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2023.08.21

Active Galactic Nuclei in the NuSTAR Era

<p>Active galactic nuclei (AGN), which represent the rapidly growing phase of the&nbsp;supermassive black holes (SMBH), radiate across the whole electromagnetic spectrum fromradio to Gamma-rays. X-rays, which are seen in most AGN, are an important tool to study the&nbsp;physics of AGN. Thanks to the launch of NuSTAR in 2012, we are able to probe AGN properties&nbsp;in the hard X-ray regime for the first time. In...</p>

2023.08.18

How tides change the orbit of binaries and a new open-source code, gyre_tides, to model stellar tides 潮汐如何改变双星系统的轨道以及介绍一个新的用于计算恒星潮汐的开源代码gyre-tides

<p>GYRE is an open-source stellar oscillation code that calculates wave frequencies and functions for the (unforced) natural modes of an input stellar model. Recently, the code&#39;s capabilities have been extended to encompass forced oscillations, allowing it to calculate the interior perturbations of a star caused by the gravitational field of a companion. The standard approach to simulating tides i...</p>

2023.08.16

Simulating the first stars, galaxies, and black holes in the Universe

<p>Prof. John Wise from Georgia Tech and the director at the Center for Relativistic Astrophysics (CRA)Host: Song Huan</p>

2023.08.15

Dynamics of Transneptunian Objects under the Influence of a Rogue Planet (Thesis Talk) 海王星外天体在流浪行星影响下的动力学

<p>Over the past two decades, our knowledge of the Solar System’s transneptunian region (often called the Kuiper Belt) has been gradually increasing. Observational surveys have greatly expanded the inventory of Trans-Neptunian Objects (TNOs), which are distant icy bodies thought to be relics from the giant planet formation era.In the distant Kuiper Belt, several striking features seem to challeng...</p>

2023.07.13

Can Artificial Intelligence Generate Meaningful Scientific Hypotheses?

<p>The field of Artificial Intelligence (AI) has taken great strides in recent years, particularly with advancements in Large Language Models (LLMs) like ChatGPT. This progress has stirred much public curiosity. However, general-purpose language models like ChatGPT sometimes &#39;hallucinate&#39; or invent non-existent information when handling specialized subjects. This tendency has led to a common belie...</p>

2023.07.28

Towards Optimal Inference of Cosmological Large Scale Structures with Neural Quantile Estimation

<p>Traditional analysis of cosmological Large Scale Structures assumes that the likelihood is Gaussian, which unfortunately is not optimal and may even be biased in the non linear regime. Simulation Based Inference (SBI), also known as Likelihood Free Inference or Implicit Likelihood Inference, directly models the Bayesian optimal posterior, but typically needs a large number of simulations to con...</p>

2023.07.24

Invasion of Alien Planet

<p>This talk is on dynamics of the solar system, we show strong evidence that an alien planet once invaded our solar system. There is a long unsolved mystery concerning a group of asteroids called Jupiter Trojans. Mathematically, there are two symmetric relative equilibrium points for the Sun-Jupiter system, L4 and L5. However, there is a large difference in numbers of observed asteroids: L4 has 6...</p>

2023.07.26

Modeling dwarf galaxy formation with UniverseMachine

<p>Dwarf galaxies provide unique and rich constraints on galaxy formation and the nature of dark matter. However, the galaxy-halo mass connection at these low-masses still have a lot of uncertainty. &nbsp;With an influx of newly discovered dwarfs near and far, it is becoming increasingly important to place dwarf galaxies in a cosmological context and model their evolution in a self-consistent way. I wi...</p>

2023.08.14

Inferred stellar parameters from 220 million XP spectra using an empirical forward model

<p>Gaia data release 3 (GDR3) provides a trove of 220 million low-resolution BP/RP (XP) fluxcalibrated spectra. In order to properly exploit the XP spectra, we need to accurately model them as a function of stellar type, extinction and distance. We build a machine-learning model based on the subset of XP stars with LAMOST LRS counterparts, whose stellar types are precisely determined by the higher...</p>

2023.08.11

KiDS-1000: Cosmology with improved cosmic shear measurements

<p>Weak gravitational lensing by large-scale structure, also known as cosmic shear, plays a crucial role in modern cosmology, powerfully probing the Universe&#39;s matter distribution. Interestingly, recent cosmic shear results from the KiDS, DES, and HSC surveys show an intriguing discrepancy with Planck&#39;s CMB observations concerning the amplitude of matter fluctuations. In this talk, I will discuss ...</p>