Abstract
We have used the Goddard High-Resolution Spectrograph on the Hubble Space Telescope to search for chromospheric emission in the ultraviolet C II 1335 Å lines of eight A-type stars. The B-V colors of these stars range from 0.12 to 0.22. We have detected emission in the spectrum of the A7 V star Altair, but in no other star. We present tentative evidence that the emission from Altair is blueshifted by ∼60 km s-1 or more with respect to the photospheric spectrum of this star. We interpret this as expansion and suggest that the base of the A star winds that we have proposed in earlier work may lie within the chromosphere. Together with IUE spectra, our observations indicate that in ordinary main-sequence stars the onset of convection zones capable of supporting detectable chromospheres occurs in the close vicinity of B-V = 0.22.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 319-323 |
| Number of pages | 5 |
| Journal | Astrophysical Journal |
| Volume | 428 |
| Issue number | 1 |
| State | Published - Jun 10 1994 |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science