DISCOVERY OF TWO NEW THERMALLY BLOATED LOW-MASS WHITE DWARFS AMONG THE<i>KEPLER</i>BINARIES

Rappaport, S.; Nelson, L. A.; Levine, Alan M.; Sanchis-Ojeda, Roberto; Gandolfi, D.; Nowak, G.; Πάλλη, Ε.; Prša, Andrej

doi:10.1088/0004-637x/803/2/82

Cited by 55 publications

(72 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However thermally bloated WDs, which are believed to have recently had their envelopes stripped by companions, are 10 to 100 times lower in luminosity, and 3 to 10 times smaller in radius, than their more massive companions (e.g., Carter et al 2011;Maxted et al 2014;Rappaport et al 2015). sdA stars differ because they are the primaries: sdA stars dominate the light of their systems, and sdA stars in the eclipsing binaries presented here have comparable radii to their companions.…”

Section: Introductionmentioning

confidence: 73%

The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

Brown

Kilic²,

Gianninas³

2017

ApJ

View full text Add to dashboard Cite

We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ∼1 dex error for sdA stars, likely explained by metal line blanketing below 9000 K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ≃1.2 M ⊙ main sequence stars with ≃0.8 M ⊙ companions. While WDs must exist at sdA temperatures, only ∼1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A-F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.

show abstract

Section: Introductionmentioning

confidence: 73%

The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

Brown

Kilic²,

Gianninas³

2017

ApJ

View full text Add to dashboard Cite

show abstract

“…Similar to Fig.13 but for the WD mass distributions. The filled triangles and stars are for EL CVn-type stars (Maxted et al 2013) and Kepler objects (van Kerkwijk et al 2010;Carter, Rappaport & Fabrycky 2011;Breton et al 2012;Rappaport et al 2015), respectively. curves.…”

Section: Distributions Of Binary Parametersmentioning

confidence: 99%

The Formation of EL CVn-type Binaries

Chen

Maxted

et al. 2017

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

EL CVn-type binaries are eclipsing binaries that contain an A-or F-type dwarf star and a very low mass (∼ 0.2M ⊙ ) helium white dwarf precursor (proto-He WD). A number of such objects have been discovered in the WASP and Kepler photometric surveys. Here we have studied the formation of EL CVn-type binaries and give the properties and the space density of this population of stars in the Galaxy. We show that EL CVn binaries cannot be produced by common envelope evolution as previously believed because this process leads to merging of the components when giants have such low-mass cores. Stable mass transfer in low-mass binaries, from more than 65,000 runs of Population I binary evolution, may well reproduce the properties of EL CVn stars such as the evolutionary phase, mass ratios and the WD mass-period (M WD − P ) relation. The study shows that the most common donor mass range for producing the observed EL CVn-type stars is 1.15 − 1.20M ⊙ and that the lifetime of such objects increases dramatically with decreasing proto-He WD mass. This leads to an intrinsic peak mass around the minimum mass of proto-He WDs of ∼ 0.16M ⊙ . The most probable proto-He WD mass is 0.17 − 0.21M ⊙ after selection effects included. We estimated the number of EL CVn stars with P ≤ 2.2 d to be 2 − 5 × 10 6 in the Galaxy, indicating a local density of 4 − 10 × 10 −6 pc −3 . We conclude that many more EL CVntype binaries remain to be discovered and that these binaries will be predominantly low-mass systems in old stellar populations.

show abstract

“…The 4 systems add to the 6 previously known short-period dA+pre-He-WD EBs in the Kepler data (Rowe et al 2010;van Kerkwijk et al 2010;Carter et al 2011;Bloemen et al 2012;Breton et al 2012;Matson et al 2015;Rappaport et al 2015), and the 18 such WASP systems (Maxted et al 2011(Maxted et al , 2013(Maxted et al , 2014. All of the 6 Kepler systems and 3 of the WASP systems have accurate measurements of the primary and secondary mass, radius, and T eff .…”

Section: Summary and Discussionmentioning

confidence: 81%

“…Using this method they discovered 17 short-period EBs with pre-He-WD secondaries. More recently, Rappaport et al (2015) used a similar approach for the Kepler EB catalog. They visually inspected the light curves of EBs with the Kepler Input Catalog (KIC) T eff >7000 K and discovered two new short-period dA +pre-He-WD EBs.…”

Section: Introductionmentioning

confidence: 99%

BEER ANALYSIS OFKEPLERANDCoRoTLIGHT CURVES. IV. DISCOVERY OF FOUR NEW LOW-MASS WHITE DWARF COMPANIONS IN THEKEPLERDATA

Faigler

Kull

Mazeh

et al. 2015

ApJ

View full text Add to dashboard Cite

We report the discovery of four short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white dwarf (WD) secondary (dA+WD)-KIC 4169521, KOI-3818, KIC 2851474, and KIC 9285587. The systems show BEaming, Ellipsoidal and Reflection (BEER) phase modulations together with primary and secondary eclipses. These add to the 6 Kepler and 18 WASP short-period eclipsing dA+WD binaries that were previously known. The light curves, together with follow-up spectroscopic observations, allow us to derive the masses, radii, and effective temperatures of the two components of the four systems. The orbital periods, of 1.17-3.82 days, and WD masses, of 0.19-0.22 M e , are similar to those of the previously known systems. The WD radii of KOI-3818, KIC 2851474, and KIC 9285587 are 0.026, 0.035, and 0.026 R e , respectively, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries. These three binaries extend the previously known population to older systems with cooler and smaller WD secondaries. KOI-3818 displays evidence for a fast-rotating primary and a minute but significant eccentricity, ∼1.5×10 . These features are probably the outcome of the mass-transfer process.

show abstract

DISCOVERY OF TWO NEW THERMALLY BLOATED LOW-MASS WHITE DWARFS AMONG THEKEPLERBINARIES

Cited by 55 publications

References 68 publications

The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

The Formation of EL CVn-type Binaries

BEER ANALYSIS OFKEPLERANDCoRoTLIGHT CURVES. IV. DISCOVERY OF FOUR NEW LOW-MASS WHITE DWARF COMPANIONS IN THEKEPLERDATA

Contact Info

Product

Resources

About