Search

During the past decade, state-of-the-art planet-finder instruments like SPHERE@VLT, coupling coronagraphic devices and extreme adaptive optics systems, unveiled, thanks to large surveys, around 20 planetary mass companions at semi-major axis greater than 10 astronomical units. Direct imaging being the only detection technique to be able to probe this outer region of planetary systems, the SPHERE infrared survey for exoplanets (SHINE) was designed and conducted from 2015 to 2021 to study the demographics of such young gas giant planets around 400 young nearby solar-type stars. In this paper, we present the observing strategy, the data quality, and the point sources analysis of the full SHINE statistical sample as well as snapSHINE. Both surveys used the SPHERE@VLT instrument with the IRDIS dual band imager in conjunction with the integral field spectrograph IFS and the angular differential imaging observing technique. All SHINE data (650 datasets), corresponding to 400 stars, including the targets of the F150 survey, are processed in a uniform manner with an advanced post-processing algorithm called PACO ASDI. An emphasis is put on the classification and identification of the most promising candidate companions. Compared to the previous early analysis SHINE F150, the use of advanced post-processing techniques significantly improved by one or 2 magnitudes (x3-x6) the contrast detection limits, which will allow us to put even tighter constraints on the radial distribution of young gas giants. This increased sensitivity directly places SHINE as the largest and deepest direct imaging survey ever conducted. We detected and classified more than 3500 physical sources. One additional substellar companion has been confirmed during the second phase of the survey (HIP 74865 B), and several new promising candidate companions are awaiting second epoch confirmations., Comment: Accepted for publication in A&A. 19 pages, 19 figures. Abstract shortened to comply with ArxiV standards. Data ingestion at the CDS is ongoing

PDS 70 is a unique system as it hosts a protoplanetary disk with two confirmed forming planets, making it an ideal target for characterizing dust in such disks. We present new high-contrast polarimetric differential imaging of PDS 70 using the $N\_R$ filter on SPHERE/ZIMPOL, combined with archival VLT/SPHERE data across five wavelengths ($N\_R$, $VBB$, $J$, $H$, and $Ks$) spanning seven epochs over eight years. For each epoch, we corrected smearing effects from instrument resolution, analyzed azimuthal brightness profiles, and derived intrinsic disk-integrated polarized reflectivity and brightness contrasts. Our analysis reveals significant temporal variability in both integrated polarized reflectivity and azimuthal brightness profiles, suggesting variable shadowing on the outer disk from unresolved inner disk structures. Nonetheless, we observe a systematic wavelength-dependent contrast between the near and far sides of the inclined disk, highlighting the need to consider shadowing from the inner disk and surface geometry of the reflecting disk in data interpretation., Comment: The main text includes 6 pages and 4 figures, appendix has 4 pages; accepted by A&A Letters

This paper presents near-infrared spectropolarimetric and velocimetric observations of the young planet-hosting T Tauri star PDS 70, collected with SPIRou at the 3.6m Canada-France-Hawaii Telescope from 2020 to 2024. Clear Zeeman signatures from magnetic fields at the surface of PDS 70 are detected in our data set of 40 circularly polarized spectra. Longitudinal fields inferred from Zeeman signatures, ranging from -116 to 176 G, are modulated on a timescale of 3.008$\pm$0.006 d, confirming that this is the rotation period of PDS 70. Applying Zeeman-Doppler imaging to subsets of unpolarized and circularly polarised line profiles, we show that PDS 70 hosts low-contrast brightness spots and a large-scale magnetic field in its photosphere, featuring in particular a dipole component of strength 200-420 G that evolves on a timescale of months. From the broadening of spectral lines, we also infer that PDS 70 hosts a small-scale field of 2.51$\pm$0.12 kG. Radial velocities derived from unpolarized line profiles are rotationally modulated as well, and exhibit additional longer-term chromatic variability, most likely attributable to magnetic activity rather than to a close-in giant planet (with a 3sigma upper limit on its minimum mass of ~4 Mjup at a distance of ~0.2 au). We finally confirm that accretion occurs at the surface of PDS 70, generating modulated red-shifted absorption in the 1083.3-nm He i triplet, and show that the large-scale magnetic field, often strong enough to disrupt the inner accretion disc up to the corotation radius, weakens as the star gets fainter and redder (as in 2022), suggesting that dust from the disc more easily penetrates the stellar magnetosphere in such phases., Comment: MNRAS in press (20 pages, 12 figures, 5 tables)

Recent observations suggest that planets formation starts early, in protostellar disks of $\le10^5$ yrs, which are characterized by strong interactions with the environment, e.g., through accretion streamers and molecular outflows. To investigate the impact of such phenomena on disk physical and chemical properties it is key to understand what chemistry planets inherit from their natal environment. 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 H$_2$CO, HDCO, and D$_2$CO towards the young planet-forming disk IRS~63. H$_2$CO probes the gas in the disk as well as in a large scale streamer (~1500 au) impacting onto the South-East (SE) disk side. We detect for the first time deuterated formaldehyde, HDCO and D$_2$CO, in a planet-forming disk, and HDCO in the streamer that is feeding it. This allows us to estimate the deuterium fractionation of H$_2$CO in the disk: [HDCO]/[H$_2$CO]$\sim0.1-0.3$ and [D$_2$CO]/[H$_2$CO]$\sim0.1$. Interestingly, while HDCO follows the H$_2$CO distribution in the disk and in the streamer, the distribution of D$_2$CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the SE disk side, where the streamer crashes onto the disk. In addition, D$_2$CO is detected in two spots along the blue- and red-shifted outflow. This suggests that: (i) in the disk, HDCO formation is dominated by gas-phase reactions similarly to H$_2$CO, while (ii) D$_2$CO was 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. These findings testify on the key role of streamers in the build-up of the disk both concerning the final mass available for planet formation and its chemical composition., Comment: 12 pages, 10 figures, accepted for publication on A&A

In this paper we report near-infrared observations of the classical T Tauri star TW Hya with the SPIRou high-resolution spectropolarimeter and velocimeter at the 3.6-m Canada-France-Hawaii Telescope in 2019, 2020, 2021 and 2022. By applying Least-Squares Deconvolution (LSD) to our circularly polarized spectra, we derived longitudinal fields that vary from year to year from -200 to +100 G, and exhibit low-level modulation on the 3.6 d rotation period of TW Hya, despite the star being viewed almost pole-on. We then used Zeeman-Doppler Imaging to invert our sets of unpolarized and circularly-polarized LSD profiles into brightness and magnetic maps of TW Hya in all 4 seasons, and obtain that the large-scale field of this T Tauri star mainly consists of a 1.0-1.2 kG dipole tilted at about 20{\deg} to the rotation axis, whereas the small-scale field reaches strengths of up to 3-4 kG. We find that the large-scale field is strong enough to allow TW Hya to accrete material from the disc on the polar regions at the stellar surface in a more or less geometrically stable accretion pattern, but not to succeed in spinning down the star. We also report the discovery of a radial velocity signal of semi-amplitude $11.1^{+3.3}_{-2.6}$ m/s (detected at 4.3$\sigma$ at a period of 8.3 d in the spectrum of TW Hya, whose origin may be attributed to either a non-axisymmetric density structure in the inner accretion disc, or to a $0.55^{+0.17}_{-0.13}$ Jupiter mass candidate close-in planet (if orbiting in the disc plane), at an orbital distance of $0.075\pm0.001$ au., Comment: MNRAS, in press (23 pages, 16 figures, 6 tables)

Context. Understanding the connection between outflows, winds, accretion and disks in the inner protostellar regions is crucial for comprehending star and planet formation process. Aims. We aim to we explore the inner 300 au of the protostar IRAS 4A2 as part of the ALMA FAUST Large Program. Methods. We analysed the kinematical structures of SiO and CH$_3$OH emission with 50 au resolution. Results. The emission arises from three zones: i) a very compact and unresolved region ($<$50 au) dominated by the ice sublimation zone, at $\pm$1.5 km s$^{-1}$ with respect to vsys, traced by methanol; ii) an intermediate region (between 50 au and 150 au) traced by both SiO and CH$_3$OH, between 2 and 6 km s$^{-1}$ with respect to vsys, with an inverted velocity gradient (with respect to the large scale emission), whose origin is not clear; iii) an extended region ($>$150 au) traced by SiO, above 7 km s$^{-1}$ with respect to vsys, and dominated by the outflow. In the intermediate region we estimated a CH$_3$OH/SiO abundance ratio of about 120-400 and a SiO/H$_2$ abundance of 10$^{-8}$. We explored various possibilities to explain the origin of this region such as, rotating disk/inner envelope, jet on the plane of the sky/precessing, wide angle disk wind. Conclusions. We propose that CH$_3$OH and SiO in the inner 100 au probe the base of a wide-angle disk wind. The material accelerated in the wind crosses the plane of the sky, giving rise to the observed inverted velocity gradient, and sputtering the grain mantles and cores releasing CH$_3$OH and SiO. This is the first detection of a disk wind candidate in SiO, and the second ever in CH$_3$OH., Comment: Accepted in A&A Letters

