Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748

Steinfadt, Justin D. R.; Kaplan, D. L.; Shporer, Avi; Bildsten, Lars; Howell, Steve B.

doi:10.1088/2041-8205/716/2/l146

Cited by 82 publications

(114 citation statements)

References 42 publications

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“…Moreover, NLTT 11748 is not associated with a known radio source, therefore based on these considerations alone we may conclude that the companion to NLTT 11748 is another white dwarf with a mass above average. Indeed, after this work was submitted for publication, Steinfadt et al (2010) announced the discovery of primary and secondary eclipses in NLTT 11748 confirming the secondary star as a white dwarf. Their analysis confirms the ELM nature of the primary star and corroborates our analysis of the binary properties.…”

Section: Discussionmentioning

confidence: 99%

“…Their orbital period measurement, based on eclipse timing, agrees with our spectroscopic period within error bars. Finally, our ephemeris allows us to identifiy the primary and secondary eclipses observed by Steinfadt et al (2010) with the corresponding orbital conjunctions.…”

Section: Discussionmentioning

confidence: 99%

“…Based on our orbital analysis alone, we find that the minimum mass of the companion is 0.75 M . However, the companion has independently been identified as a faint white dwarf (Steinfadt et al 2010), and assuming a mass of 0.75 M , we constrained the companion temperature to ≤9600 K (DA) or ≤7200 K (DC). The kinematics of NLTT 11748 also place the system in the Galactic halo.…”

Section: Discussionmentioning

confidence: 99%

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The double degenerate system NLTT 11748

Kawka

Vennes

Vaccaro

2010

A&A

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We show that the extremely low-mass white dwarf NLTT 11748 (0.17 M ) is in a close binary with a fainter companion. We obtained a series of radial velocity measurements of the low-mass white dwarf using the Hα core and determined an orbital period of 5.64 h. The velocity semi-amplitude (K = 274.8 km s −1 ) and orbital period imply that it is a degenerate star, and that the minimum mass for the companion is 0.75 M (assuming a mass of 0.167 M for the primary). Our analysis of Balmer line profiles shows that a 0.75 M white dwarf companion does not contribute more than 2% or 5% of the flux (V-band) for helium-or hydrogen-rich surfaces, respectively. The kinematics of the system suggest that it belongs to the Galactic halo.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The double degenerate system NLTT 11748

Kawka

Vennes

Vaccaro

2010

A&A

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“…(The radii of these objects are usually determined from mass-radius relations.) Recently, the NLTT 11748 system (Kawka & Vennes 2009;Kawka et al 2010) has been identified as the first ELM-white dwarf eclipsing binary (Steinfadt et al 2010), allowing a direct estimation of an ELM radius. On the other hand, the KOI 74 system again distinguishes itself from these systems, owing to the mass of the primary A1 star.…”

Section: The Low-mass Transiting White Dwarf Koi 74bmentioning

confidence: 99%

SOPHIE velocimetry ofKeplertransit candidates

Ehrenreich¹,

Lagrange²,

Bouchy³

et al. 2010

A&A

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The Kepler mission has detected transits and occultations of a hot compact object around an early-type star, the Kepler Object of Interest KOI 74. The mass of this transiting object was photometrically assessed in a previous study using the presence of the relativistic beaming effect (so-called "Doppler boosting") in the light curve. Our aim was to provide a spectroscopic validation of this pioneering approach. We measured the radial velocity variations of the A1V star KOI 74 with the SOPHIE spectrograph at the 1.93-m telescope of the Observatoire de Haute-Provence (France). Radial velocity measurements of this star are challenging because of the high level of stellar pulsations and the few available spectral lines. Using a technique dedicated to early-type main-sequence stars, we measured radial velocity variations compatible with a companion of mass 0.252 ± 0.025 M , in good agreement with the value derived from the Kepler light curve. This work strengthens the scenario suggesting that KOI 74 is a blue straggler orbited by a stellar core despoiled of its envelope, the low-mass white dwarf KOI 74b.

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“…All known detached double-degenerate systems with very low-mass WDs have much shorter periods (Steinfadt et al 2010, and references therein), which may again be caused by selection effects.…”

Section: Discussionmentioning

confidence: 99%

Binaries discovered by the SPY survey

Geier

Napiwotzki

Heber

et al. 2011

A&A

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Hot subdwarf B stars (sdBs) in close binary systems are assumed to be formed via common envelope ejection. According to theoretical models, the amount of energy and angular momentum deposited in the common envelope scales with the mass of the companion. That low mass companions near or below the core hydrogen-burning limit are able to trigger the ejection of this envelope is well known. The currently known systems have very short periods 0.1-0.3 d. Here we report the discovery of a low mass companion (M 2 > 0.14 M ) orbiting the sdB star and central star of a planetary nebula EGB 5 with an orbital period of 16.5 d at a minimum separation of 23 R . Its long period is only just consistent with the energy balance prescription of the common envelope. The marked difference between the short and long period systems will provide strong constraints on the common envelope phase, in particular if the masses of the sdB stars can be measured accurately. Due to selection effects, the fraction of sdBs with low mass companions and similar or longer periods may be quite high. Low mass stellar and substellar companions may therefore play a significant role for the still unclear formation of hot subdwarf stars. Furthermore, the nebula around EGB 5 may be the remnant of the ejected common envelope making this binary a unique system to study this short und poorly understood phase of binary evolution.

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Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748

Cited by 82 publications

References 42 publications

The double degenerate system NLTT 11748

The double degenerate system NLTT 11748

SOPHIE velocimetry ofKeplertransit candidates

Binaries discovered by the SPY survey

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