学术报告—Dispersing star-light in the near-infrared: stellar parameters and abundances

Abstract：

Stellar spectroscopy stands as a fundamental method that offers a wealth of information on various types of stars. The significance of stellar parameters (e.g., temperature, gravity, metallicity and elemental abundances) determined in the near-infrared spectra has been on the rise recently. The spectra in this wavelength range provide us the capability to observe stars in areas like the galactic bulge, which are heavily affected by extinction. Moreover, it enables the measurement of elemental abundances that are difficult in the optical. However, the spectroscopic determination of stellar parameters in the infrared isn't a straightforward endeavor. During this presentation, I will focus on my research involving YJ-band (0.9-1.3 um) stellar spectra obtained from the WINERED spectrograph (http://lihweb.kyoto-su.ac.jp/WINERED/). The talk will begin with the determination of essential stellar parameters, the effective temperature, followed by an exploration of the elemental abundances that can be measured. Lastly, I will delve into the behavior of a helium transition at 10830A.

Bio:
Mingjie Jian is a postdoc in Stockholm University working on the 4MOST large-scale spectroscopic survey with Karin Lind. He finished his bachelor at Beijing Normal University, China, then went to Japan for his master and PhD at the University of Tokyo. His main research interest includes determining the stellar parameters from the spectra, for example using the line-depth ratio for probing the effective temperature and logg in the YJ bands, the behavior of helium spectral lines at 10830A, and light variation on early-type stars.