TY - JOUR
T1 - Blocking metal accretion onto population III stars by stellar wind
AU - Tanaka, Shuta J.
AU - Chiaki, Gen
AU - Tominaga, Nozomu
AU - Susa, Hajime
N1 - Funding Information:
S.J.T. would like to thank Y. Ohira, T. Terasawa, T. Suzuki, D. Kinoshita, K. Takaharashi, T. Hartwig, K. Omukai, and T. Hosokawa for useful and helpful discussions. The authors would also like to thank the anonymous referee for useful and helpful comments. This work is supported by Grants-in-Aid for Scientific Research Nos. 17K18270 (ST), 15H05440 (NT), 17H02869 (HS), and 17H01101 (HS). G.C. is supported by JSPS Research Fellowships for Young Scientists.
Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017
Y1 - 2017
N2 - Low-mass population III (PopIII) stars of 0.8 M could survive up until the present. The nondetection of low-mass PopIII stars in our Galaxy has already put a stringent constraint on the initial mass function (IMF) of PopIII stars, suggesting that PopIII stars have a top-heavy IMF. On the other hand, some claim that the lack of such stars stems from metal enrichment of their surfaces by the accretion of heavy elements from the interstellar medium (ISM). We investigate the effects of the stellar wind on metal accretion onto low-mass PopIII stars because accretion of the local ISM onto the Sun is prevented by the solar wind, even for neutrals. The stellar wind and radiation of low-mass PopIII stars are modeled based on knowledge of nearby low-mass stellar systems, including our Sun. We find that low-mass PopIII stars traveling across the Galaxy form a stellar magnetosphere in most of their life. Once the magnetosphere is formed, most of the neutral interstellar particles are photoionized before reaching the stellar surface and are blown away by the wind. Especially, the accretion abundance of iron will be reduced by a factor of <10 -12 compared with Bondi-Hoyle-Lyttleton accretion. The metal accretion can enhance iron abundance [Fe/H] only up to ∼−14. This demonstrates that low-mass PopIII stars remain pristine and will be found as metal-free stars and that further searches for them are valuable in constraining the IMF of PopIII stars.
AB - Low-mass population III (PopIII) stars of 0.8 M could survive up until the present. The nondetection of low-mass PopIII stars in our Galaxy has already put a stringent constraint on the initial mass function (IMF) of PopIII stars, suggesting that PopIII stars have a top-heavy IMF. On the other hand, some claim that the lack of such stars stems from metal enrichment of their surfaces by the accretion of heavy elements from the interstellar medium (ISM). We investigate the effects of the stellar wind on metal accretion onto low-mass PopIII stars because accretion of the local ISM onto the Sun is prevented by the solar wind, even for neutrals. The stellar wind and radiation of low-mass PopIII stars are modeled based on knowledge of nearby low-mass stellar systems, including our Sun. We find that low-mass PopIII stars traveling across the Galaxy form a stellar magnetosphere in most of their life. Once the magnetosphere is formed, most of the neutral interstellar particles are photoionized before reaching the stellar surface and are blown away by the wind. Especially, the accretion abundance of iron will be reduced by a factor of <10 -12 compared with Bondi-Hoyle-Lyttleton accretion. The metal accretion can enhance iron abundance [Fe/H] only up to ∼−14. This demonstrates that low-mass PopIII stars remain pristine and will be found as metal-free stars and that further searches for them are valuable in constraining the IMF of PopIII stars.
KW - Early universe
KW - Outflows
KW - Stars: Population III
KW - Stars: abundances
KW - Stars: chemically peculiar
KW - Stars: low-mass
KW - Stars: winds
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U2 - 10.3847/1538-4357/aa7e2c
DO - 10.3847/1538-4357/aa7e2c
M3 - Article
AN - SCOPUS:85045935439
VL - 844
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 137
ER -