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2012

Time evolution of X-ray jet’s velocity

[Speaker 1]
Nobuharu Sako
[Title]
Time evolution of X-ray jet’s velocity
[Abstract]
An X-ray jet is a kind of flares in the Sun. The model of X-ray jets based on magnetic reconnection (Shibata et al. 1992) predicts that two flows with the different velocities are included in one X-ray jet. The velocity of one flow roughly equals to Alfven velocity (~1000 km/s), and the flow is accelerated by the magnetic force. The other one is
accelerated by the pressure gradient and its velocity is similar to the sound velocity (~200 km/s). However, the observational results (e.g. Shimojo et al. 2000) before the Hinode era show that the velocities of most X-ray jets are slower than the sound velocity.
Because the X-ray telescope (XRT) aboard the Hinode satellite has capability to observe the corona with the high temporal (< 1 min) and high spatial (~ 1 arcsec) resolutions, the XRT data revealed that an X-ray jet includes two components with the different velocities (Cirtain et al. 2007). The properties of the components have some differences from the model. For example, the components are not observed simultaneously. One component with sound velocity continues to appear until the peak time of the X-ray jet. The other one with Alfven velocity appear transiently. There is only one report using four X-ray jets by Cirtain et al. (2007) and their result does not show the time evolution of the velocity in X-ray jets, yet. In order to reveal the evolution of the X-ray jet's velocity, and investigate how the high velocity component occurs transiently in an X-ray jet, we detected 13 polar X-ray jets from the coronal data observed with XRT and investigated the time evolution of the velocity of the X-ray jets. The result shows that it is common that an X-ray jet includes the plural components with the different velocities. However, we could detect component with Alfven velocity in only three of the 13 events. In the talk, I introduce our data analysis and show the details of our result.

NEAR INFARED CIRCULAR POLARIZATION IMAGES OF NGC 6334 V / Association of Polar faculae with the Polar magnetic patches as observed by Hinode

[Speaker 1]
Jungmi Kwon
[Title]
NEAR INFARED CIRCULAR POLARIZATION IMAGES OF NGC 6334 V
[Abstract]
We present results from deep imaging polarimetry measurements of circularly and linearly polarized light towards the massive star forming region NGC 6334-V. These observations show high degrees of circular polarization (CP) in the Ks band of as much as 22 % with an asymmetric positive/negative pattern, measured in the infrared nebula associated with the outflow. The CP region is very extended (~80″ or 0.65 pc). Both the large CP and the extended size of the CP region are comparable to those seen in the Orion CP region. The CP pattern is shifted along the axial axis and such an asymmetry does not conform to the classical alternating symmetry seen in other objects and models.
The asymmetry may be a clue indicating the range of influence of a helical field. Three-dimensional Monte Carlo light-scattering models are used to show that this may occur with a scattering geometry, which contains a dusty envelope surrounding the accretion disk as well as aligned grains. The detection of the large and extended CP in this source and the Orion supports the CP origin of the biological homochirality on Earth.
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[Speaker 2]
Anjali John K
[Title]
Association of Polar faculae with the Polar magnetic patches as observed by Hinode
[Abstract]
The polar region of the Sun, as observed with Hinode SOT/SP is found to be covered by patches that harbour strong magnetic field and that the large unipolar patches with flux > 10^18 Mx determine the polarity of the polar fi eld. It is also observed that there are small
bipolar patches (< 1018Mx) with balanced flux in the polar region. The polar faculae, the small-scale bright magnetic structures observed at heliographic latitudes > 70 deg., have been considered as a good proxy for the polar magnetic fi eld. The aim of this study is to understand the magnetic properties of faculae, which are believed to be associated with the polar magnetic patches. We analysed data of the north polar region taken by the Hinode/SOT- spectropolarimeter (SP) in September 2007. There are patches without faculae and they outnumber those with faculae. Faculae are present in all the patches with flux > 10^19 Mx. Magnetic patches are not uniformly bright but contain smaller faculae inside. We find that a positive correlation exists between total flux and intensity of faculae within the magnetic patches and that the faculae intensity depends on cosine of the heliocentric angle .

