Understanding subdwarf B stars through asteroseismology

在恒星演化理论和观测恒星天文学取得了几十年的进展之后，我们银河系中大多数恒星的演化后期——在这个阶段，它们蜕去了外壳，暴露了致密的核心——隐藏了许多尚未解答的问题。最近，我们开始利用一种强大的工具——天体地震学，来探测恒星的内部，并根据恒星的振荡和脉动来模拟它们的结构。亚矮星B （sdB）恒星是位于赫兹朗-罗素图水平分支上的进化恒星，它们被认为是低质量白矮星的前身。它们的祖先是像太阳一样的恒星。迄今为止，观测的重点一直是发现新的脉动sdB恒星。随着30多个成员的发现，该领域现在已经足够成熟，可以将我们在白矮星的天体地震学应用到sdB恒星上所取得的成功。要做到这一点，需要获得足够的光度数据，以解决单个物体往往复杂的脉动结构。作为水平分支恒星，sdB恒星在其核心燃烧氦，由于其有限的氢包层，这些恒星没有壳层氢燃烧，简化了它们的结构，使它们更容易建模。到目前为止，只有少数脉动的sdB恒星有解析的脉动光谱，其中一些显示了非常有趣的结果。本研究的目标是通过解析几个额外成员的脉动光谱，将天体地震学的工具充分应用于sdB恒星。这需要大量的望远镜时间分配给国家设施，贝克天文台（由我们的国家机构运营），以及与国际合作者合作的多地点观测活动。脉动恒星也可以用来寻找行星。sdB恒星的伴星可以通过脉动相位的周期性变化来探测。这样的测量很容易对长周期的次木星质量行星敏感。更广泛的影响。本科生将协助本研究项目的数据获取和简化。通过让本科生接触研究，他们能够更好地决定天文学是否是他们正确的职业道路。此外，它允许西南密苏里州立大学的学生基于强大的本科研究经验有竞争力地申请研究生课程。

AST 0307480PI ReedAfter decades of progress in both stellar evolution theory and observational stellar astronomy, the late stages of evolution of most of the stars in our Galaxy - stages in which they shed their outer envelopes and expose their compact cores - conceal many still-unanswered questions. Recently, we have begun to exploit a powerful tool, astroseismology, for probing the interiors of stars and modeling their structure from oscillations and pulsations of the stars. Subdwarf B (sdB) stars are evolved stars located on the so-called horizontal branch of the Hertzsrung-Russell diagram, and they are thought to be the precursors of low mass white dwarf stars. Their progenitors are stars like our Sun. To date, the observational emphasis has been on discovering new pulsating sdB stars. With over 30 members discovered, the field is now mature enough to turn the success we have enjoyed applying astroseismology of white dwarfs to sdB stars. To do so requires that sufficient photometric data be obtained to resolve the often complex pulsation structure of individual objects. As horizontal branch stars, sdB stars are burning helium in their cores, With their limited hydrogen envelopes, these stars have no shell hydrogen burning simplifying their structure, and making them easier to model. Thus far only a few pulsating sdB stars have resolved pulsation spectra, some of which have revealed very interesting results. The goal of this research is to fully apply the tools of astroseismology to sdB stars by resolving the pulsation spectra of several additional members. This requires substantial telescope time to be split between national facilities, Baker Observatory (operated by our home institution), and multi-site observational campaigns with international collaborators. Pulsating stars may also be used to look for planets. Companions to sdB stars can be detected as periodic variations in the pulsation phases. Such measurements are readily sensitive to sub-Jupiter mass planets with long periods. Broader impacts. Undergraduate students will assist in obtaining and reducing the data in this research project. By exposing undergraduate students to research, they are better able to decide if astronomy is the correct career path for them. Additionally, it allows Southwest Missouri State's students to competitively apply for graduate programs based on a strong undergraduate research experience.