AM CVn stars
نویسنده
چکیده
I review our observational and theoretical knowledge of AM CVn stars, focusing on recent developments. These include newly discovered systems, the possibility that two recently discovered extremely short period objects are AM CVn stars and an update on X-ray, UV an optical studies. Theoretical advances include the study of the details of both the donor and accretor, and the physics of the helium accretion discs. I review our (limited) knowledge of the formation of AM CVn stars and the apparent success of the now more than 25 year old suggestion that in these objects the mass transfer is driven by gravitational wave radiation losses. The exciting prospect of directly detecting these gravitational waves and the possibilities this brings conclude this contribution.
منابع مشابه
The population of AM CVn stars from the Sloan Digital Sky Survey
The AM Canum Venaticorum stars are rare interacting white dwarf binaries, whose formation and evolution are still poorly known. The Sloan Digital Sky Survey provides, for the first time, a sample of 6 AM CVn stars (out of a total population of 18) that is sufficiently homogeneous that we can start to study the population in some detail. We use the Sloan sample to ‘calibrate’ theoretical populat...
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We study two models for AM CVn stars: white dwarfs accreting (i) from a helium white dwarf companion and (ii) from a helium-star donor. We show that in the first model possibly no accretion disk forms at the onset of mass transfer. The stability and the rate of mass transfer then depend on the tidal coupling between the accretor and the orbital motion. In the second model the formation of AM CV...
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We report the results of a synthetic spectral analysis of Hubble STIS spectra of the AM CVn-type cataclysmic variable CP Eri obtained when the system was in quiescence. The FUV spectrum is best fitted by a helium-dominated, hybrid composition (DBAZ) white dwarf with Teff ∼ 17, 000K ± 1000K, log g∼ 8, He abundance ∼ 1000× solar, H abundance ∼ 0.1× solar, metallicity Z ∼ 0.05× solar, V sin i ∼ 40...
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We present absolute parallaxes and relative proper motions for five AM CVn stars, which we obtained using the Fine Guidance Sensors on board the Hubble Space Telescope. Our parallax measurements translate into distances dAMCVn = 606 +135 −93 pc; dHPLib = 197 +14 −12 pc; dCRBoo = 337 +44 −35 pc; dV803Cen = 347 +32 −27 pc; and dGPCom = 75 +2 −2 pc. From these distances we estimate the space densi...
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