We carried out very deep VLT/SPHERE imaging polarimetry of the nearby system Eps Eri based on 38.5 hours of integration time with a 600 - 900 nm broadband filter to search for polarized scattered light from a planet or from circumstellar dust using AO, coronagraphy, high precision differential polarimetry, and angular differential imaging. We have improved several data reduction and post-processing techniques and also developed new ones to further increase the sensitivity of SPHERE/ZIMPOL. The data provide unprecedented contrast limits, but no significant detection of a point source or an extended signal from circumstellar dust. For each observing epoch, we obtained a point source contrast for the polarized intensity between $2\cdot 10^{-8}$ and $4\cdot 10^{-8}$ at the expected separation of the planet Eps Eri b of 1'' near quadrature phase. The polarimetric contrast limits are about six to 50 times better than the intensity limits because polarimetric imaging is much more efficient in speckle suppression. Combining the entire 14-month data set to the search for a planet moving on a Keplerian orbit with the K-Stacker software further improves the contrast limits by a factor of about two, to about $8 \cdot 10^{-9}$ at 1''. This would allow the detection of a planet with a radius of about 2.5 Jupiter radii. The surface brightness contrast limits achieved for the polarized intensity from an extended scattering region are about 15 mag arcsec$^{-2}$ at 1'', or up to 3 mag arcsec$^{-2}$ deeper than previous limits. For Eps Eri, these limits exclude the presence of a narrow dust ring and they constrain the dust properties. This study shows that the polarimetric contrast limits for reflecting planets with SPHERE/ZIMPOL can be improved to a level $<10^{-8}$ simply by collecting more data over many nights and using the K-Stacker software., Comment: 26 pages, 20 figures, 5 tables. Accepted for publication in A&A

Over the past few years, chemical studies have revealed multiple structures in the vicinity of young stellar objects (YSOs). It has become evident that specific physical conditions are associated with the emission of particular molecular lines, allowing us to use molecular probes of the YSO physics. Consequently, chemical surveys are now necessary to fully constrain the origin of the observed structures. Several surveys have been conducted to explore the chemistry of YSOs, focusing on Class 0 and Class II objects. However, our knowledge of intermediate objects, that are Class I objects, remains limited. To bridge the gap and establish the relationship between observed structures and molecular line emission at the Class I evolutionary stage, we investigate the spatial distribution of key molecular gas species in the low-mass Class I protostar L1489 IRS (IRAS 04016+2610), a source part of the ChemYSO survey. We performed a 3mm line survey at high spatial and high spectral resolution using the NOEMA interferometer and the IRAM-30m telescope. We present here the ten brightest lines of our survey, in which we identified a new ~ 3 000 au long streamer in HC3N, C2H, and c-C3H2 emission, likely associated with more localized accretion shocks probed in SO. In addition, two ~ 10 000 au bubbles are seen with the dense molecular tracers HCO+, CS, and HCN around the YSO. Additionally, potential indicators of a second outflow appear in CS and HCN emission, but its nature remains to be confirmed. The late infall identified at large scales may originate from the nearby prestellar core L1489 and is likely responsible for the formation of an external warped disk in this system. The detection of a potential second outflow could be the direct evidence of a binary system. Finally, we hypothesize that the bubbles may result from the magnetic pressure as observed in numerical simulations., Comment: 16 pages, 12 figures, accepted for publication in Astronomy & Astrophysics

The origin of the chemical diversity observed around low-mass protostars probably resides in the earliest history of these systems. We aim to investigate the impact of protostellar feedback on the chemistry and grain growth in the circumstellar medium of multiple stellar systems. In the context of the ALMA Large Program FAUST, we present high-resolution (50 au) observations of CH$_3$OH, H$_2$CO, and SiO and continuum emission at 1.3 mm and 3 mm towards the Corona Australis star cluster. Methanol emission reveals an arc-like structure at $\sim$1800 au from the protostellar system IRS7B along the direction perpendicular to the major axis of the disc. The arc is located at the edge of two elongated continuum structures that define a cone emerging from IRS7B. The region inside the cone is probed by H$_2$CO, while the eastern wall of the arc shows bright emission in SiO, a typical shock tracer. Taking into account the association with a previously detected radio jet imaged with JVLA at 6 cm, the molecular arc reveals for the first time a bow shock driven by IRS7B and a two-sided dust cavity opened by the mass-loss process. For each cavity wall, we derive an average H$_2$ column density of $\sim$7$\times$10$^{21}$ cm$^{-2}$, a mass of $\sim$9$\times$10$^{-3}$ M$_\odot$, and a lower limit on the dust spectral index of $1.4$. 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., Comment: 12 pages, 8 figures, 3 tables. Accepted Letter in Astronomy & Astrophysics

iCOMs are species commonly found in the interstellar medium. They are believed to be crucial seed species for the build-up of chemical complexity in star forming regions as well as our own Solar System. Thus, understanding how their abundances evolve during the star formation process and whether it enriches the emerging planetary system is of paramount importance. We use data from the ALMA Large Program FAUST to study the compact line emission towards the [BHB2007] 11 proto-binary system (sources A and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disk has previously been detected. More than 45 CH3OCHO lines are clearly detected, as well as 8 CH3OCH3 transitions , 1 H2CCO transition and 4 t-HCOOH transitions. We compute the abundance ratios with respect to CH3OH for CH3OCHO, CH3OCH3, H2CCO, t-HCOOH (as well as an upper limit for CH3CHO) through a radiative transfer analysis. We also report the upper limits on the column densities of nitrogen bearing iCOMs, N(C2H5CN) and N(C2H3CN). The emission from the detected iCOMs and their precursors is compact and encompasses both protostars, which are separated by only 0.2" (~ 28 au). The integrated intensities tend to align with the Southern filament, revealed by the high spatial resolution observations of the dust emission at 1.3 mm. A PV and 2D analysis are performed on the strongest and uncontaminated CH3OCH3 transition and show three different spatial and velocity regions, two of them being close to 11B (Southern filament) and the third one near 11A. All our observations suggest that the detected methanol, as well as the other iCOMs, are generated by the shocked gas from the incoming filaments streaming towards [BHB2007] 11A and 11B, respectively, making this source one of the few where chemical enrichment of the gas caused by the streaming material is observed., Comment: Accepted in A&A

We report new observations of the classical T~Tauri star CI~Tau with the SPIRou near-infrared spectropolarimeter and velocimeter at the Canada-France-Hawaii Telescope (CFHT) in late 2019, 2020 and 2022, complemented with observations obtained with the ESPaDOnS optical spectropolarimeter at CFHT in late 2020. From our SPIRou and ESPaDOnS spectra, to which we applied Least-Squares Deconvolution, we infer longitudinal fields clearly modulated with the 9-d rotation period of CI~Tau. Using Zeeman-Doppler imaging, we reconstruct the large-scale magnetic topology, first from SPIRou data only in all three seasons, then from our 2020 SPIRou and ESPaDOnS data simultaneously. We find that CI~Tau hosts a mainly axisymmetric poloidal field, with a 1~kG dipole slightly tilted to the rotation axis and dark spots close to the pole that coincide with the footpoints of accretion funnels linking the star to the inner disc. Our results also suggest that CI~Tau accretes mass from the disc in a stable fashion. We further find that radial velocities (RV) derived from atomic and CO lines in SPIRou spectra are both rotationally modulated, but with a much lower amplitude than that expected from the putative candidate planet CI~Tau~b. We confirm the presence of a RV signal at a period of 23.86~d reported in a separate analysis, but detect it clearly in CO lines only and not in atomic lines, suggesting that it likely traces a non-axisymmetric structure in the inner disc of CI~Tau rather than a massive close-in planet., Comment: MNRAS, in press (22 pages, 11 figures, 6 tables)

