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| Paper: |
II Peg: Quiescent Cromospheric Emission and Flares in 1994-1996 |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1477 |
| Authors: |
Berdyugina, S.; Ilyin, I.; Tuominen, I. |
| Abstract: |
Simultaneous observations of Ca 2 K, Ca 2 8498 AA, He 1 D3, and photospheric lines in 1994-1996 with the high-resolution spectrograph SOFIN at the Nordic Optical Telescope have revealed correlation of the strength of the He 1 D3 line and the Ca 2 emission with the spot position on the stellar disk. A two-component structure is seen in the quiescent chromosphere of II Peg, as it is seen in the corona, and a filament visible in the corona seems to be based on the largest spot visible in the surface images of the star. Also, two flares were serendipitously observed. The first one, which started on July 19, 1995, was noticed in the He 1 D3 line which appeared as a nonsymmetric, red-shifted, narrow (FWHM ~50 km {s}^{-1}) emission, while other lines kept their quiescent shapes. The emission in the He 1 line was seen until the end of the observing run (July 23, 1995) and reached the maximum on July 22, 1995, when in addition to the narrow component, a broad (FWHM ~100 km {s}^{-1}) blue-shifted one was seen in both the He 1 line and the Ca 2 K line. At that moment, the two-component emission was observed in cores of many other absorption lines as well. The amount of energy released in different lines at the maximum of the flare is estimated. From the radial velocity curve of the He 1 emission the location of the radiating matter is deduced. It appears to be close to the largest spot (or group of spots) which is seen from the surface imaging. The second flare was noticed on Oct. 26, 1996, in three spectra, again as a narrow emission in the He 1 line, but without susequent development in other lines. |
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