Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS: II. Discovery of two new GW Vir stars: TIC 333432673 and TIC 095332541
Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS: II. Discovery of two new GW Vir stars: TIC 333432673 and TIC 095332541
复制标题
用 TESS 观测到的脉动缺氢白矮星和前白矮星：II。
DOI：
10.1051/0004-6361/202141253
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发表时间：
2021
影响因子：
6.5
通讯作者：
Vučković, M.
中科院分区：
文献类型：
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作者：
Uzundag, M.;Córsico, A. H.;Kepler, S. O.;Althaus, L. G.;Werner, K.;Reindl, N.;Bell, K. J.;Higgins, M.;da Rosa, G. O.;Vučković, M.
凌日系外行星巡天卫星（TESS）使命是星震学研究领域的一场革命，特别是对脉动白色和前白矮星的研究，从而延续了其前身开普勒任务的动力。我们确认它们是两颗新的GW Vir星，TIC 333432673和TIC 095332541。我们应用的工具，asteroseismology的目的是推导出它们的结构参数和地震学distance.MethodsWe进行了光谱分析和光谱拟合的TIC 333432673和TIC 095332541。对这两颗目标星的高精度TESS光度光变曲线进行了处理和分析，得到了它们的振荡频率。我们进行了一个asteroseisological分析的基础上PG 1159进化模型，考虑到完整的演化的祖星。我们寻找均匀周期间隔的模式，以限制恒星的恒星质量。我们采用了个别观察到的周期，以寻找一个有代表性的地震model.ResultsThe的TESS光变曲线的TIC 333432673和TIC 095332541的分析揭示了存在的几个振荡周期范围从350到500秒与典型的重力（g）模式。从后续的地基光谱分析中，我们发现这两颗恒星具有相似的有效温度（Teff= 120 000 ± 10 000 K）和表面重力（logg= 7.5 ± 0.5），但其大气的He/C组成不同。 根据PG 1159的演化轨迹，我们导出了这两颗星的光谱质量M_（1159）=。我们对TIC 333432673的星震学分析使我们找到了一个与恒星质量M = 0.60 − 0.61 M相适应的恒定周期间隔，以及一个恒星质量M = 0.589 ± 0.020 M的星星的星震学模型，以及一个pc的地震学距离。 对于这颗星星，我们发现不同的方法来推断恒星质量之间的一个很好的协议，也与盖亚（pc）测量的地震学距离之间的协议。对于TIC 095332541，我们发现了一个可能的周期间隔，表明恒星质量为M 0.55 − 0.57 M。 不幸的是，我们还没有能够找到这个星星的asteroseisological model。ConclusionsUsing收集的高质量的数据TESS空间使命和后续光谱，我们已经能够发现和表征两个新的GW Vir星。TESS使命正在并将继续对白矮星星震学领域产生前所未有的影响。
ContextThe Transiting Exoplanet Survey Satellite (TESS) mission is revolutionizing the blossoming area of asteroseismology, particularly of pulsating white dwarfs and pre-white dwarfs, thus continuing the impulse of its predecessor, theKeplermission.AimsIn this paper, we present the observations from the extended TESS mission in both 120 s short-cadence and 20 s ultra-short-cadence mode of two pre-white dwarf stars showing hydrogen deficiency. We identify them as two new GW Vir stars, TIC 333432673 and TIC 095332541. We apply the tools of asteroseismology with the aim of deriving their structural parameters and seismological distances.MethodsWe carried out a spectroscopic analysis and a spectral fitting of TIC 333432673 and TIC 095332541. We also processed and analyzed the high-precision TESS photometric light curves of the two target stars, and derived their oscillation frequencies. We performed an asteroseismological analysis of these stars on the basis of PG 1159 evolutionary models that take into account the complete evolution of the progenitor stars. We searched for patterns of uniform period spacings in order to constrain the stellar mass of the stars. We employed the individual observed periods to search for a representative seismological model.ResultsThe analysis of the TESS light curves of TIC 333432673 and TIC 095332541 reveals the presence of several oscillations with periods ranging from 350 to 500 s associated to typical gravity (g)-modes. From follow-up ground-based spectroscopy, we find that both stars have a similar effective temperature (Teff= 120 000 ± 10 000 K) and surface gravity (logg= 7.5 ± 0.5), but a different He/C composition of their atmosphere. On the basis of PG 1159 evolutionary tracks, we derived a spectroscopic mass ofM⋆= for both stars. Our asteroseismological analysis of TIC 333432673 allowed us to find a constant period spacing compatible with a stellar massM⋆∼ 0.60 − 0.61M⊙, and an asteroseismological model for this star with a stellar massM⋆= 0.589 ± 0.020M⊙, as well as a seismological distance of pc. For this star, we find an excellent agreement between the different methods to infer the stellar mass, and also between the seismological distance and that measured withGaia( pc). For TIC 095332541, we have found a possible period spacing that suggests a stellar mass ofM⋆∼ 0.55 − 0.57M⊙. Unfortunately, we have not been able to find an asteroseismological model for this star.ConclusionsUsing the high-quality data collected by the TESS space mission and follow-up spectroscopy, we have been able to discover and characterize two new GW Vir stars. The TESS mission is having, and will continue to have, an unprecedented impact on the area of white-dwarf asteroseismology.