The lithium abundance in sunspots
The solar lithium abundance was determined using an empirical model for an observed sunspot umbra. The atmospheric model is deduced from a number of spectral lines. In addition to the lithium (I) line doublets from Li(6) and Li(7) at 670.8 nm eight different line profiles were observed with high spectrographic resolution. A magnetically sensitive line was included in order to determine the magnetic field strength. An estimation for the influence of molecular blends caused by CN and TiO was taken into account. Under the assumption of LTE a lithium abundance of epsilon_Li =1.02 +/-0.12 was derived. Some evidence for the existence of a small but notable amount of Li(6) is found, however only an upper limit of Li(6/Li^7<=) 0.03 can be derived. A more precise determination of the isotopic ratio is hampered by the uncertainties induced by the presence of TiO blends.On the logarithmic scale, where the abundance of hydrogen is epsilon_H =12.
Astronomy and Astrophysics
- Pub Date:
- December 1997