Browsing by Author "Isella, A."
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item A gap in the planetesimal disc around HD 107146 and asymmetric warm dust emission revealed by ALMA(Oxford University Press, 2018) Marino, S.; Carpenter, J.; Wyatt, M.C.; Booth, M.; Casassus, S.; Faramaz, V.; Guzman, V.; Hughes, A.M.; Isella, A.; Kennedy, G.M.; Matrà, L.; Ricci, L.; Corder, S.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 characterized by a circular gap extending from 60 to 100 au in which the continuum emission drops by about 50 per cent. 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 millimetre 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 disc 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 require 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 μμm 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.Item Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70(EDP Sciences, 2018) Keppler, M.; Benisty, M.; Müller, A.; Henning, Th.; van Boekel, R.; Cantalloube, F.; Ginski, C.; van Holstein, R.G.; Maire, A.-L.; Pohl, A.; Samland, M.; Avenhaus, H.; Baudino, J.-L.; Boccaletti, A.; de Boer, J.; Bonnefoy, M.; Chauvin, G.; Desidera, S.; Langlois, M.; Lazzoni, C.; Marleau, G.-D.; Mordasini, C.; Pawellek, N.; Stolker, T.; Vigan, A.; Zurlo, A.; Birnstiel, T.; Brandner, W.; Feldt, M.; Flock, M.; Girard, J.; Gratton, R.; Hagelberg, J.; Isella, A.; Janson, M.; Juhasz, A.; Kemmer, J.; Kral, Q.; Lagrange, A.-M.; Launhardt, R.; Matter, A.; Ménard, F.; Milli, J.; Mollière, P.; Olofsson, J.; Pérez, L.; Pinilla, P.; Pinte, C.; Quanz, S.P.; Schmidt, T.; Udry, S.; Wahhaj, Z.; Williams, J.P.; Buenzli, E.; Cudel, M.; Dominik, C.; Galicher, R.; Kasper, M.; Lannier, J.; Mesa, D.; Mouillet, D.; Peretti, S.; Perrot, C.; Salter, G.; Sissa, E.; Wildi, F.; Abe, L.; Antichi, J.; Augereau, J.-C.; Baruffolo, A.; Baudoz, P.; Bazzon, A.; Beuzit, J.-L.; Blanchard, P.; Brems, S.S.; Buey, T.; De Caprio, V.; Carbillet, M.; Carle, M.; Cascone, E.; Cheetham, A.; Claudi, R.; Costille, A.; Delboulbé, A.; Dohlen, K.; Fantinel, D.; Feautrier, P.; Fusco, T.; Giro, E.; Gluck, L.; Gry, C.; Hubin, N.; Hugot, E.; Jaquet, M.; Le Mignant, D.; Llored, M.; Madec, F.; Magnard, Y.; Martinez, P.; Maurel, D.; Meyer, M.; Möller-Nilsson, O.; Moulin, T.; Mugnier, L.; Origné, A.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Puget, P.; Rabou, P.; Ramos, J.; Rigal, F.; Rochat, S.; Roelfsema, R.; Rousset, G.; Roux, A.; Salasnich, B.; Sauvage, J.-F.; Sevin, A.; Soenke, C.; Stadler, E.; Suarez, M.; Turatto, M.; Weber, L.Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features. Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk–planet interactions and other evolutionary processes. Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes. Results. We detect a point source within the gap of the disk at about 195 mas (~22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of ~54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than ~17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains. Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet–disk interactions, planetary atmospheres, and evolutionary models.Item Dust modeling of the combined ALMA and SPHERE datasets of HD 163296. Is HD 163296 really a Meeus group II disk?(EDP Sciences, 2018) Muro-Arena, G.A.; Dominik, C.; Waters, L.B.F.M.; Min, M.; Klarmann, L.; Ginski, C.; Isella, A.; Benisty, M.; Pohl, A.; Garufi, A.; Hagelberg, J.; Langlois, M.; Menard, F.; Pinte, C.; Sezestre, E.; van der Plas, G.; Villenave, M.; Delboulbé, A.; Magnard, Y.; Möller-Nilsson, O.; Pragt, J.; Rabou, P.; Roelfsema, R.Context. Multiwavelength observations are indispensable in studying disk geometry and dust evolution processes in protoplanetary disks. Aims. We aim to construct a three-dimensional model of HD 163296 that is capable of reproducing simultaneously new observations of the disk surface in scattered light with the SPHERE instrument and thermal emission continuum observations of the disk midplane with ALMA. We want to determine why