MENU

天文学教室 談話会

last-update:2025/06/12

  第1806回 天文学教室談話会

2025年4月8日(火) 15:00-16:00

Title: Tidal Disruption Events and Their Radio Flares

Speaker: Tatsuya Matsumoto 松本達矢 (Department of Astronomy 天文学教室)

Language: Japanese 日本語

Most galaxies harbor a supermassive black hole (BH) at their center. When a star approaches too close to the BH, it is destroyed by a strong tidal force of the BH. Such tidal disruption events (TDEs) have been discovered by wide field surveys in optical and X-rays. In the former part of this talk, I will review the basics of TDEs and their observational status. In the latter part, I will talk about my recent studies focusing on radio flares accompanying TDEs.

 

  第1807回 天文学教室談話会

2025年4月15日(火) 16:15-17:15

Title: The Role of Protostellar Variability in Stellar Mass Assembly

Speaker: Gregory Herczeg (KIAA/Peking University)

Language: English

Young stellar objects are notoriously variable. The largest amplitudes are seen on FU Ori objects, bursts of a factor of ∼1000 in accretion rate that may last for centuries. However, the importance of such large bursts in stellar assembly remains uncertain. In this talk, I will discuss the role that variability plays at the different stages of evolution of young stellar objects and consequences for planet formation. I will highlight the JCMT Transient Program, the first dedicated sub-mm monitoring program, to measure the role of bursts in the earliest stages of stellar assembly, and will discuss future prospects for protostellar monitoring.

 

  第1808回 天文学教室談話会

2025年4月22日(火) 16:15-17:15

Title: Planet formation scenarios with observational constraints

Speaker: Satoshi Ohashi 大橋聡史 (Department of Astronomy 天文学教室)

Language: Japanese 日本語

Planet formation has been investigated with great attention for long because this question is related to the origin of our life. Coagulation of dust grains in a circum-stellar disk has been studied as one of the most reliable processes to form planets since Hayashi 1980. However, recent ALMA observations have been revealing a variety of structures in disks, which were not previously considered. In this talk, I will review the basic ideas of several methods to form planets especially focused on the coagulation process and compare those with observations. Then I will focus on the future prospects with on-going projects such as ng-VLA and SKA.

 

  第1809回 天文学教室談話会

2025年5月13日(火) 16:15-17:15

Title: Probing dark matter with resonant dynamics of the Galactic bar

Speaker: Rimpei Chiba 千葉凛平 (Department of Astronomy 天文学教室)

Language: English

Galactic bars are elongated, rotating structures observed in more than two thirds of disk galaxies, including our own Milky Way. In the presence of dark matter in our Universe, these bars are predicted to gradually spin down by gravitationally transferring their energy and angular momentum to dark matter, a process known as dynamical friction. In contrast, modified gravity theories predict no bar slowdown, suggesting that the spin-down of galactic bars is a key indication of the existence of dark matter. I will present the first implication for this deceleration of the galactic bar in the Milky Way from the kinematics and chemistry of stars trapped in resonance with the bar: just like tree rings, the resonantly trapped phase-space evolves inside-out, capturing new stars by expanding its surface as it sweeps towards larger angular momentum, while conserving the internal distribution. Using the recent data from the Gaia satellite, I will show that the bar’s corotation resonance bears this tree-ring structure, allowing us to infer the bar’s evolutionary history.

 

  第1810回 天文学教室談話会

2025年5月20日(火) 16:15-17:15

Title: Tumultuous lives of massive binary stars

Speaker: Jim Fuller (Caltech)

Language: English

Abstract: Massive binary stars create exotic supernovae, energetic gamma-ray bursts, merging black holes, and other high-energy phenomena that are affected by processes that occur during the progenitor star’s evolution. For instance, helium stars spun up by tidal forces can produce highly spinning black holes that may be observed in LIGO data or via gamma-ray bursts. I will discuss our current understanding of angular momentum transport in stars, and expectations for black hole spins. I will also discuss new calculations of tidal spin-up in massive helium stars that predict low spins in most cases. In supernova progenitor stars with a close binary companion, mass transfer can accelerate enormously at the end of the star’s life, creating very dense circumstellar material observed in type IIn and Ibn supernovae. Finally, new simulations of stable mass transfer measure the amount of angular momentum lost during this process, with key implications for orbital contraction and the formation of gravitational wave sources.

