Context. The consortium of the Spectro-Polarimetric High-contrast Exoplanet REsearch installed at the Very Large Telescope (SPHERE/VLT) has been operating its guaranteed observation time (260 nights ...over five years) since February 2015. The main part of this time (200 nights) is dedicated to the detection and characterization of young and giant exoplanets on wide orbits. Aims. The large amount of data must be uniformly processed so that accurate and homogeneous measurements of photometry and astrometry can be obtained for any source in the field. Methods. To complement the European Southern Observatory pipeline, the SPHERE consortium developed a dedicated piece of software to process the data. First, the software corrects for instrumental artifacts. Then, it uses the speckle calibration tool (SpeCal) to minimize the stellar light halo that prevents us from detecting faint sources like exoplanets or circumstellar disks. SpeCal is meant to extract the astrometry and photometry of detected point-like sources (exoplanets, brown dwarfs, or background sources). SpeCal was intensively tested to ensure the consistency of all reduced images (cADI, Loci, TLoci, PCA, and others) for any SPHERE observing strategy (ADI, SDI, ASDI as well as the accuracy of the astrometry and photometry of detected point-like sources. Results. SpeCal is robust, user friendly, and efficient at detecting and characterizing point-like sources in high contrast images. It is used to process all SPHERE data systematically, and its outputs have been used for most of the SPHERE consortium papers to date. SpeCal is also a useful framework to compare different algorithms using various sets of data (different observing modes and conditions). Finally, our tests show that the extracted astrometry and photometry are accurate and not biased.
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 carving the disk around PDS 70. Here, we present a sample of 15 protoplanetary disks showing substructures in SPHERE scattered-light images and a homogeneous derivation of planet detection limits in these systems. To obtain mass limits we rely on different post-formation luminosity models based on distinct formation conditions, which are critical in the first million years of evolution. 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 J1604.3-2130A, RX J1615.3-3255, Sz Cha, HD 135344B, and HD 34282. We reach typical mass limits in these cavities of 3–10
M
Jup
. For planets in the gaps between rings, we find that the detection limits of SPHERE high-contrast imaging 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 the 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 indicate that perturbers are not the only way of creating substructures.
Context.
A large portion of stars is found to be part of binary or higher-order multiple systems. The ubiquity of planets found around single stars raises the question of whether and how planets in ...binary systems form. Protoplanetary disks are the birthplaces of planets, and characterizing them is crucial in order to understand the planet formation process.
Aims.
Our goal is to characterize the morphology of the GG Tau A disk, one of the largest and most massive circumbinary disks. We also aim to trace evidence for binary-disk interactions.
Methods.
We obtained observations in polarized scattered light of GG Tau A using the SPHERE/IRDIS instrument in the
H
-band filter. We analyzed the observed disk morphology and substructures. We ran 2D hydrodynamical models to simulate the evolution of the circumbinary ring over the lifetime of the disk.
Results.
The disk and also the cavity and the inner region are highly structured, with several shadowed regions, spiral structures, and streamer-like filaments. Some of these are detected here for the first time. The streamer-like filaments appear to connect the outer ring with the northern arc. Their azimuthal spacing suggests that they may be generated through periodic perturbations by the binary, which tear off material from the inner edge of the outer disk once during each orbit. By comparing observations to hydrodynamical simulations, we find that the main features, in particular, the gap size, but also the spiral and streamer filaments, can be qualitatively explained by the gravitational interactions of a binary with a semimajor axis of ~35 au on an orbit coplanar with the circumbinary ring.
Abstract
HD 169142 is an excellent target for investigating signs of planet–disk interaction due to previous evidence of gap structures. We perform
J
-band (∼1.2
μ
m) polarized intensity imaging of ...HD 169142 with VLT/SPHERE. We observe polarized scattered light down to 0.″16 (∼19 au) and find an inner gap with a significantly reduced scattered-light flux. We confirm the previously detected double-ring structure peaking at 0.″18 (∼21 au) and 0.″56 (∼66 au) and marginally detect a faint third gap at 0.″70–0.″73 (∼82–85 au). We explore dust evolution models in a disk perturbed by two giant planets, as well as models with a parameterized dust size distribution. The dust evolution model is able to reproduce the ring locations and gap widths in polarized intensity but fails to reproduce their depths. However, it gives a good match with the ALMA dust continuum image at 1.3 mm. Models with a parameterized dust size distribution better reproduce the gap depth in scattered light, suggesting that dust filtration at the outer edges of the gaps is less effective. The pileup of millimeter grains in a dust trap and the continuous distribution of small grains throughout the gap likely require more efficient dust fragmentation and dust diffusion in the dust trap. Alternatively, turbulence or charging effects might lead to a reservoir of small grains at the surface layer that is not affected by the dust growth and fragmentation cycle dominating the dense disk midplane. The exploration of models shows that extracting planet properties such as mass from observed gap profiles is highly degenerate.
Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star ...surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation. Aims. We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT. Methods. We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μm). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b. Results. PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 RJ with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr. Conclusions. This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.
