ALMA 1.3 Millimeter Map of the HD 95086 System

ALMA 1.3 Millimeter Map of the HD 95086 System

Authors:

Su et al

Abstract:

Planets and minor bodies such as asteroids, Kuiper-belt objects and comets are integral components of a planetary system. Interactions among them leave clues about the formation process of a planetary system. The signature of such interactions is most prominent through observations of its debris disk at millimeter wavelengths where emission is dominated by the population of large grains that stay close to their parent bodies. Here we present ALMA 1.3 mm observations of HD 95086, a young early-type star that hosts a directly imaged giant planet b and a massive debris disk with both asteroid- and Kuiper-belt analogs. The location of the Kuiper-belt analog is resolved for the first time. The system can be depicted as a broad (ΔR/R∼0.84), inclined (30\arcdeg±3\arcdeg) ring with millimeter emission peaked at 200±6 au from the star. The 1.3 mm disk emission is consistent with a broad disk with sharp boundaries from 106±6 to 320±20 au with a surface density distribution described by a power law with an index of --0.5±0.2. Our deep ALMA map also reveals a bright source located near the edge of the ring, whose brightness at 1.3 mm and potential spectral energy distribution are consistent with it being a luminous star-forming galaxy at high redshift. We set constraints on the orbital properties of planet b assuming co-planarity with the observed disk.

Directly-Imaged Planet HD 131399 Ab may be a False Positive

Evidence that the Directly-Imaged Planet HD 131399 Ab is a Background Star

Authors:

Nielsen et al

Abstract:
We present evidence that the recently discovered, directly-imaged planet HD 131399 Ab is a background star with non-zero proper motion. From new JHK1L' photometry and spectroscopy obtained with the Gemini Planet Imager, VLT/SPHERE, and Keck/NIRC2, and a reanalysis of the discovery data obtained with VLT/SPHERE, we derive colors, spectra, and astrometry for HD 131399 Ab. The broader wavelength coverage and higher data quality allow us to re-investigate its status. Its near-infrared spectral energy distribution excludes spectral types later than L0 and is consistent with a K or M dwarf, which are the most likely candidates for a background object in this direction at the apparent magnitude observed. If it were a physically associated object, the projected velocity of HD 131399 Ab would exceed escape velocity given the mass and distance to HD 131399 A. We show that HD 131399 Ab is also not following the expected track for a stationary background star at infinite distance. Solving for the proper motion and parallax required to explain the relative motion of HD 131399 Ab, we find a proper motion of 12.3 mas/yr. When compared to predicted background objects drawn from a galactic model, we find this proper motion to be high, but consistent with the top 4% fastest-moving background stars. From our analysis we conclude that HD 131399 Ab is a background K or M dwarf.

Imaging an 80 AU Radius Dust Ring Around the F5V Star HD 157587

Imaging an 80 AU Radius Dust Ring Around the F5V Star HD 157587

Authors:

Millar-Blanchaer et al

Abstract:

We present H-band near-infrared polarimetric imaging observations of the F5V star HD~157587 obtained with the Gemini Planet Imager (GPI) that reveal the debris disk as a bright ring structure at a separation of ∼80−100~AU. The new GPI data complement recent HST/STIS observations that show the disk extending out to over 500~AU. The GPI image displays a strong asymmetry along the projected minor axis as well as a fainter asymmetry along the projected major axis. We associate the minor and major axis asymmetries with polarized forward scattering and a possible stellocentric offset, respectively. To constrain the disk geometry we fit two separate disk models to the polarized image, each using a different scattering phase function. Both models favor a disk inclination of $\sim 70\degr$ and a 1.5±0.6 AU stellar offset in the plane of the sky along the projected major axis of the disk. We find that the stellar offset in the disk plane, perpendicular to the projected major axis is degenerate with the form of the scattering phase function and remains poorly constrained. The disk is not recovered in total intensity due in part to strong adaptive optics residuals, but we recover three point sources. Considering the system's proximity to the galactic plane and the point sources' positions relative to the disk, we consider it likely that they are background objects and unrelated to the disk's offset from the star.

