We present the scientific performance results of pynpoint, our Python-based software package that uses principal component analysis to detect and estimate the flux of exoplanets in two-dimensional ...imaging data. Recent advances in adaptive optics and imaging technology at visible and infrared wavelengths have opened the door to direct detections of planetary companions to nearby stars, but image processing techniques have yet to be optimized. We show that the performance of our approach gives a marked improvement over what is presently possible using existing methods such as loci. To test our approach, we use real angular differential imaging (ADI) data taken with the adaptive optics-assisted high resolution near-infrared camera NACO at the VLT. These data were taken during the commissioning of the apodizing phase plate (APP) coronagraph. By inserting simulated planets into these data, we test the performance of our method as a function of planet brightness for different positions on the image. We find that in all cases pynpoint has a detection threshold that is superior to that given by our loci analysis when assessed in a common statistical framework. We obtain our best improvements for smaller inner working angles (IWAs). For an IWA of ∼0.29 arcsec we find that we achieve a detection sensitivity that is a factor of 5 better than loci. We also investigate our ability to correctly measure the flux of planets. Again, we find improvements over loci, with pynpoint giving more stable results. Finally, we apply our package to a non-APP data set of the exoplanet β Pictoris b and reveal the planet with high signal-to-noise. This confirms that pynpoint can potentially be applied with high fidelity to a wide range of high-contrast imaging data sets.
We present H- and K sub(s)-band polarized differential images of the Herbig Ae/Be star HD142527, revealing its optically thick outer disk and the nearly empty gap. The very small inner working angle ...(~0".1) and high-resolution achievable with an 8 m class telescope, together with a careful polarimetric calibration strategy, allow us to achieve images that surpass the quality of previous scattered-light images. Previously known substructures are resolved more clearly and new structures are seen. Specifically, we are able to resolve (1) half a dozen spiral structures in the disk, including previously known outer-disk spirals as well as new spiral arms and arcs close to the inner rim of the disk, (2) peculiar holes in the polarized surface brightness at position angles (P.A.'s) of ~0degrees and ~160degrees, (3) the inner rim on the eastern side of the disk, and (4) the gap between the outer and inner disk, ranging from the inner working angle of 0."1 out to between 0."7 and 1."0, which is nearly devoid of dust. We then use a Markov Chain Monte Carlo algorithm to determine several structural parameters of the disk, using very simple assumptions, including its inclination, eccentricity, and the scale height of the inner rim. We compare our results with previous work on this object and try to produce a consistent picture of the system and its transition disk.
Aims. We predict the exoplanet yield of a space-based mid-infrared nulling interferometer using Monte Carlo simulations. We quantify the number and properties of detectable exoplanets and identify ...those target stars that have the highest or most complete detection rate. We investigate how changes in the underlying technical assumptions and uncertainties in the underlying planet population impact the scientific return. Methods. We simulated 2000 exoplanetary systems, based on planet occurrence statistics from Kepler with randomly orientated orbits and uniformly distributed albedos around each of 326 nearby (d< 20 pc) stars. Assuming thermal equilibrium and blackbody emission, together with the limiting spatial resolution and sensitivity of our simulated instrument in the three specific bands 5.6, 10.0, and 15.0 μm, we quantified the number of detectable exoplanets as a function of their radii and equilibrium temperatures. Results. Approximately 315-77+113 exoplanets, with radii 0.5 REarth ≤ Rp ≤ 6 REarth, were detected in at least one band and half were detected in all three bands during ~0.52 years of mission time assuming throughputs 3.5 times worse than those for the James Webb Space Telescope and ~40% overheads. Accounting for stellar leakage and (unknown) exozodiacal light, the discovery phase of the mission very likely requires 2−3 years in total. The uncertainties in planet yield are dominated by uncertainties in the underlying planet population, but the distribution of the Bond albedos also has a significant impact. Roughly 50% of the detected planets orbit M stars, which also have the highest planet yield per star; the other 50% orbit FGK stars, which show a higher completeness in the detectability. Roughly 85 planets could be habitable (0.5 REarth ≤ Rp ≤ 1.75 REarth and 200 K ≤ Teq ≤ 450 K) and are prime targets for spectroscopic observations in a second mission phase. Comparing these results to those of a large optical/near-infrared telescope, we find that a mid-infrared interferometer would detect more planets and the number of planets depends less strongly on the wavelength. Conclusions. An optimized space-based nulling interferometer operating in the mid-infrared would deliver an unprecedented dataset for the characterization of (small) nearby exoplanets including dozens of potentially habitable worlds.
