High-Frequency VLBI as a Tool for Stellar Astrophysics

This research program will deepen our understanding of the final stages of stellar evolution, specifically focusing on red giants, which play a crucial role in enriching our Galaxy with elements essential for forming new stars and planets. The investigators will study how these dying stars shed mass through molecular "masers”. Masers are the radio wavelength equivalent of lasers, and they arise from molecules in the atmospheres of some red giants owing to the specific combination of gas density, temperature, and velocity.

The presence of masers provides a unique tool to study the gas motions and physical conditions within these stars. This investigation will employ the Very Long Baseline Interferometry (VLBI), extending observations to wavelengths as short as 1 millimeter. This research program will provide training opportunities for undergraduate students and a postdoctoral researcher, fostering the next generation of scientific talent.

Additionally, collaboration with science educators will produce accessible podcast episodes that communicate project findings to the public, enhancing scientific literacy and engagement.

The project addresses critical gaps in our understanding of late-stage stellar mass loss, particularly focusing on the mechanisms driving winds from red supergiants and asymptotic giant branch stars. These winds are major contributors to the enrichment of galaxies with heavy elements and dust. The study will utilize VLBI observations across multiple frequencies, including unprecedented measurements above 200 GHz, enabling spatial resolutions as fine as 10–500 microarcseconds.

This high resolution is essential for mapping the regions where stellar winds are launched, particularly using SiO maser lines. Methodologically, the project will develop advanced data processing techniques and calibration methods tailored for high-frequency VLBI observations. These innovations will be shared with the wider scientific community, enhancing the capability to study complex astrophysical phenomena.

Coupled with ongoing research on evolved star atmospheres, this effort promises to deliver some of the most comprehensive views to date of red giant dynamics. In addition to its scientific contributions, the project will produce two podcast episodes aimed at broadening public understanding of stellar evolution and its implications. These episodes will feature project updates and interviews with team members, contributing to public engagement with astronomy and astrophysics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.