the spectral energy distribution of HD 163296 is intermediary between the otherwise well-separated group I and group II Herbig stars. Methods. The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the inclination of the inner disk component and turbulence and grain growth in the outer disk. Results. While three rings are observed in the disk midplane in millimeter thermal emission at ~80, 124, and 200 AU, only the innermost of these is observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide two models that are capable of explaining this difference. The first model uses increased settling in the outer disk as a mechanism to bring the small dust grains on the surface of the disk closer to the midplane and into the shadow cast by the first ring. The second model uses depletion of the smallest dust grains in the outer disk as a mechanism for decreasing the optical depth at optical and near-infrared wavelengths. In the region outside the fragmentation-dominated regime, such depletion is expected from state-of-the-art dust evolution models. We studied the effect of creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I sources.Item FAUST - V. Hot methanol in the [BHB2007] 11 protobinary system; hot corino versus shock origin(EDP Sciences, 2022) Vastel, C.; Alves, F.; Ceccarelli, C.; Bouvier, M.; Jiménez-Serra, I.; Sakai, T.; Caselli, P.; Evans, L.; Fontani, F.; Gal, R. Le; Chandler, C.J.; Svoboda, B.; Maud, L.; Codella, C.; Sakai, N.; Lόpez-Sepulcre, A.; Moellenbrock, G.; Aikawa, Y.; Balucani, N.; Bianchi, E.; Busquet, G.; Caux, E.; Charnley, S.; Cuello, N.; Simone, M. De; Dulieu, F.; Durân, A.; Fedele, D.; Feng, S.; Francis, L.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Imai, M.; Isella, A.; Johnstone, D.; Lefloch, B.; Loinard, L.; Maureira, M.; Murillo, N.M.; Mercimek, S.; Mori, S.; Menard, F.; Miotello, A.; Nakatani, R.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Ospina-Zamudio, J.; Oya, Y.; Pineda, J.E.; Podio, L.; Rimola, A.; Cox, D. Segura; Shirley, Y.; Testi, L.; Viti, S.; Watanabe, N.; Watanabe, Y.; Witzel, A.; Xue, C.; Zhang, Y.; Zhao, B.; Yamamoto, S.Aims.Methanol is a ubiquitous species commonly found in the molecular interstellar medium. It is also a crucial seed species for the build-up of chemical complexity in star forming regions. Thus, understanding how its abundance evolves during the star formation process and whether it enriches the emerging planetary system is of paramount importance.Methods. We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disc/envelope system of solar protostars) to study the methanol line emission towards the [BHB2007] 11 protobinary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disc has previously been detected.Results. Twelve methanol lines have been detected with upper energies in the [45–537] K range along with one 13CH3OH transition and one methyl formate (CH3OCHO) line blended with one of the methanol transitions. The methanol emission is compact (FWHM ~ 0.5″) and encompasses both protostars, which are separated by only 0.2″ (28 au). In addition, the overall methanol line emission presents three velocity components, which are not spatially resolved by our observations. Nonetheless, a detailed analysis of the spatial origin of these three components suggests that they are associated with three different spatial regions, with two of them close to 11B and the third one associated with 11A. A radiative transfer analysis of the methanol lines gives a kinetic temperature of [100–140] K, an H2 volume density of 106–107 cm−3 and column density of a few 1018 cm−2 in all three components with a source size of ~0.15″. Thus, this hot and dense gas is highly enriched in methanol with an abundance as high as 10−5. Using previous continuum data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects.Conclusions. Although we cannot firmly exclude other possibilities, we suggest that the detected hot methanol is resulting from the shocked gas from the incoming filaments streaming towards [BHB2007] 11A and B, respectively. Higher spatial resolution observations are necessary to confirm this hypothesis.Item FAUST - XIII. Dusty cavity and molecular shock driven by IRS7B in the Corona Australis cluster(EDP Sciences, 2024) Sabatini, G.; Podio, L.; Codella, C.; Watanabe, Y.; Simone, M. De; Bianchi, E.; Ceccarelli, C.; Chandler, C. J.; Sakai, N.; Svoboda, B.; Testi, L.; Aikawa, Y.; Balucani, N.; Bouvier, M.; Caselli, P.; Caux, E.; Chahine, L.; Charnley, S.; Cuello, N.; Dulieu, F.; Evans, L.; Fedele, D.; Feng, S.; Fontani, F.