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arXiv 1702.03343astro-ph.SR
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四个新的大质量脉动白矮星包括一个超大质量DAV

Four New Massive Pulsating White Dwarfs Including an Ultramassive DAV

Brandon Curd, A. Gianninas, Keaton J. Bell, Mukremin Kilic, A. D. Romero, Carlos Allende Prieto, D. E. Winget, K. I. Winget

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13 pages, 9 figures
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摘要：

我们报告了四个大质量（$M > 0.8\,M_\odot$）ZZ Ceti白矮星的发现，包括一个超大质量$1.16\,M_\odot$星。我们从斯隆数字巡天数据发布7和数据发布10中获得了13颗白矮星的地基时间序列测光，其大气参数将它们置于ZZ Ceti不稳定带内。我们在三个目标（J1053，J1554和J2038）中检测到单周期脉动，并在J 0840中识别出三个脉动周期（173，327和797 s）。对其余9个物体的傅立叶分析未表明变异性高于$4\langle{A}\rangle$检测阈值。我们对J 0840的初步星震分析得出恒星质量为$M=1.14\pm 0.01\,M_{\odot}$，氢和氦包层质量为$M_H = 5.8 \times 10^{-7}\,M_{\odot}$和$M_{He}=4.5 \times 10^{-4}\,M_{\odot}$，预期核心结晶质量比为50-70\%。J1053、J1554和J2038的质量在$0.84-0.91 M_\odot$范围内，并且预期具有CO核;然而，考虑到其高质量，J 0840的核可能由高度结晶的CO或ONeMg组成。这些新发现的大质量结晶器代表了已知的CZ Ceti白矮星数量的显着增加，质量为$M > 0.85\,M_\odot$，J 0840的详细的星震模型将允许在CO和ONeMg核心白矮星中对结晶理论进行重大测试。

英文摘要：

We report the discovery of four massive ($M > 0.8\,M_\odot$) ZZ Ceti white dwarfs, including an ultramassive $1.16\,M_\odot$ star. We obtained ground based, time-series photometry for thirteen white dwarfs from the Sloan Digital Sky Survey Data Release 7 and Data Release 10 whose atmospheric parameters place them within the ZZ Ceti instability strip. We detect mono-periodic pulsations in three of our targets (J1053, J1554, and J2038) and identify three periods of pulsation in J0840 (173, 327, and 797 s). Fourier analysis of the remaining nine objects do not indicate variability above the $4\langle{A}\rangle$ detection threshold. Our preliminary asteroseismic analysis of J0840 yields a stellar mass $M=1.14\pm 0.01\,M_{\odot}$, hydrogen and helium envelope masses of $M_H = 5.8 \times 10^{-7}\,M_{\odot}$ and $M_{He}=4.5 \times 10^{-4}\,M_{\odot}$, and an expected core crystallized mass ratio of 50-70\%. J1053, J1554, and J2038 have masses in the range $0.84-0.91 M_\odot$ and are expected to have a CO core; however, the core of J0840 could consist of highly crystallized CO or ONeMg given its high mass. These newly discovered massive pulsators represent a significant increase in the number of known ZZ Ceti white dwarfs with mass $M > 0.85\,M_\odot$, and detailed asteroseismic modeling of J0840 will allow for significant tests of crystallization theory in CO and ONeMg core white dwarfs.

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