Discovery of A New Class of Pulsating Stars: Gravity-mode Pulsators among Subdwarf B Stars |
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| Authors: | Elizabeth M Green Keith Callerame Ivo R Seitenzahl Brooke A White Elaina A Hyde Melissa Giovanni Mike Reed Gilles Fontaine Roy Østensen |
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| Institution: | (1) Steward Observatory, University of Arizona, Tucson, AZ 85721, USA;(2) Physics, Astronomy, & Material Science, SW Missouri State University, Springfield, MO 65804, USA;(3) Dépt. de Physique, Université de Montréal, CP6128, Station Centreville, Montréal, QC, H3C 3J7, Canada;(4) Isaac Newton Group of Telescopes, 37800 Santa Cruz de La Palma, Canary Islands, Spain |
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| Abstract: | During the course of an ongoing CCD monitoring program to investigate low-level light variations in subdwarf B (sdB) stars, weserendipitously discovered a new class of multimode pulsators withperiods of the order of an hour. These periods are a factor of tenlonger than those of previously known multimode sdB pulsators (EC14026 stars), implying the new pulsations are due to gravity modes rather than pressure modes. The iron opacity instability that drives the short period EC 14026 stars is effective in hot sdB's. Thelong period pulsators are found only among cooler sdB stars, wherethey are surprisingly common. The mechanism responsible for excitingthe deeper g-modes in cool sdB's is currently unknown, but thetemperature and gravity range in which these stars occur must be animportant clue. We present the first observational results for thisnew class of pulsating sdB stars, and discuss some possible implications. |
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| Keywords: | pulsating sdB stars gravity modes |
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