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Isella, A.; Jímenez-Serra, I.; Johnstone, D.; Lefloch, B.; Gal, R. Le; Loinard, L.; Liu, H. B.; López-Sepulcre, A.; Maud, L. T.; Maureira, M. J.; Menard, F.; Miotello, A.; Moellenbrock, G.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Oya, Y.; Pineda, J.; Rimola, A.; Sakai, T.; Segura-Cox, D.; Shirley, Y.; Vastel, C.; Viti, S.; Watanabe, N.; Zhang, Y.; Zhang, Z. E.; Yamamoto, S.Context.The origin of the chemical diversity observed around low-mass protostars probably resides in the earliest history of these systems.Aims. We aim to investigate the impact of protostellar feedback on the chemistry and grain growth in the circumstellar medium of multiple stellar systems. Methods. In the context of the ALMA Large Program FAUST, we present high-resolution (50 au) observations of CH3OH, H2CO, and SiO and continuum emission at 1.3 mm and 3 mm towards the Corona Australis star cluster.Results. Methanol emission reveals an arc-like structure at ∼1800 au from the protostellar system IRS7B along the direction perpendicular to the major axis of the disc. The arc is located at the edge of two elongated continuum structures that define a cone emerging from IRS7B. The region inside the cone is probed by H2CO, while the eastern wall of the arc shows bright emission in SiO, a typical shock tracer. Taking into account the association with a previously detected radio jet imaged with JVLA at 6 cm, the molecular arc reveals for the first time a bow shock driven by IRS7B and a two-sided dust cavity opened by the mass-loss process. For each cavity wall, we derive an average H 2 column density of ∼7 × 1021 cm−2, a mass of ∼9 × 10−3 M⊙, and a lower limit on the dust spectral index of 1.4.Conclusions. These observations provide the first evidence of a shock and a conical dust cavity opened by the jet driven by IRS7B, with important implications for the chemical enrichment and grain growth in the envelope of Solar System analogues.Item FAUST - XVII. Super deuteration in the planet-forming system IRS 63 where the streamer strikes the disk(EDP Sciences, 2024) Podio, L.; Ceccarelli, C.; Codella, C.; Sabatini, G.; Segura-Cox, D.; Balucani, N.; Rimola, A.; Ugliengo, P.; Chandler, C. J.; Sakai, N.; Svoboda, B.; Pineda, J.; Simone, M. De; Bianchi, E.; Caselli, P.; Isella, A.; Aikawa, Y.; Bouvier, M.; Caux, E.; Chahine, L.; Charnley, S. B.; Cuello, N.; Dulieu, F.; Evans, L.; Fedele, D.; Feng, S.; Fontani, F.; Hama, T.; Hanawa, T.; Herbst, E.; Hirota, T.; Jiménez-Serra, I.; Johnstone, D.; Lefloch, B.; Gal, R. Le; Loinard, L.; Liu, H. Baobab; López-Sepulcre, A.; Maud, L. T.; Maureira, M. J.; Menard, F.; Miotello, A.; Moellenbrock, G.; Nomura, H.; Oba, Y.; Ohashi, S.; Okoda, Y.; Oya, Y.; Sakai, T.; Shirley, Y.; Testi, L.; Vastel, C.; Viti, S.; Watanabe, N.; Watanabe, Y.; Zhang, Y.; Zhang, Z. E.; Yamamoto, S.Context. Recent observations suggest that planet formation starts early, in protostellar disks of ≤105 yr, which are characterized by strong interactions with the environment, such as through accretion streamers and molecular outflows.Aims. To investigate the impact of such phenomena on the physical and chemical properties of a disk, it is key to understand what chemistry planets inherit from their natal environment. Methods. In the context of the ALMA large program Fifty AU Study of the chemistry in the disk/envelope system of solar-like protostars (FAUST), we present observations on scales from ∼1500 au to ∼60 au of