Call for applications to doctoral programs 2024B in UST KASI School

Korea Astronomy and Space Science Institute (KASI) School via the University of Science and Technology (UST) is offering doctoral (direct and integrated) scholarships starting from September 2024. PhD scholarships are provided with a competitive salary of about $1600 per month for the doctoral program. KASI is located in Daejeon, a high tech, educational and research oriented city. Convenient accommodation would be provided to students for the first 3 years in the campus.

KASI is actively involved in various fields of astronomy and astrophysics, from astronomical instrumentation to observation and theory, and participates in international collaborative and stand-alone projects including GMT, ALMA, SDSS4, DESI, LSST, KMTNet, and KVN. This semester KASI is accepting applications for the following research area:

• Radio Astronomy (supervisor: Prof. Sang-Sung Lee (sslee@kasi.re.kr)

• Exoplanets - supervisor: Prof. Byeong-Cheol Lee (bclee@kasi.re.kr) 

• Star Formation - supervisor: Prof. Chang Won Lee (cwl@kasi.re.kr) 

and for the detailed description of the specific research topic, see the list attached or in our major homepage (https://www.kasi.re.kr/eng/pageView/140).

We encourage qualified international students to apply. Competent students with BSc degrees can apply for an integrated PhD program. Students with MSc degrees may apply directly to the PhD program.

Questions on each research area should be sent to each assigned professor, while other questions are sent to the Chief Major Professor (Sang-Sung Lee, sslee@kasi.re.kr). For more information of application, please see the UST web page (https://ust.ac.kr/admission_eng.do). Applications are considered only if they are submitted during April 17 to May 8 (17:00 KST).

Best regards,

Sang-Sung Lee

Chief Major Professor

1. Prof. Sang-Sung Lee (sslee@kasi.re.kr) and Prof. Youngjoo Yun (yjyun@kasi.re.kr) 

This project is for a PhD or integrated PhD student.

At the late stage of stellar evolution, stars expel most of their mass through the strong winds which are driven by the stellar pulsation and dust condensation in the circumstellar envelopes. The high mass-loss rate of evolved stars strongly regulates the stellar fate, influencing the morphological variety of planetary nebulae, the population of white dwarfs, supernovae, the fate of exoplanets orbiting them, and ultimately contributing to the chemical enrichment of the interstellar medium. The circumstellar envelopes of evolved stars are optically thick due to the expelled stellar material, so the radio emission is an important tracer to study the physical environments of the surrounding gas and dust, as well as the stars themselves. 

This project aims to study the stellar evolution from the asymptotic giant branch (AGB) to the planetary nebula (PN), during which stars undergo the radical changes in terms of their morphology, chemical composition, and interior structure. The strong stellar pulsation of late-type stars is the main driving mechanism for the large fluctuations of stellar luminosity and copious mass loss. The periods of these pulsations span a few years, allowing them to be observed during a human lifetime. Thus, monitoring observations toward individual stars located in different evolutionary stages along the AGB track enable us to trace the mass loss history of stars and study the dynamical/chemical processes during late stellar evolutions.

The stellar masers are commonly observed in most evolved stars and their excitation conditions are very sensitive to the physical properties of the circumstellar envelopes. Furthermore, the temporal variability of maser intensity shows a strong correlation with the period of stellar pulsation. Thus, the radio observations for the stellar masers can lead us to the rigorous study of physical properties along the stellar pulsation cycle. The stellar masers are sharply collimated in a specific direction and trace the high-density regions during their propagations within the circumstellar envelopes. The VLBI can resolve individual maser spots, enabling us to see the innermost regions of circumstellar envelopes with high spatial resolutions.

The Korean VLBI Network (KVN) can observe stellar masers simultaneously at four frequency bands, allowing different maser lines to be observed at the same time. Each maser line is triggered by different physical conditions, indicating various locations from the central star. This implies that we can obtain information about the physical conditions along the radial directions through the circumstellar envelopes. Since 2014, this project has accumulated VLBI data from KVN observations towards numerous evolved stars, producing outstanding outcomes almost every year based on the accumulated results. There still remain many VLBI data to be analyzed for a comprehensive understanding of the late stage of stellar evolution.

PhD students in this project are expected to carry out the data reduction of accumulated KVN data and study the dynamical evolution of circumstellar envelopes by tracing temporal and spatial variabilities of stellar masers. During their PhD courses, students can uncover the mass-loss history of individual stars and acquire statistical characteristics of stellar masers corresponding to different evolutionary stages. Furthermore, students should propose their own VLBI observations, conduct the observations, and perform data reduction to complete their scientific investigations. Their PhD thesis can contribute a crucial piece to the puzzle of stellar evolutions.

2. Prof. Byeong-Cheol Lee (bclee@kasi.re.kr) 

This project is for a PhD or integrated PhD student.

In this project, we want to achieve two main goals. First of all, we expect various achievements through efficient use and cooperation of the research equipment of the Korea Astronomy and Space Science Institute (KASI) through microlensing research using KASI/KMTNet. 

- Exploration of exoplanets using KMTNet (Earth-like planet discovery, lonely planet discovery, etc)

- Development of an event detection algorithm

- Improved photometric precision and development of planetary signal detection algorithmsIn addition, by laying the foundation for the field of exoplanet atmosphere research using spectroscopy/Transit, we will increase our capacity to prepare for the future GMT era.

- TESS Follow-up observations by using high-resolution spectrograph.

- Atmospheric research on exoplanets using transmission spectroscopy (absorption spectroscopy) methodIn order to carry out the above project, we require students in a PhD or integrated course with related research experience.

3. Prof. Chang Won Lee (cwl@kasi.re.kr) 

This project is for a PhD or integrated PhD student.

Our project aims to study early processes in stellar and/or substellar formation in observational ways to understand fundamental formation mechanisms of stars and substellar objects in the molecular clouds and dense cores. Observing targets are dense cores, filamentary clouds, and stellar/substellar objects. Successful applicants will devote their efforts to identify velocity coherent filaments, dense cores, prestellar cores/pre-brown dwarfs, protostellar objects, proto-brown dwarfs, and the signatures of proto-planets to figure out how they form, by using existing spectroscopic and continuum data obtained from various radio observations by TRAO, KVN, JCMT, and ALMA.