Using the POLISH instrument, I am unable to reproduce the large-amplitude polarimetric observations of Berdyugina et al. (2008) to the >99.99% confidence level. I observe no significant polarimetric variability in the HD 189733 system, and the upper limit to variability from the exoplanet is Delta_P < 7.9 x 10^(-5) with 99% confidence in the 400 nm to 675 nm wavelength range. Berdyugina et al. (2008) report polarized, scattered light from the atmosphere of the HD 189733b hot Jupiter with an amplitude of two parts in 10^4. Such a large amplitude is over an order of magnitude larger than expected given a geometric albedo similar to other hot Jupiters. However, my non-detection of polarimetric variability phase-locked to the orbital period of the exoplanet, and the lack of any significant variability, shows that the polarimetric modulation reported by Berdyugina et al. (2008) cannot be due to the exoplanet.
The measurement of the light scattered from extrasolar planets informs atmospheric and formation models. With the discovery of many hot Jupiter planets orbiting nearby stars, this motivates the development of robust methods of characterisation from follow up observations. In this paper we discuss two methods for determining the planetary albedo in transiting systems. First, the most widely used method for measuring the light scattered by hot Jupiters (Collier Cameron et al.) is investigated for application for typical echelle spectra of a transiting planet system, showing that detection requir…
There is a long-standing debate regarding the origin of the terrestrial planets' water as well as the hydrated C-type asteroids. Here we show that the inner Solar System's water is a simple byproduct of the giant planets' formation. Giant planet cores accrete gas slowly until the conditions are met for a rapid phase of runaway growth. As a gas giant's mass rapidly increases, the orbits of nearby planetesimals are destabilized and gravitationally scattered in all directions. Under the action of aerodynamic gas drag, a fraction of scattered planetesimals are deposited onto stable orbits interior…
It has long been hypothesised that the Jupiter-family comets (JFCs) come from the scattered disc, an unstable planetesimal population beyond Neptune. This viewpoint has been widely accepted, but a few issues remain, the most prominent of which are the total number of visible JFCs with a perihelion distance q<2.5 AU and the corresponding number of objects in the scattered disc. In this work we give a robust estimate of the number of visible JFCs with q<2.5 AU and diameter D>2.3 km based on recent observational data. This is combined with numerical simulations that use a simple fading law applie…
We have investigated the impact of circumplanetary rings consisting of spherical micrometer-sized particles on the net scattered light polarization of extrasolar gas giants. Using the three-dimensional Monte Carlo radiative transfer code POLARIS, we studied the impact of the macroscopic parameters that define the ring, such as its radius and inclination, and the chemical composition of the ring particles on the net scattered polarization. For the spherical ring particles, we applied the Mie scattering theory. We studied the flux and polarization of the scattered stellar radiation as a function…
There are growing amount of very high-resolution polarized scattered light images of circumstellar disks. Nascent giant planets planets are surrounded by their own circumplanetary disks which may scatter and polarize both the planetary and stellar light. Here we investigate whether we could detect circumplanetary disks with the same technique and what can we learn from such detections. Here we created scattered light mock observations at 1.245 microns (J band) for instruments like SPHERE and GPI, for various planetary masses (0.3, 1.0, 5.0, 10.0 $\rm{M_{Jup}}$), disk inclinations (90, 60, 30, …
Direct imaging surveys have found that long-period super-Jupiters are rare. By contrast, recent modeling of the widespread gaps in protoplanetary disks revealed by ALMA suggests an abundant population of smaller Neptune to Jupiter-mass planets at large separations. The thermal emission from such lower-mass planets is negligible at optical and near-infrared wavelengths, leaving only their weak signals in reflected light. Planets do not scatter enough light at these large orbital distances, but there is a natural way to enhance their reflecting area. Each of the four giant planets in our solar s…
We present the first spatially resolved polarized scattered light H-band detection of the DoAr 28 transitional disk. Our two epochs of imagery detect the scattered light disk from our effective inner working angle of 0.10" (13 AU) out to 0.50" (65 AU). This inner working angle is interior to the location of the system's gap inferred by previous studies using SED modeling (15 AU). We detected a candidate point source companion 1.08" northwest of the system; however, our second epoch of imagery strongly suggests that this object is a background star. We constructed a grid of Monte Carlo Radiativ…