H2CO, HDCO, and D2CO toward the young planet-forming disk IRS 63. Results. The H2CO probes the gas in the disk as well as in a large scale streamer (∼1500 au) impacting onto the southeast disk side. We detected for the first time deuterated formaldehyde, HDCO and D2CO, in a planet-forming disk and HDCO in the streamer that is feeding it. These detections allowed us to estimate the deuterium fractionation of H2CO in the disk: [HDCO]/[H2CO] ∼ 0.1 − 0.3 and [D2CO]/[H2CO] ∼ 0.1. Interestingly, while HDCO follows the H2CO distribution in the disk and in the streamer, the distribution of D2CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the southeast disk side, where the streamer crashes onto the disk. In addition, D2CO was detected in two spots along the blue- and redshifted outflow. This suggests that (i) in the disk, HDCO formation is dominated by gas-phase reactions in a manner similar to H2CO, while (ii) D2CO is mainly formed on the grain mantles during the prestellar phase and/or in the disk itself and is at present released in the gas phase in the shocks driven by the streamer and the outflow. Conclusions. These findings testify to the key role of streamers in the buildup of the disk concerning both the final mass available for planet formation and its chemical composition.Item Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA(EDP Sciences, 2015) van der Marel, N.; van Dishoeck, E.F.; Bruderer, S.; Pérez, L.; Isella, A.Context. Transitional disks with large dust cavities are important laboratories in which to study planet formation and disk evolution. Cold gas may still be present inside these cavities, but quantying this gas is challenging. The gas content is important for constraining the origin of the dust cavity. Aims. We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of 12CO 6–5 and 690 GHz (Band 9) continuum of five well-studied transitional disks. In addition, we analyze previously published Band 7 observations of a disk in the 12CO 3–2 line and 345 GHz continuum. The observations are used to set constraints on the gas and dust surface density profiles, in particular, the drop δgas of the gas density inside the dust cavity. Methods. The physical-chemical modeling code DALI was used to simultaneously analyze the gas and dust images. We modeled SR21, HD 135344B, LkCa15, SR24S, and RX J1615-3255 (Band 9) and J1604-2130 (Band 7). The spectral energy distribution and continuum visibility curve constrain the dust surface density. Then we used the same model to calculate the 12CO emission, which we compared with the observations through spectra and intensity cuts. The amount of gas inside the cavity was quantified by varying the δgas parameter. Results. Model fits to the dust and gas indicate that gas is still present inside the dust cavity for all disks, but at a reduced level. The gas surface density drops inside the cavity by at least a factor 10, while the dust density drops by at least a factor 1000. Disk masses are comparable with previous estimates from the literature, cavity radii are found to be smaller than in the data obtained with the 345 GHz SubMillimeter Array. Conclusions. The derived gas surface density profiles suggest that the cavity was cleared by one or more companions in all cases, which trapped the millimeter-sized dust at the edge of the cavity.Item High-contrast imaging of HD 163296 with the Keck/NIRC2 L′-band vortex coronograph(Oxford University Press, 2018) Guidi, G.; Ruane, G.; Williams, J.P.; Mawet, D.; Testi, L.; Zurlo, A.; Absil, O.; Bottom, M.; Choquet, E.; Christiaens, V.; Castellá, B. Femenía; Huby, E.; Isella, A.; Kastner, J.; Meshkat, T.; Reggiani, M.; Riggs, A.; Serabyn, E.; Wallack, N.We present observations of the nearby (D∼100 pc) Herbig star HD 163296 taken with the vortex coronograph at Keck/NIRC2 in the L′ band (3.7 μμm) to search for planetary mass companions in the ringed disc surrounding this pre-main-sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely associated with the first bright ring detected