Discovery of Three Pulsating, Mixed-Atmosphere, Extremely Low-Mass White Dwarf Precursors*

Gianninas, A.; Curd, Brandon; Fontaine, G.; Brown, Warren R.; Kilic, Mukremin

doi:10.3847/2041-8205/822/2/l27

Cited by 36 publications

(71 citation statements)

References 28 publications

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“…Multi-periodic pulsations with periods comparable to those found in WASP 0247−25B and WASP 1628+10B have also been discovered recently in three other ELM proto-WDs (Gianninas et al 2016) 4 . Those belong to more frequent single-lined binary systems consisting of an essentially invisible primary, presumed to be a normal CO-core WD, and of an ELM proto-WD as the secondary.…”

Section: Introductionmentioning

confidence: 84%

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A Model of the Pulsating Extremely Low-mass White Dwarf Precursor WASP 0247–25B

Istrate

Fontaine

Heuser

2017

ApJ

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We present an analysis of the evolutionary and pulsation properties of the extremely low-mass white dwarf precursor (B) component of the double-lined eclipsing system WASP 0247−25. Given that the fundamental parameters of that star have been obtained previously at a unique level of precision, WASP 0247−25B represents the ideal case for testing evolutionary models of this newly-found category of pulsators. Taking into account the known constraints on the mass, orbital period, effective temperature, surface gravity, and atmospheric composition, we present a model that is compatible with these constraints and show pulsation modes that have periods very close to the observed values. Importantly, these modes are predicted excited. Although the overall consistency remains perfectible, the observable properties of WASP 0247−25B are closely reproduced. A key ingredient of our binary evolutionary models is represented by rotational mixing as the main competitor against gravitational settling. Depending on assumptions made about the values of the degree index for the observed pulsation modes, we found three possible seismic solutions. We discuss two tests, rotational splitting and multicolor photometry, that should readily identify the modes and discriminate between these solutions. However, this will require improved temporal resolution and higher S/N observations than currently available.

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Section: Introductionmentioning

confidence: 84%

“…2015;Córsico et al 2016;Gianninas et al 2016). In this context, Gianninas et al (2016) provided the first empirical evidence that pulsations in ELM proto-WDs can only occur if a significant amount of He is present in the atmosphere and, by extension, in the driving region.…”

Section: Introductionmentioning

confidence: 99%

A Model of the Pulsating Extremely Low-mass White Dwarf Precursor WASP 0247–25B

Istrate

Fontaine

Heuser

2017

ApJ

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“…Objects with constraints on a lack of pulsations from time series photometry are marked with × symbols (this work; Hermes et al 2012aHermes et al , 2013a. Pulsating pre-ELM WDs from Maxted et al (2013Maxted et al ( , 2014; Corti et al (2016) and Gianninas et al (2016) are marked with orange narrow diamonds. Typical log g ∼ 8 ZZ Ceti pulsators from Gianninas et al (2011), corrected for 3D convection effects (Tremblay et al 2013), are marked with yellow triangles.…”

Section: Discussionmentioning

confidence: 99%

“…Corti et al (2016) reported on two variable stars that occupy a region of parameter space where they could plausibly be either pre-ELM WD or SX Phoenicis pulsators. Finally, Gianninas et al (2016) discovered three pre-ELMs with mixed H/He atmospheres that pulsate at higher temperatures than an extrapolation of the empirical DA WD instability strip due to the presence of He in their atmospheres. have explored the properties of pre-ELM WD pulsations in the evolutionary models of Althaus et al (2013).…”

Section: Introductionmentioning

confidence: 99%

Pruning The ELM Survey: Characterizing Candidate Low-mass White Dwarfs through Photometric Variability

Bell

Gianninas

Hermes

et al. 2017

ApJ

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We assess the photometric variability of nine stars with spectroscopic T eff and log g values from the ELM Survey that locate them near the empirical extremely low-mass (ELM) white dwarf instability strip. We discover three new pulsating stars: SDSS J135512.34+195645.4, SDSS J173521.69+213440.6 and SDSS J213907.42+222708.9. However, these are among the few ELM Survey objects that do not show radial velocity variations to confirm the binary nature expected of helium-core white dwarfs. The dominant 4.31-hr pulsation in SDSS J135512.34+195645.4 far exceeds the theoretical cutoff for surface reflection in a white dwarf, and this target is likely a high-amplitude δ Scuti pulsator with an overestimated surface gravity. We estimate the probability to be less than 0.0008 that the lack of measured radial velocity variations in four of eight other pulsating candidate ELM white dwarfs could be due to low orbital inclination. Two other targets exhibit variability as photometric binaries. Partial coverage of the 19.342-hr orbit of WD J030818.19+514011.5 reveals deep eclipses that imply a primary radius > 0.4 R -too large to be consistent with an ELM white dwarf. The only object for which our time series photometry adds support to the ELM white dwarf classification is SDSS J105435.78−212155.9, with consistent signatures of Doppler beaming and ellipsoidal variations. We interpret that the ELM Survey contains multiple false positives from another stellar population at T eff 9,000 K, possibly related to the sdA stars recently reported from SDSS spectra.

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“…[23]- [27] found pulsations in eight of these ELMs, similar to the pulsations seen in DAVs (ZZ Ceti stars), as described in [29]. [30] found 17 pre-ELMs, i.e., helium-core white dwarf precursors, and [31,32] report pulsations in six of them. Pulsations are an important tool to study the stellar interior, and [33] - [37] report on theoretical models and pulsations of ELMs.…”

Section: Interacting Binariesmentioning

confidence: 62%

Pulsating white dwarfs

Romero

2017

EPJ Web Conf.

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Abstract. The Sloan Digital Sky Survey has allowed us to increase the number of known white dwarfs by a factor of five and consequently the number of known pulsating white dwarfs also by a factor of five. It has also led to the discovery of new types of variable white dwarfs, as the variable hot DQs, and the pulsating Extremely Low Mass white dwarfs. With the Kepler Mission, it has been possible to discover new phenomena, the outbursts present in a few pulsating white dwarfs.

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Discovery of Three Pulsating, Mixed-Atmosphere, Extremely Low-Mass White Dwarf Precursors*

Cited by 36 publications

References 28 publications

A Model of the Pulsating Extremely Low-mass White Dwarf Precursor WASP 0247–25B

A Model of the Pulsating Extremely Low-mass White Dwarf Precursor WASP 0247–25B

Pruning The ELM Survey: Characterizing Candidate Low-mass White Dwarfs through Photometric Variability

Pulsating white dwarfs

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