NOAO >   Observing Info >   Approved Programs >   2009B-0179

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Proposal Information for 2009B-0179


PI: Andrzej Baran, Cracow Pedagogical University, sfbaran@cyf-kr.edu.pl
Address: Mathematics, Physics and Material Science, Podchorazych 2, Krakow 30-084, Poland

CoI: Mike Reed, Missouri State University
CoI: Justin Gilker, Missouri State University

Title: RATJ0455+1305 - a prominent candidate for probing the interiors of subdwarf B stars

Abstract: Hot subdwarfs pulsators (sdBV) of hybrid nature (p- and g-modes in one star) constitute a small but important sample of sdBV stars discovered so far. Their p-modes sample their outer layers, while the g- modes probe deeper into the star. Additionally, there are many more model g-mode periods then observed ones, so the p-modes are critical for primary model constraints. As such, the hybrid pulsators are currently unique for understanding sdB stars from surface to core. For this project we will obtain photometry of a newly detected hybrid sdBV star: RAT0455+1305. The Fourier spectrum of some preliminary data shows that at least one high-amplitude pressure (p-)mode and one gravity (g-)mode is present in the star. However, the amplitude of the g-mode is near the detection threshold and its presence should be confirmed with better quality data. These proposed data will seek to confirm the g-mode period and detect more frequencies (of both p- and g-mode) to allow a full asteroseismic analysis. A fully resolved frequency spectrum allows us to build up a theoretical model, which is equivalent to the derivation of stellar mass, radius, mass of the hydrogen envelope and time since the Zero-Age-Extended-Horizontal-Branch. These parameters are necessary to understand the evolution of hot subdwarf stars, which themselves are important for diffusive processes, stellar population synthesis, and a complete picture of stellar evolution.


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