2023 November KNAG Meeting

Post: 2023-10-24 / Last Update: 2023-11-03

The Korea Numerical Astrophysics Group (KNAG) is pleased to invite you to our upcoming meeting on November 10th at Korea Astronomy and Space Science Institute (KASI).
This meeting will bring together astrophysicists and researchers to discuss the latest developments in astrophysics research.

Meeting Details

1. Date: 10th November (Fri.) 2023
2. Time: 14:30 ~ 17:30 (tentative)
3. Venue: Korea Astronomy and Space Science Institute (KASI), Lee Won Chul Hall (LWC) 102
4. Program

• 14:30 ~ 15:10 Non-relativistic disk-wind-driven expanding radio-emitting shell in tidal disruption events (Kimitake Hayasaki, CBNU)
• 15:10 ~ 15:30 Discussion & Coffee Break 1
• 15:30 ~ 16:10 Probing 3D magnetic fields using dust polarization and grain alignment (Thiem Hoang, KASI)
• 16:10 ~ 16:30 Discussion & Coffee Break 2
• 16:30 ~ 17:10 Gravitational-waves and highly eccentric binary black holes (Yeong-Bok Bae, IBS)
• 17:10 ~ 17:30 Discussion & Coffee Break 3
• 17:30 ~ Dinner

Sessions

• Non-relativistic disk-wind-driven expanding radio-emitting shell in tidal disruption events

  • Speaker: Kimitake Hayasaki (CBNU)
  • Languages:
    • Speaking: English
    • Slide: English
  • Abstract: Tidal disruption events (TDEs) are a good probe of supermassive black holes (SMBHs) at the center of inactive galaxies. As a star approaches an SMBH in a parabolic orbit, its tidal force destroys it, and the disrupted remnant falls back to the SMBH, producing a characteristic thermal flare that lasts for several months mainly in the optical/ultraviolet and/or soft-X-ray wavebands. Recent radio observations have revealed there are several radio-emitting TDEs without relativistic jet signatures and these TDE candidates are even increasing. We study the evolution and dynamics of a non-relativistically expanding shell in the TDE context based on a time-dependent, one-dimensional spherically symmetric thin shell model. We find that no simple power-law of time solution exists in early to middle times because the mass loss rate varies over time, affecting the shell dynamics. The application of our model to the observed radio-emitting TDE, AT2019dsg, is also discussed.

• Probing 3D magnetic fields using dust polarization and grain alignment

  • Speaker: Thiem Hoang (KASI)
  • Languages:
    • Speaking: English
    • Slide: English
  • Abstract: Magnetic fields are ubiquitous in the universe and are thought to play an important role in various astrophysical processes. Polarization of thermal dust emission from dust grains aligned with the magnetic field is widely used to measure the two-dimensional magnetic field projected onto the plane of the sky (POS), but the component along the line of sight (LOS) is not yet reliably constrained with dust polarization. In this talk, we introduce a new method to infer three-dimensional (3D) magnetic fields using thermal dust polarization and grain alignment physics. We first present a physical model of thermal dust polarization using the modern grain alignment theory based on the magnetically enhanced radiative torque (MRAT) alignment theory. We then test this model with synthetic observations of magnetohydrodynamic (MHD) simulations of a filamentary cloud with our updated POLARIS code. Combining the tested physical polarization model with synthetic polarization, we show that the B-field inclination angle can be accurately constrained by the polarization degree from synthetic observations. Compared to the true 3D magnetic fields, our method with grain alignment is more accurate than the previous methods that assume uniform grain alignment. This new technique paves the way for tracing 3D B-fields using thermal dust polarization and grain alignment theory and for constraining dust properties and grain alignment physics.

• Gravitational-waves and highly eccentric binary black holes

  • Speaker: Yeong-Bok Bae (IBS)
  • Languages:
    • Speaking: English
    • Slide: English
  • Abstract: To date, about 90 gravitational-wave sources have been identified, and around 90% of them are binary black holes. Nonetheless, gravitational-wave detections with current detectors have mostly been limited to binary black holes with quasi-circular orbits or those with small eccentricities. In this talk, we will explore interesting features including gravitational waveforms from binary black holes with large eccentricity. Lastly, I will introduce recent studies on ringdown waves from scattering black hole orbits.

Direction

To visit KASI, please use the map applications below.
Kakao Map   Naver Map

Registration

To attend the meeting, interested individuals must register by filling out the registration form at the following link:
Register November Meeting

We look forward to your participation in this exciting event and hope to see you at the meeting.