Astronomy and Astrophysics – Astrophysics
Scientific paper
2000-01-13
Astronomy and Astrophysics
Astrophysics
6 pages including 3 figures, to appear in ApJ Letters
Scientific paper
10.1086/312514
We suggest that if the astrophysical site for r-process nucleosynthesis in the early Galaxy is confined to a narrow mass range of Type II supernova (SN II) progenitors, with a lower mass limit of Mms = 20 Msun, a unique feature in the observed distribution of [Ba/Mg] vs.[Mg/H] for extremely metal-poor stars can be adequately reproduced. We associate this feature, a bifurcation of the observed elemental ratios into two branches in the Mg abundance interval -2.7 < [Mg/H] < -2.3, with two distinct processes. The first branch, which we call the ``y''-branch, is associated with the production of Ba and Mg from individual massive supernovae. We conclude that SNe II with Mms = 20 Msun are the dominant source of r-process nucleosynthesis in the early Galaxy. An SN-induced chemical evolution model with this Mms-dependent Ba yield creates the y-branch, reflecting the different nucleosynthesis yields of [Ba/Mg] for each SN II with Mms > 20 Msun. The second branch, which we call the ``i''-branch, is associated with the elemental abundance ratios of stars which were formed in the dense shells of the interstellar medium swept up by SNe II with Mms < 20 Msun that do not synthesize r-process elements, and applies to stars with observed Mg abundances in the range [Mg/H] < -2.7. The Ba abundances in these stars reflect those of the interstellar gas at the (later) time of their formation. The existence of a [Ba/Mg] i-branch strongly suggests that SNe II which are associated with stars of progenitor mass Mms < 20 Msun are infertile sources for the production of r-process elements. We predict the existence of this i-branch for other r-process elements, such as europium (Eu), to the extent that their production site is in common with Ba.
Shigeyama Toshikazu
Tsujimoto Takuji
Yoshii Yuzuru
No associations
LandOfFree
Probing the Site for r-Process Nucleosyntheis with Abundances of Barium and Magnesium in Extremely Metal-Poor Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Probing the Site for r-Process Nucleosyntheis with Abundances of Barium and Magnesium in Extremely Metal-Poor Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Probing the Site for r-Process Nucleosyntheis with Abundances of Barium and Magnesium in Extremely Metal-Poor Stars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-360405