DISCOVERY OF THREE PULSATING, MIXED-ATMOSPHERE, EXTREMELY LOW-MASS WHITE DWARF PRECURSORS

被引：28

作者：

Gianninas, A. ^{[1
]}

Curd, Brandon ^{[1
]}

Fontaine, G. ^{[2
]}

Brown, Warren R. ^{[3
]}

Kilic, Mukremin ^{[1
]}

机构：

[1] Univ Oklahoma, Homer L Dodge Dept Phys & Astron, 440 W Brooks St, Norman, OK 73019 USA

[2] Univ Montreal, Dept Phys, CP 1628, Montreal, PQ H3C 3J7, Canada

[3] Smithsonian Astrophys Observ, 60 Garden St, Cambridge, MA 02138 USA

来源：

ASTROPHYSICAL JOURNAL LETTERS | 2016年 / 822卷 / 02期

基金：

加拿大自然科学与工程研究理事会; 美国国家科学基金会;

关键词：

asteroseismology; stars: individual (SDSS J075610.71+670424.7; SDSS J114155.56+385003.0; SDSS J115734.46+054645.6); techniques: photometric; white dwarfs; RED-GIANT STAR; EVOLUTIONARY SEQUENCES; INSTABILITY STRIP; ZZ CETI; BINARY; FRAME; BRIGHT; MODES; RICH;

D O I：

10.3847/2041-8205/822/2/L27

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We report the discovery of pulsations in three mixed-atmosphere, extremely low-mass white dwarf (ELM WD, M <= 0.3M(circle dot)) precursors. Following the recent discoveries of pulsations in both ELM and pre-ELM WDs, we targeted pre-ELM WDs with mixed H/He atmospheres with high-speed photometry. We find significant optical variability in all three observed targets with periods in the range 320-590 s, consistent in timescale with theoretical predictions of p-mode pulsations in mixed-atmosphere approximate to 0.18M(circle dot) He-core pre-ELM WDs. This represents the first empirical evidence that pulsations in pre-ELM WDs can only occur if a significant amount of He is present in the atmosphere. Future, more extensive, timeseries photometry of the brightest of the three new pulsators offers an excellent opportunity to constrain the thickness of the surface H layer, which regulates the cooling timescales for ELM WDs.

引用

页数：5

共 30 条

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