The sample of planet-forming disks observed by high-contrast imaging campaigns over the last decade is mature enough to enable the demographical analysis of individual star-forming regions. We present the full census of Taurus sources with VLT/SPHERE polarimetric images available. The whole sample sums up to 43 targets (of which 31 have not been previously published) corresponding to one-fifth of the Class II population in Taurus and about half of such objects that are observable. A large fraction of the sample is apparently made up of isolated faint disks (equally divided between small and large self-shadowed disks). Ambient signal is visible in about one-third of the sample. This probes the interaction with the environment and with companions or the outflow activity of the system. The central portion of the Taurus region almost exclusively hosts faint disks, while the periphery also hosts bright disks interacting with their surroundings. The few bright disks are found around apparently older stars. The overall picture is that the Taurus region is in an early evolutionary stage of planet formation. Yet, some objects are discussed individually, as in an intermediate or exceptional stage of the disk evolution. This census provides a first benchmark for the comparison of the disk populations in different star forming regions., Comment: Accepted by A&A

We present JWST imaging from 2$\mu$m to 21$\mu$m of the edge-on protoplanetary disk around the embedded young star IRAS04302+2247. The structure of the source shows two reflection nebulae separated by a dark lane. The source extent is dominated by the extended filamentary envelope at $\sim$4.4$\mu$m and shorter wavelengths, transitioning at 7$\mu$m and longer wavelengths to more compact lobes of scattered light from the disk itself. The dark lane thickness does not vary significantly with wavelength, which we interpret as an indication for intermediate-sized ($\sim10\mu$m) grains in the upper layers of the disk. Intriguingly, we find that the brightest nebula of IRAS40302 switches side between 12.8$\mu$m and 21$\mu$m. We explore the effect of a tilted inner region on the general appearance of edge-on disks. We find that radiative transfer models of a disk including a tilted inner region can reproduce an inversion in the brightest nebula. In addition, for specific orientations, the model also predicts strong lateral asymmetries, which can occur for more than half possible viewing azimuths. A large number of edge-on protoplanetary disks observed in scattered light show such lateral asymmetries (15/20), which suggests that a large fraction of protoplanetary disks might host a tilted inner region. Stellar spots may also induce lateral asymmetries, which are expected to vary over a significantly shorter timescale. Variability studies of edge-on disks would allow to test the dominant scenario for the origin of these asymmetries., Comment: Accepted for publication in ApJ

Context. The study of protoplanetary disks is fundamental to understand their evolution and interaction with the surrounding environment, and to constrain planet formation mechanisms. Aims. We aim at characterising the young binary system HD 34700 A, which shows a wealth of structures. Methods. Taking advantage of the high-contrast imaging instruments SPHERE at the VLT, LMIRCam at the LBT, and of ALMA observations, we analyse this system at multiple wavelengths. We study the rings and spiral arms morphology and the scattering properties of the dust. We discuss the possible causes of all the observed features. Results. We detect for the first time, in the H${\alpha}$ band, a ring extending from $\sim$65 au to ${\sim}$120 au, inside the ring already known from recent studies. These two have different physical and geometrical properties. Based on the scattering properties, the outer ring may consist of grains of typical size $a_{out} > 4 {\mu}m$, while the inner ring of smaller grains ($a_{in} <= 0.4 {\mu m}$). Two extended logarithmic spiral arms stem from opposite sides of the disk. The outer ring appears as a spiral arm itself, with a variable radial distance from the centre and extended substructures. ALMA data confirm the presence of a millimetric dust substructure centred just outside the outer ring, and detect misaligned gas rotation patterns for HD 34700 A and B. Conclusions. The complexity of HD 34700 A, revealed by the variety of observed features, suggests the existence of one or more disk-shaping physical mechanisms. Possible scenarios, compatible with our findings, involve the presence inside the disk of a yet undetected planet of several Jupiter masses and the system interaction with the surroundings by means of gas cloudlet capture or flybys. Further observations with JWST/MIRI or ALMA (gas kinematics) could shed more light on these., Comment: Accepted for publication on A&A. 14 + 5 pages, 9 + 7 figures (text + appendix)

Scattered light imaging of protoplanetary disks provides key insights on the geometry and dust properties in the disk surface. Here we present JWST 2--21\,$\mu$m images of a 1000\,au-radius edge-on protoplanetary disk surrounding an 0.4\,$M_\odot$ young star in Taurus, 2MASS\,J04202144+2813491. These observations represent the longest wavelengths at which a protoplanetary disk is spatially resolved in scattered light. We combine these observations with HST optical images and ALMA continuum and CO mapping. We find that the changes in the scattered light disk morphology are remarkably small across a factor of 30 in wavelength, indicating that dust in the disk surface layers is characterized by an almost gray opacity law. Using radiative transfer models, we conclude that grains up to $\gtrsim10\,\mu$m in size are fully coupled to the gas in this system, whereas grains $\gtrsim100\,\mu$m are strongly settled towards the midplane. Further analyses of these observations, and similar ones of other edge-on disks, will provide strong empirical constraints on disk dynamics and evolution and grain growth models. In addition, the 7.7 and 12.\,$\mu$m JWST images reveal an X-shaped feature located above the warm molecular layer traced by CO line emission. The highest elevations at which this feature is detectable roughly match the maximal extent of the disk in visible wavelength scattered light as well as of an unusual kinematic signature in CO. We propose that these phenomena could be related to a disk wind entraining small dust grains., Comment: Accepted for publication in the Astronomical Journal

An edge-on debris disk was detected in 2015 around the young, nearby A0V star HD 110058. The disk showed features resembling those seen in the disk of beta Pictoris that could indicate the presence of a perturbing planetary-mass companion in the system. We investigated new and archival scattered light images of the disk in order to characterise its morphology and spectrum. In particular, we analysed the disk's warp to constrain the properties of possible planetary perturbers. Our work uses data from two VLT/SPHERE observations and archival data from HST/STIS. We measured the morphology of the disk by analysing vertical profiles along the length of the disk to extract the centroid spine position and vertical height. We extracted the surface brightness and reflectance spectrum of the disk. We detect the disk between 20 au (with SPHERE) and 150 au (with STIS), at a position angle of 159.6$^\circ\pm$0.6$^\circ$. Analysis of the spine shows an asymmetry between the two sides of the disk, with a 3.4$^\circ\pm$0.9$^\circ$ warp between ~20 au and 60 au. The disk is marginally vertically resolved in scattered light, with a vertical aspect ratio of 9.3$\pm$0.7% at 45 au. The extracted reflectance spectrum is featureless, flat between 0.95 micron and 1.1 micron, and red from 1.1 micron to 1.65 micron. The outer parts of the disk are also asymmetric with a tilt between the two sides compatible with a disk made of forward-scattering particles and seen not perfectly edge-on, suggesting an inclination of <84$^\circ$. The presence of an undetected planetary-mass companion on an inclined orbit with respect to the disk could explain the warp. The misalignment of the inner parts of the disk with respect to the outer disk suggests a warp that has not yet propagated to the outer parts of the disk, favouring the scenario of an inner perturber as the origin of the warp., Comment: 17 pages, 15 figures, 3 tables; accepted for publication in A&A

Early dust grain growth in protostellar envelopes infalling on young discs has been suggested in recent studies, supporting the hypothesis that dust particles start to agglomerate already during the Class 0/I phase of young stellar objects (YSOs). If this early evolution were confirmed, it would impact the usually assumed initial conditions of planet formation, where only particles with sizes $\lesssim 0.25 \mu$m are usually considered for protostellar envelopes. We aim to determine the maximum grain size of the dust population in the envelope of the Class 0/I protostar L1527 IRS, located in the Taurus star-forming region (140 pc). We use Atacama Large millimetre/sub-millimetre Array (ALMA) and Atacama Compact Array (ACA) archival data and present new observations, in an effort to both enhance the signal-to-noise ratio of the faint extended continuum emission and properly account for the compact emission from the inner disc. Using observations performed in four wavelength bands and extending the spatial range of previous studies, we aim to place tight constraints on the spectral ($\alpha$) and dust emissivity ($\beta$) indices in the envelope of L1527 IRS. We find a rather flat $\alpha \sim$ 3.0 profile in the range 50-2000 au. Accounting for the envelope temperature profile, we derive values for the dust emissivity index, 0.9 < $\beta$ < 1.6, and reveal a tentative, positive outward gradient. This could be interpreted as a distribution of mainly ISM-like grains at 2000 au, gradually progressing to (sub-)millimetre-sized dust grains in the inner envelope, where at R=300 au, $\beta$ = 1.1 +/- 0.1. Our study supports a variation of the dust properties in the envelope of L1527 IRS. We discuss how this can be the result of in-situ grain growth, dust differential collapse from the parent core, or upward transport of disc large grains., Comment: Accepted for publication in A&A. Contains 18 pages, 21 figures, 5 tables Replacement on Nov 22 to change title number of FAUST series from "X" to "IX."

