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2018.05.07-05.13


5月7日(月)13:30~15:00  太陽天体プラズマセミナー   院生セミナー室   
May 7 Mon       Solar and Space Plasma Seminar  Student Seminar Room, Subaru Bldg. 

5月8日(火)13:30~14:30  理論コロキウム         輪講室  
May 8 Tue          DTA colloquium       Rinko-room 

5月8日(火)13:30~15:00  太陽系小天体セミナー    南棟2階会議室  
May 8 Tue      Solar System Minor Body Seminar  Conference Room, South Bldg.2F 

5月10日(木)15:00~16:30 理論コロキウム         輪講室  
May 10 Thu          DTA colloquium       Rinko-room 

5月11日(金)16:00~17:00  国立天文台談話会      大セミナー室  
May 11 Fri          NAOJ Seminar        Large Seminar Room 

詳細は以下をご覧下さい。

5月7日(月)

Campus
Mitaka
Seminar
Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic
Sporadic
Date and time
7 May (Mon), 13:30-15:00
Place
Student Seminar Room, Subaru Bldg.
Speaker
Junho Shin
Affiliation
Kyung Hee University / NAOJ
Title
Off-Axis Characteristics of Grazing Incidence Mirror Telescopes for X-Ray Solar Physics
Abstract
Coronal hole has an important meaning not only in the field of solar physics but also in relation to the space weather because it is known as a birthplace of fast and slow solar winds. The detailed mechanism of coronal heating leading to the solar wind acceleration is, however, still unknown. To theoretically model the three-dimensional coronal structures is sensitive to the values of plasma properties at the base of solar corona and thus requires beforehand accurate empirical description of those properties. Therefore, the detailed study on the physical conditions of solar plasma in the coronal holes and also at the off-the-limb areas will give us a clue to understand the boundary conditions and constraints on the theoretical mechanisms of heating the coronal plasma. Two Japanese grazing incidence mirror telescopes, the Yohkoh Soft X-ray Telescope (SXT) and the Hinode X-Ray Telescope (XRT), have provided solar X-ray images for more than a couple of decades and contributed to the progress in our understanding of coronal physics. An astronomical telescope is, in general, designed such that the best-focused image of an object is achieved at or very close to the optical axis and inevitably the optical performance deteriorates away from the center. The Sun is, however, a large object of about half a degree in diameter and targets near the limb area are placed in the off-axis region of full-disk (synoptic) images. The optical design of a solar X-ray telescope should thus consider the uniformity of imaging quality over a wide field-of-view. Even after such a design effort, the off-axis performance such as the effects due to vignetting and the scattered light should be characterized carefully in order for the data to be properly interpreted. This talk will explain the importance of accurate calibration of these effects, especially for the data taken in the off-axis region, which have been studied so far and also should be done in the near future.

Facilitator
-Name:Shin Toriumi
Comment

5月8日(火)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled/Sporadic
Regularly Scheduled
Date and time
May 8, 2018, 13:30-14:30
Place
Rinko room
Speaker
Yoshiyuki Inoue
Affiliation
Riken
Title
Coronal Magnetic Activity in a Nearby Active Supermassive Black Hole
Abstract
Black hole coronae are believed to be heated by their magnetic activity like the Sun. However, magnetic fields in the vicinity of active supermassive black holes have never been measured. Recently, we proposed a coronal radio synchrotron emission model for Seyfert galaxies. Here, we report the first detection of coronal radio synchrotron emission from a nearby Seyfert galaxy, which enables us to estimate the coronal magnetic field strength. We also found that coronae are composed of thermal and non-thermal electrons. Our results indicate that magnetic activity cannot sustain X-ray emitting coronae. Existence of non-thermal electrons in coronae implies that Seyfert galaxies may explain not only the cosmic X-ray background radiation but also the cosmic MeV gamma-ray background radiation.

Facilitator
-Name:Tomoya Takiwaki
-E-mail:takiwaki.tomoya_at_nao.ac.jp
-Telephone extension:3734
Comment
in English

5月8日(火)

キャンパス
三鷹
セミナー名
太陽系小天体セミナー
定例・臨時の別
定例
日時
5月8日(火曜日)13時30分~15時
場所
南棟2階会議室
講演者
古荘玲子

連絡先
 名前:渡部潤一
備考
テレビ会議またはスカイプによる参加も可

5月10日(木)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled/Sporadic
Sporadic
Date and time
May 10, 2018, 15:00-16:30
Place
Rinko room
Speaker
Keiichi Maeda
Affiliation
Kyoto University
Title
Progenitor Evolutions and Explosion Mechanisms of Type Ia Supernovae
Abstract
I will provide a review on the current status of observational constraints on the progenitor systems and explosion mechanisms of type Ia Supernovae (SNe Ia). Recent development in the field is highlighted by accumulating observational discoveries of diversities found for SNe Ia. An idea is emerging that SNe Ia are perhaps not at all a uniform system as previously believed for many years, and thermonuclear explosions may lead to various outcomes which could correspond to various types of transients. In this talk, I will summarize different observational constraints placed for different sub-types of SNe Ia and related phenomena, and connect these findings to different types of progenitors and modes of explosions which have been theoretically predicted.

Facilitator
-Name:Tomoya Takiwaki

Comment
in English

5月11日(金)

キャンパス
三鷹
セミナー名
談話会
定例・臨時の別
定例
日時
5月11日(金曜日)16時~17時
場所
大セミナー室
講演者
釜江 常好
所属
東京大学/スタンフォード大学 

タイトル
「ローカルバブルの白色矮星起源のGeV宇宙線 」
“GeV Cosmic Rays come from White Dwarfs in the Local Bubble”

Abstract
硬X線とガンマ線の観測データと、Voyager-1やAMS02などで得られた宇宙線スペクトルを照合
することで、地球に飛来するGeV領域の宇宙線のかなりの部分は、ローカルバブル内にある白色矮星
(磁化された激変星とNova)が過去に放出したものであることを示すことができた。
その結果、原子核宇宙線のスペクトルが100GeVあたりで折れ曲がるのは、磁化された激変星や
Novaの粒子加速メカニズムが、それ以上に加速できないことを反映していることが判った。
この白色矮星起源の宇宙線は、星間ガスと相互作用し、数GeVのガンマ線を発生させる。
このようなGeVの「こぶ」が、Fermi衛星が観測した銀河系の中心部分のガンマ線スペクトルに見られる。
このことから、中心部分では、白色矮星起源の宇宙線のフラックスが、非常に高いことが判った。

連絡先
-名前:松田 有一

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