A detailed study of opacity in the upper atmosphere of Proxima Centauri

摘要: We present far-UV and UV spectroscopic observations of Proxima Centauri obtained as part our continued investigation into the optically thin approximation assumed for transition regions late-type stars. Significant opacity is found in C III lines during both quiescent flaring states Cen, with up to 70% expected flux being lost latter. Our findings cast some doubt on suitability λ977 line estimating electron density stellar atmospheres. However, has no significant effect observed widths. calculate optical depths homogeneous inhomogeneous geometries estimate an 6 × 1010 cm-3 region using O IV ratios at 1400 A. The combination depth indicates path lengths low ≈10 km, which are excellent agreement estimates small-scale structure seen solar region.