More than 50% of solar-mass stars form in multiple systems. It is therefore crucial to investigate how multiplicity affects the star and planet formation processes at the protostellar stage. We report continuum and C$^{18}$O (2-1) observations of the VLA 1623-2417 protostellar system at 50 au angular resolution as part of the ALMA Large Program FAUST. The 1.3 mm continuum probes the disks of VLA 1623A, B, and W, and the circumbinary disk of the A1+A2 binary. The C$^{18}$O emission reveals, for the first time, the gas in the disk-envelope of VLA 1623W. We estimate the dynamical mass of VLA 1623W, $M_{\rm dyn}=0.45\pm0.08$ M$_{\odot}$, and the mass of its disk, $M_{\rm disk}\sim6\times10^{-3}$ M$_{\odot}$. C$^{18}$O also reveals streamers that extend up to 1000 au, spatially and kinematically connecting the envelope and outflow cavities of the A1+A2+B system with the disk of VLA 1623W. The presence of the streamers, as well as the spatial ($\sim$1300 au) and velocity ($\sim$2.2 km/s) offset of VLA 1623W suggest that either sources W and A+B formed in different cores, interacting between them, or that source W has been ejected from the VLA 1623 multiple system during its formation. In the latter case, the streamers may funnel material from the envelope and cavities of VLA 1623AB onto VLA 1623W, thus concurring to set its final mass and chemical content., Comment: 10 pages, 5 figures, accepted by MNRAS

We present new VLA observations, between 6.8mm and 66mm, of the edge-on Class~I disk IRAS04302+2247. Observations at 6.8mm and 9.2mm lead to the detection of thermal emission from the disk, while shallow observations at the other wavelengths are used to correct for emission from other processes. The disk radial brightness profile transitions from broadly extended in previous ALMA 0.9mm and 2.1mm observations to much more centrally brightened at 6.8mm and 9.2mm, which can be explained by optical depth effects. The radiative transfer modeling of the 0.9mm, 2.1mm, and 9.2mm data suggests that the grains are smaller than 1cm in the outer regions of the disk and allows us to obtain the first lower limit for the scale height of grains emitting at millimeter wavelengths in a protoplanetary disk. We find that the millimeter dust scale height is between 1au and 6au at a radius 100au from the central star, while the gas scale height is estimated to be about 7au, indicating a modest level of settling. The estimated dust height is intermediate between less evolved Class 0 sources, that are found to be vertically thick, and more evolved Class II sources, which show a significant level of settling. This suggests that we are witnessing an intermediate stage of dust settling., Comment: Accepted for publication in the Astrophysical Journal

Birth environments of young stars have strong imprints on the star itself and their surroundings. We present a detailed analysis of the wealthy circumstellar environment around the young Herbig Ae/Be star TCrA. Our aim is to understand the nature of the stellar system and the extended circumstellar structures as seen in scattered light images. We conduct our analysis combining archival data, and new adaptive optics high-contrast and high-resolution images. The scattered light images reveal the presence of a complex environment composed of a bright forward scattering rim of the disk's surface that is seen at very high inclination, a dark lane of the disk midplane, bipolar outflows, and streamer features likely tracing infalling material from the surrounding birth cloud onto the disk. The analysis of the light curve suggests the star is a binary with a period of 29.6yrs. The comparison of the scattered light images with ALMA continuum and 12CO line emission shows the disk is in keplerian rotation, with the northern side of the outflowing material receding, while the southern side approaching the observer. The disk is itself seen edge-on. The direction of the outflows seen in scattered light is in agreement with the direction of the more distant molecular hydrogen emission-line objects (MHOs) associated to the star. Modeling of the SED using a radiative transfer scheme well agrees with the proposed configuration, as well as the hydrodynamical simulation performed using a Smoothed Particle Hydrodynamics code. We find evidence of streamers of accreting material around TCrA. These streamers connect the filament along which TCrA is forming with the outer parts of the disk, suggesting that the strong misalignment between the inner and outer disk is due to a change in the direction of the angular momentum of the material accreting on the disk during the late phase of star formation., Comment: 17 pages, 14 figures

[Full abstract in the paper] We aim to better constrain the atmospheric properties of the directly imaged exoplanet 51~Eri~b by using a retrieval approach on higher signal-to-noise data than previously reported. In this context, we also compare the results of using the atmospheric retrieval code \texttt{petitRADTRANS} vs a self-consistent model to fit atmospheric parameters. We present a higher signal-to-noise $YH$ spectrum of the planet and revised $K1K2$ photometry (M$_{K1} = 15.11 \pm 0.04$ mag, M$_{K2} = 17.11 \pm 0.38$ mag). The best-fit parameters obtained using an atmospheric retrieval differ from previous results using self-consistent models. In general, we find that our solutions tend towards cloud-free atmospheres (e.g. log $\tau_{\rm clouds} = -5.20 \pm 1.44$). For our ``nominal'' model with new data, we find a lower metallicity ([Fe/H] $= 0.26\pm$0.30 dex) and C/O ratio ($0.38\pm0.09$), and a slightly higher effective temperature (T$_{\rm{eff}} = 807\pm$45 K) than previous studies. The surface gravity (log $g = 4.05\pm0.37$) is in agreement with the reported values in the literature within uncertainties. We estimate the mass of the planet to be between 2 and 4 M$_{\rm{Jup}}$. When comparing with self-consistent models, we encounter a known correlation between the presence of clouds and the shape of the $P-T$ profiles. Our findings support the idea that results from atmospheric retrievals should not be discussed in isolation, but rather along with self-consistent temperature structures obtained using the retrieval's best-fit parameters., Comment: Accepted for publication in A&A. 21 pages, 7 figures in the main text and 9 figures in the Appendix

We present new optical and near-IR images of debris disk around the F-type star HD 114082. We obtained direct imaging observations and analysed the TESS photometric time series data of this target with a goal to search for planetary companions and to characterise the morphology of the debris disk and the scattering properties of dust particles. HD 114082 was observed with the VLT/SPHERE instrument: the IRDIS camera in the K band together with the IFS in the Y, J and H band using the ADI technique as well as IRDIS in the H band and ZIMPOL in the I_PRIME band using the PDI technique. The scattered light images were fitted with a 3D model for single scattering in an optically thin dust disk. We performed aperture photometry in order to derive the scattering and polarized phase functions, polarization fraction and spectral scattering albedo for the dust particles in the disk. This method was also used to obtain the reflectance spectrum of the disk to retrieve the disk color and study the dust reflectivity in comparison to the debris disk HD 117214. We also performed the modeling of the HD 114082 light curve measured by TESS using the models for planet transit and stellar activity to put constraints on radius of the detected planet and its orbit. The debris disk appears as an axisymmetric debris belt with a radius of ~0.37$"$ (35 au), inclination of ~83$^\circ$ and a wide inner cavity. Dust particles in HD 114082 have a maximum polarization fraction of ~17% and a high reflectivity which results in a spectral scattering albedo of 0.65. The analysis of TESS photometric data reveals a transiting planetary companion to HD 114082 with a radius of $\sim$1~$\rm R_{J}$ on an orbit with a semi-major axis of $0.7 \pm 0.4$ au. Combining different data, we reach deep sensitivity limits in terms of companion masses down to ~5$M_{\rm Jup}$ at 50 au, and ~10 $M_{\rm Jup}$ at 30 au from the central star., Comment: 27 pages

