A Ground-Based Measurement of the Relativistic Beaming Effect in a Detached Double White Dwarf Binary

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

doi:10.1088/2041-8205/725/2/l200

Cited by 89 publications

(77 citation statements)

References 20 publications

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“…It was predicted to be seen in Kepler data by Loeb & Gaudi (2003) and Zucker et al (2007), and has recently been observed in several systems from ground-based data as well as Kepler and CoRoT light curves (see e.g. Mazeh & Faigler 2010;van Kerkwijk et al 2010;Shporer et al 2010;Bloemen et al 2011). Based on the radial velocity measurements of the primary star (semi-amplitude, K = 11.78 kms −1 -see Table 3), we estimate that Doppler beaming should have a significant contribution in the light from the red giant in KIC 5006817, of the order of ∼300 ppm.…”

Section: The Puzzling Absence Of a Doppler Beaming Signalmentioning

confidence: 56%

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Beck

Hambleton

Vos

et al. 2014

A&A

133

151

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Context. The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red giant stars and binary stars. Seismology allows us to constrain the properties of red giants. In addition to eclipsing binaries, eccentric non-eclipsing binaries that exhibit ellipsoidal modulations have been detected with Kepler. Aims. We aim to study the properties of eccentric binary systems containing a red giant star and to derive the parameters of the primary giant component. Methods. We applied asteroseismic techniques to determine the masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques were applied to extract the parameters of the system and its primary component. Stellar evolution and its effects on the evolution of the binary system were studied from theoretical models. Results. The paper presents the asteroseismic analysis of 18 pulsating red giants in eccentric binary systems, for which masses and radii were constrained. The orbital periods of these systems range from 20 to 440 days. The results of our ongoing radial velocity monitoring programme with the Hermes spectrograph reveal an eccentricity range of e = 0.2 to 0.76. As a case study we present a detailed analysis of KIC 5006817, whose rich oscillation spectrum allows for detailed seismic analysis. From seismology we constrain the rotational period of the envelope to be at least 165 d, which is roughly twice the orbital period. The stellar core rotates 13 times faster than the surface. From the spectrum and radial velocities we expect that the Doppler beaming signal should have a maximum amplitude of 300 ppm in the light curve. Fixing the mass and radius to the asteroseismically determined values, we find from our binary modelling a value of the gravity darkening exponent that is significantly larger than expected. Through binary modelling, we determine the mass of the secondary component to be 0.29 ± 0.03 M . Conclusions. For KIC 5006817 we exclude pseudo-synchronous rotation of the red giant with the orbit. The comparison of the results from seismology and modelling of the light curve shows a possible alignment of the rotational and orbital axis at the 2σ level. Red giant eccentric systems could be progenitors of cataclysmic variables and hot subdwarf B stars.

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Section: The Puzzling Absence Of a Doppler Beaming Signalmentioning

confidence: 56%

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Beck

Hambleton

Vos

et al. 2014

A&A

133

151

View full text Add to dashboard Cite

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“…Given the short duration of the eclipse (≈3 minutes), any remaining variations in the relative photometry due to transparency or airmass changes could be ignored; we did not attempt to model the out-of-eclipse data (cf. Shporer et al 2010). …”

Section: Ultracam Observationsmentioning

confidence: 99%

Properties of an Eclipsing Double White Dwarf Binary NLTT 11748

Kaplan

Marsh

Walker

et al. 2013

ApJ

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We present high-quality ULTRACAM photometry of the eclipsing detached double white dwarf binary NLTT 11748. This system consists of a carbon/oxygen white dwarf and an extremely low mass (<0.2 M ) helium-core white dwarf in a 5.6 hr orbit. To date, such extremely low-mass white dwarfs, which can have thin, stably burning outer layers, have been modeled via poorly constrained atmosphere and cooling calculations where uncertainties in the detailed structure can strongly influence the eventual fates of these systems when mass transfer begins. With precise (individual precision ≈1%), high-cadence (≈2 s), multicolor photometry of multiple primary and secondary eclipses spanning >1.5 yr, we constrain the masses and radii of both objects in the NLTT 11748 system to a statistical uncertainty of a few percent. However, we find that overall uncertainty in the thickness of the envelope of the secondary carbon/oxygen white dwarf leads to a larger (≈13%) systematic uncertainty in the primary He WD's mass. Over the full range of possible envelope thicknesses, we find that our primary mass (0.136-0.162 M ) and surface gravity (log(g) = 6.32-6.38; radii are 0.0423-0.0433 R ) constraints do not agree with previous spectroscopic determinations. We use precise eclipse timing to detect the Rømer delay at 7σ significance, providing an additional weak constraint on the masses and limiting the eccentricity to e cos ω = (−4 ± 5) × 10 −5 . Finally, we use multicolor data to constrain the secondary's effective temperature (7600±120 K) and cooling age (1.6-1.7 Gyr).

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“…The pulsational properties of ELM WDs have been explored theoretically by Van Grootel et al (2013) and Córsico & Althaus (2014, 2016. The DA WD instability strip is both empirically and theoretically found to shift to lower T eff with lower log g, intersecting the population of sdAs Shporer et al 2010;Kilic et al 2011b;Hermes et al 2014). In the case of the 12.75-minute binary SDSS J0651+2844, these have enabled the measurement of orbital decay from gravitational radiation (Hermes et al 2012b).…”

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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A Ground-Based Measurement of the Relativistic Beaming Effect in a Detached Double White Dwarf Binary

Cited by 89 publications

References 20 publications

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Properties of an Eclipsing Double White Dwarf Binary NLTT 11748

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

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