Collaborative Research: Polarimetric Asteroseismology of Massive Hot Stars

Massive hot stars are the greatest sources of energy and new material in the Galaxy. A collaboration of astronomers at the Monterey Institute for Research in Astronomy (MIRA), Florida Gulf Coast University, The SETI Institute, the University of Maryland Baltimore County, and the University of Wisconsin Madison, along with their international partners aim to determine the interior structures of these stars by the application of a new technique: polarimetric asteroseismology. Seismic waves bounce around the interiors of stars disturbing their surfaces as if in a perpetual star-quake. The collaboration will make observations of this phenomenon in key stars in tandem with ground- and space-based telescopes (including the NASA TESS mission). A new network of the World's most sensitive polarimeters, spanning a third of the Earth will be used to detect the surface oscillations caused by these seismic waves. The team will also build on established code to develop sophisticated new computer models to interpret the multi-faceted data. College undergraduate and high school students, including some from traditionally under-represented groups, will assist with the project and gain their first hands-on experience of observational astronomy and modeling. Citizen scientists will also be involved, and the project will form part of MIRA's public education programs. A very extensive data set will allow the team to determine the interior structures of about 10 beta Cephei and Slowly Pulsating B-type stars in various stages of evolution. This will be enabled by a large-scale coordinated high-precision polarimetric observing campaign. To achieve the needed phase coverage, it will involve multiple observatories, all equipped with state-of-the-art PICSARR polarimeters. To obtain the necessary S/N and frequency resolution (which depends on temporal baseline) will require many thousands of new polarimetric observations spanning more than 2 years, matched to corresponding photometry and spectroscopy – including new and archival data. The observations will be followed by an intensive multi-part analysis involving sophisticated radiative transfer modeling. Integral to the work is the creation of a new software program that combines pulsating star and polarized radiative transfer codes to properly account for the significant effects of rotation. This program will make mode identification feasible using polarimetry in rapidly rotating stars. The results will enable stellar evolution models to be properly calibrated and extrapolated to the supernova stage. 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.