Goddard High-Resolution Spectrograph Observations of the B III Resonance Doublet in Early B Stars: Abundances and Isotope Ratios

Details Goddard High-Resolution Spectrograph Observations of the B III Resonance Doublet in Early B Stars: Abundances and Isotope Ratios Goddard High-Resolution Spectrograph Observations of the B III Resonance Doublet in Early B Stars: Abundances and Isotope Ratios

May 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...516..342p&link_type=abstract

The Astrophysical Journal, Volume 516, Issue 1, pp. 342-348.

Astronomy and Astrophysics

Astronomy

19

Stars: Abundances, Stars: Early-Type, Ultraviolet: Stars

Scientific paper

Boron abundances and isotope ratios in two early B stars have been measured by using the Hubble Space Telescope's Goddard High-Resolution Spectrograph (GHRS) in order to observe the B III resonance doublet near 2066 Å. We also report new experimental and theoretical results for the wavelengths, isotope shift, and hyperfine structure of these boron lines. In HD 886 (gamma Pegasi; B2 IV), and HD 35299 (B1 V) the abundance of boron is about a factor of 2 lower than that inferred from solar system meteorites. The ^11B/^10B isotope ratio in HD 886 is determined to be 4.7^+1.1_-1.0, and for HD 35299 a value of 3.7^+0.8_-0.6 is found. These values are consistent with the solar system isotope ratio. In a third star, HD 3360 (zeta Cassiopeiae; B2 IV), our GHRS observations show that the boron abundance is a factor of 40 below the solar system abundance. Our results for HD 886 and HD 35299 appear to be consistent with little dispersion in the initial boron-to-oxygen ratio among Population I stars and a universal ^11B/^10B isotope ratio. However, the abundance measured for HD 3360 shows that either some stars suffer significant boron depletion while still in the core-hydrogen burning phase of their evolution, or there is indeed a very wide variation in initial Population I boron abundances. A much-improved understanding of boron astration in early B stars will be required before this question can be resolved.

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