SPHERE+ is a proposed upgrade of the SPHERE instrument at the VLT, which is intended to boost the current performances of detection and characterization for exoplanets and disks. SPHERE+ will also serve as a demonstrator for the future planet finder (PCS) of the European ELT. The main science drivers for SPHERE+ are 1/ to access the bulk of the young giant planet population down to the snow line ($3-10$ au), to bridge the gap with complementary techniques (radial velocity, astrometry); 2/ to observe fainter and redder targets in the youngest ($1-10$\,Myr) associations compared to those observed with SPHERE to directly study the formation of giant planets in their birth environment; 3/ to improve the level of characterization of exoplanetary atmospheres by increasing the spectral resolution in order to break degeneracies in giant planet atmosphere models. Achieving these objectives requires to increase the bandwidth of the xAO system (from $\sim$1 to 3\,kHz) as well as the sensitivity in the infrared (2 to 3\,mag). These features will be brought by a second stage AO system optimized in the infrared with a pyramid wavefront sensor. As a new science instrument, a medium resolution integral field spectrograph will provide a spectral resolution from 1000 to 5000 in the J and H bands. This paper gives an overview of the science drivers, requirements and key instrumental trade-off that were done for SPHERE+ to reach the final selected baseline concept., Comment: To appear in the Proceedings of the SPIE Astronomical Telescopes + Instrumentation (2022), 13 pages, 6 figure

Methanol is a ubiquitous species commonly found in the molecular interstellar medium. It is also a crucial seed species for the building-up of the 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. We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disk/envelope system of Solar-like 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 disk has been previously detected. Twelve methanol lines have been detected with upper energies in the range [45-537] K along with one 13CH3OH transition. The methanol emission is compact and encompasses both protostars, separated by only 28 au and presents three velocity components, not spatially resolved by our observations, associated with three different spatial regions, with two of them close to 11B and the third one associated with 11A. A non-LTE radiative transfer analysis of the methanol lines concludes that the gas is hot and dense and highly enriched in methanol with an abundance as high as 1e-5. Using previous continuum data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects. 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] 11 A and B, respectively. Higher spatial resolution observations are necessary to confirm this hypothesis., Comment: 17 pages, accepted in A&A

Planets have been detected in circumbinary orbits in several different systems, despite the additional challenges faced during their formation in such an environment. We investigate the possibility of planetary formation in the spectroscopic binary CS Cha by analyzing its circumbinary disk. The system was studied with high angular resolution ALMA observations at 0.87mm. Visibilities modeling and Keplerian fitting are used to constrain the physical properties of CS Cha, and the observations were compared to hydrodynamic simulations. 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). 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., Comment: 18 pages, 13 figures, accepted in A&A. Watch a 3min summary by the first author in https://youtu.be/6j5ROSj2N-U

Context. HD 95086 is a young nearby Solar System analog hosting a giant exoplanet orbiting at 57 au from the star between an inner and outer debris belt. The existence of additional planets has been suggested as the mechanism that maintains the broad cavity between the two belts. Aims. We present a dedicated monitoring of HD 95086 with the VLT/SPHERE instrument to refine the orbital and atmospheric properties of HD 95086 b, and to search for additional planets in this system. Methods. SPHERE observations, spread over ten epochs from 2015 to 2019 and including five new datasets, were used. Combined with archival observations, from VLT/NaCo (2012-2013) and Gemini/GPI (2013-2016), the extended set of astrometric measurements allowed us to refine the orbital properties of HD 95086 b. We also investigated the spectral properties and the presence of a circumplanetary disk around HD 95086 b by using the special fitting tool exploring the diversity of several atmospheric models. In addition, we improved our detection limits in order to search for a putative planet c via the K-Stacker algorithm. Results. We extracted for the first time the JH low-resolution spectrum of HD 95086 b by stacking the six best epochs, and confirm its very red spectral energy distribution. Combined with additional datasets from GPI and NaCo, our analysis indicates that this very red color can be explained by the presence of a circumplanetary disk around planet b, with a range of high-temperature solutions (1400-1600 K) and significant extinction (Av > 10 mag), or by a super-solar metallicity atmosphere with lower temperatures (800-1300 K), and small to medium amount of extinction (Av < 10 mag). We do not find any robust candidates for planet c, but give updated constraints on its potential mass and location., Comment: 29 pages, 20 figures, A&A, accepted

High dust density in the midplane of protoplanetary disks is favorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. Vertical settling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin and high density regions. In this work, we aim to study these mechanisms in the highly inclined protoplanetary disk SSTC2D J163131.2-242627 (Oph163131, i~84deg). We present new high angular resolution continuum and 12CO ALMA observations of Oph163131. The gas emission appears significantly more extended in the vertical and radial direction compared to the dust emission, consistent with vertical settling and possibly radial drift. In addition, the new continuum observations reveal two clear rings. The outer ring, located at ~100 au, is well resolved in the observations, which allows us to put stringent constraints on the vertical extent of millimeter dust particles. We model the disk using radiative transfer and find that the scale height of millimeter sized grains is 0.5au or less at 100au from the central star. This value is about one order of magnitude smaller than the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of the large grains is occurring in the disk. When adopting a parametric dust settling prescription, we find that the observations are consistent with a turbulent viscosity coefficient of about alpha<=10^-5 at 100au. Finally, we find that the thin dust scale height measured in Oph163131 is favorable for planetary growth by pebble accretion: a 10 M_Earth planet may grow within less than 10 Myr, even in orbits exceeding 50au., Comment: Accepted for publication in ApJ

We present near-infrared Large Binocular Telescope Interferometer LMIRCam imagery of the disk around the Herbig Ae/Be star AB Aurigae. A comparison of surface brightness at Ks (2.16 ${\mu}$m), H2O narrowband (3.08 ${\mu}$m), and L' (3.7 ${\mu}$m) allows us to probe the presence of icy grains in this (pre)transitional disk environment. By applying Reference Differential Imaging PSF subtraction, we detect the disk at high signal to noise in all three bands. We find strong morphological differences between bands, including asymmetries consistent with observed spiral arms within 100 AU in L'. An apparent deficit of scattered light at 3.08 ${\mu}$m relative to bracketing wavelengths (Ks and L') is evocative of ice absorption at the disk surface layer. However, the ${\Delta}$(Ks-H2O) color is consistent with grains with little to no ice (0-5% by mass). The ${\Delta}$(H2O-L') color, conversely, suggests grains with a much higher ice mass fraction (~0.68), and the two colors cannot be reconciled under a single grain population model. Additionally, we find the extremely red ${\Delta}$(Ks-L') disk color cannot be reproduced under conventional scattered light modeling with any combination of grain parameters or reasonable local extinction values. We hypothesize that the scattering surfaces at the three wavelengths are not co-located, and optical depth effects result in each wavelength probing the grain population at different disk surface depths. The morphological similarity between Ks and H2O suggests their scattering surfaces are near one another, lending credence to the ${\Delta}$(Ks-H2O) disk color constraint of < 5% ice mass fraction for the outermost scattering disk layer., Comment: Accepted for publication in AJ

The formation of multiple stellar systems is a natural by-product of the star-formation process, and its impact on the properties of protoplanetary discs and on the formation of planets is still to be fully understood. To date, no detailed uniform study of the gas emission from a sample of protoplanetary discs around multiple stellar systems has been performed. Here we analyse new ALMA observations at a $\sim$21 au resolution of the molecular CO gas emission targeting discs in eight multiple stellar systems in the Taurus star-forming regions. $^{12}$CO gas emission is detected around all primaries and in seven companions. With these data, we estimate the inclination and the position angle for all primary discs and for five secondary or tertiary discs, and measure the gas disc radii of these objects with a cumulative flux technique on the spatially resolved zeroth moment images. When considering the radius including 95\% of the flux as a metric, the estimated gas disc size in multiple stellar systems is found to be on average $\sim 4.2$ times larger than the dust disc size. This ratio is higher than what was recently found in a population of more isolated and single systems. On the contrary, when considering the radius including 68\% of the flux, no difference between multiple and single discs is found in the distribution of ratios. This discrepancy is due to the sharp truncation of the outer dusty disc observed in multiple stellar systems. The measured gas disc sizes are consistent with tidal truncation models in multiple stellar systems assuming eccentricities of $\sim0.15$-$0.5$, as expected in typical binary systems., Comment: 25 pages, 29 figures, 9 tables. Accepted for publication in A&A