How Common are Free Floating Exoplanets?

Constraining the Frequency of Free-Floating Planets from a Synthesis of Microlensing, Radial Velocity, and Direct Imaging Survey Results

Authors:

Clanton et al

Abstract:

A microlensing survey by Sumi et al. (2011) exhibits an overabundance of short-timescale events (STEs; t_E<2 a="" alone="" and="" as="" been="" between="" brown="" by="" cannot="" data="" days="" distinguish="" down="" due="" dwarf="" events="" excess="" expected="" extrapolation="" from="" has="" however="" interpreted="" is="" known="" main-sequence="" microlensing="" nearly="" objects="" of="" outnumber="" population="" populations="" power-law="" regime.="" relative="" smooth="" stars="" stellar="" that="" the="" this="" to="" twofold="" upiter-mass="" what="" wide-separation="">~10 AU) and free-floating planets. Assuming these STEs are indeed due to planetary-mass objects, we aim to constrain the fraction of these events that can be explained by bound but wide-separation planets. We fit the observed timescale distribution with a lens mass function comprised of brown dwarfs, main-sequence stars, and stellar remnants, finding and thus corroborating the initial identification of an excess of STEs. We then include a population of bound planets that are expected not to show signatures of the primary lens (host) in their microlensing light curves and that are also consistent with results from representative microlensing, radial velocity, and direct imaging surveys. We find that bound planets alone cannot explain the entire STE excess without violating the constraints from the surveys we consider and thus some fraction of these events must be due to free-floating planets, if our model for bound planets holds. We estimate a median fraction of STEs due to free-floating planets to be f=0.67 (0.23-0.85 at 95% confidence) when assuming "hot-start" planet evolutionary models and f=0.58 (0.14-0.83 at 95% confidence) for "cold-start" models. Assuming a delta-function distribution of free-floating planets of mass m_p=2 M_Jup yields a number of free-floating planets per main-sequence star of N=1.4 (0.48-1.8 at 95% confidence) in the "hot-start" case and N=1.2 (0.29-1.8 at 95% confidence) in the "cold-start" case.

New Optical Chip may Help Directly Detect Exoplanets

One of the central reasons exoplanets around distant stars can be so hard to spot directly is because the light of their parent star is so much brighter than the light being reflected by the plant it tends to block them from view. Scientists at Australian National University (ANU) have come up with a new optical chip that can be used with a telescope to help resolve the picture.

Few of the exoplanets discovered over the past two decades have been directly imaged with a telescope. Most have been found using other indirect techniques, such as Doppler spectroscopy, which is a way of analyzing a star's "wobble" caused by the gravitational pull of orbiting planets, or the transit method, where the small drop in brightness as a planet passes, or transits, in front of the star is detected.

ANU Associate Professor Steve Madden likens the new optical chip to working in a similar fashion to noise-canceling headphones, but for light instead of sound.

link.

Princeton is Directly Imaging Exoplanets Using CHARIS

The revelation that there are thousands of planets out there, orbiting other stars, is mostly due to the success of the Kepler mission. But now that we know these exoplanets are there, we want to know all about them. We want to know their mass, their temperature, how old they are, and pretty much everything else about them.

Now, a new instrument called the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) has captured the light from one of those exoplanets. This has the researchers excited about what they can see.

link.

CVSO 30c? A new Directly Imaged Gas Giant

Direct Imaging discovery of a second planet candidate around the possibly transiting planet host CVSO 30

Authors:

Schmidt et al

Abstract:

We surveyed the 25 Ori association for direct-imaging companions. This association has an age of only few million years. Among other targets, we observed CVSO 30, which has recently been identified as the first T Tauri star found to host a transiting planet candidate. We report on photometric and spectroscopic high-contrast observations with the Very Large Telescope, the Keck telescopes, and the Calar Alto observatory. They reveal a directly imaged planet candidate close to the young M3 star CVSO 30. The JHK-band photometry of the newly identified candidate is at better than 1 sigma consistent with late-type giants, early-T and early-M dwarfs, and free-floating planets. Other hypotheses such as galaxies can be excluded at more than 3.5 sigma. A lucky imaging z' photometric detection limit z'= 20.5 mag excludes early-M dwarfs and results in less than 10 MJup for CVSO 30 c if bound. We present spectroscopic observations of the wide companion that imply that the only remaining explanation for the object is that it is the first very young (less than 10 Myr) L-T-type planet bound to a star, meaning that it appears bluer than expected as a result of a decreasing cloud opacity at low effective temperatures. Only a planetary spectral model is consistent with the spectroscopy, and we deduce a best-fit mass of 4-5 Jupiter masses (total range 0.6-10.2 Jupiter masses). This means that CVSO 30 is the first system in which both a close-in and a wide planet candidate are found to have a common host star. The orbits of the two possible planets could not be more different: they have orbital periods of 10.76 hours and about 27000 years. The two orbits may have formed during a mutual catastrophic event of planet-planet scattering.

Imaging Extrasolar Giant Planets

Imaging Extrasolar Giant Planets

Authors:

Bowler et al

Abstract:

High-contrast adaptive optics imaging is a powerful technique to probe the architectures of planetary systems from the outside-in and survey the atmospheres of self-luminous giant planets. Direct imaging has rapidly matured over the past decade and especially the last few years with the advent of high-order adaptive optics systems, dedicated planet-finding instruments with specialized coronagraphs, and innovative observing and post-processing strategies to suppress speckle noise. This review summarizes recent progress in high-contrast imaging with particular emphasis on observational results, discoveries near and below the deuterium-burning limit, and a practical overview of large-scale surveys and dedicated instruments. I conclude with a statistical meta-analysis of deep imaging surveys in the literature. Based on observations of 384 unique and single young (≈5--300~Myr) stars spanning stellar masses between 0.1--3.0~\Msun, the overall occurrence rate of 5--13~\Mjup \ companions at orbital distances of 30--300~AU is 0.6+0.7−0.5\% assuming hot-start evolutionary models. The most massive giant planets regularly accessible to direct imaging are about as rare as hot Jupiters are around Sun-like stars. Dividing this sample into individual stellar mass bins does not reveal any statistically-significant trend in planet frequency with host mass: giant planets are found around 2.8+3.7−2.3\% of BA stars, less than 4.1\% of FGK stars, and less than 3.9\% of M dwarfs. Looking forward, extreme adaptive optics systems and the next generation of ground- and space-based telescopes with smaller inner working angles and deeper detection limits will increase the pace of discovery to ultimately map the demographics, composition, evolution, and origin of planets spanning a broad range of masses and ages.

HD 131399Ab: a Directly Imaged 4 Jupiter Mass Gas Giant in a Trinary System

Direct imaging discovery of a Jovian exoplanet within a triple-star system

Authors:

Wagner et al

Abstract:

Direct imaging allows for the detection and characterization of exoplanets via their thermal emission. We report the discovery via imaging of a young Jovian planet in a triple star system and characterize its atmospheric properties through near-infrared spectroscopy. The semi-major axis of the planet is closer relative to that of its hierarchical triple star system than for any known exoplanet within a stellar binary or triple, making HD 131399 dynamically unlike any other known system. The location of HD 131399Ab on a wide orbit in a triple system demonstrates that massive planets may be found on long and possibly unstable orbits in multi-star systems. HD 131399Ab is one of the lowest mass (4 ± 1 MJup) and coldest (850 ± 50 K) exoplanets to have been directly imaged.

pop sci links 1st, 2nd, 3rd.

Spectroscopic Characterization of Directly Imaged gas Giant HD 95086b

Spectroscopic characterization of HD 95086 b with the Gemini Planet Imager

Authors:

de Rosa et al

Abstract:

We present new H (1.5-1.8 μm) photometric and K1 (1.9-2.2 μm) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The H-band magnitude has been significantly improved relative to previous measurements, whereas the low resolution K1 (λ/δλ≈66) spectrum is featureless within the measurement uncertainties, and presents a monotonically increasing pseudo-continuum consistent with a cloudy atmosphere. By combining these new measurements with literature L′ photometry, we compare the spectral energy distribution of the planet to other young planetary-mass companions, field brown dwarfs, and to the predictions of grids of model atmospheres. HD 95086 b is over a magnitude redder in K1−L′ color than 2MASS J12073346-3932539 b and HR 8799 c and d, despite having a similar L′ magnitude. Considering only the near-infrared measurements, HD 95086 b is most analogous to the brown dwarfs 2MASS J2244316+204343 and 2MASS J21481633+4003594, both of which are thought to have dusty atmospheres. Morphologically, the spectral energy distribution of HD 95086 b is best fit by low temperature (Teff= 800-1300 K), low surface gravity spectra from models which simulate high photospheric dust content. This range of effective temperatures is consistent with field L/T transition objects, but the spectral type of HD 95086 b is poorly constrained between early L and late T due to its unusual position the color-magnitude diagram, demonstrating the difficulty in spectral typing young, low surface gravity substellar objects. As one of the reddest such objects, HD 95086 b represents an important empirical benchmark against which our current understanding of the atmospheric properties of young extrasolar planets can be tested.

Imaging the dust sublimation front of a circumbinary disk

Imaging the dust sublimation front of a circumbinary disk

Authors:

Hillen et al

Abstract:

Aims.

We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.

Methods.

A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed by combining the data of all spectral channels using the SPARCO method.

Results.

We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of ~4% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in Hα.

Conclusions.

Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.

Geometric Effect as a Probe of Planetary Obliquity

Frequency Modulation of Directly Imaged Exoplanets: Geometric Effect as a Probe of Planetary Obliquity

Authors:

Kawahara et al

Abstract:

We consider the time-frequency analysis of a scattered light curve by a directly imaged exoplanet. We show that the geometric effect due to planetary obliquity and orbital inclination induce the frequency modulation of the apparent diurnal periodicity. We construct a model of the frequency modulation and compare with the instantaneous frequency extracted from the pseudo-Wigner distribution of the simulated light curves of a cloudless Earth. The model provides good agreement with the simulated modulation factor even for the light curve with Gaussian noise comparable to the signal. Notably, the shape of the instantaneous frequency is sensitive to the difference between prograde, retrograde, and pole-on spin rotations. Whereas our technique requires the static property of the albedo map, it does not need to solve the albedo map of the planet. The time-frequency analysis is complementary to other methods which utilize the amplitude modulation. This paper demonstrates the importance of the frequency domain of the photometric variability to the characterization of directly imaged exoplanet in future.

A Statistical Framework for Utilization of Simultaneous Pupil Plane and Focal Plane Telemetry for Exoplanet Imaging

A Statistical Framework for Utilization of Simultaneous Pupil Plane and Focal Plane Telemetry for Exoplanet Imaging, Part II: The Science Camera Image as a Function of the Wavefront Sensor Field

Author:

Frazin

Abstract:

