The ellipsoidal variable stars

Morris, Steven L.

doi:10.1086/163359

Cited by 216 publications

(220 citation statements)

References 0 publications

Supporting

Mentioning

206

Contrasting

Order By: Relevance

“…The mutual gravitational interaction between members of a binary will induce nominally prolate distortions of their surfaces having major axes along the line connecting their centers. As a result, the sky-projected cross-sectional area, and consequently the observed flux, is time variable (Morris 1985; see also Pfahl et al 2008). For a circular orbit, the expected maxima of this variation occur twice per orbit at the quadratures (generating a large cos(2φ) amplitude).…”

Section: Doppler Boostingmentioning

confidence: 98%

“…For a circular orbit, the expected maxima of this variation occur twice per orbit at the quadratures (generating a large cos(2φ) amplitude). Kopal (1959) calculated the ELV contribution to the out-ofeclipse harmonic content as (where we follow the notation by Morris 1985):…”

Section: Doppler Boostingmentioning

confidence: 99%

“…In our calculations, we assume a fixed linear limbdarkening parameter (u = 0.44; according to Sing 2010 for the KIC stellar parameters listed in Section 2.1) and a gravity darkening parameter that depends on temperature according to the von Zeipel law (Equation (10) in the work by Morris 1985). The contribution to the ELV due to the distortion of the secondary by the primary is smaller by a factor of at least (R 2 /R 1 ) 3 (F 2 /F 1 )/q 2 ∼ 0.05% and is therefore safely ignored.…”

Section: Doppler Boostingmentioning

confidence: 99%

See 2 more Smart Citations

A THIRD HOT WHITE DWARF COMPANION DETECTED BYKEPLER

Carter

Rappaport

Fabrycky

2011

ApJ

114

View full text Add to dashboard Cite

We have found a system listed in the Kepler Binary Catalog (P orb = 3.273 days) that we have determined is comprised of a low-mass, thermally bloated, hot white dwarf orbiting an A star of about 2.3 M . In this work, we designate the object, KIC 10657664, simply as "KHWD3" (Kepler Hot White Dwarf 3). We use the transit depth of ∼0.66%, the eclipse depth of ∼1.9%, and regular smooth periodic variations at the orbital frequency and twice the orbital frequency to analyze the system parameters. The smooth periodic variations are identified with the classical ellipsoidal light variation (ELV) and illumination (ILL) effects, and the newly utilized Doppler boosting (DB) effect. Given the measured values of R/a and inclination angle of the binary, both the ELV and DB effects are mostly sensitive to the mass ratio, q = M 2 /M 1 , of the binary. The two effects yield values of q which are somewhat inconsistent-presumably due to unidentified systematic effects-but which nonetheless provide a quite useful set of possibilities for the mass of the white dwarf (either 0.26 ± 0.04 M or 0.37 ± 0.08 M ). All of the other system parameters are determined fairly robustly. In particular, we show that the white dwarf has a radius of 0.15 ± 0.01 R , which is extremely bloated over the radius it would have as a fully degenerate object, and an effective temperature T eff 14,500 K. Binary evolution scenarios and models for this system are discussed. We suggest that the progenitor binary was comprised of a primary of mass ∼2.2 M (the progenitor of the current hot white dwarf) and a secondary of mass ∼1.4 M (the progenitor of the current A star in the system). We compare this new system with three other white dwarfs in binaries that likely were formed via stable Roche-lobe overflow (KOI-74, KOI-81, and the inner Regulus binary).

show abstract

Section: Doppler Boostingmentioning

confidence: 98%

Section: Doppler Boostingmentioning

confidence: 99%

Section: Doppler Boostingmentioning

confidence: 99%

See 1 more Smart Citation

A THIRD HOT WHITE DWARF COMPANION DETECTED BYKEPLER

Carter

Rappaport

Fabrycky

2011

ApJ

114

View full text Add to dashboard Cite

show abstract

“…where u = 1.2 is the linear limb-darkening coefficient in the Kepler passband, τ g ∼ 0.32 the gravity-darkening coefficient estimated for the primary LHS 6343 A, and we neglected the effects related to the precession constant and the (small) eccentricity of the orbit (cf., Morris 1985). Note that at mid-eclipse, M = M e , and the ellipsoidal variation is at a minimum, while for M = M e ± π/2, that is, in quadrature, it reaches a maximum.…”

