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2018.01.22-01.28

1月23日(火)13:30~15:00  太陽系小天体セミナー     南棟2階会議室
Jan 23 Tue      Solar System Minor Body Seminar  Conference Room, South Bldg.2F

1月24日(水)10:30~12:00  総研大コロキウム      講義室
Jan 24 Wed         SOKENDAI colloquium    Lecture Room

1月24日(水)13:30~14:30  理論コロキウム       院生セミナー室
Jan 24 Wed          DTA colloquium      Student Seminar Room, Subaru Bldg.

1月26日(金)10:30~12:00   赤外ゼミ         ALMA棟102室     
Jan 26 Fri         Infrared Seminar       ROOM102 ALMA Bldg.

1月26日(金)13:30~15:00 太陽天体プラズマセミナー    院生セミナー室    
Jan 26 Fri       Solar and Space Plasma Seminar  Student Seminar Room, Subaru Bldg. 

詳細は以下をご覧下さい。

1月23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
1月23日(火曜日)13時30分~15時
場所
南棟2階会議室
講演者
大澤亮
所属
東大天文センター

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

1月24日(水)

Campus
Mitaka
Seminar
SOKENDAI colloquium
Regularly Scheduled/Sporadic
Regular
Date and time
January 24, 2018, 10:30 -12:00

Place
Lecture Room

Speaker
Nagaaki Kambara
Affiliation
SOKENDAI 3rd year (D1)(Supervisor: Takashi Sekii,Tetsuya Watanabe,Masahito Kubo)
Title
The double-ridge problem: current status and issues Abstract (if you like):

Speaker
Koki Okutomi
Affiliation
SOKENDAI 5th year (D3)(Supervisor: Yoichi Aso,Raffaele Flaminio,Ryutaro Takahashi)
Title
Control of 13.5-meter-tall Suspension system for Main Mirrors in KAGRA Abstract (if you like):

Please note that the presenter information posted here is not necessarily listed in order of presentation.

Facilitator
-Name:Nagaaki Kambara

Comment
TV conference system is available connecting from Nobeyama, Hawaii, Mizusawa, and Okayama.

1月24日(水)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled
Date and time
Jan. 24 2018, 13:30-14:30
Place
Insei Seminar Room
Speaker
Hiroshi Kobayashi
Affiliation
NAOJ
Title
Three-Dimensional Radiation-Hydrodynamic Simulation of Clumpy Outflow and Its Application to Supercritical Accretors around Black Holes
Abstract
We study clumpy outflows from supercritical accretion flow around a stellar mass black hole by means of global three-dimensional (3-D) radiation-hydrodynamic (RHD) simulations. In this work, we find that the radiatively driven outflow with the outflow rate of ~10 LEdd/c2 fragments into many clumps above the photosphere located at a few hundreds of Schwarzschild radius (rS) from the central black hole. Such clumps have a shape of a torn sheet, and are rotating around the central black hole with a sub-Keplerian velocity. The typical clump size is 30 rS or less in the radial direction and is more elongated in the angular directions, ~ hundreds of rS at most. When such clumps pass across the line of the sight of a distant observer, stochastic luminosity variations will be produced. The variation timescales are several seconds for a stellar-mass black hole with mass of ten to several tens of the solar mass and are in rough agreement with the observational results of some ultraluminous X-ray sources (ULXs). Our results thus provide a strong support of a hypothesis that the ULXs are powered by the supercritical accretion onto the stellar mass black hole.
Facilitator
-Name:Tomoya Takiwaki

Comment
in Japanese

1月26日(金)

キャンパス
三鷹
セミナー名
赤外ゼミ
定例・臨時の別
定例
日時
1月26日(金曜日)10:30~12:00
場所
ALMA棟102室
講演者
谷本 悠太(東大)
タイトル
PTFO8-8695の可視赤外同時トランジット観測

連絡先
-名前:大宮正士・石川裕之

備考
後半11:30~12:00には新着論文の情報交換です。
   ZOOM、TV会議システムでの参加も可能です。

1月26日(金)

Campus
Mitaka
Seminar
Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic
Regular
Date and time
26 January (Fri), 13:30-15:00
Place
Student Seminar Room, Subaru Bldg.
Speaker
Yoshiki Hatta
Affiliation
SOKENDAI/NAOJ
Title
Asteroseismology of a possible blue straggler KIC11145123
Abstract
Asteroseismology is a branch of stellar physics in which we probe interiors of stars based on observation of their oscillations. It has been greatly advanced with the advent of space-borne missions such as MOST, CoRoT, and Kepler. KIC11145123 is one of the stars that have been observed by Kepler. Asteroseismology of the star has revealed that the envelope of the star rotates slightly faster than the core, suggesting that the star has obtained angular momentum from the outside via mass accretion, or stellar collision, etc. The hypothesis is strongly supported by the fact that the star is spectroscopically a blue straggler which is believed to be born via interactions with other celestial objects. However, the model of the star, which had been used in asteroseismic inferences, does not reproduce the observed p-mode frequencies well.
To model the star better and deepen the understanding of its properties, we have carried out structure inversion and rotation inversion. The former aims at fitting the observed frequencies individually by modifying the internal structure of the model. The latter on the other hand attempts to estimate the internal rotation of the star.
As the starting point, we have calculated a model of the star based on Takada-Hidai et al. (2017). Modules for Experimenting Stellar Astrophysics (MESA) was used to calculate a single star evolution. We have subsequently solved linear adiabatic non-radial oscillation by GYRE, a community code which solves linear non-radial oscillation of a star, to obtain structure kernels for structure inversion. After the confirmation of the validity of the kernels, structure inversion has been performed. We have used 15 observed g-mode frequencies. The Optimally Localized Averaging (OLA) method has been used. Based on the results of the structure inversion, and a theoretical prediction of Miglio et al. (2008) as a guidance, we have found a new model that reproduces the observed frequencies better than the previous model.
Then, the refined model has been used to calculate rotation kernels by solving linear adiabatic oscillation, and rotation inversion has been carried out to estimate 2-dimensional internal rotation. We have used 15 g-mode frequencies and 5 p-mode ones. The estimates have been determined via three inversion techniques, namely, the OLA method, the Regularizing Least-Squares method, and Pinsker estimator. They have been compared to obtain valid results.
As a result of structure inversion, we have found that an effect of diffusion is much smaller than that used in calculating the previous model, indicating the existence of some extra mixing which disturbs the diffusion process near the edge of the convective core of the star. This is the first case in which we have succeeded in probing mixing processes by fitting individual g-mode frequencies. Furthermore, we have found that the initial helium abundance is 0.247 which is smaller than that of the former model (Y=0.297) to explain the observed p-mode frequencies.
There is a significant difference between the observed atmospheric parameters (the effective temperature and the surface gravity) and the modeled ones, indicating the persistent difficulty in modeling the star as an ordinary single star, and suggesting the possibility of the star having experienced mass transfer.
We have confirmed the same trend of the internal rotation of the star as suggested by Kurtz et al. (2014), that the envelope rotates slightly faster than the core does. This result has been obtained based on the new refined model. We have also discovered the latitudinal dependence of the internal rotation which is consistent with an anti-solar-like rotation predicted by Brun et al. (2017) for such a slowly rotating star. The above result also suggests the possibility of a mass transfer event in the past.

Facilitator
-Name:Shin Toriumi

Comment

Home > Solar and Space Plasma (SSP) Seminar | 太陽系小天体セミナー | 理論コロキウム | 総研大コロキウム | 赤外ゼミ > 2018.01.22-01.28

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