総合研究大学院大学 天文科学専攻 特別公開 2012

今年も例年通り、総合研究大学院大学/天文科学専攻の特別公開が、国立天文台の特別公開に合わせ2012/10/26~27の期間、共同で開催されました。天文科学専攻に所属する約30名の学生は、それぞれの所属部署と総研大の両方で準備を進めながら、当日は”総研大生の研究ライフ2012″と言う企画運営に携わりました。当日はお子さんから10~20代の若者、お子さんの親御さん世代の30~40代、更にはお孫さんがいらっしゃる50~60代の方々と幅広い年齢層の方々が来場されました。企画中にアンケートを取った結果(アンケート集計人数は263人)、”大学院での生活がどのようなものなのか、日常・非日常で分けていて、とてもイメージがつきやすかったです。非日常で、色んな観測所で観測をしているのが印象に残りました“と言うコメントを頂き、学生らしさが出た企画が好評を博していました。また、”(総研大の)存在を初めて知ったので、何もかもが印象的でした“と言うコメントなども頂き、総研大と言う存在を初めて知った方も多くいらっしゃったようです。総研大のPRを兼ねている特別公開なので、企画が持っている目標が十二分に達成されたと言えそうです。一方で、所属部署と総研大企画のシフト調整が直前まで行われていなかったり、折角上手に出来ている動画の配置場所が悪かったりと、反省点も挙げられています。来年の企画立案の際にはこれらの反省を活かし、更に良いものにして貰えればと思います。

毎年好評の総研大企画の景品や会場の様子!
20121027a.jpg
クイズの景品は毎年豪華!
20121027b.jpg
学生の日常を紹介中!
20121027c.jpg
クイズに正解すると、景品が貰えます!

文責: 総合研究大学院大学 天文科学専攻 博士過程4年 坂井 伸行

Absolute Proper Motion of CB 3 Away from the Galactic Plane Measured with VERA in a Galactic Superbubble / Powerful high-contrast imaging techniques on direct detection of exoplnaets

[Speaker 1]
Nobuyuki Sakai
[Title]
Absolute Proper Motion of CB 3 Away from the Galactic Plane Measured with VERA in a Galactic Superbubble
[Abstract]
TBA
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[Speaker 2]
Daehyun Oh
[Title]
Powerful high-contrast imaging techniques on direct detection of exoplnaets
[Abstract]
Direct detections of very faint exoplanets and brown dwarfs near bright stars are essential in understanding substellar for- mation and evolution around stars. The task is dauntingly difficult. The exoplanet or brown dwarf image is usually much fainter than the background from the brilliant PSF image. Aside from the Poisson noise, ground-based tele- scopes suffer from atmospheric turbulence that produces random short-lived speckles that mask faint companions. I will talk about two techniques called ADI and LOCI, can be used on ground-based altitude/ azimuth telescopes to subtract a significant fraction of the stellar quasistatic noise.

Near-infrared Imaging Polarimetric Study of Orion A molecular cloud / Revealing the lower side of IMF and Searching for planetary mass objects

[Speaker 1]
Amnart Sukom
[Title]
Near-infrared Imaging Polarimetric Study of Orion A molecular cloud
[Abstract]
Orion Molecular Cloud (OMC) is the nearest region of massive star formation, which was intensively studied as a representative of star-forming regions. The northern part of Orion A molecular cloud,
OMC-1, -2, -3, and the southern part, OMC-4, are often referred to Integral Shape Filament (ISF), and contain intermediate-sized molecular cores, low and high mass young stars, dozens of Herbig-Haro (HH) objects and molecular outflows.
We present the first wide-field deep near-infrared images of 15′ x 50′ area of the Orion A ISF, obtained by SIRPOL, simultaneous JHKs imaging polarimeter on the IRSF telescope. Point-source aperture polarimetry suggest the magnetic field orientations are perpendicular to the elongation of the filament. Moreover, the hour-glassed shape magnetic field pattern in OMC-1 is confirmed by our polarization maps.
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[Speaker 2]
Takuya Suenaga
[Title]
Revealing the lower side of IMF and Searching for planetary mass objects
[Abstract]
Initial mass function (IMF) is one of the most important physical parameters in the star formation theory. Many author have investigated the IMF for a long time, however it has not been completely understood. I’m studying the lower side of IMF, in particular the bottom. Here, I’ll introduce some studies related to IMF, and my ongoing works.

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