Section: Models Of the Doppler-beaming And Ellipticity Effectmentioning

confidence: 90%

Doppler-beaming in theKeplerlight curve of LHS 6343 A

Herrero¹,

Lanza²,

Ribas³

et al. 2014

A&A

View full text Add to dashboard Cite

Context. Kepler observations revealed a brown dwarf eclipsing the M-type star LHS 6343 A with a period of 12.71 days. In addition, an out-of-eclipse light modulation with the same period and a relative semi-amplitude of ∼2 × 10 −4 was observed showing an almost constant phase lag to the eclipses produced by the brown dwarf. In a previous work, we concluded that this was due to the light modulation induced by photospheric active regions in LHS 6343 A. Aims. In the present work, we prove that most of the out-of-eclipse light modulation is caused by the Doppler-beaming induced by the orbital motion of the primary star. Methods. We introduce a model of the Doppler-beaming for an eccentric orbit and also considered the ellipsoidal effect. The data were fitted using a Bayesian approach implemented through a Markov chain Monte Carlo method. Model residuals were analysed by searching for periodicities using a Lomb-Scargle periodogram. Results. For the first seven quarters of Kepler observations and the orbit previously derived from the radial velocity measurements, we show that the light modulation of the system outside eclipses is dominated by the Doppler-beaming effect. A period search performed on the residuals shows a significant periodicity of 42.5 ± 3.2 days with a false-alarm probability of 5 × 10 −4 , probably associated with the rotational modulation of the primary component.

show abstract

“…However, as mentioned by Loeb & Gaudi (2003) and by Zucker et al (2007), for short-period binaries and planets, the amplitude of the beaming effect might be comparable to (or even smaller than) another two photometric effectsthe ellipsoidal and the reflection light variations. The ellipsoidal variation is caused by tidal interactions between the two components of the binary (e.g., Morris 1985;Mazeh 2008). The reflection variation is caused by the brightness difference between A&A 580, A21 (2015) the "day" side and the "night" side of each component (e.g., Wilson 1990;Harrison et al 2003).…”

Section: Introductionmentioning

confidence: 99%

BEER analysis ofKeplerand CoRoT light curves

Tal-Or

Faigler

Mazeh

2015

A&A

View full text Add to dashboard Cite

Context. The BEER algorithm searches stellar light curves for the BEaming, Ellipsoidal, and Reflection photometric modulations that are caused by a short-period companion. These three effects are typically of very low amplitude and can mainly be detected in light curves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. Aims. Applying the algorithm to wide-field photometric surveys such as CoRoT and Kepler offers an opportunity to better understand the statistical properties of short-period binaries. It also widens the window for detecting intrinsically rare systems, such as shortperiod brown-dwarf and massive-planetary companions to main-sequence stars. Methods. Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87 mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiberallocations with dedicated softwares, we acquired six spectra for 231 candidates and seven spectra for another 50 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842 Å, yielded a radial-velocity precision of ∼1 km s −1 . Spectra containing lines of more than one star were analyzed with the two-dimensional correlation algorithm TODCOR. Results. The measured radial velocities confirmed the binarity of seventy of the BEER candidates -45 single-line binaries, 18 doubleline binaries, and 7 diluted binaries. We show that red giants introduce a major source of false candidates and demonstrate a way to improve BEER's performance in extracting higher fidelity samples from future searches of CoRoT light curves. The periods of the confirmed binaries span a range of 0.3-10 days and show a rise in the number of binaries per ΔlogP toward longer periods. The estimated mass ratios of the double-line binaries and the mass ratios assigned to the single-line binaries, assuming an isotropic inclination distribution, span a range of 0.03-1. On the low-mass end, we have detected two brown-dwarf candidates on a ∼1 day period orbit. Conclusions. This is the first time non-eclipsing beaming binaries are detected in CoRoT data, and we estimate that ∼300 such binaries can be detected in the CoRoT long-run light curves.

show abstract

The ellipsoidal variable stars

Cited by 216 publications

References 0 publications

A THIRD HOT WHITE DWARF COMPANION DETECTED BYKEPLER

A THIRD HOT WHITE DWARF COMPANION DETECTED BYKEPLER

Doppler-beaming in theKeplerlight curve of LHS 6343 A

BEER analysis ofKeplerand CoRoT light curves

Contact Info

Product

Resources

About