Direct imaging has paved the way for atmospheric characterization of young and self-luminous gas giants. Scattering in a horizontally-inhomogeneous atmosphere causes the disk-integrated polarization of the thermal radiation to be linearly polarized, possibly detectable with the newest generation of high-contrast imaging instruments. We aim to investigate the effect of latitudinal and longitudinal cloud variations, circumplanetary disks, atmospheric oblateness, and cloud particle properties on the integrated degree and direction of polarization in the near-infrared. We have developed a three-di…
Vega has been shown to host multiple dust populations, including both hot exo-zodiacal dust at sub-AU radii and a cold debris disk extending beyond 100 AU. We use dynamical simulations to show how Vega's hot dust can be created by long-range gravitational scattering of planetesimals from its cold outer regions. Planetesimals are scattered progressively inward by a system of 5-7 planets from 30-60 AU to very close-in. In successful simulations the outermost planets are typically Neptune-mass. The back-reaction of planetesimal scattering causes these planets to migrate outward and continually in…
The solar system's Zodiacal Cloud is visible to the unaided eye, yet the origin of its constituent dust particles is not well understood, with a wide range of proposed divisions between sources in the asteroid belt and Jupiter Family comets. The amount of dust contributed by Oort Cloud comets is uncertain. Knowledge of the Zodiacal Cloud's structure and origins would help with NASA's aim of characterizing potentially Earth-like planets around nearby stars, since the exo-Earths must be studied against the light scattered from extrasolar analogs of our cloud. As the only example where the parent…
Debris disks or belts are important signposts for the presence of colliding planetesimals and, therefore, for ongoing planet formation and evolution processes in young planetary systems. Imaging of debris material at small separations from the star is very challenging but provides valuable insights into the spatial distribution of so-called hot dust produced by solid bodies located in or near the habitable zone. We report the first detection of scattered light from the hot dust around the nearby (d = 28.33 pc) A star HD 172555. We want to constrain the geometric structure of the detected debri…
Observations of scattered light and thermal emission from hot Jupiter exoplanets have suggested the presence of inhomogeneous aerosols in their atmospheres. 3D general circulation models (GCMs) that attempt to model the effects of aerosols have been developed to understand the physical processes that underlie their dynamical structures. In this work, we investigate how different approaches to aerosol modeling in GCMs of hot Jupiters affect high-resolution thermal emission spectra throughout the duration of the planet's orbit. Using results from a GCM with temperature-dependent cloud formation,…
Probing dust properties through polarized scattered-light images of a sample of ring-shaped protoplanetary disks
Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学）；Astronomy Department, University of California Berkeley（加州大学伯克利分校天文学系）；Department of Earth Science and Astronomy, The University of Tokyo（东京大学地球科学和天文系）；School of Natural Sciences, Center for Astronomy, University of Galway（戈尔韦大学自然科学学院天文学中心）
We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 $M_{\rm Jup}$; 1.46 $R_{\rm Jup}$) in a 4.9-day, near-aligned ($λ= 8.1 \pm 3.6^\circ$) orbit around CD-24 102 ($V$=10.7; F9). WASP-28b is an inflated, Jupiter-mass planet (0.91 $M_{\rm Jup}$; 1.21 $R_{\rm Jup}$) in a 3.4-day, near-aligned ($λ= 8 \pm 18^\circ$) orbit around a $V$=12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars ($7^{+2}_{-1}$ Gyr for WASP-20 and $5^{+3}_{-2}$ Gyr for WA…
We present high-precision linear polarization observations of four bright hot Jupiter systems ($τ$ Boo, HD 179949, HD 189733 and 51 Peg) and use the data to search for polarized reflected light from the planets. The data for 51 Peg are consistent with a reflected light polarization signal at about the level expected with 2.8$σ$ significance and a false alarm probability of 1.9 per cent. More data will be needed to confirm a detection of reflected light in this system. HD 189733 shows highly variable polarization that appears to be most likely the result of magnetic activity of the host star. T…
Magnetic fields play essential roles in protoplanetary disks. Magnetic fields in the disk atmosphere are of particular interest, as they are connected to the wind-launching mechanism. In this work, we study the polarization of the light scattered off of magnetically aligned grains in the disk atmosphere, focusing on the deviation of the polarization orientation from the canonical azimuthal direction, which may be detectable in near-IR polarimetry with instruments such as VLT/SPHERE. We show with a simple disk model that the polarization can even be oriented along the radial (rather than azimut…