with ALMA in the λ = 1.3 mm dust continuum at ∼65 au. We also detect a point-like source at ∼0.5 arcsec projected separation in the north-east direction, close to the inner edge of the second gap in the millimetre images. Comparing the point source photometry with the atmospheric emission models of non-accreting giant planets, we obtain a mass of 6–7 MJ for a putative protoplanet, assuming a system age of 5 Myr. Based on the contrast at a 95 per cent level of completeness calculated on the emission-free regions of our images, we set upper limits for the masses of giant planets of 8–15 MJ, 4.5–6.5 MJ, and 2.5–4.0 MJ at the locations of the first, second, and third gap in the millimetre dust continuum, respectively. Further deep, high-resolution thermal IR imaging of the HD 163296 system are warranted to confirm the presence and nature of the point source and to better understand the structure of the dust disc.Item Shadows and asymmetries in the T Tauri disk HD 143006: evidence for a misaligned inner disk(EDP Sciences, 2018) Benisty, M.; Juhász, A.; Facchini, S.; Pinilla, P.; Boer, J. de; Pérez, L. M.; Keppler, M.; Muro-Arena, G.; Villenave, M.; Andrews, S.; Dominik, C.; Dullemond, C.P.; Gallenne, A.; Garufi, A.; Ginski, C.; Isella, A.Context. While planet formation is thought to occur early in the history of a protoplanetary disk, the presence of planets embedded in disks, or of other processes driving disk evolution, might be traced from their imprints on the disk structure. Aims. We study the morphology of the disk around the T Tauri star HD 143006, located in the ~5–11 Myr-old Upper Sco region, and we look for signatures of the mechanisms driving its evolution. Methods. We observed HD 143006 in polarized scattered light with VLT/SPHERE at near-infrared (J-band, 1.2 μm) wavelengths, reaching an angular resolution of ~0.037′′ (~6 au). We obtained two datasets, one with a 145 mas diameter coronagraph, and the other without, enabling us to probe the disk structure down to an angular separation of ~0.06′′ (~10 au). Results. In our observations, the disk of HD 143006 is clearly resolved up to ~0.5′′ and shows a clear large-scale asymmetry with the eastern side brighter than the western side. We detect a number of additional features, including two gaps and a ring. The ring shows an overbrightness at a position angle (PA) of ~140°, extending over a range in position angle of ~60°, and two narrow dark regions. The two narrow dark lanes and the overall large-scale asymmetry are indicative of shadowing effects, likely due to a misaligned inner disk. We demonstrate the remarkable resemblance between the scattered light image of HD 143006 and a model prediction of a warped disk due to an inclined binary companion. The warped disk model, based on the hydrodynamic simulations combined with three-dimensional radiative transfer calculations, reproduces all major morphological features. However, it does not account for the observed overbrightness at PA ~ 140°. Conclusions. Shadows have been detected in several protoplanetary disks, suggesting that misalignment in disks is not uncommon. However, the origin of the misalignment is not clear. As-yet-undetected stellar or massive planetary companions could be responsible for them, and naturally account for the presence of depleted inner cavities.Item The Complex Morphology of the Young Disk MWC 758: Spirals and Dust Clumps around a Large Cavity(IOP Publishing, 2018) Boehler, Y.; Ricci, L.; Weaver, E.; Isella, A.; Benisty, M.; Carpenter, J.; Grady, C.; Shen, Bo-Ting; Tang, Ya-Wen; Perez, L.We present Atacama Large Millimeter Array observations at an angular resolution of 0farcs1–0farcs2 of the disk surrounding the young Herbig Ae star MWC 758. The data consist of images of the dust continuum emission recorded at 0.88 millimeter, as well as images of the 13CO and C18O J = 3–2 emission lines. The dust continuum emission is characterized by a large cavity of roughly 40 au in radius which might contain a mildly inner warped disk. The