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2018.05.14-05.20


5月15日(火)13:30~14:30  理論コロキウム         輪講室  
May 15 Tue          DTA colloquium       Rinko-room 

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

5月15日(火)15:00~16:00 国立天文台野辺山談話会     野辺山宇宙電波観測所 本館 輪講室  
May 15 Tue          NRO seminar        Seminar Room, Nobeyama 

5月18日(金)16:00~17:00  国立天文台談話会       大セミナー室  
May 18 Fri          NAOJ Seminar        Large Seminar Room 

詳細は以下をご覧下さい。

5月15日(火)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled
Date and time
May 15, 2017, 13:30-14:30
Place
Lecture room
Speaker
Kyohei Kawaguchi
Affiliation
ICRR
Title
Radiative-transfer simulation for the optical and near-infrared electromagnetic counterparts to GW170817
Abstract
Recent detection of gravitational waves from a binary-neutron star merger (GW170817) and the subsequent observations of electromagnetic counterparts provide a great opportunity to study the physics of compact binary mergers. The optical and near-infrared counterparts to GW170817 are found to be consistent with a kilonova/macronova scenario with red and blue components. However, in most of previous studies in which contribution from each ejecta component to the lightcurves is separately calculated and composited, the red component is too massive as dynamical ejecta and
the blue component is too fast as post-merger ejecta. In this talk, I present our recent works performing 2-dimensional radiative-transfer simulations for a kilonova/macronova consistently taking the interplay of multiple ejecta components into account, and show that the lightcurves of optical and near-infrared counterparts can be reproduced naturally by a setup consistent with the prediction of the numerical-relativity simulations.

Facilitator
-Name:Tomoya Takiwaki

Comment
in English

5月15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15日(火曜日)13時30分~15時
場所
南棟2階会議室
講演者
秋澤宏樹

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15日(火)

Campus
Nobeyama
Seminar
NRO seminar
Regularly Scheduled/Sporadic
Sporadic
Date and time
May 15 15:00-16:00
Place
seminar room (Rinko-shitsu) in NRO main building
Speaker
Shunya takekawa
Affiliation
Nobeyama Radio Observatory
Title
High-Velocity Molecular Clouds in the Galactic Center
Abstract
The nucleus of our Galaxy, Sgr A*, is surrounded by a rapidly rotating ring of dense molecular gas, which is referred to as the circumnuclear disk (CND). The CND is considered to be a mass reservoir for feeding the nucleus. Within 300 pc from the nucleus, a number of compact clouds with broad velocity widths, namely high-velocity compact clouds (HVCCs), have been discovered. In my Ph.D course, we conducted observational studies on the high-velocity molecular clouds in the Galactic center such as the CND and HVCCs.
First, we observed the CND and its periphery in several molecular lines using the NRO 45 m telescope, and found an emission “bridge” which connects the CND to an adjacent giant molecular cloud, M?0.13?0.08. This emission bridge indicates the physical contact between the CND and M?0.13?0.08, suggesting that M?0.13?0.08 has just fallen into the CND. The physical contact between them may cancel out their angular momentum, dissipate their kinetic energies, and thereby increase the mass accretion rate to the nucleus. This is a significant result that caught a part of the feeding process to the Galactic nucleus.
Moreover, we extended the mapping area to 20 pc radius from the nucleus with the JCMT. Two small HVCCs were detected at 10 pc from Sgr A*. Their sizes, kinematics, kinetic energies, and the absences of counterparts in other wavelengths are consistent with the formation scenario assuming the high-velocity plunge of a stellar-mass black hole into a molecular cloud. This is the first observational case that suggests a number of black holes are flying about in the vicinity of the nucleus. Theoretical calculations predicted that more than 10^8 black holes are floating in our Galaxy, and most of them are isolated and dim. Such isolated black holes could be detected as high-velocity features, such as HVCCs.
Facilitator
-Name:Gwanjeong KIM

Comment
English Language, available Video conference system acceptable

5月18日(金)

Campus
Mitaka
Seminar
NAOJ seminar
Regularly Scheduled/Sporadic
Scheduled
Date and time
Fri 18 May. 16:00~17:00
Place
Large Seminar Room
Speaker
Nader Haghighipour
Affiliation
Institute for Astronomy, University of Hawaii
Title
“Modern Simulations of Terrestrial Planet Formation and Origin of Earth’s Water”
Abstract
It is widely accepted that collisions among solid bodies, ignited by their interactions with planetary embryos is
the key process in the formation of terrestrial planets and transport of volatiles and chemical compounds to
their accretion zones. Unfortunately, due to computational limitations, these collisions are often treated
in a rudimentary way where the impacts are considered to be perfectly inelastic and volatiles to be fully
transferred from one object to the other. This perfect-merging assumption has profound effects on the mass
and composition of final planetary bodies as it grossly overestimates the masses of these objects and
the amounts of volatiles and chemical elements transferred to them. It also entirely neglects collisional-loss
of volatiles (e.g., water) and draws an unrealistic connection between these properties and the chemical
structure of the protoplanetary disk (i.e., the location of their original carriers). We have developed a new
and comprehensive methodology to simulate growth of embryos to planetary bodies where we use a combination of SPH and N-body codes to accurately model collisions as well as the transport/transfer of chemical compounds. Our methodology accounts for the loss of volatiles (e.g., ice sublimation) during the orbital evolution of their carriers and accurately tracks their transfer from one body to another. Results of our simulations show that traditional N-body modeling of terrestrial planet formation overestimates the amount of the mass and water contents of the final planets by over 60% implying that not only the amount of water they suggest is far from being realistic, small planets such as Mars can also form in these simulations when collisions are treated properly. I will present details of our methodology and discuss its implications for terrestrial planet formation and water delivery to Earth.

Facilitator
-Name: Matsuda, Yuichi

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