquitous among protoplanetary discs. This could be the case in exo-Kuiper belts as well, and evidence for this is emerging. In this paper, we present ALMA observations of the debris/planetesimal disc surrounding HD 206893, a system that also hosts two massive companions at 2 and 11 au. Our observations reveal a disc extending from 30 to 180 au, split by a 27 au wide gap centred at 74 au, and no dust surrounding the reddened brown dwarf (BD) at 11 au. The gap width suggests the presence of a 0.9MJup planet at 74 au, which would be the third companion in this system. Using previous astrometry of the BD, combined with our derived disc orientation as a prior, we were able to better constrain its orbit finding it is likely eccentric ($0.14^{+0.05}_{-0.04}$). For the innermost companion, we used radial velocity, proper motion anomaly, and stability considerations to show its mass and semimajor axis are likely in the ranges 4–100MJup and 1.4–4.5 au. These three companions will interact on secular time-scales and perturb the orbits of planetesimals, stirring the disc and potentially truncating it to its current extent via secular resonances. Finally, the presence of a gap in this system adds to the growing evidence that gaps could be common in wide exo-Kuiper belts. Out of six wide debris discs observed with ALMA with enough resolution, four to five show radial substructure in the form of gaps.

Gas detection around main sequence stars is becoming more common with around 20 systems showing the presence of CO. However, more detections are needed, especially around later spectral type stars to better understand the origin of this gas and refine our models. To do so, we carried out a survey of 10 stars with predicted high likelihoods of secondary CO detection using ALMA in band 6. We looked for continuum emission of mm-dust as well as gas emission (CO and CN transitions). The continuum emission was detected in 9/10 systems for which we derived the discs' dust masses and geometrical properties, providing the first mm-wave detection of the disc around HD 106906, the first mm-wave radius for HD 114082, 117214, HD 15745, HD 191089 and the first radius at all for HD 121191. A crucial finding of our paper is that we detect CO for the first time around the young 10-16 Myr old G1V star HD 129590, similar to our early Sun. The gas seems colocated with its planetesimal belt and its total mass is likely between $2-10 \times 10^{-5}$ M$_\oplus$. This first gas detection around a G-type main-sequence star raises questions as to whether gas may have been released in the Solar System as well in its youth, which could potentially have affected planet formation. We also detected CO gas around HD 121191 at a higher S/N than previously and find that the CO lies much closer-in than the planetesimals in the system, which could be evidence for the previously suspected CO viscous spreading owing to shielding preventing its photodissociation. Finally, we make estimates for the CO content in planetesimals and the HCN/CO outgassing rate (from CN upper limits), which we find are below the level seen in Solar System comets in some systems., Comment: Accepted for publication in MNRAS. 22 pages, 13 figures

HD 38206 is an A0V star in the Columba association, hosting a debris disc first discovered by IRAS. Further observations by Spitzer and Herschel showed that the disc has two components, likely analogous to the asteroid and Kuiper belts of the Solar System. The young age of this star makes it a prime target for direct imaging planet searches. Possible planets in the system can be constrained using the debris disc. Here we present the first ALMA observations of the system's Kuiper belt and fit them using a forward modelling MCMC approach. We detect an extended disc of dust peaking at around 180 au with a width of 140 au. The disc is close to edge on and shows tentative signs of an asymmetry best fit by an eccentricity of $0.25^{+0.10}_{-0.09}$. We use the fitted parameters to determine limits on the masses of planets interior to the cold belt. We determine that a minimum of four planets are required, each with a minimum mass of 0.64 M$_J$, in order to clear the gap between the asteroid and Kuiper belts of the system. If we make the assumption that the outermost planet is responsible for the stirring of the disc, the location of its inner edge and the eccentricity of the disc, then we can more tightly predict its eccentricity, mass and semimajor axis to be $e_{\rm{p}}=0.34^{+0.20}_{-0.13}$, $m_{\rm{p}}=0.7^{+0.5}_{-0.3}\,\rm{M}_{\rm{J}}$ and $a_{\rm{p}}=76^{+12}_{-13}\,\rm{au}$., Comment: 9 pages, 5 figures, accepted for publication in MNRAS

