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A small survey of UV-bright stars around the northern ecliptic pole: seeking new p-mode sdB variables for the TESS mission
Open Astronomy ( IF 0.5 ) Pub Date : 2019-01-01 , DOI: 10.1515/astro-2019-0005
Saskia Prins 1 , John Telting 2 , Roy Østensen 3
Affiliation  

Abstract Starting in 2019, the TESS mission will monitor the northern ecliptic pole for 1 year. Data will be collected at 30-minute and 2-minute cadences, and only a limited amount of slots will be reserved for targets requiring a 20- second cadence. Only the 20-second cadence is sufficient to sample p-mode oscillations in sdB stars. From the seismic measurements obtained with the Kepler spacecraft we have gained a wealth of new insights in structural and rotational aspects of mainly g-mode variable sdB stars. Unfortunately only one traditional p-mode sdB variable was found in the main Kepler field. The TESS mission offers the opportunity to obtain more long-time-base coverage of p-mode sdB variables, especially at the ecliptic poles where the time-base will be longest. Thus far, there were only two known (p-mode) sdBVs around the northern ecliptic pole (β > 78): LS Dra and V366 Dra. In this paper we describe our efforts to find more.We compiled a new sample of 76 sdB candidates around the northern ecliptic pole, based on GALEX and optical colours, and we used low-resolution Balmer-line spectroscopy for classification. We identified 39 new sdB stars, of which 29 have characteristics (Teff > 28000 K or a composite spectrum) that may put them in the p-mode instability strip.With our 39 new sdB stars, we augmented the number of known sdB stars in the the northern ecliptic pole area (β> 73) by 46%. Besides these sdB stars, among our spectral classifications are various sdO stars, He-sdB stars, blue horizontal-branch stars, white dwarfs, cataclysmic variables and main sequence B stars. We obtained time-resolved photometry of most of the p-mode sdB candidates, and found one new sdBV, J19384+5824, with a moderately high pulsation amplitude of ≥ 9 mmag.

中文翻译:

对北黄道极周围紫外线明亮恒星的小型调查:为 TESS 任务寻找新的 p 模式 sdB 变量

摘要 从 2019 年开始,TESS 任务将对北黄道极进行为期 1 年的监测。数据将以 30 分钟和 2 分钟的节奏收集,并且只会为需要 20 秒节奏的目标保留有限数量的位置。只有 20 秒的节奏足以对 sdB 星中的 p 模式振荡进行采样。从开普勒航天器获得的地震测量结果中,我们在主要 g 模式变 sdB 恒星的结构和旋转方面获得了丰富的新见解。不幸的是,在主开普勒场中只发现了一个传统的 p 模式 sdB 变量。TESS 任务提供了获得 p 模式 sdB 变量更多长时基覆盖的机会,尤其是在时基最长的黄道两极。迄今,在北黄道极(β > 78)周围只有两个已知的(p 模式)sdBV:LS Dra 和 V366 Dra。在本文中,我们描述了我们为寻找更多信息所做的努力。我们根据 GALEX 和光学颜色编制了一个包含 76 sdB 候选对象的新样本,其中包含北黄道极点,并使用低分辨率巴尔默线光谱进行分类。我们确定了 39 颗新 sdB 星,其中 29 颗具有可能将它们置于 p 模式不稳定带的特征(Teff > 28000 K 或复合光谱)。通过我们的 39 颗新 sdB 星,我们增加了已知 sdB 星的数量北黄道极区 (β> 73) 增加 46%。除了这些 sdB 星,我们的光谱分类中还有各种 sdO 星、He-sdB 星、蓝色水平分支星、白矮星、激变变星和主序 B 星。
更新日期:2019-01-01
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