For several transition disks (TDs), dark regions interpreted as shadows have been observed in scattered light imaging and are hypothesized to originate from misalignments between distinct disk regions. We aim to investigate the presence of misalignments in TDs. We study the inner disk geometries of 20 well-known transition disks with VLTI/GRAVITY observations and use complementary $^{12}$CO and $^{13}$CO molecular line data from ALMA to derive the orientation of the outer disk regions. We fit simple models to the GRAVITY data to derive the inner disks inclination and position angles. The outer disk geometries were derived from Keplerian fits to the ALMA velocity maps and compared to the inner disk constraints. We also predicted the locations of shadows for significantly misaligned systems. Our analysis reveals six disks to exhibit significant misalignments between their inner and outer disks. The predicted shadow positions agree well with the scattered light images of HD100453 and HD142527, and we find supporting evidence for a shadow in the disk around CQ Tau. In the other three targets for which we infer significantly misaligned disks, V1247 Ori, V1366 Ori, and RY Lup, we do not see any evident sign of shadows in the scattered light images. The scattered light shadows observed in DoAr44, HD135344B, and HD139614 are consistent with our observations, yet the underlying morphology is likely too complex to be described by our models and the accuracy achieved by our observations. Whereas we can derive precise constraints on the potential shadow positions for well-resolved inner disks around HAeBe stars, the statistical uncertainties for the marginally resolved inner disks around the TTS of our sample make it difficult to extract conclusive constraints for the presence of shadows in these systems., Comment: Accepted for publication in Astronomy \& Astrophysics

Stellar binaries represent a substantial fraction of stellar systems, especially among young stellar objects. Accordingly, binaries play an important role in setting the architecture of a large number of protoplanetary discs. Binaries in coplanar and polar orientations with respect to the circumbinary disc are stable configurations and could induce non-axisymmetric structures in the dust and gas distributions. In this work, we suggest that the structures shown in the central region of the protoplanetary disc HD 169142 are produced by the presence of an inner stellar binary and a circumbinary (P-type) planet. We find that a companion with a mass-ratio of 0.1, semi-major axis of 9.9 au, eccentricity of 0.2, and inclination of 90{\deg}, together with a 2 Jupiter Mass coplanar planet on a circular orbit at 45 au reproduce the structures at the innermost ring observed at 1.3 mm and the shape of spiral features in scattered light observations. The model predicts changes in the disc's dust structure, and star's astrometric parameters, which would allow testing its veracity by monitoring this system over the next 20 years., Comment: 11 pages, 7 figures, accepted for publication in MNRAS

To date, nearly two hundred planet-forming disks have been imaged with high resolution. Our propensity to study bright and extended objects is however biasing our view of the disk demography. In this work, we contribute to alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE that look faint in scattered light. Sources were selected based on a low far-IR excess from the spectral energy distribution. The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets is only detected from a small portion of the disk extent. The mild anti-correlation between the disk brightness and the near-IR excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk in penumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outer disk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks from the literature with either no shadow or with sign of azimuthally confined shadows., Comment: Accepted for publication in A\&A

We initiated a deep-imaging survey of Scorpius-Centaurus A-F stars with predicted warm inner and cold outer belts of debris reminiscent of the architecture of emblematic systems such as HR 8799. We present resolved SPHERE images of a narrow ring of debris around the F5-type star HD 141011 that was observed as part of our survey in 2015, 2016, and 2019. The ring extends up to ~1.1" (~141 au) from the star in the IRDIS and IFS data obtained in 2016 and 2019. The disk is not detected in the 2015 data which are of poorer quality. The disks is best reproduced by models of a noneccentric ring centered on the star with an inclination of $69.1\pm0.9^{\circ}$, a position angle of $-24.6 \pm 1.7^{\circ}$, and a semimajor axis of $127.5\pm3.8$ au. The combination of radial velocity and imaging data excludes brown-dwarf (M>13.6 MJup) companions coplanar with the disk from 0.1 to 0.9 au and from 20 au up to 500 au (90% probability). HD 141011 adds to the growing list of debris disks that are resolved in Sco-Cen. It is one of the faintest disks that are resolved from the ground and has a radial extent and fractional width ($\sim$12.5%) reminiscent of Fomalhaut. Its moderate inclination and large semimajor axis make it a good target for the James Webb Space Telescope and should allow a deeper search for putative companions shaping the dust distribution., Comment: 13 pages, 10 figures. Paper II of our Sco-Cen imaging survey. Accepted in A&A

These protoplanetary disks in T Tauri stars play a central role in star and planet formation. We spatially resolve at sub-au scales the innermost regions of a sample of T Tauri's disks to better understand their morphology and composition. We extended our homogeneous data set of 27 Herbig stars and collected near-IR K-band observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of ~4000-6000 K and ~0.4-10 Lsun. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometric data and search for trends between the properties of the disk and the central star. The best-fit models of the disk's inner rim correspond to wide rings. We extend the Radius-luminosity relation toward the smallest luminosities (0.4-10 Lsun) and find the R~L^(1/2) trend is no longer valid, since the K-band sizes measured with GRAVITY are larger than the predicted sizes from sublimation radius computation. No clear correlation between the K-band half-flux radius and the mass accretion rate is seen. Having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of the half-flux radius of the inner dusty disk. Our measurements agree with models that take into account the scattered light. The N-to-K band size ratio may be a proxy for disentangling disks with silicate features in emission from disks with weak and/or in absorption silicate features. When comparing inclinations and PA of the inner disks to those of the outer disks (ALMA) in nine objects of our sample, we detect misalignments for four objects., Comment: Accepted for publication in A&A; 20 pages, 15 figures, 9 tables

We present the experimental phase function, degree of linear polarization (DLP), and linear depolarization (deltaL) curves of a set of forsterite samples representative of low-absorbing cosmic dust particles. The samples are prepared using state-of-the-art size-segregating techniques to obtain narrow size distributions spanning a broad range of the scattering size parameter domain. We conclude that the behavior of the phase function at the side- and back-scattering regions provides information on the size regime, the position and magnitude of the maximum of the DLP curve are strongly dependent on particle size, the negative polarization branch is mainly produced by particles with size parameters in the approx. 6 to 20 range, and the deltaL is strongly dependent on particle size at all measured phase angles except for the exact backward direction. From a direct comparison of the experimental data with computations for spherical particles, it becomes clear that the use of the spherical model for simulating the phase function and DLP curves of irregular dust produces dramatic errors in the retrieved composition and size of the scattering particles: The experimental phase functions are reproduced by assuming unrealistically high values of the imaginary part of the refractive index. The spherical model does not reproduce the bell-shaped DLP curve of dust particles with sizes in the resonance and/or geometric optics size domain. Thus, the use of the Mie model for analyzing polarimetric observations might prevent locating dust particles with sizes of the order of or larger than the wavelength of the incident light., Comment: Published in ApJS

[Full abstract in the paper] In recent years, protoplanetary disks with spiral structures have been detected in scattered light, millimeter continuum, and CO gas emission. The mechanisms causing these structures are still under debate. A popular scenario to drive the spiral arms is the one of a planet perturbing the material in the disk. However, if the disk is massive, gravitational instability is usually the favored explanation. Multiwavelength studies could be helpful to distinguish between the two scenarios. So far, only a handful of disks with spiral arms have been observed in both scattered light and millimeter continuum. We aim to perform an in-depth characterization of the protoplanetary disk morphology around WaOph 6 analyzing data obtained at different wavelengths, as well as to investigate the origin of the spiral features in the disk. We present the first near-infrared polarimetric observations of WaOph 6 obtained with SPHERE at the VLT and compare them to archival millimeter continuum ALMA observations. We traced the spiral features in both data sets and estimated the respective pitch angles. We discuss the different scenarios that can give rise to the spiral arms in WaOph 6. We tested the planetary perturber hypothesis by performing hydrodynamical and radiative transfer simulations to compare them with scattered light and millimeter continuum observations., Comment: Accepted for publication in A&A. 17 pages, 9 figures in the main text and 3 figures in the Appendix

Context. Spiral arms in protoplanetary disks could be shown to be the manifestation of density waves launched by protoplanets and propagating in the gaseous component of the disk. At least two point sources have been identified in the L band in the MWC 758 system as planetary mass object candidates. Aims. We used VLT/SPHERE to search for counterparts of these candidates in the H and K bands, and to characterize the morphology of the spiral arms . Methods. The data were processed with now-standard techniques in high-contrast imaging to determine the limits of detection, and to compare them to the luminosity derived from L band observations. Results. In considering the evolutionary, atmospheric, and opacity models we were not able to confirm the two former detections of point sources performed in the L band. In addition, the analysis of the spiral arms from a dynamical point of view does not support the hypothesis that these candidates comprise the origin of the spirals. Conclusions. Deeper observations and longer timescales will be required to identify the actual source of the spiral arms in MWC 758., Comment: Accepted for publication in Astronomy and Astrophysics