We present N-body simulations of young substructured star clusters undergoing various dynamical evolutionary scenarios and examine the direct effects of interactions in the cluster on planetary ...systems. We model clusters initially in cool collapse, in virial equilibrium and expanding, and place a 1-Jupiter-mass planet at either 5 or 30 au from their host stars, with zero eccentricity. We find that after 10 Myr ∼10 per cent of planets initially orbiting at 30 au have been liberated from their parent star and form a population of free-floating planets. A small number of these planets are captured by other stars. A further ∼10 per cent have their orbital eccentricity (and less often their semimajor axis) significantly altered. For planets originally at 5 au the fractions are a factor of 2 lower. The change in eccentricity is often accompanied by a change in orbital inclination which may lead to additional dynamical perturbations in planetary systems with multiple planets. The fraction of liberated and disrupted planetary systems is highest for subvirial clusters, but virial and supervirial clusters also dynamically process planetary systems, due to interactions in the substructure.
Of the planets that become free-floating, those that remain observationally associated with the cluster (i.e. within two half-mass radii of the cluster centre) have a similar velocity distribution to the entire star cluster, irrespective of whether they were on a 5 or 30 au orbit, with median velocities typically ∼1 km s−1. Conversely, those planets that are no longer associated with the cluster have similar velocities to the non-associated stars if they were originally at 5 au (∼9 km s−1), whereas the planets originally at 30 au have much lower velocities (3.8 km s−1) than the non-associated stars (10.8 km s−1). These findings highlight potential pitfalls of concluding that (a) planets with similar velocities to the cluster stars represent the very low mass end of the initial mass function and (b) planets on the periphery of a cluster with very different observed velocities form through different mechanisms.
Abstract
We present the first part of our Disks ARound T Tauri Stars with SPHERE (DARTTS-S) survey: observations of eight T Tauri stars that were selected based on their strong (sub)millimeter ...excesses using SPHERE/IRDIS polarimetric differential imaging in the
J
and
H
bands. All observations successfully detect the disks, which appear vastly different in size, from ≈80 au in scattered light to >400 au, and display total polarized disk fluxes between 0.06% and 0.89% of the stellar flux. For five of these disks, we are able to determine the three-dimensional structure and the flaring of the disk surface, which appears to be relatively consistent across the different disks, with flaring exponents
α
between ≈1.1 and ≈1.6. We also confirm literature results with regard to the inclination and position angle of several of our disks and are able to determine which side is the near side of the disk in most cases. While there is a clear trend of disk mass with stellar ages (≈1 to >10 Myr), no correlations of disk structures with age were found. There are also no correlations with either stellar mass or submillimeter flux. We do not detect significant differences between the
J
and
H
bands. However, we note that while a high fraction (7/8) of the disks in our sample show ring-shaped substructures, none of them display spirals, in contrast to the disks around more massive Herbig Ae/Be stars, where spiral features are common.
We present long-baseline Atacama Large Millimeter/submillimeter Array observations of the 870 m dust continuum emission and CO (3-2) from the protoplanetary disk around the Herbig Ae/Be star HD ...100546, which is one of the few systems claimed to have two young embedded planets. These observations achieve a resolution of 4 au (3.8 mas), an rms noise of 66 Jy beam−1, and reveal an asymmetric ring between ∼20 and 40 au with largely optically thin dust continuum emission. This ring is well fit by two concentric and overlapping Gaussian rings of different widths and a Vortex. In addition, an unresolved component is detected at a position consistent with the central star, which may trace the central inner disk (<2 au in radius). We report a lack of compact continuum emission at the positions of both claimed protoplanets. We use this result to constrain the circumplanetary disk (CPD) mass and size of 1.44 M⊕ and 0.44 au in the optically thin and thick regimes, respectively, for the case of the previously directly imaged protoplanet candidate at ∼55 au (HD 100546 b). We compare these empirical CPD constraints to previous numerical simulations. This suggests that HD 100546 b is inconsistent with several planet accretion models, while gas-starved models are also still compatible. We estimate the planetary mass as 1.65 MJ using the relation between planet, circumstellar, and circumplanetary masses derived from numerical simulations. Finally, the CO-integrated intensity map shows a possible spiral arm feature that could match the spiral features identified in near-infrared scattered light polarized emission, which suggests a real spiral feature in the disk surface that needs to be confirmed with further observations.
We present H-band Very Large Telescope/NACO polarized light images of the Herbig Ae/Be star HD 169142 probing its protoplanetary disk as close as ~0".1 to the star. Our images trace the face-on disk ...out to ~1".7 (~250 AU) and reveal distinct substructures for the first time: (1) the inner disk (<, ~20 AU) appears to be depleted in scattering dust grains; (2) an unresolved disk rim is imaged at <25 AU; (3) an annular gap extends from ~40 to 70 AU; (4) local brightness asymmetries are found on opposite sides of the annular gap. We discuss different explanations for the observed morphology among which ongoing planet formation is a tempting, but yet to be proven, one. Outside of ~85 AU the surface brightness drops off roughly proportional, variant r super(-3.3), but describing the disk regions between 85-120 AU and 120-250 AU separately with power laws proportional, variant r super(-2.6) and proportional, variant r super(-3.9) provides a better fit hinting toward another discontinuity in the disk surface. The flux ratio between the disk-integrated polarized light and the central star is ~ 4.1 X 10 super(?3). Finally, combining our results with those from the literature, ~40% of the scattered light in the H band appears to be polarized. Our results emphasize that HD 169142 is an interesting system for future planet formation or disk evolution studies.
