Precision Models for a Reference Set of Mira Variables

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Mira variable stars are a special class of variable stars that lie at the heart of several important physical processes affecting the evolution of galaxies. They play a critical role in the galactic recycling process: over time they return much of their material to the interstellar medium and they strongly affect the appearance of galaxies. They are also extremely luminous and are excellent distance indicators, which makes them ideal candidates to map out galactic distributions. On the other hand, they are complicated stars, which can appear very differently across different wavelengths and time scales. This proposal will create the most extensive reference set of Mira variables to date, by examining a vast amount of archival data spanning several years in the past and combining them with recent observations from multiple space missions. Pairing these observations with state-of-the-art modeling tools, the team will provide a wealth of fundamental parameters for each star, such as variability periods, bolometric fluxes, radii, masses, luminosities, effective temperatures, distances. Besides the substantial direct impact on the field, the work proposed will have significant broader impacts: both the PI and Co-PI have long track-records of outreach to their local, predominantly Hispanic communities, and other members of the team are active in teaching STEM preparatory courses for young women. This study will address three fundamental questions: (1) What are the dominant pulsation modes for the various types of Miras? (2) What are the nuances in the Period-Luminosity relationship with respect to chemical subtype and mass-loss history as traced though available spectroscopic data? and (3) What is the detailed atmospheric behavior as a function of phase of molecules found at and above the photospheric surface? Most of the observations will be extracted from the Caltech-JPL’s Palomar Testbed Interferometer (PTI) using H and K bands. Periods will be determined using recent TESS data, supplemented by the long-time baseline AAVSO and AFOEV databases. The bolometric flux will be determined using 2MASS, COBE, MSX and WISE data and by custom analysis of the PTI data. Finally, distances will be determined using Gaia data. Additional photometric data will be obtained in queue mode using a dedicated, robotic 20-inch telescope. A radius-temperature modeling tool will be used to determine the additional parameters.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.