Understanding the formation and evolution of giant planets (≥1 MJup) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed strong ...constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75–5.70% at the 68% confidence level (CL) within 20–300 AU and 0.5–75 MJup, which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1–75 MJup range (95% CL). With the threesub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0–8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys.
Context.
High-contrast imaging surveys for exoplanet detection have shown that giant planets at large separations are rare. Thus, it is of paramount importance to push towards detections at smaller ...separations, which is the part of the parameter space containing the greatest number of planets. The performance of traditional methods for the post-processing of pupil-stabilized observations decreases at smaller separations due to the larger field-rotation required to displace a source on the detector in addition to the intrinsic difficulty of higher stellar contamination.
Aims.
Our goal is to develop a method of extracting exoplanet signals, which improves performance at small angular separations.
Methods.
A data-driven model of the temporal behavior of the systematics for each pixel can be created using reference pixels at a different positions, on the condition that the underlying causes of the systematics are shared across multiple pixels, which is mostly true for the speckle pattern in high-contrast imaging. In our causal regression model, we simultaneously fit the model of a planet signal “transiting” over detector pixels and non-local reference light curves describing the shared temporal trends of the speckle pattern to find the best-fitting temporal model describing the signal.
Results.
With our implementation of a spatially non-local, temporal systematics model, called TRAP, we show that it is possible to gain up to a factor of six in contrast at close separations (<3
λ
∕
D
), as compared to a model based on spatial correlations between images displaced in time. We show that the temporal sampling has a large impact on the achievable contrast, with better temporal sampling resulting in significantly better contrasts. At short integration times, (4 s) for
β
Pic data, we increase the signal-to-noise ratio of the planet by a factor of four compared to the spatial systematics model. Finally, we show that the temporal model can be used on unaligned data that has only been dark- and flat-corrected, without the need for further pre-processing.
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.
Context.
Hydrodynamical simulations of planet-disk interactions suggest that planets may be responsible for a number of the substructures frequently observed in disks in both scattered light and dust ...thermal emission. Despite the ubiquity of these features, direct evidence of planets embedded in disks and of the specific interaction features like spiral arms within planetary gaps are still rare.
Aims.
In this study we discuss recent observational results in the context of hydrodynamical simulations in order to infer the properties of a putative embedded planet in the cavity of a transition disk.
Methods.
We imaged the transition disk SR 21 in
H
-band in scattered light with SPHERE/IRDIS and in thermal dust emission with ALMA band 3 (3 mm) observations at a spatial resolution of 0.1″. We combine these datasets with existing Band 9 (430
μ
m) and Band 7 (870
μ
m) ALMA continuum data.
Results.
The Band 3 continuum data reveals a large cavity and a bright ring peaking at 53 au strongly suggestive of dust trapping. The ring shows a pronounced azimuthal asymmetry, with a bright region in the northwest that we interpret as a dust overdensity. A similarly asymmetric ring is revealed at the same location in polarized scattered light, in addition to a set of bright spirals inside the millimeter cavity and a fainter spiral bridging the gap to the outer ring. These features are consistent with a number of previous hydrodynamical models of planet-disk interactions, and suggest the presence of a ∼1
M
Jup
planet at 44 au and PA = 11 deg. This makes SR21 the first disk showing spiral arms inside the millimeter cavity, and the first disk for which the location of a putative planet can be precisely inferred.
Conclusions.
The main features of SR 21 in both scattered light and thermal emission are consistent with hydrodynamical predictions of planet-disk interactions. With the location of a possible planet being well constrained by observations, it is an ideal candidate for follow-up observations to search for direct evidence of a planetary companion still embedded in its disk.
Several exoplanets have recently been imaged at wide separations of >10 AU from their parent stars. These span a limited range of ages (<50 Myr) and atmospheric properties, with temperatures of ...800-1800 K and very red colors (J - H > 0.5 mag), implying thick cloud covers. Furthermore, substantial model uncertainties exist at these young ages due to the unknown initial conditions at formation, which can lead to an order of magnitude of uncertainty in the modeled planet mass. Here, we report the direct-imaging discovery of a Jovian exoplanet around the Sun-like star GJ 504, detected as part of the SEEDS survey. The system is older than all other known directly imaged planets; as a result, its estimated mass remains in the planetary regime independent of uncertainties related to choices of initial conditions in the exoplanet modeling. Using the most common exoplanet cooling model, and given the system age of 160160 super(+350) sub(-60) Myr, GJ 504b has an estimated mass of 4 super(+45) sub(-1.0) Jupiter masses, among the lowest of directly imaged planets. Its projected separation of 43.5 AU exceeds the typical outer boundary of ~30 AU predicted for the core accretion mechanism. GJ 504b is also significantly cooler (510 super(+30) sub(-20) K) and has a bluer color (J - H = -0.23 mag) than previously imaged exoplanets, suggesting a largely cloud-free atmosphere accessible to spectroscopic characterization. Thus, it has the potential of providing novel insights into the origins of giant planets as well as their atmospheric properties.
PDF
