Population synthesis of DA white dwarfs: constraints on soft X-ray spectra evolution


Abstract in English

Extending the population synthesis method to isolated young cooling white dwarfs we are able to confront our model assumptions with observations made in ROSAT All-Sky Survey (Fleming et al., 1996). This allows us to check model parameters such as evolution of spectra and separation of heavy elements in DA WD envelopes. It seems like X-ray spectrum temperature of these objects is given by the formula T_{X-ray} = min(T_eff, T_max). We have obtained DA WDs birth rate and upper limit of the X-ray spectrum temperature: DA birth rate $= 0.61times 10^{-12}$ in cubic parsec per year and T_max = 41000 K. These values are in good correspondence with values obtained by other authors (Liebert et al., 2004; Wolff et al., 1996). From this fact we also conclude that our population synthesis method is applicable to the population of close-by isolated cooling white dwarfs as well as to the population of the isolated cooling neutron stars.

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