Skip to main content Accessibility help
×
Home

Very Low-Mass Stars with Extremely Low Metallicity in the Milky Way's Halo

  • Wako Aoki (a1), Timothy C. Beers (a2), Takuma Suda (a3), Satoshi Honda (a4) and Young Sun Lee (a5)...

Abstract

Large surveys and follow-up spectroscopic studies in the past few decades have been providing chemical abundance data for a growing number of very metal-poor ([Fe/H] <−2) stars. Most of them are red giants or main-sequence turn-off stars having masses near 0.8 solar masses. Lower mass stars with extremely low metallicity ([Fe/H] <−3) are yet to be explored. Our high-resolution spectroscopic study for very metal-poor stars found with SDSS has identified four cool main-sequence stars with [Fe/H] <−2.5 among 137 objects (Aoki et al. 2013). The effective temperatures of these stars are 4500–5000 K, corresponding to a mass of around 0.5 solar masses. Our standard analysis of the high-resolution spectra based on 1D-LTE model atmospheres has obtained self-consistent chemical abundances for these objects, assuming small values of micro-turbulent velocities compared with giants and turn-off stars. The low temperature of the atmospheres of these objects enables us to measure their detailed chemical abundances. Interestingly, two of the four stars have extreme chemical-abundance patterns: one has the largest excesses of heavy neutron-capture elements associated with the r-process abundance pattern known to date (Aoki et al. 2010), and the other exhibits low abundances of the α-elements and odd-Z elements, suggested to be signatures of the yields of very massive stars (> 100 solar masses; Aoki et al. 2014). Although the sample size is still small, these results indicate the potential of very low-mass stars as probes to study the early stages of the Milky Way's halo formation.

    • Send article to Kindle

      To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

      Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

      Find out more about the Kindle Personal Document Service.

      Very Low-Mass Stars with Extremely Low Metallicity in the Milky Way's Halo
      Available formats
      ×

      Send article to Dropbox

      To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

      Very Low-Mass Stars with Extremely Low Metallicity in the Milky Way's Halo
      Available formats
      ×

      Send article to Google Drive

      To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

      Very Low-Mass Stars with Extremely Low Metallicity in the Milky Way's Halo
      Available formats
      ×

Copyright

References

Hide All
Aoki, W., Beers, T. C., Honda, S., & Carollo, D. 2010, ApJL, 723, L201
Aoki, W., Beers, T. C., Lee, Y. S., et al. 2013, AJ, 145, 13
Aoki, W., Tominaga, N., Beers, T. C., Honda, S., & Lee, Y. S. 2014, Science, 345, 912
Frebel, A., & Norris, J. E. 2015, ARAA, in press, arXiv:1501.06921
Ishimaru, Y., Wanajo, S., & Prantzos, N. 2015, ApJL, 804, L35
Kim, Y.-C., Demarque, P., Yi, S. K., & Alexander, D. R. 2002, ApJS, 143, 499
Lee, Y. S., Beers, T. C., Sivarani, T., et al. 2008, AJ, 136, 2022
Ohkubo, T., Umeda, H., Maeda, K., et al. 2006, ApJ, 645, 1352
Suda, T., Katsuta, Y., Yamada, S., et al. 2008, PASJ, 60, 1159
Wehmeyer, B., Pignatari, M., & Thielemann, F.-K. 2015, MNRAS, 452, 1970
Yong, D., & Lambert, D. L. 2003a, PASP, 115, 796
Yong, D., Lambert, D. L., & Ivans, I. I. 2003b, ApJ, 599, 1357
York, D. G., Adelman, J., Anderson, J. E., et al. 2000, AJ, 120 1579
MathJax
MathJax is a JavaScript display engine for mathematics. For more information see http://www.mathjax.org.

Keywords

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed