scholarly journals HD 117214 debris disk: scattered-light images and constraints on the presence of planets

2020 ◽  
Vol 635 ◽  
pp. A19 ◽  
Author(s):  
N. Engler ◽  
C. Lazzoni ◽  
R. Gratton ◽  
J. Milli ◽  
H. M. Schmid ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Scattered Light ◽  
High Sensitivity ◽  
3D Models ◽  
Ring Structure ◽  
Geometrical Parameters ◽  
Debris Disks ◽  
Disk Structure ◽  
Ring Structures ◽  
Debris Disk

Context. Young stars with debris disks are the most promising targets for an exoplanet search because debris indicate a successful formation of planetary bodies. Debris disks can be shaped by planets into ring structures that give valuable indications on the presence and location of planets in the disk. Aims. We performed observations of the Sco-Cen F star HD 117214 to search for planetary companions and to characterize the debris disk structure. Methods. 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 the highest spatial resolution of 25 mas and an inner working angle <0.1″. With the observations with IRDIS and IFS we derived detection limits for substellar companions. The geometrical parameters of the detected disk were constrained by fitting 3D models for the scattering of an optically thin dust disk. Investigating the possible origin of the disk gap, we introduced putative planets therein and modeled the planet–disk and planet–planet dynamical interactions. The obtained planetary architectures were compared with the detection limit curves. Results. The debris disk has an axisymmetric ring structure with a radius of 0.42(±0.01)″ or ~45 au and an inclination of 71(±2.5)° and exhibits a 0.4″ (~40 au) wide inner cavity. From the polarimetric data, we derive a polarized flux contrast for the disk of (Fpol)disk/F∗ = (3.1 ± 1.2) × 10−4 in the RI band. Conclusions. The fractional scattered polarized flux of the disk is eight times lower than the fractional IR flux excess. This ratio is similar to the one obtained for the debris disk HIP 79977, indicating that dust radiation properties are similar for these two disks. Inside the disk cavity we achieve high-sensitivity limits on planetary companions with a mass down to ~4 MJ at projected radial separations between 0.2″ and 0.4″. We can exclude stellar companions at a radial separation larger than 75 mas from the star.

scholarly journals Constraining the detectability of water ice in debris disks

2019 ◽  
Vol 629 ◽  
pp. A141
Author(s):  
M. Kim ◽  
S. Wolf ◽  
A. Potapov ◽  
H. Mutschke ◽  
C. Jäger
Keyword(s):  
Scattered Light ◽  
Spectral Energy ◽  
Debris Disks ◽  
Water Ice ◽  
Spatially Resolved ◽  
Infrared Telescope ◽  
Effective Medium Theories ◽  
Debris Disk ◽  
Highly Porous ◽  
Entire Planet

Context. Water ice is important for the evolution and preservation of life. Identifying the distribution of water ice in debris disks is therefore of great interest in the field of astrobiology. Furthermore, icy dust grains are expected to play important roles throughout the entire planet formation process. However, currently available observations only allow deriving weak conclusions about the existence of water ice in debris disks. Aims. We investigate whether it is feasible to detect water ice in typical debris disk systems. We take the following ice destruction mechanisms into account: sublimation of ice, dust production through planetesimal collisions, and photosputtering by UV-bright central stars. We consider icy dust mixture particles with various shapes consisting of amorphous ice, crystalline ice, astrosilicate, and vacuum inclusions (i.e., porous ice grains). Methods. We calculated optical properties of inhomogeneous icy dust mixtures using effective medium theories, that is, Maxwell-Garnett rules. Subsequently, we generated synthetic debris disk observables, such as spectral energy distributions and spatially resolved thermal reemission and scattered light intensity and polarization maps with our code DMS. Results. We find that the prominent ~3 and 44 μm water ice features can be potentially detected in future observations of debris disks with the James Webb Space Telescope (JWST) and the Space Infrared telescope for Cosmology and Astrophysics (SPICA). We show that the sublimation of ice, collisions between planetesimals, and photosputtering caused by UV sources clearly affect the observational appearance of debris disk systems. In addition, highly porous ice (or ice-rich aggregates) tends to produce highly polarized radiation at around 3 μm. Finally, the location of the ice survival line is determined by various dust properties such as a fractional ratio of ice versus dust, physical states of ice (amorphous or crystalline), and the porosity of icy grains.

scholarly journals Warm Debris Disks with WISE and HST

2015 ◽  
Vol 10 (S314) ◽  
pp. 175-178 ◽  
Author(s):  
Deborah Padgett ◽  
Karl Stapelfeldt
Keyword(s):  
Scattered Light ◽  
Terrestrial Planets ◽  
Wide Field ◽  
Debris Disks ◽  
Circumstellar Material ◽  
Excess Emission ◽  
Sky Survey ◽  
Debris Disk ◽  
Infrared Survey

AbstractUsing 22 μm data from the Wide Field Infrared Survey Explorer (WISE), we have completed a sensitive all-sky survey for debris disks in Hipparcos and Tycho catalog stars within 120 pc. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets. Several hundred previously unknown debris disk candidates were identified. We are currently performing follow-up observations to characterize the stars, companions, and circumstellar material in these systems with a variety of facilities including Keck, Herschel, and HST. Thirteen WISE debris disks have been observed to date using HST/STIS coronagraphy. Five of these disks have been detected in scattered light. One is a large and highly asymmetric edge-on disk which appears to be both warped and bifurcated.

scholarly journals The Debris Disk Fraction for M-dwarfs in Nearby Young Moving Groups

2015 ◽  
Vol 10 (S314) ◽  
pp. 159-162 ◽  
Author(s):  
Alex Binks
Keyword(s):  
Stellar Wind ◽  
Rapid Decline ◽  
Debris Disks ◽  
M Dwarfs ◽  
Disk Structure ◽  
Debris Disk ◽  
The Absolute ◽  
Moving Groups ◽  
M Dwarf

AbstractI present the first substantial work to measure the fraction of debris disks for M-dwarfs in nearby moving groups (MGs). Utilising the AllWISE IR catalog, 17 out of 151 MG members are found with an IR photometric excess indicative of disk structure. The M-dwarf debris disk fraction is ≲6 per cent in MGs younger than 40 Myr, and none are found in the groups older than 40 Myr. Simulations show, however, that debris disks around M-dwarfs are not present above a WISEW1-W4 colour of ~2.5, making calculating the absolute disk fractions difficult. The debris disk dissipation timescale appears to be faster than for higher-mass stars, and mechanisms such as enhanced stellar wind drag and/or photoevaporation could account for the more rapid decline of disks observed amongst M-dwarfs.

scholarly journals HD141569A: Disk Dissipation Caught in Action

2015 ◽  
Vol 10 (S314) ◽  
pp. 201-202 ◽  
Author(s):  
J. Péricaud ◽  
E. Di Folco ◽  
A. Dutrey ◽  
J.-C. Augereau ◽  
V. Piétu ◽  
...  
Keyword(s):  
Scattered Light ◽  
Dust Emission ◽  
Debris Disks ◽  
Debris Disk ◽  
Multiple Rings

AbstractDebris disks are usually thought to be gas-poor, the gas being dissipated by accretion or evaporation during the protoplanetary phase. HD141569A is a 5 Myr old star harboring a famous debris disk, with multiple rings and spiral features. I present here the first PdBI maps of the 12CO(2−1), 13CO(2−1) gas and dust emission at 1.3 mm in this disk. The analysis reveals there is still a large amount of (primordial) gas extending out to 250 AU, i.e. inside the rings observed in scattered light. HD141569A is thus a hybrid disk with a huge debris component, where dust has evolved and is produced by collisions, with a large remnant reservoir of gas.

An x-ray microprobe based upon a close-coupled focal-spot / glass capillary arrangement

1992 ◽  
Vol 50 (2) ◽  
pp. 1758-1759
Author(s):  
D. A. Carpenter ◽  
M. A. Taylor
Keyword(s):  
Imaging Techniques ◽  
Fluorescence Analysis ◽  
High Sensitivity ◽  
Specimen Preparation ◽  
X Rays ◽  
Glass Capillary ◽  
Close Coupling ◽  
X Ray ◽  
Point To Point ◽  
Beam Damage

The development of intense sources of x rays has led to renewed interest in the use of microbeams of x rays in x-ray fluorescence analysis. Sparks pointed out that the use of x rays as a probe offered the advantages of high sensitivity, low detection limits, low beam damage, and large penetration depths with minimal specimen preparation or perturbation. In addition, the option of air operation provided special advantages for examination of hydrated systems or for nondestructive microanalysis of large specimens.The disadvantages of synchrotron sources prompted the development of laboratory-based instrumentation with various schemes to maximize the beam flux while maintaining small point-to-point resolution. Nichols and Ryon developed a microprobe using a rotating anode source and a modified microdiffractometer. Cross and Wherry showed that by close-coupling the x-ray source, specimen, and detector, good intensities could be obtained for beam sizes between 30 and 100μm. More importantly, both groups combined specimen scanning with modern imaging techniques for rapid element mapping.

scholarly journals Optical Imaging of Beta-Amyloid Plaques in Alzheimer’s Disease

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 255
Author(s):  
Ziyi Luo ◽  
Hao Xu ◽  
Liwei Liu ◽  
Tymish Y. Ohulchanskyy ◽  
Junle Qu
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Optical Imaging ◽  
Imaging Techniques ◽  
High Sensitivity ◽  
Pathological Feature ◽  
Promising Tool ◽  
Abnormal Accumulation ◽  
Accumulation Mechanism ◽  
The Brain

Alzheimer’s disease (AD) is a multifactorial, irreversible, and incurable neurodegenerative disease. The main pathological feature of AD is the deposition of misfolded β-amyloid protein (Aβ) plaques in the brain. The abnormal accumulation of Aβ plaques leads to the loss of some neuron functions, further causing the neuron entanglement and the corresponding functional damage, which has a great impact on memory and cognitive functions. Hence, studying the accumulation mechanism of Aβ in the brain and its effect on other tissues is of great significance for the early diagnosis of AD. The current clinical studies of Aβ accumulation mainly rely on medical imaging techniques, which have some deficiencies in sensitivity and specificity. Optical imaging has recently become a research hotspot in the medical field and clinical applications, manifesting noninvasiveness, high sensitivity, absence of ionizing radiation, high contrast, and spatial resolution. Moreover, it is now emerging as a promising tool for the diagnosis and study of Aβ buildup. This review focuses on the application of the optical imaging technique for the determination of Aβ plaques in AD research. In addition, recent advances and key operational applications are discussed.

scholarly journals A High Sensitivity Self-Powered Wind Speed Sensor Based on Triboelectric Nanogenerators (TENGs)

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 2951
Author(s):  
Yangming Liu ◽  
Jialin Liu ◽  
Lufeng Che
Keyword(s):  
Wind Speed ◽  
High Sensitivity ◽  
Electrical Signal ◽  
Geometrical Parameters ◽  
Sensor Systems ◽  
Speed Sensor ◽  
Speed Range ◽  
Self Powered ◽  
Triboelectric Nanogenerators ◽  
Application Prospects

Triboelectric nanogenerators (TENGs) have excellent properties in harvesting tiny environmental energy and self-powered sensor systems with extensive application prospects. Here, we report a high sensitivity self-powered wind speed sensor based on triboelectric nanogenerators (TENGs). The sensor consists of the upper and lower two identical TENGs. The output electrical signal of each TENG can be used to detect wind speed so that we can make sure that the measurement is correct by two TENGs. We study the influence of different geometrical parameters on its sensitivity and then select a set of parameters with a relatively good output electrical signal. The sensitivity of the wind speed sensor with this set of parameters is 1.79 μA/(m/s) under a wind speed range from 15 m/s to 25 m/s. The sensor can light 50 LEDs at the wind speed of 15 m/s. This work not only advances the development of self-powered wind sensor systems but also promotes the application of wind speed sensing.

scholarly journals High Sensitivity Plasmonic Sensor Based on Fano Resonance with Inverted U-Shaped Resonator

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1164
Author(s):  
Gongli Xiao ◽  
Yanping Xu ◽  
Hongyan Yang ◽  
Zetao Ou ◽  
Jianyun Chen ◽  
...  
Keyword(s):  
Fano Resonance ◽  
Figure Of Merit ◽  
High Sensitivity ◽  
Refractive Index Sensor ◽  
Multimode Interference ◽  
Geometrical Parameters ◽  
The Finite Element Method ◽  
Plasmonic Sensor ◽  
Coupled Mode ◽  
Plasmonic Nanosensor

Herein, we propose a tunable plasmonic sensor with Fano resonators in an inverted U-shaped resonator. By manipulating the sharp asymmetric Fano resonance peaks, a high-sensitivity refractive index sensor can be realized. Using the multimode interference coupled-mode theory and the finite element method, we numerically simulate the influences of geometrical parameters on the plasmonic sensor. Optimizing the structure parameters, we can achieve a high plasmonic sensor with the maximum sensitivity for 840 nm/RIUand figure of merit for 3.9 × 105. The research results provide a reliable theoretical basis for designing high sensitivity to the next generation plasmonic nanosensor.

scholarly journals The Complementary Role of ToF-SIMS in the Assessment of Imiquimod Permeated into the Skin from a Microemulsion Dosage Form

2019 ◽  
pp. 196-210
Keyword(s):  
Dosage Form ◽  
Secondary Ion Mass Spectrometry ◽  
Imaging Techniques ◽  
Skin Permeation ◽  
High Sensitivity ◽  
Tof Sims ◽  
Complementary Role ◽  
Nodular Lesions ◽  
Superficial Basal Cell Carcinoma ◽  
Fluorescent Tags

The assessment of drug permeation into/across the skin is traditionally accomplished using Franz diffusion cells with subsequent analysis by conventional chromatographic methods such as HPLC and more recently using advanced imaging techniques. In this context, time of flight-secondary ion mass spectrometry (ToF-SIMS) offers distinctive advantages in mapping drugs within skin with high sensitivity and chemical specificity without the need for fluorescent tags or radiolabels. The work in this paper uses the combination of conventional and advanced methods to evaluate imiquimod permeation into the skin. This approach provides complementary and detailed information regarding the permeated mass, the permeation depth and the spatial distribution and localisation of drugs within skin. Imiquimod is an immune modulator drug approved by the FDA for the treatment of superficial basal cell carcinoma (BCC) but not the nodular lesions. As other studies have reported that Aldara™ cream (imiquimod 5% w/w) has some limitations in the treatment of nodular BCC lesions due to the cream’s inability to deliver imiquimod into the deeper more invasive nodular lesions, an enhancement of imiquimod permeation is thought to be useful to overcome these limitations. Therefore, an attempt to improve delivery of imiquimod into the deeper skin layers using microemulsions was investigated. Imiquimod microemulsions were formulated and characterised in our previous work are now tested for skin permeation enhancement. However, the assessment of imiquimod permeation from the formulated microemulsions using HPLC and ToF-SIMS demonstrated a limited ability of the microemulsions to improve delivery of imiquimod over Aldara™ cream. This was attributed to the poor release of imiquimod from the microemulsion formulas due to the high affinity of imiquimod for the oil phase and the encapsulation of the oil droplets by the S/Co-S mixture. This is thought to be, the first time that ToF-SIMS has been used to assess permeation of imiquimod from a microemulsion dosage form.

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