In an effort to transcend the limitations of differential imaging of exoplanets in the era of extremely large telescopes (ELTs), the first paper in this series established a rigorous, fully polarimetric framework for determining the science camera (SC) image given a turbulent wavefront and unknown aberrations in multiple planes the optical system. This article builds on the structure developed in Paper I in order to rigorously express the polarimetric SC image in terms of the field impinging on the wavefront sensor (WFS), thereby providing a direct connection between the measurements made in both subsystems. This formulation allows the SC image to be written as a function of the WFS measurements, including the following unknown quantities which can, in principle, be estimated via statistical inference: the non-common path aberration (NCPA), WFS gain errors, aberrations downstream of the beamsplitter, and the planetary image. It is demonstrated that WFS bias error is mathematically equivalent to NCPA. Thus, with the ability to treat WFS bias and gains, the method should not be overly sensitive to WFS calibration problems. Importantly, this formulation includes stochastic processes that represent noisy measurement of the SC image, noisy WFS measurements, and high-frequency components of the wavefront to which the WFS is insensitive. It is shown that wavefront error due to noise in the WFS measurements has a convenient semi-analytical representation in terms of the WFS measurement operator's singular functions. Further, the first and second order statistics of these processes are specified, thereby setting the stage for the application of statistical inference methods to be describe in later papers in this series.

Hybrid Shaped Pupil Design Apodized Pupil Lyot Coronagraphs for Imaging Earth-like Planets with Future Space Observatories

Apodized pupil Lyot coronagraphs for arbitrary apertures. V. Hybrid Shaped Pupil designs for imaging Earth-like planets with future space observatories

Authors:

N'Diaye et al

Abstract:

We introduce a new class of solutions for Apodized Pupil Lyot Coronagraphs (APLC) with segmented aperture telescopes to remove broadband diffracted light from a star with a contrast level of 1010. These new coronagraphs provide a key advance to enabling direct imaging and spectroscopy of Earth twins with future large space missions. Building on shaped pupil (SP) apodization optimizations, our approach enables two-dimensional optimizations of the system to address any aperture features such as central obstruction, support structures or segment gaps. We illustrate the technique with a design that could reach 1010 contrast level at 34\,mas for a 12\,m segmented telescope over a 10\% bandpass centered at a wavelength λ0=500\,nm. These designs can be optimized specifically for the presence of a resolved star, and in our example, for stellar angular size up to 1.1\,mas. This would allow probing the vicinity of Sun-like stars located beyond 4.4\,pc, therefore fully retiring this concern. If the fraction of stars with Earth-like planets is $\eta_{\Earth}=0.1$, with 18\% throughput, assuming a perfect, stable wavefront and considering photon noise only, 12.5 exo-Earth candidates could be detected around nearby stars with this design and a 12\,m space telescope during a five-year mission with two years dedicated to exo-Earth detection (one total year of exposure time and another year of overheads). Our new hybrid APLC/SP solutions represent the first numerical solution of a coronagraph based on existing mask technologies and compatible with segmented apertures, and that can provide contrast compatible with detecting and studying Earth-like planets around nearby stars. They represent an important step forward towards enabling these science goals with future large space missions.

Sharpest View Ever of Dusty Disk Around Evolved Host Star IRAS 08544-4431

link.

Toward Direct Imaging of Low-Mass Gas-Giants with the James Webb Space Telescope

Toward Direct Imaging of Low-Mass Gas-Giants with the James Webb Space Telescope

Authors:

Schlieder et al

Abstract:

In preparation for observations with the James Webb Space Telescope (JWST), we have identified new members of the nearby, young M dwarf sample and compiled an up to date list of these stars. Here we summarize our efforts to identify young M dwarfs, describe the current sample, and detail its demographics in the context of direct planet imaging. We also describe our investigations of the unprecedented sensitivity of the JWST when imaging nearby, young M dwarfs. The JWST is the only near term facility capable of routinely pushing direct imaging capabilities around M dwarfs to sub-Jovian masses and will provide key insight into questions regarding low-mass gas-giant properties, frequency, formation, and architectures.

First Scattered-Light Image of HD 131835's Debris Disk

First Scattered-Light Image of the Debris Disk around HD 131835 with the Gemini Planet Imager

Authors:

Hung et al

Abstract:

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 ∼15 Myr old A2IV star at a distance of ∼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 ∼75 to ∼210 AU in the disk plane with roughly flat surface density. Our Monte Carlo radiative transfer model can well describe the observations with a model disk composed of a mixture of silicates and amorphous carbon. In addition to the obvious brightness asymmetry due to stronger forward scattering, we discover a weak brightness asymmetry along the major axis with the northeast side being 1.3 times brighter than the southwest side at a 3-{\sigma} level.

