High-dispersion IUE observations of hybrid-chromosphere stars
Abstract
High dispersion, wavelength calibrated IUE spectra of the hybrid-chromosphere stars alpha TrA (K2 IIb-IIa) and upsilon Aql (K3 II) are presented. These observations allow accurate measurement of the wind terminal velocities as seen in the Mg II emission line profiles. The terminal velocities deduced for upsilon Aql and alpha TrA are 110 and 120 km/sec respectively. The terminal velocity for alpha TrA is significantly reduced from the 180 km/sec seen in spectra obtained 2 yr earlier. The intersystem emission lines of C I (1993 A), C II (2325 A), C III (1908 A), O I (1641 A; fluoresced) and Si III (1892 A) are at essentially their rest wavelengths. The upsilon Aql C II intersystem multiplet line fluxes indicate an electron density near 1 billion/cc in their line formation region. Results suggest that the transition region intersystem lines are unlikely to be formed in the high velocity wind seen in the Mg II lines but are certainly formed in a region with significant turbulence.
- Publication:
-
New Insights in Astrophysics. Eight Years of UV Astronomy with IUE
- Pub Date:
- September 1986
- Bibcode:
- 1986ESASP.263..169B
- Keywords:
-
- Chromosphere;
- Iue;
- Stellar Spectra;
- Stellar Winds;
- Electron Density Profiles;
- Terminal Velocity;
- Wind Velocity Measurement;
- Astronomy