Low mass stars might offer today the best opportunities to detect and characterise planetary systems, especially those harbouring close-in low mass temperate planets. Among those stars, TRAPPIST-1 is exceptional since it has seven Earth-sized planets, of which three could sustain liquid water on their surfaces. Here we present new and deep ALMA observations of TRAPPIST-1 to look for an exo-Kuiper belt which can provide clues about the formation and architecture of this system. Our observations at 0.88 mm did not detect dust emission, but can place an upper limit of 23$��$Jy if the belt is smaller than 4 au, and 0.15 mJy if resolved and 100 au in radius. These limits correspond to low dust masses of $\sim10^{-5}-10^{-2}$ $M_\oplus$, which are expected after 8 Gyr of collisional evolution unless the system was born with a $>20$ $M_\oplus$ belt of 100 km-sized planetesimals beyond 40 au or suffered a dynamical instability. This $20$ $M_\oplus$ mass upper limit is comparable to the combined mass in TRAPPIST-1 planets, thus it is possible that most of the available solid mass in this system was used to form the known planets. A similar analysis of the ALMA data on Proxima Cen leads us to conclude that a belt born with a mass $\gtrsim1$ $M_\oplus$ in 100 km-sized planetesimals could explain its putative outer belt at 30 au. We recommend that future characterisations of debris discs around low mass stars should focus on nearby and young systems if possible., accepted for publication in MNRAS, 7 pages, 5 figures

Resolved ALMA and VLA observations indicate the existence of two dust traps in the protoplanetary disc MWC 758. By means of 2D gas+dust hydrodynamical simulations post-processed with 3D dust radiative transfer calculations, we show that the spirals in scattered light, the eccentric, asymmetric ring and the crescent-shaped structure in the (sub)millimetre can all be caused by two giant planets: a 1.5-Jupiter mass planet at 35 au (inside the spirals) and a 5-Jupiter mass planet at 140 au (outside the spirals). The outer planet forms a dust-trapping vortex at the inner edge of its gap (at ~85 au), and the continuum emission of this dust trap reproduces the ALMA and VLA observations well. The outer planet triggers several spiral arms which are similar to those observed in polarised scattered light. The inner planet also forms a vortex at the outer edge of its gap (at ~50 au), but it decays faster than the vortex induced by the outer planet, as a result of the disc's turbulent viscosity. The vortex decay can explain the eccentric inner ring seen with ALMA as well as the low signal and larger azimuthal spread of this dust trap in VLA observations. Finding the thermal and kinematic signatures of both giant planets could verify the proposed scenario., 18 pages, 8 figures, accepted for publication in MNRAS

The inclination distribution of the Kuiper belt provides unique constraints on its origin and dynamical evolution, motivating vertically resolved observations of extrasolar planetesimal belts. We present ALMA observations of millimeter emission in the near edge-on planetesimal belt around $\beta$ Pictoris, finding that the vertical distribution is significantly better described by the sum of two Gaussians compared to a single Gaussian. This indicates that, as for the Kuiper belt, the inclination distribution of $\beta$ Pic's belt is better described by the sum of dynamically hot and cold populations rather than a single component. The hot and cold populations have RMS inclinations of 8.9$^{+0.7}_{-0.5}$ and 1.1$^{+0.5}_{-0.5}$ degrees. We also report that an axisymmetric belt model provides a good fit to new and archival ALMA visibilities, and confirm that the midplane is misaligned with respect to $\beta$ Pic b's orbital plane. However, we find no significant evidence for either the inner disk tilt observed in scattered light and CO emission or the South-West/North-East (SW/NE) asymmetry previously reported for millimeter emission. Finally, we consider the origin of the belt's inclination distribution. Secular perturbations from $\beta$ Pic b are unlikely to provide sufficient dynamical heating to explain the hot population throughout the belt's radial extent, and viscous stirring from large bodies within the belt alone cannot reproduce the two populations observed. This argues for an alternative or additional scenario, such as planetesimals being born with high inclinations, or the presence of a `$\beta$ Pic c' planet, potentially migrating outwards near the belt's inner edge., Comment: 19 pages, 12 figures; Accepted for publication in AJ

The large crescents imaged by ALMA in transition disks suggest that azimuthal dust trapping concentrates the larger grains, but centimetre-wavelengths continuum observations are required to map the distribution of the largest observable grains. A previous detection at ~1cm of an unresolved clump along the outer ring of MWC758 (Clump1), and buried inside more extended sub-mm continuum, motivates followup VLA observations. Deep multiconfiguration integrations reveal the morphology of Clump 1 and additional cm-wave components which we characterize via comparison with a deconvolution of recent 342GHz data (~1mm). Clump1, which concentrates ~1/3 of the whole disk flux density at ~1cm, is resolved as a narrow arc with a deprojected aspect ratio Chi>5.6, and with half the azimuthal width than at 342 GHz. The spectral trends in the morphology of Clump1 are quantitatively consistent with the Lyra-Lin prescriptions for dust trapping in an anticyclonic vortex, provided with porous grains (f~0.2+-0.2) in a very elongated (Chi~14+-3) and cold (T~23+-2K) vortex. The same prescriptions constrain the turbulence parameter alpha and the gas surface density Sigma_g through log10( alpha x Sigma_g /g/cm2)~-2.3+-0.4, thus requiring values for Sigma_g larger than a factor of a few compared to that reported in the literature from the CO isotopologues, if alpha, Comment: accepted to MNRAS