scholarly journals Direct Imaging of Exoplanets Living an Exciting Life

2015 ◽  
Vol 10 (S314) ◽  
pp. 213-219
Author(s):  
G. Chauvin
Keyword(s):  
Physical Properties ◽  
Imaging Techniques ◽  
Formation Mechanisms ◽  
Contrast Imaging ◽  
The Past ◽  
High Contrast Imaging ◽  
Nearby Stars ◽  
Formation And Evolution ◽  
Observing Techniques

AbstractWith the development of high contrast imaging techniques and instruments, vast efforts have been devoted during the past decades to detect and characterize lighter, cooler and closer companions to nearby stars, and ultimately image new planetary systems. Complementary to other planet-hunting techniques, this approach has opened a new astrophysical window to study the physical properties and the formation mechanisms of brown dwarfs and planets. In this review, I will briefly describe the different observing techniques and strategies used, the main samples of targeted nearby stars, finally the main results obtained so far about exoplanet discoveries characterization of their physical properties, and study of their occurrence and possible formation and evolution mechanisms.

scholarly journals Adaptive Optics Observations of Exoplanets, Brown Dwarfs, and Binary Stars

2011 ◽  
Vol 7 (S282) ◽  
pp. 181-188
Author(s):  
Sasha Hinkley
Keyword(s):  
Adaptive Optics ◽  
Binary Stars ◽  
Imaging Techniques ◽  
Contrast Ratio ◽  
Brown Dwarfs ◽  
Formation Mechanisms ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Low Mass

AbstractThe current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Further, the prevalence of aperture masking interferometry in the field of high contrast imaging is also allowing observers to sense massive, young planets at solar system scales (~3–30 AU)— separations out of reach to conventional direct imaging techniques. Such observations can provide snapshots at the earliest phases of planet formation—information essential for constraining formation mechanisms as well as evolutionary models of planetary mass companions. As a demonstration of the power of this technique, I briefly review recent aperture masking observations of the HR 8799 system. Moreover, all of the aforementioned techniques are already extremely adept at detecting low-mass stellar companions to their target stars, and I present some recent highlights.

scholarly journals The value of Contrast-Enhanced Ultrasound in the characterization of vascular pattern of solid pancreatic lesions

2015 ◽  
Vol 17 (1) ◽  
pp. 16 ◽  
Author(s):  
Melania Ardelean ◽  
Roxana Sirli ◽  
Ioan Sporea ◽  
Simona Bota ◽  
Mirela Danila ◽  
...  
Keyword(s):  
Gold Standard ◽  
Imaging Techniques ◽  
Late Phase ◽  
Reference Method ◽  
Pancreatic Tumors ◽  
Imaging Method ◽  
Contrast Imaging ◽  
Cross Sectional ◽  
Solid Lesions

The aim of our study was to evaluate the accuracy of CEUS in the characterization of pancreatic solid lesions, considering cross sectional imaging techniques (CE-CT/MRI) as the “gold standard” methods. Material and methods: We performed a retrospective, monocentric study that included 91 solid pancreatic lesions which were evaluated by CEUS and by a second- line contrast imaging technique (CT or MRI), considered as the reference method. Results: The rate of a conclusive diagnosis based on a typical enhancement pattern was 94% (78/83 cases). In 72 cases out of 83 (86.7%) there was a perfect concordance between CEUS and the “gold-standard” imaging method (CE-CT/MRI). In our study, 88% (73/83) of the pancreatic lesions were categorized as malignant due to their typical wash-out aspect in the late phase. The overall accuracy of CEUS for the differential diagnosis of solid pancreatic tumors was approximately 81%. The accuracy of CEUS for the diagnosis of hypoen- hancing pancreatic tumors was approximately 89.1%; while for the diagnosis of hyperenhancing pancreatic tumors it was ap- proximately 72.8%. Conclusion: CEUS allows the differentiation between hypo- vs. hyperenhancing pancreatic solid lesions, with a considerable diagnostic accuracy, a fundamental step in the precise diagnosis of pancreatic tumors.

How many suns are in the sky? Multiplicity surveys of exoplanet host stars

2018 ◽  
Vol 14 (S345) ◽  
pp. 316-317 ◽  
Author(s):  
M. Mugrauer ◽  
C. Ginski ◽  
N. Vogt ◽  
R. Neuhäuser ◽  
C. Adam
Keyword(s):  
Milky Way ◽  
Planet Formation ◽  
High Contrast ◽  
Contrast Imaging ◽  
Direct Imaging ◽  
High Contrast Imaging ◽  
Multiple Stars ◽  
First Results ◽  
Formation And Evolution ◽  
Host Stars

AbstractIn order to determine the true impact of stellar multiplicity on the formation and evolution of planets, we initiated direct imaging surveys to search for (sub)stellar companions of exoplanet host stars on close orbits, as their gravitational impact on the planet bearing disk at first and on formed planets afterwards is expected to be maximal. According to theory these are the most challenging environments for planet formation and evolution but might occur quite frequently in the milky way, due to the large number of multiple stars within our galaxy. On this poster we showed results, obtained so far in the course of our AO and Lucky-imaging campaigns of exoplanet host stars, conducted with NACO/ESO-VLT for southern and with AstraLux/CAHA2.2m for northern targets, respectively. In addition, we introduced our new high contrast imaging survey with SPHERE/ESO-VLT to search for close companions of southern exoplanet host stars, and presented some first results.

Physical characterization of HfO2deposited on Ge substrates by MOCVD.

