scholarly journals A Direct Imaging Study to Search for and to Characterize Planetary Mass Companions

2013 ◽  
Vol 8 (S299) ◽  
pp. 74-75
Author(s):  
K. Ward-Duong ◽  
J. Patience ◽  
R. J. De Rosa ◽  
A. Rajan ◽  
P. Hinz ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Imaging Study ◽  
High Angular Resolution ◽  
Evolutionary Models ◽  
Direct Imaging ◽  
Planetary Mass ◽  
Substellar Companions ◽  
Imaging And Spectroscopy ◽  
M Stars

AbstractWe present preliminary results from two parallel programs to search for new substellar companions to nearby, young M-stars and to characterize the atmospheres of known planetary mass and temperature substellar companions. For the M-star survey, we are analyzing high angular resolution archival data on systems within 15pc, complementing a subset with well-determined young ages based on measurements of several age indicators. The results include stellar and substellar companion candidates, which we are currently pursuing with follow-up second epoch images. The characterization component of the project involves using LBT LMIRCam and MMT ARIES direct imaging and spectroscopy data to investigate the atmospheres of known young substellar companions with masses overlapping the planetary regime. These atmospheric studies will represent an analogous comparison to the atmospheres of young imaged planets, and provide a means to fundamentally test evolutionary models, enhancing our understanding of the overall substellar population.

Direct Imaging and Spectroscopy of Substellar Companions Next to Young Nearby Stars in TWA

2002 ◽  
pp. 381-388 ◽  
Author(s):  
Ralph Neuhäuser ◽  
Eike Guenther ◽  
Wolfgang Brandner ◽  
Nuria Húelamo ◽  
Thomas Ott ◽  
...  
Keyword(s):  
Direct Imaging ◽  
Nearby Stars ◽  
Substellar Companions ◽  
Imaging And Spectroscopy

scholarly journals Fifteen Years of High Angular Resolution Studies of Mira's Atmosphere

1999 ◽  
Vol 191 ◽  
pp. 139-144 ◽  
Author(s):  
Margarita Karovska
Keyword(s):  
Hot Spots ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Evolutionary Models ◽  
Imaging Studies ◽  
The Past ◽  
Bipolar Outflow ◽  
Resolution Imaging

I describe here results from high-angular resolution imaging studies of o Ceti (Mira). In 1983, we discovered that the atmosphere of the prototype of Mira-type variables is not symmetric. Since then, a number of multiwavelength high-angular resolution observations have confirmed the presence of asymmetries in Mira's atmosphere, and detected asymmetries in the atmospheres of other Mira-type variables. The high-angular resolution images of Mira obtained over the past fifteen years, including recent HST observations, show that the strength and shape of the asymmetries change as a function of wavelength and time. Plausible mechanisms for these asymmetries include hot spots, nonspherical pulsations, interaction with the companion and bipolar outflow. The presence of asymmetries in Miras could have serious impact on evolutionary models, and on the development of model atmospheres.

scholarly journals Investigation of Cyg OB2 #11(O5 Ifc) by Modelling its Atmosphere

2014 ◽  
Vol 31 ◽  
Author(s):  
Olga Maryeva ◽  
Roman Zhuchkov ◽  
Eugene Malogolovets
Keyword(s):  
Angular Resolution ◽  
Stellar Atmosphere ◽  
Emission Lines ◽  
High Angular Resolution ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Carbon Abundance ◽  
Spectral Class ◽  
Moderate Resolution ◽  
Nitrogen Abundance

