LEAPS-MPS: A Systematic Investigation of Transient Behavior in RR Lyrae Variable Stars

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). RR Lyrae stars are a class of variable star whose pulsations have a relatively straightforward relationship to their intrinsic luminosities. As such, these stars provide a ‘standard candle’ against which to measure distance throughout the galaxy (and even to other galaxies). Because of their role in setting distance scales throughout the universe, pulsations of RR Lyrae stars continue to be studied decades after the broad outline of the mechanism was first described. Any change in that understanding could have significant implications on other parts of astronomy. The team will study changes in the amplitude of the fundamental mode of pulsation, along with its first overtone, as well as non-radial pulsations on these otherwise radially pulsing stars. They will make ground-based spectroscopic observations while the TESS spacecraft conducts photometric observations of the same star, allowing real-time comparison. Undergraduate students, drawn from under-represented groups at a Hispanic Serving Institution, will be involved in all aspects of the research. The team recently discovered changes in the amplitude of the fundamental pulsation mode of the double-mode RR Lyrae star V338 Boo. The fundamental pulsation’s amplitude is found to change on the scale of many tens of days, while the first overtone’s amplitude remains constant. Further, other teams have recently discovered non-radial pulsations whose amplitudes also change on the scale of tens of days. The team will observe a set of RR-Lyrae stars to look for similar changes in pulsations, and will furthermore conduct co-incident observsations with the TESS satellite to compare real-time spectroscopic variations with photometric variations. The team will observe known RR Lyrae stars; the study of these modes and variations will inform astrophysical models of stellar interiors.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.