Context. Characterizing the evolution of protoplanetary disks is necessary to improve our understanding of planet formation. Constraints on both dust and gas are needed to determine the dominant disk dissipation mechanisms. Aims. We aim to compare the disk dust masses in the Chamaeleon II (Cha II) star-forming region with other regions with ages between 1 and 10Myr. Methods. We use ALMA band 6 observations (1.3 mm) to survey 29 protoplanetary disks in Cha II. Dust mass estimates are derived from the continuum data. Results. Out of our initial sample of 29 disks, we detect 22 sources in the continuum, 10 in 12CO, 3 in 13CO, and none in C18O (J=2-1). Additionally, we detect two companion candidates in the continuum and 12CO emission. Most disk dust masses are lower than 10Mearth, assuming thermal emission from optically thin dust. We compare consistent estimations of the distributions of the disk dust mass and the disk-to-stellar mass ratios in Cha II with six other low mass and isolated star-forming regions in the age range of 1-10Myr: Upper Sco, CrA, IC 348, Cha I, Lupus, and Taurus. When comparing the dust-to-stellar mass ratio, we find that the masses of disks in Cha II are statistically different from those in Upper Sco and Taurus, and we confirm that disks in Upper Sco, the oldest region of the sample, are statistically less massive than in all other regions. Performing a second statistical test of the dust mass distributions from similar mass bins, we find no statistical differences between these regions and Cha II. Conclusions. We interpret these trends, most simply, as a sign of decline in the disk dust masses with time or dust evolution. Different global initial conditions in star-forming regions may also play a role, but their impact on the properties of a disk population is difficult to isolate in star-forming regions lacking nearby massive stars., Comment: Accepted for publication in A&A

We present the multiple stellar systems observed within the SpHere INfrared survey for Exoplanet (SHINE). SHINE searched for substellar companions to young stars using high contrast imaging. Although stars with known stellar companions within SPHERE field of view (<5.5 arcsec) were removed from the original target list, we detected additional stellar companions to 78 of the 463 SHINE targets observed so far. 27% of the systems have three or more components. Given the heterogeneity of the sample in terms of observing conditions and strategy, tailored routines were used for data reduction and analysis, some of which were specifically designed for these data sets. We then combined SPHERE data with literature and archival ones, TESS light curves and Gaia parallaxes and proper motions, to characterise these systems as completely as possible. Combining all data, we were able to constrain the orbits of 25 systems. We carefully assessed the completeness of our sample for the separation range 50-500 mas (period range a few years - a few tens of years), taking into account the initial selection biases and recovering part of the systems excluded from the original list due to their multiplicity. This allowed us to compare the binary frequency for our sample with previous studies and highlight some interesting trends in the mass ratio and period distribution. We also found that, for the few objects for which such estimate was possible, the values of the masses derived from dynamical arguments were in good agreement with the model predictions. Stellar and orbital spins appear fairly well aligned for the 12 stars having enough data, which favour a disk fragmentation origin. Our results highlight the importance of combining different techniques when tackling complex problems such as the formation of binaries and show how large samples can be useful for more than one purpose., Comment: 59 pages, 11 tables, 18 figures

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 about 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 after deprojection compared to the background Keplerian rotation, as well as an extension of about 40 au radially on both sides of the vortex and 200 degrees 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., Comment: 15 pages, 10 figures

We present high-precision photometry and polarimetry for the protoplanetary disk around HD142527, with a focus on determining the light scattering parameters of the dust. We re-reduced polarimetric differential imaging data of HD142527 in the VBB (735 nm) and H-band (1625 nm) from the ZIMPOL and IRDIS subinstruments of SPHERE/VLT. With polarimetry and photometry based on reference star differential imaging, we were able to measure the linearly polarized intensity and the total intensity of the light scattered by the circumstellar disk with high precision. We used simple Monte Carlo simulations of multiple light scattering by the disk surface to derive constraints for three scattering parameters of the dust: the maximum polarization of $P_{\rm max}$, the asymmetry parameter $g$, and the single-scattering albedo $\omega$. We measure a reflected total intensity of $51.4\pm1.5$ mJy and $206\pm12$ mJy and a polarized intensity of $11.3\pm0.3$ mJy and $55.1\pm3.3$ mJy in the VBB and H-band, respectively. We also find in the visual range a degree of polarization that varies between $28\%$ on the far side of the disk and $17\%$ on the near side. The disk shows a red color for the scattered light intensity and the polarized intensity, which are about twice as high in the near-infrared when compared to the visual. We determine with model calculations the scattering properties of the dust particles and find evidence for strong forward scattering ($g\approx 0.5-0.75$), relatively low single-scattering albedo ($\omega \approx 0.2-0.5$), and high maximum polarization ($P_{\rm max} \approx 0.5-0.75$) at the surface on the far side of the disk for both observed wavelengths. The optical parameters indicate the presence of large aggregate dust particles, which are necessary to explain the high maximum polarization, the strong forward-scattering nature of the dust, and the observed red disk color., Comment: 20 pages, 14 figures

The detection of a wide range of substructures such as rings, cavities and spirals has become a common outcome of high spatial resolution imaging of protoplanetary disks, both in the near-infrared scattered light and in the thermal millimetre continuum emission. The most frequent interpretation of their origin is the presence of planetary-mass companions perturbing the gas and dust distribution in the disk (perturbers), but so far the only bona-fide detection has been the two giant planets around PDS 70. Here, we collect a sample of 15 protoplanetary disks showing substructures in SPHERE scattered light images and present a homogeneous derivation of planet detection limits in these systems. We also estimate the mass of these perturbers through a Hill radius prescription and a comparison to ALMA data. Assuming that one single planet carves each substructure in scattered light, we find that more massive perturbers are needed to create gaps within cavities than rings, and that we might be close to a detection in the cavities of RX J1604, RX J1615, Sz Cha, HD 135344B and HD 34282. We reach typical mass limits in these cavities of 3-10 Mjup. For planets in the gaps between rings, we find that the detection limits of SPHERE are about an order of magnitude away in mass, and that the gaps of PDS 66 and HD 97048 seem to be the most promising structures for planet searches. The proposed presence of massive planets causing spiral features in HD 135344B and HD 36112 are also within SPHERE's reach assuming hot-start models.These results suggest that current detection limits are able to detect hot-start planets in cavities, under the assumption that they are formed by a single perturber located at the centre of the cavity. More realistic planet mass constraints would help to clarify whether this is actually the case, which might point to perturbers not being the only way of creating substructures., Comment: 26 pages, 33 figures, accepted for publication in A&A

Large surveys with new-generation high-contrast imaging instruments are needed to derive the frequency and properties of exoplanet populations with separations from $\sim$5 to 300 AU. A careful assessment of the stellar properties is crucial for a proper understanding of when, where, and how frequently planets form, and how they evolve. The sensitivity of detection limits to stellar age makes this a key parameter for direct imaging surveys. We describe the SpHere INfrared survey for Exoplanets (SHINE), the largest direct imaging planet-search campaign initiated at the VLT in 2015 in the context of the SPHERE Guaranteed Time Observations of the SPHERE consortium. In this first paper we present the selection and the properties of the complete sample of stars surveyed with SHINE, focusing on the targets observed during the first phase of the survey (from February 2015 to February 2017). This early sample composed of 150 stars is used to perform a preliminary statistical analysis of the SHINE data, deferred to two companion papers presenting the survey performance, main discoveries, and the preliminary statistical constraints set by SHINE. Based on a large database collecting the stellar properties of all young nearby stars in the solar vicinity (including kinematics, membership to moving groups, isochrones, lithium abundance, rotation, and activity), we selected the original sample of 800 stars that were ranked in order of priority according to their sensitivity for planet detection in direct imaging with SPHERE. The properties of the stars that are part of the early statistical sample were revisited, including for instance measurements from the GAIA Data Release 2.

