Dec 19 Tue 10:30-12:00 Solar and Space Plasma Seminar
Central Building (North) / 310, Subaru Building / Insei Seminar Room and Zoom(hybrid)
December 20 Wed 10:30-12:00 SOKENDAI Colloquium
Large Seminar Room in Subaru Building and Zoom (hybrid)
December 20 Wed 15:30-16:30 NAOJ Science Colloquium
the 3F seminar room in Instrument Development Building No.3 and Zoom (hybrid)
詳細は下記からご覧ください。
=============== December 19 Tue ===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Scheduled
Date and time：19th December (Tue), 10:30-12:00
Place： hybrid; Central Building (North) / 310, Subaru Building / Insei Seminar Room, or Zoom
Speaker：Takato Tokuno
Affiliation：University of Tokyo (D1 student)
Title：Spin evolution of the Sun and low-mass stars
Abstract：The spin rate of a low-mass star, including the Sun, is crucial
because it interacts with magnetism through the dynamo effect. Since
magnetised stellar wind transports the angular momentum from a star
(‘magnetic braking’), the star basically spins down. The spin-down of
solar-type stars has been studied by comparison between theoretical
modelling and observed stellar properties. Although the previous model
can explain observed basic trends, there remain unsolved problems. In
this seminar, I will review the current study of stellar spin-down,
including my paper.
Facilitator
-Name：Akiko Tei
Comment：in English
=============== December 20 wed===============
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Regular
Date and time：December 20, 2023 10:30-12:00
Place：Large Seminar Room in Subaru Building and Zoom
Speaker: Kousuke Ishihara
Affiliation: SOKENDAI 4th year (D2) (Supervisor: Fumitaka Nakamura, Masao Saito, Patricio Sanhueza)
Title: Observational study of the fragmentation process in nearby star-forming regions
Speaker: Yui Kasagi
Affiliation: SOKENDAI 55h year (D3) (Supervisor: Takayuki Kotani, Saeko Hayashi, Wako Aoki)
Title: Unveiling atmospheric features of an L dwarf observed with REACH/Subaru
Facilitator
-Name：Matsuda, Graduate Student Affairs Unit
=============== December 20 wed==============
Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2023 Dec. 20 (Wed.), 15:30-16:30
Place: the 3F seminar room in Instrument Development Building No.3 / Zoom (hybrid)
Speaker: GUIMARÃES Gabriel
Affiliation: The University of Tokyo
Title: Chaotic Diffusion: Importance, approaches and consequences
Abstract:
Regular motion in the dynamical systems might now be regarded as the odd phenomena instead of chaotic ones. That is because chaotic motion seems to take place more widely and commonly than periodic ones, and in Celestial Mechanics it could be no different.
Still, it is not uncommon to characterise orbits of asteroids and comets that are clearly stable as chaotic ones and vice versa. That is because of Chaotic Diffusion, which is responsible to drive dynamical systems from a regular state to a chaotic one.
Nonetheless, the onset of chaos — as well as the effective “chaoticity” of an orbit — might not be immediate nor evident, pronouncing themselves in distinct timescales, sometimes larger than the system’s own lifetime.
Such cases, those of “stable” or “weak” chaos, chaotic diffusion is thought to play a significant role in shaping and sculpting our Solar system and other extrasolar counterparts orbital architecture.
In this presentation, I will explain a bit about chaos, contextualize it within the realms of celestial mechanics and planet formation, present tools for quantification of chaotic diffusion and how to use them to estimate instability times that are comparable to observed/simulated ones without the need to intensive and extensively making use of computational resources nor sophisticated mathematical models.
Speaker: Tomohiro Yoshida
Affiliation: NAOJ (D1)
Title: The First Spatially-resolved Detection of 13CN in a Protoplanetary Disk and Evidence for Complex Carbon Isotope Fractionation
Abstract:
Recent measurements of carbon isotope ratios in both protoplanetary disks and exoplanet atmospheres have suggested a possible transfer of significant carbon isotope fractionation from disks to planets. For a clearer understanding of the isotopic link between disks and planets, it is important to measure the carbon isotope ratios in various species. In this talk, we present a detection of the 13CN N = 2−1 hyperfine lines in the TW Hya disk with the Atacama Large Millimeter/submillimeter Array.
This is the first spatially-resolved detection of 13CN in disks, which enables us to measure the spatially resolved 12CN/13CN ratio for the first time. We conducted non-local thermal equilibrium modeling of the 13CN lines in conjunction with previously observed 12CN lines to derive the kinetic temperature, H2 volume density, and column densities of 12CN and 13CN. The H2 volume density is found to range between (4 − 10) ×
10^7 cm−3, suggesting that CN molecules mainly reside in the disk atmosphere. The 12CN/13CN ratio is measured to be ~70 at 30 < r < 80 au from the central star, which is similar to the 12C/13C ratio in the interstellar medium. However, this value differs from the previously reported values found for other carbon-bearing molecules (CO and HCN) in the TW Hya disk. This could be self-consistently explained by different emission layer heights for different molecules combined with preferential sequestration of 12C into the solid phase towards the disk midplane. This study reveals the complexity of the carbon isotope fractionation operating in disks.
Facilitator
-Name: Kanji Mori
Comment: English