Transitional circumstellar disks around young stellar objects have a distinctive infrared deficit around 10 microns in their Spectral Energy Distributions (SED), recently measured by the Spitzer Infrared Spectrograph (IRS), suggesting dust depletion in the inner regions. These disks have been confirmed to have giant central cavities by imaging of the submillimeter (sub-mm) continuum emission using the Submillimeter Array (SMA). However, the polarized near-infrared scattered light images for most objects in a systematic IRS/SMA cross sample, obtained by HiCIAO on the Subaru telescope, show no e…
$\textit{Context.}$ The magnetized Solar System planets are strong radio emitters and theoretical studies suggest that the radio emission from nearby exoplanets in close-in orbits could reach intensity levels $10^{3}-10^{7}$ times higher than Jupiter's decametric emission. Detection of exoplanets in the radio domain would open up a brand new field of research, however, currently there are no confirmed detections at radio frequencies. $\textit{Aims.}$ We investigate the radio emission from Jupiter, scaled such that it mimics emission coming from an exoplanet, with low-frequency beam-formed obse…
Polarimetric observations of T Tauri and Herbig Ae/Be stars are a powerful way to image protoplanetary disks. However, interpretation of these images is difficult because the degree of polarization is highly sensitive to the angle of scattering of stellar light off the disk surface. We examine how disks with and without gaps created by planets appear in scattered polarized light as a function of inclination angle. Isophotes of inclined disks without gaps are distorted in polarized light, giving the appearance that the disks are more eccentric or more highly inclined than they truly are. Appare…
Thousands of exoplanets have been detected, but only one exoplanetary transit was potentially observed in X-rays from HD189733A. What makes the detection of exoplanets so difficult in this band? To answer this question, we run Monte-Carlo radiative transfer simulations to estimate the amount of X-ray flux reprocessed by HD189733b. Despite its extended evaporating-atmosphere, we find that the X-ray absorption radius of HD189733b at 0.7keV, the mean energy of the photons detected in the 0.25--2 keV energy band by XMM-Newton, is $\sim$1.01 times the planetary radius for an atmosphere of atomic Hy…
The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR4796A in polarised optical light. We obtained high-contrast polarimetric images of HR4796A in the wavelength range 600-900nm with the SPHERE / ZIMPO…
Three-dimensional hydrodynamic numerical simulations have demonstrated that the structure of a protoplanetary disc may be strongly affected by a planet orbiting in a plane that is misaligned to the disc. When the planet is able to open a gap, the disc is separated into an inner, precessing disc and an outer disc with a warp. In this work, we compute infrared scattered light images to investigate the observational consequences of such an arrangement. We find that an inner disc misaligned by a less than a degree to the outer disc is indeed able to cast a shadow at larger radii. In our simulation…
Hot Jupiter formation in dense stellar clusters: A Monte Carlo model applied to 47 Tucanae
Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）；Max-Planck Institute for Astronomy (MPIA)（马克斯·普朗克天文学研究所）；Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange（蔚蓝海岸大学、蔚蓝海岸天文台、法国国家科学研究中心、拉格朗日实验室）
High-contrast scattered light observations have revealed the surface morphology of several dozens of protoplanetary disks at optical and near-infrared wavelengths. Inclined disks offer the opportunity to measure part of the phase function of the dust grains that reside in the disk surface which is essential for our understanding of protoplanetary dust properties and the early stages of planet formation. We aim to construct a method which takes into account how the flaring shape of the scattering surface of an (optically thick) protoplanetary disk projects onto the image plane of the observer. …
Recent coronagraphic imaging of the AB Aurigae disk has revealed a region of low polarized scattered light suggestive of perturbations from a planet at a radius of ~100 AU. We model this darkened region using our fully non-plane-parallel radiative-transfer code combined with a simple hydrostatic equilibirum approximation to self-consistently solve for the structure of the disk surface as seen in scattered light. By comparing the observations to our models, we find that the observations are consistent with the absence of a planet, with an upper limit of 1 Jupiter mass.