2004 ◽  
Vol 811 ◽  
Author(s):  
S. Van Elshocht ◽  
B. Brijs ◽  
M. Caymax ◽  
T. Conard ◽  
S. De Gendt ◽  
...  
Keyword(s):  
Physical Properties ◽  
Gate Dielectric ◽  
Substrate Material ◽  
Silicon Substrates ◽  
Enabling Technology ◽  
The Past ◽  
High K ◽  
Alternative Approach ◽  
Made In

ABSTRACTGermanium is because of its intrinsically higher mobility than Si, currently under consideration as an alternative approach to improve transistor performance. Germanium oxide, however, is thermodynamically unstable, preventing formation of the gate dielectric by simple oxidation. At present, high-k dielectrics might be considered as an enabling technology as much progress has been made in the deposition of thin high-quality layers.In this paper, we study the growth and physical properties of HfO2 deposited on Ge by MOCVD, using TDEAH and O2 as precursors, and compare the results to similar layers deposited on silicon substrates. Our results show that the physical properties of MOCVD-deposited HfO2 layers on Ge are very similar to what we have observed in the past for Si. Unfortunately, some of the negative aspects observed for Si, such as diffusion of substrate material in the high-k layer, a low density for thinner layers, or a rough top surface, are also observed for the case of Ge. However, careful surface pretreatments such as NH3 annealing the Ge substrate prior to deposition, can greatly improve the physical properties. An important observation is the very thin interfacial layer between HfO2 and Ge substrate, allowing a more aggressive scaling for Ge.

scholarly journals Direct characterization of young giant exoplanets at high spectral resolution by coupling SPHERE and CRIRES+

2021 ◽  
Vol 646 ◽  
pp. A150
Author(s):  
G. P. P. L. Otten ◽  
A. Vigan ◽  
E. Muslimov ◽  
M. N’Diaye ◽  
E. Choquet ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Extrasolar Planets ◽  
Signal To Noise Ratio ◽  
Detection Limits ◽  
Spectral Lines ◽  
High Spectral Resolution ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
The Impact

Studies of atmospheres of directly imaged extrasolar planets with high-resolution spectrographs have shown that their characterization is predominantly limited by noise on the stellar halo at the location of the studied exoplanet. An instrumental combination of high-contrast imaging and high spectral resolution that suppresses this noise and resolves the spectral lines can therefore yield higher quality spectra. We study the performance of the proposed HiRISE fiber coupling between the direct imager SPHERE and the spectrograph CRIRES+ at the Very Large Telescope for spectral characterization of directly imaged planets. Using end-to-end simulations of HiRISE we determine the signal-to-noise ratio (S/N) of the detection of molecular species for known extrasolar planets in H and K bands, and compare them to CRIRES+. We investigate the ultimate detection limits of HiRISE as a function of stellar magnitude, and we quantify the impact of different coronagraphs and of the system transmission. We find that HiRISE largely outperforms CRIRES+ for companions around bright hosts like β Pictoris or 51 Eridani. For an H = 3.5 host, we observe a gain of a factor of up to 16 in observing time with HiRISE to reach the same S/N on a companion at 200 mas. More generally, HiRISE provides better performance than CRIRES+ in 2 h integration times between 50 and 350 mas for hosts with H < 8.5 and between 50 and 700 mas for H < 7. For fainter hosts like PDS 70 and HIP 65426, no significant improvements are observed. We find that using no coronagraph yields the best S/N when characterizing known exoplanets due to higher transmission and fiber-based starlight suppression. We demonstrate that the overall transmission of the system is in fact the main driver of performance. Finally, we show that HiRISE outperforms the best detection limits of SPHERE for bright stars, opening major possibilities for the characterization of future planetary companions detected by other techniques.

Physical characterization of HfO2 deposited on Ge substrates by MOCVD

2004 ◽  
Vol 809 ◽  
Author(s):  
S. Van Elshocht ◽  
B. Brijs ◽  
M. Caymax ◽  
T. Conard ◽  
S. De Gendt ◽  
...  
Keyword(s):  
Physical Properties ◽  
Gate Dielectric ◽  
Substrate Material ◽  
Silicon Substrates ◽  
Enabling Technology ◽  
The Past ◽  
High K ◽  
Alternative Approach ◽  
Made In

ABSTRACTGermanium is because of its intrinsically higher mobility than Si, currently under consideration as an alternative approach to improve transistor performance. Germanium oxide, however, is thermodynamically unstable, preventing formation of the gate dielectric by simple oxidation. At present, high-k dielectrics might be considered as an enabling technology as much progress has been made in the deposition of thin high-quality layers.In this paper, we study the growth and physical properties of HfO2 deposited on Ge by MOCVD, using TDEAH and O2 as precursors, and compare the results to similar layers deposited on silicon substrates. Our results show that the physical properties of MOCVDdeposited HfO2 layers on Ge are very similar to what we have observed in the past for Si. Unfortunately, some of the negative aspects observed for Si, such as diffusion of substrate material in the high-k layer, a low density for thinner layers, or a rough top surface, are also observed for the case of Ge. However, careful surface pretreatments such as NH3 annealing the Ge substrate prior to deposition, can greatly improve the physical properties. An important observation is the very thin interfacial layer between HfO2 and Ge substrate, allowing a more aggressive scaling for Ge.

scholarly journals Characterization of a photon counting EMCCD for space-based high contrast imaging spectroscopy of extrasolar planets

2014 ◽  
Author(s):  
Ashlee N. Wilkins ◽  
Michael W. McElwain ◽  
Timothy J. Norton ◽  
Bernie J. Rauscher ◽  
Johannes F. Rothe ◽  
...  
Keyword(s):  
Extrasolar Planets ◽  
Imaging Spectroscopy ◽  
Photon Counting ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging
Sign in / Sign up

Export Citation Format

Share Document