AbstractWe continue the study of O-supergiants belonging to the association Cyg OB2 using moderate-resolution spectra. In this paper we present results of the modelling of the stellar atmosphere of Cyg OB2 #11. This object belongs to the spectral class Ofc, which was recently introduced and is yet small in numbers. Ofc class consists of stars with normal spectra with CIII λλ4647, 4650, 4652 emission lines of comparable intensity to those of the Of-defining lines NIII λλ4634, 4640, 4642. We combined new spectral data obtained by the 1.5-m Russian–Turkish telescope with spectra from MAST and CASU archives and determined physical parameters of the wind and chemical composition of the stellar atmosphere using cmfgen code. The estimated nitrogen abundance is lower than one in atmospheres of ‘normal’ O-supergiants (i.e. O4-6 supergiants without additional spectral index ‘n’ or ‘c’) and carbon abundance is solar. Also we find an excess in silicon. We present an illustrative comparison of our modelling results with current Geneva evolutionary models for rotating massive stars. The position on the Hertzsprung–Russell diagram corresponds to the star mass of about 50 M⊙ and age about 4.5 Myr. Moreover, we carried out the high angular resolution (~ 0.02arcsec) observations on the Russian 6-m telescope aiming to find weaker companions of this star, which did not reveal any.

Direct Imaging and Spectroscopy of Substellar Companions Next to Young Nearby Stars in TWA

2006 ◽  
pp. 383-390 ◽  
Author(s):  
Ralph Neuhäuser ◽  
Eike Guenther ◽  
Wolfgang Brandner ◽  
Nuria Húelamo ◽  
Thomas Ott ◽  
...  
Keyword(s):  
Direct Imaging ◽  
Nearby Stars ◽  
Substellar Companions ◽  
Imaging And Spectroscopy

scholarly journals Direct Imaging and Spectroscopy of a Planetary-Mass Candidate Companion to a Young Solar Analog

2008 ◽  
Vol 689 (2) ◽  
pp. L153-L156 ◽  
Author(s):  
David Lafrenière ◽  
Ray Jayawardhana ◽  
Marten H. van Kerkwijk
Keyword(s):  
Direct Imaging ◽  
Planetary Mass ◽  
Imaging And Spectroscopy

Small-Angle Electron Scattering (SAES) of Polymers

1985 ◽  
Vol 43 ◽  
pp. 78-79
Author(s):  
Ralph Oralor ◽  
Pamela Lloyd ◽  
Satish Kumar ◽  
W. W. Adams
Keyword(s):  
Electron Scattering ◽  
Small Angle ◽  
Angular Resolution ◽  
Structural Features ◽  
Objective Lens ◽  
High Angular Resolution ◽  
Push Button ◽  
First Case ◽  
Diffraction Mode ◽  
Very High

Small angle electron scattering (SAES) has been used to study structural features of up to several thousand angstroms in polymers, as well as in metals. SAES may be done either in (a) long camera mode by switching off the objective lens current or in (b) selected area diffraction mode. In the first case very high camera lengths (up to 7Ø meters on JEOL 1Ø ØCX) and high angular resolution can be obtained, while in the second case smaller camera lengths (approximately up to 3.6 meters on JEOL 1Ø ØCX) and lower angular resolution is obtainable. We conducted our SAES studies on JEOL 1ØØCX which can be switched to either mode with a push button as a standard feature.

Large-angle convergent-beam electron-diffraction study of coherent precipitates and decorated dislocations

1996 ◽  
Vol 54 ◽  
pp. 1002-1004
Author(s):  
J.M.K. Wiezorek ◽  
H.L. Fraser
Keyword(s):  
Electron Diffraction ◽  
Angular Resolution ◽  
Large Angle ◽  
Electron Diffraction Study ◽  
Convergent Beam Electron Diffraction ◽  
Crystal Defects ◽  
High Angular Resolution ◽  
Beam Electron ◽  
Diffraction Plane ◽  
Convergent Beam

Conventional methods of convergent beam electron diffraction (CBED) use a fully converged probe focused on the specimen in the object plane resulting in the formation of a CBED pattern in the diffraction plane. Large angle CBED (LACBED) uses a converged but defocused probe resulting in the formation of ‘shadow images’ of the illuminated sample area in the diffraction plane. Hence, low-spatial resolution image information and high-angular resolution diffraction information are superimposed in LACBED patterns which enables the simultaneous observation of crystal defects and their effect on the diffraction pattern. In recent years LACBED has been used successfully for the investigation of a variety of crystal defects, such as stacking faults, interfaces and dislocations. In this paper the contrast from coherent precipitates and decorated dislocations in LACBED patterns has been investigated. Computer simulated LACBED contrast from decorated dislocations and coherent precipitates is compared with experimental observations.

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