Type Ia supernovae （SNe Ia） play a key role in measuring cosmological parameters, in which the Phillips relation is adopted. However, the origin of the relation is still unclear. Several parameters are suggested, e.g. the relative content of carbon to oxygen （C/O） and the central density of the white dwarf （WD） at ignition. These parameters are mainly determined by the WD＇s initial mass and its cooling time, respectively. Using the progenitor model developed by Meng ＆ Yang, we present the distributions of the initial WD mass and the cooling time. We do not find any correlation between these parameters. However, we notice that as the range of the WD＇s mass decreases, its average value increases with the cooling time. These results could provide a constraint when simulating the SN Ia explosion, i.e. the WDs with a high C/O ratio usually have a lower central density at ignition, while those having the highest central density at ignition generally have a lower C/O ratio. The cooling time is mainly determined by the evolutionary age of secondaries, and the scatter of the cooling time decreases with the evolutionary age. Our results may indicate that WDs with a long cooling time have more uniform properties than those with a short cooling time, which may be helpful to explain why SNe Ia in elliptical galaxies have a more uniform maximum luminosity than those in spiral galaxies.
Binary stars are common in star clusters and galaxies, but the detailed ef- fects of binary evolution are not taken into account in some color-magnitude diagram （CMD） studies. This paper studies the CMDs of twelve globular clusters via binary- star stellar populations. The observational CMDs of the star clusters are compared to those of binary-star populations, and then the stellar metallicities, ages, distances and reddenings of these star clusters are obtained. The paper also tests the different effects of binary and single stars on CMD studies. It is shown that binaries can better fit the observational CMDs of the sample globular clusters compared to single stars. This suggests that the effects of binary evolution should be considered when modeling the CMDs and stellar populations of star clusters and galaxies.
Zhong-Mu LiCai-Yan MaoRu-Heng LiRu-Xi LiMao-Cai Li
Although type Ia supernovae(SNe Ia) show their importance in many astrophysical fields,the nature of the progenitors of SNe Ia is still unclear.At present,the single degenerate(SD) model is presented to be a very likely progenitor model.Following the comprehensive SD model developed by Meng & Yang(2010),we show the initial and final state of the progenitor systems of SNe Ia in an orbital period—the secondary mass(log Pi,M2i) plane.Our results may explain the location of some supersoft X-ray sources and recurrent novae in the(log Pi,M2i) plane,and be helpful to judge whether an SD system is the potential progenitor system of SNe Ia,as well as to simulate the interaction between SN ejecta and its companion.
MENG XiangCun1,YANG WuMing1 & LI ZhongMu2,3 1School of Physics and Chemistry,Henan Polytechnic University,Jiaozuo 454000,China
This paper presents new CCD BV RI light curves of the newly discovered RS CVn eclipsing binary V1034 Her in 2009 and 2010, the shapes of which are different from previously published results. They show an asymmetric outside eclipse, and we try to use a spot model to explain the phenomenon. Using the Wilson-Devinney program with a one-spot or two-spot model, photometric solutions of the system and starspot parameters were derived. Comparing the two results shows that the case of two spots is more successful in reproducing light-curve distortions. Looking at all the spot longitudes, the trend is towards active longitude belts and each active longitude belt may switch. Comparing the light curves from 2009 and 2010, we can see that the light curve changes over the long time scale of a year, especially in phase 0.25. In addition, we also collected the values of the maximum amplitudes of photometric distortion of the short-period RS CVn binary. We found for the first time that there is a trend of increasing activity with decreasing orbital period. Finally, fitting all available light minimum times including our newly obtained ones with a polynomial function confirmed that the orbital period of V1034 Her increased.