 

  第1811回 天文学教室談話会

2025年5月27日(火) 16:15-17:15

Title: Supernova Explosions and Their Aftermath

Speaker: Daniel Kasen (University of California, Berkeley/RESCEU)

Language: English

Abstract: Understanding how massive stars die in core-collapse supernova explosions  is a long standing challenge, with simulations struggling to reproduce successful explosions and fully capture the diversity of observed events. Recent advances in 3D multi-physics simulations are now finding success and shedding light on how stellar properties and environments influence explosion dynamics, the formation of neutron stars and black holes, and the nucleosynthesis of heavy elements. At the same time, observations are revealing surprising phenomena—supernovae with extreme luminosities or unusual X-ray and radio behavior—pointing to ongoing energy input from the central engine well after the initial blast. I will highlight recent developments in supernova modeling, which now track the entire sequence from explosion onset and stellar disruption through to the observable signatures in light curves and spectra. The convergence of simulations and observations is offering a more complete understanding of how massive stars end their lives—and what they leave behind.

 

  第1812回 天文学教室談話会

2025年6月3日(火) 16:15-17:15

Title: FUV-irradiated molecular clouds and proto-planetary disks as seen by JWST

Speaker: Emilie Habart (Institut d’Astrophysique Spatiale, Orsay, France)

Language: English

Abstract: Nearby Photo-Dissociation Regions (PDRs) in the two giant Orion molecular clouds has been successfully observed in imaging and spectroscopy as part of the JWST ERS program PDRs4All (https://pdrs4all.org/) and GTO 1192. This allows to study with great precision at small spatial scales the effects of FUV radiative feedback from massive stars on interstellar molecular clouds and proto-planetary disks. This presentation overviews the observations and the dominant physical and chemical processes that lead to the infrared emission that JWST will detect in many environments. I will discuss how FUV radiation influence the physical structure, dust evolution, chemistry, dynamics and how it is connected. Robust diagnostics to constrain the gas and
grain properties will be highlighted, as well as,  the importance of still little-used microphysical/chemical processes such as the excitation of molecular hydrogen, with direct consequences on the water and carbon chemistry.

 

  第1813回 天文学教室談話会

2025年6月10日(火) 16:15-17:15

Title: A Quantum-like perspective for the dark matter: Implications in our nearby Universe

Speaker: Victor Robles (Rensselaer Polytechnic Institute, USA)

Language: English

Abstract: Satellite abundance in Milky Way-like halos plays a crucial role in distinguishing dark matter models, in particular, in dark matter models where a suppression of substructure is expected below a mass scale. One model that has gained recent interest is the Quantum/Fuzzy or Wave Dark Matter model, where the dark matter is assumed to be very small (~10-22-10-21eV/c2), this model predicts a sharp suppression of small-scale structures. Capturing the intrinsic quantum field inference has been numerically challenging with current codes. I will show that with the new implemented fluid-wave hybrid scheme in the code GAMER-2 code, we have achieved a self-consistent Wave Dark Matter cosmological simulation of a Milky Way-size halo with a dark Matter particle mass of m=2×10-23eV, which simultaneously resolves the solitonic core of the host halo and captures the complex tidal evolution of subhaloes down to z=0. In this talk, I will discuss the implications of the wave dark matter in dwarf mass halos in isolation and the evolution of Wave DM subhalos inside a MW-mass host. I will mention some consequences on the current and future constraints to the quantum-like hypothesis from observations of the satellite abundance and dynamical mass content of nearby dwarf galaxies.

 

  今後の予定

7月1日(火) Li Siyang (John Hopkins University, USA)

7月8日(火) Patricio Sanhueza (Department of Astronomy, U. Tokyo)

7月15日(火) Ryuta Orihara (Department of Astronomy, U. Tokyo)

7月22日(火) Chinami Kato (Department of Physics, U. Tokyo)

11月18日(火) Masahiro Machida (Kyushu University)

  天文学教育研究センター談話会について

天文学教育研究センター談話会については、こちらをご覧ください。

  本郷キャンパスでの天文・宇宙物理関係のセミナーアナウンスについて

東大本郷キャンパスの天文・宇宙物理関連のセミナーをアナウンスする際は、
hongo-astrotalks (at-sign) astron.s.u-tokyo.ac.jp
をお使いください。 このアドレスにメールを出すと、以下のグループの構成員に展開されます。

  • 天文学教室
  • RESCEU
  • 物理学教室
    • 安東研究室
    • 宇宙理論研究室
    • 日下研究室
    • 馬場研究室
    • 山本研究室

幅広い関係者にメールが展開されることに留意して、多くの人が興味を 持ちそうなセミナー・教室談話会などのアナウンスにお使いください。

 

  過去の談話会