Over the past decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) from their host stars. To understand their formation and evolution mechanisms, we have initiated in 2015 the SPHERE infrared survey for exoplanets (SHINE), a systematic direct imaging survey of young, nearby stars to explore their demographics.} {We aim to detect and characterize the population of giant planets and brown dwarfs beyond the snow line around young, nearby stars. Combined with the survey completeness, our observations offer the opportunity to constrain the statistical properties (occurrence, mass and orbital distributions, dependency on the stellar mass) of these young giant planets.} {In this study, we present the observing and data analysis strategy, the ranking process of the detected candidates, and the survey performances for a subsample of 150 stars, which are representative of the full SHINE sample. The observations were conducted in an homogeneous way from February 2015 to February 2017 with the dedicated ground-based VLT/SPHERE instrument equipped with the IFS integral field spectrograph and the IRDIS dual-band imager covering a spectral range between 0.9 and 2.3 $\mu$m. We used coronographic, angular and spectral differential imaging techniques to reach the best detection performances for this study down to the planetary mass regime.}

As the earliest stage of planet formation, massive, optically thick, and gas rich protoplanetary disks provide key insights into the physics of star and planet formation. When viewed edge-on, high resolution images offer a unique opportunity to study both the radial and vertical structures of these disks and relate this to vertical settling, radial drift, grain growth, and changes in the midplane temperatures. In this work, we present multi-epoch HST and Keck scattered light images, and an ALMA 1.3 mm continuum map for the remarkably flat edge-on protoplanetary disk SSTC2DJ163131.2-242627, a young solar-type star in $\rho$ Ophiuchus. We model the 0.8 $\mu$m and 1.3 mm images in separate MCMC runs to investigate the geometry and dust properties of the disk using the MCFOST radiative transfer code. In scattered light, we are sensitive to the smaller dust grains in the surface layers of the disk, while the sub-millimeter dust continuum observations probe larger grains closer to the disk midplane. An MCMC run combining both datasets using a covariance-based log-likelihood estimation was marginally successful, implying insufficient complexity in our disk model. The disk is well characterized by a flared disk model with an exponentially tapered outer edge viewed nearly edge-on, though some degree of dust settling is required to reproduce the vertically thin profile and lack of apparent flaring. A colder than expected disk midplane, evidence for dust settling, and residual radial substructures all point to a more complex radial density profile to be probed with future, higher resolution observations., Comment: Accepted for publication in AJ

Gas-rich circumstellar disks are the cradles of planet formation. As such, their evolution will strongly influence the resulting planet population. In the ESO DESTINYS large program, we study these disks within the first 10 Myr of their development with near-infrared scattered light imaging. Here we present VLT/SPHERE polarimetric observations of the nearby class II system SU Aur in which we resolve the disk down to scales of ~7 au. In addition to the new SPHERE observations, we utilize VLT/NACO, HST/STIS and ALMA archival data. The new SPHERE data show the disk around SU Aur and extended dust structures in unprecedented detail. We resolve several dust tails connected to the Keplerian disk. By comparison with ALMA data, we show that these dust tails represent material falling onto the disk. The disk itself shows an intricate spiral structure and a shadow lane, cast by an inner, misaligned disk component. Our observations suggest that SU Aur is undergoing late infall of material, which can explain the observed disk structures. SU Aur is the clearest observational example of this mechanism at work and demonstrates that late accretion events can still occur in the class II phase, thereby significantly affecting the evolution of circumstellar disks. Constraining the frequency of such events with additional observations will help determine whether this process is responsible for the spin-orbit misalignment in evolved exoplanet systems., Comment: 18 pages, 12 figures, published in ApJL on 18-02-2021

Aims. We present MCFOST-art, a new non-local thermodynamic equilibrium radiative transfer solver for multilevel atomic systems. The code is embedded in the 3D radiative transfer code MCFOST and is compatible with most of the MCFOST modules. The code is versatile and designed to model the close environment of stars in 3D. Methods. The code solves for the statistical equilibrium and radiative transfer equations using the Multilevel Accelerated Lambda Iteration (MALI) method. We tested MCFOST-art on spherically symmetric models of stellar photospheres as well as on a standard model of the solar atmosphere. We computed atomic level populations and outgoing fluxes and compared these values with the results of the TURBOspectrum and RH codes. Calculations including expansion and rotation of the atmosphere were also performed. We tested both the pure local thermodynamic equilibrium and the out-of-equilibrium problems. Results. In all cases, the results from all codes agree within a few percent at all wavelengths and reach the sub-percent level between RH and MCFOST-art. We still note a few marginal discrepancies between MCFOST-art and TURBOspectrum as a result of different treatments of background opacities at some critical wavelength ranges.

We present K-band interferometric observations of the PDS 70 protoplanets along with their host star using VLTI/GRAVITY. We obtained K-band spectra and 100 $\mu$as precision astrometry of both PDS 70 b and c in two epochs, as well as spatially resolving the hot inner disk around the star. Rejecting unstable orbits, we found a nonzero eccentricity for PDS 70 b of $0.17 \pm 0.06$, a near-circular orbit for PDS 70 c, and an orbital configuration that is consistent with the planets migrating into a 2:1 mean motion resonance. Enforcing dynamical stability, we obtained a 95% upper limit on the mass of PDS 70 b of 10 $M_\textrm{Jup}$, while the mass of PDS 70 c was unconstrained. The GRAVITY K-band spectra rules out pure blackbody models for the photospheres of both planets. Instead, the models with the most support from the data are planetary atmospheres that are dusty, but the nature of the dust is unclear. Any circumplanetary dust around these planets is not well constrained by the planets' 1-5 $\mu$m spectral energy distributions (SEDs) and requires longer wavelength data to probe with SED analysis. However with VLTI/GRAVITY, we made the first observations of a circumplanetary environment with sub-au spatial resolution, placing an upper limit of 0.3~au on the size of a bright disk around PDS 70 b., Comment: 30 pages, 9 figures, Accepted for publication in AJ

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 <0.1% in the degree of polarization. We report the first detection of polarization originating from substellar companions, with a polarization of several tenths of a percent for DH Tau B and GSC 6214-210 B in H-band. By comparing the measured polarization with that of nearby stars, we find that the polarization is unlikely to be caused by interstellar dust. Because the companions have previously measured hydrogen emission lines and red colors, the polarization most likely originates from circumsubstellar disks. Through radiative transfer modeling, we constrain the position angles of the disks and find that the disks must have high inclinations. The presence of these disks as well as the misalignment of the disk of DH Tau B with the disk around its primary star suggest in situ formation of the companions. For the 18 other companions, we do not detect significant polarization and place subpercent upper limits on their degree of polarization. These non-detections may indicate the absence of circumsubstellar disks, a slow rotation rate of young companions, the upper atmospheres containing primarily submicron-sized dust grains, and/or limited cloud inhomogeneity. Finally, we present images of the circumstellar disks of DH Tau, GQ Lup, PDS 70, Beta Pic, and HD 106906., Comment: Accepted for publication in A&A. Shortened abstract. 29 pages, 22 figures

Sirius-like systems are wide binaries composed of a white dwarf (WD) and a companion of a spectral type earlier than M0. The WD progenitor evolves in isolation, but its wind during the AGB phase pollutes the companion surface and transfers some angular momentum. Within SHINE survey that uses SPHERE at the VLT, we acquired images of HD2133, HD114174, and CD-567708 and combined this data with high resolution spectra of the primaries, TESS, and literature data. We performed accurate abundance analyses for the MS. We found brighter J and K magnitudes for HD114174B than obtained previously and extended the photometry down to 0.95 micron. Our new data indicate a higher temperature and then shorter cooling age (5.57+/-0.02 Gyr) and larger mass (0.75+/-0.03 Mo) for this WD than previously assumed. This solved the discrepancy previously found with the age of the MS star. The two other WDs are less massive, indicating progenitors of ~1.3 Mo and 1.5-1.8 Mo for HD2133B and CD-56 7708B, respectively. We were able to derive constraints on the orbit for HD114174 and CD-56 7708. The composition of the MS stars agrees fairly well with expectations from pollution by the AGB progenitors of the WDs: HD2133A has a small enrichment of n-capture elements, which is as expected for pollution by an AGB star with a mass <1.5 Mo; CD-56 7708A is a previously unrecognized mild Ba-star, which is expected due to pollution by an AGB star with a mass in the range of 1.5-3.0 Mo; and HD114174 has a very moderate excess of n-capture elements, which is in agreement with the expectation for a massive AGB star to have a mass >3.0 Mo. On the other hand, none of these stars show the excesses of C that are expected to go along with those of n-capture elements. This might be related to the fact that these stars are at the edges of the mass range where we expect nucleosynthesis related to thermal pulses., Comment: Accepted on Astronomy and Astrophysics. 19 pages, 15 figures