July 1 Mon 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom
July 2 Tue 10:00-11:30
太陽系小天体セミナー (Solar System Minor Body Seminar)
Zoom
July 3 Wed 10:00-12:00
SOKENDAI Colloquium
hybrid; Large Seminar Room in Subaru Building and Zoom
July 3 Wed 15:00-16:30
Solar and Space Plasma Seminar
hybrid; Insei Seminar Room in Subaru Building and Zoom
July 3 Wed 15:30-16:30
NAOJ Science Colloquium
Zoom
詳細は下記からご覧ください。
=============== July 1 Mon===============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：1 July (Mon), 15:00-16:30
Place： Insei Seminar Room and Zoom
Speaker：Dr. Othman Michel Benomar
Affiliation：NAOJ
Title： Constraining Magnetic Activity Latitudes in Sun-like Stars using asteroseismology
Abstract：
I will discuss a recently developed framework for measuring the activity of Sun-like stars and constraining the latitudes of magnetic activity (Benomar et al. 2023). This framework expresses in a phenomenological manner the effects of activity on low-degree pulsation frequencies, which are global standing waves within stars. Due to various effects, a star is not exactly spherical, and neither is the cavity in which those global modes propagate. The main reason for the departure from sphericity of the mode cavities is the centrifugal force. As this effect is proportional to the square of the rotation rate, it becomes increasingly important as rotation increases. Another cause of asphericity is the magnetic field. A strong magnetic field, such as the one observed in the Sun’s active zones and localized in a specific region of the star, changes the propagation path of the waves and eventually results in a perturbation of the overall cavity shapes of global modes.
Here, I will first show that utilizing a simple single-band activity model on Sun-like stars, it is possible to determine the active latitudes of a star. The method is demonstrated to work on solar data
using the VIRGO instrument aboard the SoHo satellite. I will also show that in an ensemble of 103 Kepler stars, many exhibit signs of activity.
The results indicate a complex pattern of activity bands that essentially depend on stellar effective temperature and stellar rotation. This latter work may provide new insights into the longstanding question about the processes surrounding the dynamo mechanism in other stars.
Facilitator
-Name：Akiko Tei
Comment：Japanese (Slides will be in English)
=============== July 2 Tue===============
キャンパス：三鷹
セミナー名：太陽系小天体セミナー (Solar System Minor Body Seminar)
定例・臨時の別：定例
日時： 7月 2日（火曜日）10時00分～11時30分
場所：zoom
講演者：秋澤宏樹
タイトル: 論文紹介
Abstract:
V.Oldani, et al., Comet 81P/Wild 2: changes in the spin axis orientation during the last five apparitions, Accepted for publication on “Icarus”. https://arxiv.org/abs/2405.19975
世話人の連絡先
-名前：渡部潤一
備考：zoomでの参加
===============July 3 Wed==============
Campus：Mitaka
Seminar：SOKENDAI Colloquium
Regularly Scheduled/Sporadic：Scheduled
Date and time：July 03 10:00-12:00
Place：Large Seminar Room in Subaru Building and Zoom
Speaker：Tadashi Hirose
Affiliation：SOKENDAI 1st year (M1) (Supervisor:Noriyuki Narukage, Takashi Sekii, Masumi Shimojo)
Title：Coronal heating associated with filament eruption
Speaker：Shunsuke Sasaki
Affiliation：SOKENDAI 5th year (D3) (Supervisor:Tomoya Takiwaki, Mami Machida, Takashi Moriya)
Title：Progenitor dependence of core-collapse supernovae
Speaker：Yoshihiro Naito
Affiliation：Not entered
Title：Not entered
Facilitator
-Name：Yoshiaki Sato
Comment：Language: English
===============July 3 Wed==============
Campus： Mitaka
Seminar： Solar and Space Plasma Seminar
Regularly Scheduled/Sporadic： Sporadic
Date and time：3 July (Wed), 15:00-16:30
Place： Insei Seminar Room and Zoom
Speaker：Prof. Petr Heinzel
Affiliation：
Czech Academy of Sciences, Czech Republic
University of Wroclaw, Poland
Title： Do stellar flare fluxes indicate a presence of cool loops ?
Abstract：
On the Sun we routinely resolve the flare ribbons and overlying loop arcades, while stellar fluxes integrate the emission from both. Stellar flare spectra and light curves are usually interpreted in terms of heating of the lower atmospheric layers (ribbons), using the radiation-hydrodynamical simulations (RADYN or FLARIX codes). However, the loop arcades on cool stars are expected to be extended and namely cool loops can thus contribute significantly to flare fluxes. This idea was implemented by Heinzel and Shibata (2018) for Kepler white-light observations. Later on, motivated by TESS observations, MHD simulations of loops have been performed to interpret the observed secondary flare peaks (Yang et al. 2023). The loop arcade was also inferred from time-modulated TESS light curves (Bicz et al. 2023). On the other hand, high-dispersion line spectroscopy shows the signatures of cool-plasma downflows in flare loops which is consistent with the non-LTE radiative-transfer simulations (Wollmann et al. 2023). We will review these new findings and discuss future prospects.
Facilitator
-Name：Akiko Tei
Comment：Japanese (Slides will be in English)
===============July 3 Wed==============
Campus: Mitaka
Seminar: NAOJ Science Colloquium
Date and time: 2024 July 3 (Wed.), 15:30-16:30 JST
Place: Zoom
Speaker: Tetsuya Hashimoto
Affiliation: Department of Physics, National Chung Hsing University
Title: Mysterious fast radio bursts and the new radio telescope in
Taiwan: BURSTT
Abstract:
Fast radio bursts (FRBs) are mysterious coherent radio pulses with millisecond timescales, most of which emerge from galaxies at cosmological distances. Uncovering the origin of FRBs is one of the central foci in astronomy. However, their origin is yet to be known due to the major observational challenge of FRBs: when and where they happen in the sky are unknown. Bustling Universe Radio Survey Telescope in Taiwan (BURSTT) is a new radio array dedicated to detecting mysterious FRBs in the nearby Universe. Within a few years, BURSTT will overcome this observational challenge with its unique capabilities of nearly all-sky monitoring (10,000 deg2) and accurate localization (< 1 arcsec), and none of the current FRB facilities have both of these capabilities.
In this presentation, I will summarize the expected science cases with unique FRB samples of BURSTT. In contrast to the current FRB facilities, BURSTT will observe the same sky as multi-messenger instruments, including gravitational waves and neutrinos. This BURSTT’s design will maximize the chance of the simultaneous detection of multi-messengers or multi-wavelength counterparts, which would strongly constrain the FRB progenitor scenarios. BURSTT will provide a unique window into FRB applications from environments, progenitors, to cosmology.
Facilitator
-Name: Shubham Bhardwaj
Comment: English