J-type Carbon Stars: A Dominant Source of 14N-rich Presolar SiC Grains of Type AB
Abstract
We report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB (14N/15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%-15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2017
- DOI:
- 10.3847/2041-8213/aa7d4c
- arXiv:
- arXiv:1707.00084
- Bibcode:
- 2017ApJ...844L..12L
- Keywords:
-
- circumstellar matter;
- meteorites;
- meteors;
- meteoroids;
- nuclear reactions;
- nucleosynthesis;
- abundances;
- stars: AGB and post-AGB;
- stars: carbon;
- stars: dwarf novae;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 4 figures