Some surprises concerning the origin of the light elements

✍ Scribed by D.K. Duncan

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 225 KB
• Volume: 621
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(97)00202-9

✦ Synopsis

The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to obtain spectra of the boron 2500 ~ region in a total of 11 stars ranging from [Fe/H] = -0.35 to -2.96, including the most metal-poor star ever observed for B. Spectrum synthesis was used to determine the boron abundance for each star, with particular attention paid to the errors of each point, to permit judgement of the goodness-of-fit of models of Galactic chemical evolution.

A straight line of slope close to 1 gives an excellent fit to a plot of log e(B) vs. [Fe/H] or log e(B) vs. [O/H] 1, suggesting that the production of light elements such as B and Be are directly related to the production of heavier elements. There is no indication of a change in slope between halo and disk metallicities. The B/Be ratio is typically 10; NLTE effects can potentially raise this. Our data support a model in which most light element production comes from cosmic ray spallation of C and O nuclei onto protons and He nuclei, probably in the vicinity of massive supernovae (SN) in star-forming regions.

They do not support the long-held ([12]Reeves, Fowler, & Hoyle 1970) theory that light element production primarily occurs in the general ISM from the spallation of high-energy protons and alpha particles onto CNO nuclei.

It is possible that the gamma rays recently detected from the Orion Nebula region are the signature of this process in action. Nevertheless, the light element data alone give the strongest evidence supporting a new model for the formation of the light elements.