Retrieval of Planetary Rotation and Albedo From DSCOVR Data for Direct Imaging of Exoplanets

Retrieval of Planetary Rotation and Albedo from DSCOVR data

Authors:

Kane et al

Abstract:

The field of exoplanets has rapidly expanded from the exclusivity of exoplanet detection to include exoplanet characterization. A key step towards this characterization will be retrieval of planetary albedos and rotation rates from highly undersampled imaging data. The Deep Space Climate Observatory (DSCOVR) provides a unique opportunity to test such retrieval methods using high cadence data of the sunlit surface of the Earth. There are two NASA instruments on board DSCOVR that can be used to achieve this task: the NASA instruments Earth Polychromatic Imaging Camera (EPIC) and the National Institute of Standards and Technology Advanced Radiometer (NISTAR). Here we briefly describe the properties of these instruments and the exoplanetary science that can be explored with their data products. These are described within the context of future NASA direct imaging missions for exoplanets.

A Method to Directly Image Exoplanets in Multi-stellar Systems

A method to directly image exoplanets in multi-star systems such as Alpha-Centauri

Authors:

Thomas et al

Abstract:

Direct imaging of extra-solar planets is now a reality, especially with the deployment and commissioning of the first generation of specialized ground-based instruments such as the Gemini Planet Imager and SPHERE. These systems will allow detection of Jupiter-like planets 107 times fainter than their host star. Obtaining this contrast level and beyond requires the combination of a coronagraph to suppress light coming from the host star and a wavefront control system including a deformable mirror (DM) to remove residual starlight (speckles) created by the imperfections of telescope. However, all these current and future systems focus on detecting faint planets around single host stars, while several targets or planet candidates are located around nearby binary stars such as our neighboring star Alpha Centauri. Here, we present a method to simultaneously correct aberrations and diffraction of light coming from the target star as well as its companion star in order to reveal planets orbiting the target star. This method works even if the companion star is outside the control region of the DM (beyond its half-Nyquist frequency), by taking advantage of aliasing effects.

Designing a Space Telescope to Directly Image a World in Alpha Centauri's Habitable Zone

Space telescope design to directly image the habitable zone of Alpha Centauri

Authors:

Bendek et al

Abstract:

The scientific interest in directly image and identifying Earth-like planets within the Habitable Zone (HZ) around nearby stars is driving the design of specialized direct imaging mission such as ACESAT, EXO-C, EXO-S and AFTA-C. The inner edge of Alpha Cen A and B Habitable Zone is found at exceptionally large angular separations of 0.7 and 0.4 arcseconds respectively. This enables direct imaging of the system with a 0.3m class telescope. Contrast ratios in the order of 1e-10 are needed to image Earth-brightness planets. Low-resolution (5-band) spectra of all planets, will allow establishing the presence and amount of an atmosphere. This star system configuration is optimal for a specialized small, and stable space telescope, that can achieve high-contrast but has limited resolution. This paper describes an innovative instrument design and a mission concept based on a full Silicon Carbide off-axis telescope, which has a Phase Induce Amplitude Apodization coronagraph embedded in the telescope. This architecture maximizes stability and throughput. A Multi-Star Wave Front algorithm is implemented to drive a deformable mirror controlling simultaneously diffracted light from the on-axis and binary companion star. The instrument has a Focal Plane Occulter to reject starlight into a high-precision pointing control camera. Finally we utilize a Orbital Differential Imaging (ODI) post-processing method that takes advantage of a highly stable environment (Earth-trailing orbit) and a continuous sequence of images spanning 2 years, to reduce the final noise floor in post processing to 2e-11 levels, enabling high confidence and at least 90 percent completeness detections of Earth-like planets.