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Figure 1:
Descendants of components of close binaries depending on the radius of the star at RLOF. The boundary between progenitors of He and CO-WDs is uncertain by several ![]() ![]() ![]() |
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Figure 2:
Sensitivity limits of GW detectors and the regions of the ![]() ![]() |
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Figure 3:
The maximum initial orbital period (in hours) of two point masses which will coalesce due to gravitational wave emission in a time interval shorter than 1010 yr, as a function of the initial eccentricity ![]() ![]() ![]() ![]() |
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Figure 4:
Evolutionary scenario for the formation of neutron stars or black holes in close binaries. |
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Figure 5:
Formation of close binary dwarfs and their descendants (scale and colour-coding are arbitrary). |
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Figure 6:
The age of merging pairs of helium WDs. Two components of the distribution correspond to the systems that experienced in the course of formation two or one common envelope episodes, respectively. |
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Figure 7:
Known close binaries with two WD components, or a WD and a sd component. Green circles mark systems known prior to the SPY project. Black filled symbols mark the positions of DDs and WD + sd systems detected in the SPY project. A blue triangle marks the positions of the WD component of the binary planetary nebula nucleus PN G135.9+55.9 detected by Tovmassian et al. [404]. (Courtesy R. Napiwotzki.) |
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Figure 8:
The position of the primary components of known DDs in the “orbital-period–mass” diagram. The underlying gray scale plot is a model prediction from Nelemans et al. [286]. (Figure from [277].) |
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Figure 9:
Mass-loss rate vs. orbital period for “typical” AM CVn-stars: an interacting double degenerate system with initial masses of donor and accretor ![]() ![]() ![]() ![]() ![]() |
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Figure 10:
Dependence of the dimensionless strain amplitude for a WD + WD detached system with initial masses of the components of ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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Figure 11:
GWR background produced by detached and semidetached double white dwarfs as it would be detected at the Earth. The assumed integration time is 1 yr. The ‘noisy’ black line gives the total power spectrum, the white line the average. The dashed lines show the expected LISA sensitivity for a ![]() ![]() ![]() |
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Figure 12:
The number of systems per bin on a logarithmic scale. Semidetached double white dwarfs contribute to the peak between ![]() ![]() |
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Figure 13:
Fraction of bins that contain exactly one system (solid line), empty bins (dashed line), and bins that contain more than one system (dotted line) as function of the frequency of the signals. (Figure from [286].) |
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Figure 14:
Gravitational waves background formed by the Galactic population of white dwarfs and signal amplitudes produced by some of the most compact binaries with white dwarf components ([273]). The green line presents results from [286], the black one from [287], while the red one presents a model with all assumptions similar to [287], but with the ![]() |
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Figure 15:
Strain amplitude ![]() ![]() ![]() |
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Figure 16:
Distribution of short period AM CVn-type systems detectable in soft X-rays and as optical sources as a function of orbital period and distance. Top panel: systems detectable in X-rays only (blue pluses), direct impact systems observable in X-ray and V -band (red filled circles), systems detectable in X-ray with an optically visible donor (green squares), and systems detectable in X-rays and with an optically visible disc (large filled triangles). Bottom panel: direct impact systems (red open circles), systems with a visible donor (green squares), and systems with a visible accretion disc (small open triangles). The overlap of these systems with systems observable in gravitational waves is shown in Figure 17. (Updated figure from [287], see also [274].) |
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Figure 17:
Short-period AM CVn systems, subdivided in different types. Each panel shows the total population as the white histogram. The top left panel shows 11,000 systems that can be resolved by LISA in gray, and they are subdivided into the ones that have optical counterparts (GWR + Opt), X-ray counterparts (GWR + X), and both (GWR + Opt + X). The top right panel shows the systems that are in the direct impact phase of accretion in gray, and they are subdivided in GWR and X-ray sources. The bottom two panels show (again in gray) the populations that are detectable in the optical band (left panel) and the X-ray band (right panel). The distribution of sources detectable both in optical and X-ray bands is shown as hatched bins in both lower panels (Opt + X). (Figure from [287].) |
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Figure 18:
Effects of a finite entropy of donors on the properties of AM CVn-stars. The left panel shows the relation between ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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