outer disk features two bright emission clumps at radii of ~47 and 82 au that present azimuthal extensions and form a double-ring structure. The comparison with radiative transfer models indicates that these two maxima of emission correspond to local increases in the dust surface density of about a factor 2.5 and 6.5 for the south and north clumps, respectively. The optically thick 13CO peak emission, which traces the temperature, and the dust continuum emission, which probes the disk midplane, additionally reveal two spirals previously detected in near-IR at the disk surface. The spirals seen in the dust continuum emission present, however, a slight shift of a few au toward larger radii and one of the spirals crosses the south dust clump. Finally, we present different scenarios to explain the complex structure of the disk.Item The morphology of CS Cha circumbinary disk suggesting the existence of a Saturn-mass planet(EDP Sciences, 2022) Kurtovic, N.T.; Pinilla, P.; Penzlin, Anna B.T.; Benisty, M.; Pérez, L.; Ginski, C.; Isella, A.; Kley, W.; Menard, F.; Pérez, S.; Bayo, A.Context.Planets have been detected in circumbinary orbits in several different systems, despite the additional challenges faced during their formation in such an environment.Aims.We investigate the possibility of planetary formation in the spectroscopic binary CS Cha by analyzing its circumbinary disk.Methods. The system was studied with high angular resolution ALMA observations at 0.87 mm. Visibilities modeling and Keplerian fitting are used to constrain the physical properties of CS Cha, and the observations were compared to hydrodynamic simulations.Results.Our observations are able to resolve the disk cavity in the dust continuum emission and the 12CO J:3–2 transition. We find the dust continuum disk to be azimuthally axisymmetric (less than 9% of intensity variation along the ring) and of low eccentricity (of 0.039 at the peak brightness of the ring).Conclusions. Under certain conditions, low eccentricities can be achieved in simulated disks without the need of a planet, however, the combination of low eccentricity and axisymmetry is consistent with the presence of a Saturn-like planet orbiting near the edge of the cavity.Item Vortex-like kinematic signal, spirals, and beam smearing effect in the HD 142527 disk(EDP Sciences, 2021) Boehler, Y.; Ménard, F.; Robert, C. M. T.; Isella, A.; Pinte, C.; Gonzalez, J.-F.; Plas, G. van der; Weaver, E.; Teague, R.; Garg, H.; Méheut, H.Vortices are one of the most promising mechanisms to locally concentrate millimeter dust grains and allow the formation of planetesimals through gravitational collapse. The outer disk around the binary system HD 142527 is known for its large horseshoe structure with azimuthal contrasts of ~3–5 in the gas surface density and of ~50 in the dust. Using 13CO and C18O J = 3–2 transition lines, we detect kinematic deviations to the Keplerian rotation, which are consistent with the presence of a large vortex around the dust crescent, as well as a few spirals in the outer regions of the disk. Comparisons with a vortex model suggest velocity deviations up to 350 m s−1 after deprojection compared to the background Keplerian rotation, as well as an extension of ±40 au radially and ~200° azimuthally, yielding an azimuthal-to-radial aspect ratio of ~5. Another alternative for explaining the vortex-like signal implies artificial velocity deviations generated by beam smearing in association with variations of the gas velocity due to gas pressure gradients at the inner and outer edges of the circumbinary disk. The two scenarios are currently difficult to differentiate and, for this purpose, would probably require the use of multiple lines at a higher spatial resolution. The beam smearing effect, due to the finite spatial resolution of the observations and gradients in the line emission, should be common in observations of protoplanetary disks and may lead to misinterpretations of the gas velocity, in particular around ring-like structures.