On the structure of the Sun and α Centauri A and B in the light of seismic and non-seismic constraints
Makaleler > Tam Makale · 2008
Yazarlar: Mutlu YILDIZ
Monthly Notices of the Royal Astronomical Society, SCI Expanded İndekslerine Giren Dergi, Uluslararası, Wos, 2008, cilt 388, ss 1143-1151
DOI: 10.1111/j.1365-2966.2008.13352.x
Özet
The small separation (δν01, δν02 and δν13) between oscillations with low degree l is dependent primarily on the sound speed profile within the stellar core, where nuclear evolution occurs. The detection of such oscillations in a star offers a very good opportunity to determine the stage of its nuclear evolution, and hence its age. In this context, we investigate the Sun and α Cen A and B. For α Cen A and B, each of the small separations δν01, δν02 and δν13 gives a different age. Therefore, in our fitting process, we also employ the second difference, defined as νn,2− 2νn,1+νn,0, which is 2δν01−δν02. In addition to this, we use the frequency ratio (νn,0/νn,2). For the Sun, these expressions are equivalent and give an age of about 4.9–5.0 Gyr. For α Cen A and B, however, the small separation and the second difference give very different ages. This conflict may be resolved by the detection of oscillation frequencies that can be measured much more precisely than the current frequencies. When we fit the models to the observations, we find that (i) Z0= 0.020, t= 3.50 Gyr and MB= 1.006 M⊙ from the small separations δν01, δν02 and δν13 of α Cen B; and (ii) a variety of solutions from the non-seismic constraints and δν02 of α Cen A and B, in which the masses of α Cen A and B are slightly modified and the age of the system is about 5.2–5.3 Gyr. For Z= 0.025, the closest masses we find to the observed masses are MB= 0.922 M⊙ and MA= 1.115 M⊙. The differences between these masses and the corresponding observed masses are about 0.01 M⊙.