HD 100453AB is a 10 2 Myr old binary whose protoplanetary disk was recently revealed to host a global two-armed spiral structure. Given the relatively small projected separation of the binary (1 05, ...or ∼108 au), gravitational perturbations by the binary seemed to be a likely driving force behind the formation of the spiral arms. However, the orbit of these stars remained poorly understood, which prevented a proper treatment of the dynamical influence of the companion on the disk. We observed HD 100453AB between 2015 and 2017, utilizing extreme adaptive optics systems on the Very Large Telescope and the Magellan Clay Telescope. We combined the astrometry from these observations with published data to constrain the parameters of the binary's orbit to a = 1 06 0 09, e = 0.17 0.07, and i = 32 5 6 5. We utilized publicly available ALMA 12CO data to constrain the inclination of the disk, , which is relatively coplanar with the orbit of the companion and consistent with previous estimates from scattered light images. Finally, we input these constraints into hydrodynamic and radiative transfer simulations to model the structural evolution of the disk. We find that the spiral structure and truncation of the circumprimary disk in HD 100453 are consistent with a companion-driven origin. Furthermore, we find that the primary star's rotation, its outer disk, and the companion exhibit roughly the same direction of angular momentum, and thus the system likely formed from the same parent body of material.
Context. Elemental abundances of Sun-like stars have been shown to be crucial for understanding the detailed properties of planets surrounding them. However, accurately measuring elemental abundances ...of M stars, the most abundant class of stars in the solar neighbourhood, is challenging due to their faintness and pervasive molecular features in optical photospheric spectra. As a result, elemental abundances of Sun-like stars have been proposed to constrain those of M stars, particularly by scaling X/H given measured Fe/H. Aims. This work aims to test the robustness of this convenient practice based on two selected sets of M- and GK-dwarf stellar abundances and a set of rigorous statistical methods. Methods. We compiled the elemental abundances of a sample of up to 43 M dwarfs for ten major rock-forming elements (Fe, C, O, Mg, Si, Al, Ca, Na, Ni, and Ti) from high-resolution near-infrared stellar surveys including APOGEE, CARMENES, and Subaru. We carried out bootstrap-based linear regressions on the selected sample of M dwarfs to constrain the statistical trends of X/H versus Fe/H and then compare them with those of GK dwarfs (sampled from the GALAH database). We then applied a two-sample, multivariate Mahalanobis Distance test to assess the significance of the differences in the X/H-Fe/H trends for individual elemental pairs between M and GK dwarfs. Results. We find that the null hypothesis – that is, no significant difference in the chemical trends of X/H versus Fe/H between M and GK dwarfs – is strongly rejected for all elements except for Si, for which the rejection is marginal ( p -value close to 0.05), and Na and Ni, for which the results are inconclusive. This finding suggests that assuming no difference may result in biased results, and thus inaccurate constraints on characterising rocky planets around M dwarfs by scaling the (unmeasured) chemical abundances of planet-hosting M dwarfs from the chemical trends of X/H–Fe/H determined by GK dwarfs. Conclusions. It is therefore crucial for both the stellar and exoplanet communities to be aware of these observed differences. To better understand these differences, we advocate for dedicated modelling techniques for M-dwarf atmospheres and an increasing set of benchmark, homogeneous abundance analyses. Intermediately, our statistically constrained trends of X/H–Fe/H for M dwarfs provide a new constraint on estimating M-dwarf elemental abundances given measured Fe/H and further on characterising the detailed properties of M-dwarf-hosted rocky worlds.
ABSTRACT
Gravitational interactions in star-forming regions are capable of disrupting and destroying planetary systems, as well as creating new ones. In particular, a planet can be stolen, where it ...is directly exchanged between passing stars during an interaction; or captured, where a planet is first ejected from its birth system and is free-floating for a period of time, before being captured by a passing star. We perform sets of direct N-body simulations of young, substructured star-forming regions, and follow their evolution for 10 Myr in order to determine how many planets are stolen and captured, and their respective orbital properties. We show that in high-density star-forming regions, stolen and captured planets have distinct properties. The semimajor axis distribution of captured planets is significantly skewed to wider orbits compared to the semimajor axis distribution of stolen planets and planets that are still orbiting their parent star (preserved planets). However, the eccentricity and inclination distributions of captured and stolen planets are similar, but in turn very different to the inclination and eccentricity distributions of preserved planets. In low-density star-forming regions these differences are not as distinct but could still, in principle, be used to determine whether observed exoplanets have likely formed in situ or have been stolen or captured. We find that the initial degree of spatial and kinematic substructure in a star-forming region is as important a factor as the stellar density in determining whether a planetary system will be altered, disrupted, captured, or stolen.
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