Using the NICMOS coronagraph, we have obtained high-contrast 2.0 micron imaging polarimetry and 1.1 micron imaging of the circumstellar disk around AB Aurigae on angular scales of 0.3-3 arcsec (40-550 AU). Unlike previous observations, these data resolve the disk in both total and polarized intensity, allowing accurate measurement of the spatial variation of polarization fraction across the disk. Using these observations we investigate the apparent "gap" in the disk reported by Oppenheimer et al. 2008. In polarized intensity, the NICMOS data closely reproduces the morphology seen by Oppenheime…
While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant ($M_\star= 1.53 \pm 0.12 M_\odot$, $R_\star= 2.90 \pm 0.14 R_\odot$) in the $\textit{TESS}$ Southern Continuous Viewing Zone. The planet was flagged as a false positive by the $\textit{TESS}$ Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline t…
We present new spectroscopic and photometric observations of the transiting exoplanetary system WASP-3. Spectra obtained during two separate transits exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the sky-projected angle between the planetary orbital axis and the stellar rotation axis, lambda = 3.3^{+2.5}_{-4.4} degrees. This alignment between the axes suggests that WASP-3b has a low orbital inclination relative to the equatorial plane of its parent star. During our first night of spectroscopic measurements, we observed an unexpected redshift briefly exceeding the expecte…
We present the first scattered-light image of the debris disk around HD 131835 in $H$ band using the Gemini Planet Imager. HD 131835 is a $\sim$15 Myr old A2IV star at a distance of $\sim$120 pc in the Sco-Cen OB association. We detect the disk only in polarized light and place an upper limit on the peak total intensity. No point sources resembling exoplanets were identified. Compared to its mid-infrared thermal emission, the disk in scattered light shows similar orientation but different morphology. The scattered-light disk extends from $\sim$75 to $\sim$210 AU in the disk plane with roughly …
Polarimetry is a novel tool to detect and characterize exoplanets and their atmospheres. Polarized scattered light from the non-transiting hot Jupiter $\upsilon$~And~b is measured to further constrain its orbit, mass, density, and geometrical albedo. We obtained polarimetric measurements in the $UBV$ bands over the orbital period and deduce an average peak-to-peak amplitude of $(49 \pm 5)\times10^{-6}$ in both Stokes $q$ and $u$. From our data we evaluate the orbit inclination $i=111\degr\pm11\degr$, longitude of the ascending node $Ω=236\degr\pm12\degr$ (or equivalently 56\degr), the effectiv…
We observe a significant change in the TW Hya disk interior to 40~AU via archival unpolarized multi-wavelength Hubble Space Telescope/STIS and NICMOS images with an inner working angle (IWA) of 0\farcs4 (22~AU). Our images show the outer edge of a clearing at every wavelength with similar behavior, demonstrating that the feature is structural, rather than due to some property of polarized light in the disk. We compare our observations to those taken by Akiyama et al. (2015) and Rapson et al. (2015), and discuss the spectral evolution of the disk interior to 80~AU. We construct a model with two…
The variety of observed protoplanetary disks in polarimetric light motivates a taxonomical study to constrain their evolution and establish the current framework of this type of observations. We classified 58 disks with available polarimetric observations into six major categories (Ring, Spiral, Giant, Rim, Faint, and Small disks) based on their appearance in scattered light. We re-calculated the stellar and disk properties from the newly available GAIA DR2 and related these properties with the disk categories. More than a half of our sample shows disk sub-structures. For the remaining sources…
We present the complete sample of protoplanetary disks from the Gemini- Large Imaging with GPI Herbig/T-tauri Survey (Gemini-LIGHTS) which observed bright Herbig Ae/Be stars and T-Tauri stars in near-infrared polarized light to search for signatures of disk evolution and ongoing planet formation. The 44 targets were chosen based on their near- and mid-infrared colors, with roughly equal numbers of transitional, pre-transitional, and full disks. Our approach explicitly did not favor well-known, "famous" disks or those observed by ALMA, resulting in a less-biased sample suitable to probe the maj…
Recently, high angular resolution imaging instruments such as SPHERE and GPI have discovered many spiral-arm-like features in near-infrared scattered light images of protoplanetary disks. Theory and simulations have suggested that these arms are most likely excited by planets forming in the disks; however, a quantitative relation between the arm-to-disk brightness contrast and planet mass is still missing. Using 3D hydrodynamics and radiative transfer simulations, we examine the morphology and contrast of planet-induced arms in disks. We find a power-law relation for the face-on arm contrast (…
We performed observations of the Sco-Cen F star HD 117214 aiming at a search for planetary companions and the characterization of the debris disk structure. HD 117214 was observed with the SPHERE subsystems IRDIS, IFS and ZIMPOL at optical and near-IR wavelengths using angular and polarimetric differential imaging techniques. This provided the first images of scattered light from the debris disk with a spatial resolution reaching 25 mas and an inner working angle $< 0.1''$. With the observations with IRDIS and IFS we derive detection limits for substellar companions. The geometrical parameters…
This paper introduces the quadrant polarization parameters $Q_{000}$, $Q_{090}$, $Q_{180}$, $Q_{270}$ for Stokes $Q$ and $U_{045}$, $U_{135}$, $U_{225}$, $U_{315}$ for Stokes $U$ for the characterization of the azimuthal dependence of the scattering polarization of spatially resolved circumstellar disks illuminated by the central star. These parameters are based on the natural Stokes $Q$ and $U$ quadrant pattern produced by circumstellar scattering. They provide a simple test of the deviations of the disk geometry from axisymmetry and can be used to constrain the scattering phase function for …
Azimuthally asymmetric structures have been discovered in millimeter continuum emission from many protoplanetary disks. One hypothesis is that they are vortices produced by the Rossby wave instability, for example at edges of planet-opened gaps or deadzones. Confirming the vortex nature of these structures will have profound implications to planet formation. One way to test the hypothesis is to compare the observed morphology of vortex candidates in near-infrared scattered light with theoretical expectations. To this end, we synthesize the appearance of vortices in H-band polarized light by co…
