Ultra-Short Period Double-Degenerate Binaries

Cropper, Mark; Ramsay, Gavin; Wu, Kinwah; Hakala, Pasi

doi:10.1017/s0252921100002281

Cited by 12 publications

(16 citation statements)

References 21 publications

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“…The unipolar-inductor model avoids the above difficulties of the accretion models. Although the model is generally consistent with existing observations (see Cropper et al 2004), there are some concerns regarding whether or not it is applicable to RX J1914+24 and RX J0806+15, which are presumably compact white-dwarf pairs (e.g. Barros et al 2005Barros et al , 2007Laine, Lin & Dong 2008;Wood 2009).…”

Section: K Wusupporting

confidence: 76%

“…The unipolar-inductor model, however, suggested that the emission of X-rays is caused by ohmic dissipation of electric currents in the white-dwarf atmosphere. An assessment of the models can be found in Cropper et al (2004). In the face-on IP model, a moderately magnetized white dwarf is accreting material from a mainsequence donor star.…”

Section: Candidate Unipolar-inductor Ultra-compact Double Degeneratesmentioning

confidence: 99%

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Magnetic interaction in ultra-compact binary systems

2009

Res. Astron. Astrophys.

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This article reviews the current works on ultra-compact double-degenerate binaries in the presence of magnetic interaction, in particular, unipolar induction. The orbital dynamics and evolution of compact white-dwarf pairs are discussed in detail. Models and predictions of electron cyclotron masers from unipolar-inductor compact binaries and unipolar-inductor white-dwarf planetary systems are presented. Einstein-Laub effects in compact binaries are briefly discussed.

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Section: K Wusupporting

confidence: 76%

Section: Candidate Unipolar-inductor Ultra-compact Double Degeneratesmentioning

confidence: 99%

Magnetic interaction in ultra-compact binary systems

2009

Res. Astron. Astrophys.

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“…The properties of RX J0806.3+1527 and its "twin" RX J1914.4+2456 (V407 Vul), which displays a 569-s (9.5-min) modulation and overall similar X-ray and optical properties, are interpreted in the framework of a double-degenerate binary that hosts two interacting white dwarfs (WDs), where the observed pulsation is due to orbital motion (see Cropper et al 2004; Solheim 2010 for reviews). Roelofs et al (2010) showed in RX J0806.3+1527 a clear modulation of He emission lines in both radial velocity and amplitude on the 5.4-min period (see also Mason et al 2010).…”

Section: Introductionmentioning

confidence: 99%

SwiftX-ray and ultraviolet observations of the shortest orbital period double-degenerate system RX J0806.3+1527 (HM Cnc)

Esposito

Israel

Dall’Osso

et al. 2014

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The system RX J0806.3+1527 (HM Cnc) is a pulsating X-ray source with 100 per cent modulation on a period of 321.5 s (5.4 min). This period reflects the orbital motion of a close binary consisting of two interacting white dwarfs. Here we present a series of simultaneous X-ray (0.2-10 keV) and near-ultraviolet (2600 Å and 1928 Å) observations that were carried out with the Swift satellite. In the near-ultraviolet, the counterpart of RX J0806.3+1527 was detected at flux densities consistent with a blackbody with a temperature of (27 ± 8) × 10 3 K. We found that the emission at 2600 Å is modulated at the 321.5-s period with the peak ahead of the X-ray one by 0.28 ± 0.02 cycles and is coincident within ±0.05 cycles with the optical. This phase-shift measurement confirms that the X-ray hot spot (located on the primary white dwarf) is at about 80• -100• from the direction that connects the two white dwarfs. Albeit at lower significance, the 321.5-s signature is also present in the 1928-Å data; at this wavelength, however, the pulse peak is better aligned with that observed at X-rays. We use the constraints on the source luminosity and the geometry of the emitting regions to discuss the merits and limits of the main models for RX J0806.3+1527.

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“…The observational constraints for the systems HM Cnc and V407 Vul were discussed in detail in Paper I (also see Cropper et al 2004). Briefly, the systems are characterized by ‘on/off’ X‐ray light curves that trail the optical light curves by roughly 0.2 in phase (Barros et al 2007, and references therein), no hard X‐rays are detected, the observed periods are decreasing with time at a rate consistent with gravitational radiation angular momentum loss (Strohmayer 2003, 2004; Ramsay, Cropper & Hakala 2006), and flickering is minimal or absent (Barros et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Synthetic direct impact light curves of the ultracompact AM CVn binary systems V407 Vul and HM Cnc

Wood

2009

Monthly Notices of the Royal Astronomical Society

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The interacting binary white dwarf (AM CVn) systems HM Cnc and V407 have orbital periods of 5.4 and 9.5 min, respectively. The two systems are characterized by an ‘on/off’ behaviour in the X‐ray light curve, and optical light curves that are nearly sinusoidal and which lead the X‐ray light curves in phase by about 0.2 in both systems. Of the models that have been proposed to explain the observations, the one that seems to require the least fine‐tuning is the direct impact model of Marsh & Steeghs. In this model, the white dwarf primary is large enough relative to the semimajor axis that the accretion stream impacts the surface of the primary white dwarf directly without forming an accretion disc. Marsh & Steeghs proposed that in this situation there could be a flow setup around the equator with a decreasing surface temperature, the further one measured from the impact point. In this study, we estimate the light curves that might result from such a temperature distribution, and find them to be reasonable approximations to the observations. One unexpected result is that two distinct X‐ray spots must exist to match the shape of the X‐ray light curves.

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Ultra-Short Period Double-Degenerate Binaries

Cited by 12 publications

References 21 publications

Magnetic interaction in ultra-compact binary systems

Magnetic interaction in ultra-compact binary systems

SwiftX-ray and ultraviolet observations of the shortest orbital period double-degenerate system RX J0806.3+1527 (HM Cnc)

Synthetic direct impact light curves of the ultracompact AM CVn binary systems V407 Vul and HM Cnc

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