| Type Ia supernova research is one of the most forward projects in astrophysicsand basic physics in21st century. Type Ia supernovae (SNe Ia) are used as cosmicdistance indicators because their luminosity can be calibrated based on the empiricalrelation between light curve shape and peak luminosity. This leads to the discoveryof the accelerating expansion of the present Universe, providing the evidence for theexistence of dark energy. This is a great discovery, not only in astronomy, but alsoin physics. However，the nature of progenitors and the explosion physics of SNe Iaremain unclear.SNe Ia are widely believed to be arisen from thermonuclear explosions of carbon-oxygen white dwarfs (C-O WDs) by accreting material from their non-degenerate (i.e.,single degenerate scenario [SD]) or degenerate (i.e., double degenerate scenario [DD])companion stars. One of the obvious diference between SD and DD scenario is thatthe SD model predicts the companion star would survive from the explosion, but theDD model leaves no companion remnant after the explosion. Therefore, it is a promis-ing approach to distinguish and identify the SD and DD model by directly searchingfor the surviving companion star in Galactic SN Ia remnant. In present paper, basedon the SD progenitor model, we performed three dimensional hydrodynamical sim-ulations of the impact of SN Ia explosion on their companion stars employing thesmoother particle hydrodynamics (SPH) method. We investigated the details of the in-teractions between the SN Ia ejecta and the companion star. We presented some pecu-liar characteristics and observable qualities of surviving companion stars of SNe Ia. InChapter1of present paper, we introduced the research histories, classifications of SNeand the research goal of this work. The observational properties (light curves and spec-tra), progenitor models (SD and DD models) and explosion models (Chandrasekhar,sub-Chandrasekhar and super-Chandrasekhar models) of SNe Ia were introduced de-tailedly in Chapter2. Moreover, the research methods and numerical codes used inthis work were presented in Chapter3. Finally, we introduced our research works ofthis paper in detail. Primary results obtained in this work are shown as following: (1) Based on WD+MS progenitor scenario, we obtained some more realistic com-panion star models than previous work by using consistent binary evolution calcula-tions. Our SPH simulations show that the SN Ia impact always strips of0.1M⊙companion mass and delivers the companion star a kick velocity of50–105km s1.Moreover, we found that the degree of compactness of the companion star and the bi-nary separation are the most important factors to determine the amount of the strippedmass and kick velocity. However, the evolutionary state of the companion star at themoment of the explosion is also very important. In our simulations, the amount ofthe stripped mass is far more than the most stringent upper limit of0.01M⊙for thenon-detection of H emission in late time spectra, suggesting that the stripped H mayappear in nebular spectra of SD SNe Ia.(2) By including the orbital motion and spin of the companion star into our SPHsimulations, it is found that the rotation of the companion star does not significantlyafect the amount the stripped companion mass and the kick velocity caused by the SNimpact. However, in our simulations, the SN impact can significantly strip of14%–23%of initial companion mass, which carries away55%–89%of its initial angularmomentum. Moreover, the companion star extremely expands after the explosion dueto the SN heating. Therefore, the rotational velocity of the companion star is signifi-cantly reduced to about14%–32%of its pre-explosion value.(3) Compared to the observed rotational velocity of the presumed companion starof Tycho’s supernova, Tycho G, of～6km s1, the final rotational velocity we obtainin our simulations is still higher by at least a factor of two. However, we cannot roleout the possibility of the Tycho G as a candidate of the surviving companion star of SN1572base on its small rotational velocity. Furthermore, based on binary populationsynthesis results for WD+MS systems, we presented for the first time the expecteddistribution of rotational velocities of companion stars after the SN explosion, whichprovides very useful information for the identification of the surviving companion starin observational research in historical SN remnants.(4) Based on WD+HE Chandrasekhar explosion scenario, hydrodynamical sim-ulations obtain that only2%–5%of the He companion mass are stripped of by theSN impact. However, the heavy elements of SN ejecta can significantly pollute the outer layers of companion stars, leading to the companion stars show some signaturesof enrichment of heavy elements. This provides a potential way to identify survivingcompanion stars in the WD+HE scenario. Moreover, we predicted that the survivingcompanion star has a high spatial velocity and is rapidly rotating after the SN explo-sion, which should be easy to be identified by observations.(5) We performed three-dimensional hydrodynamical simulations of the impactof SN Ia explosions on their MS companion stars adopting the new pure deflagrationexplosion model. We found that the SN impact strips of a quite small amount of H (0.01M⊙) from the surface of MS companion star because the pure deflagration modelproduces a small explosion energy after the explosion. This is consistent with thebest observational limits (0.01M⊙) for non-detection of H lines in nebular spectraof normal SNe Ia. Therefore, we predicted that the stripped H would be hidden innebular spectra of SN2002cx-like SNe Ia. This might explain the fact of the absenceof H lines in nebular spectra of SD SNe Ia.With this work, we provided reliable predictions and theoretical evidences forhunting and identifying the surviving companion stars in observational research inhistorical SN remnants. Moreover, it plays an important role in putting constraints onthe progenitor models of SNe Ia. |
PDF Full Text Request