Solar-like Activities On The Late-type Stars

In the first section of the thesis, the research history of solar-like activities on late-type stars is looked back, and the present status of this research field is reviewed. Then, the important research branch in this field is suggested, and the research goal of this thesis is established.In the main section of the thesis, at first, we have described the spectroscopic observations of two late-type stars II Peg and UX Ari with solar-like activities, which have lasted for three years. The parameters of the instrument using in the observations are given. The processing procedure of observed image data is explained, the related steps, methods and some key points are shown in detail. According to this procedure, all echelle spectra are reduced by means of the IRAF package, and the result 1-D spectra have been derived, which can be used to do further analysis and calculation. Then, we have obtained the structure of photospheric spot active regions for above two stars by using Doppler imaging technique, and their chromospheric activity indicators with the aid of synthesized spectral subtraction technique. Finally, we have analyzed these results and made some discussion. For the spectroscopic study of the two stars lasted three years, the conclusions have been drawn as follows. Our study has demonstrated that the main spot active regions of II Peg are always located in the high-latitude (about 60 degree) regions from 1999 to 2001. The main spot features switch to another active longitude in 2001, which is separated about half of the rotational period from the original activelongitude. The event is not consistent to the long-term spot activity trend of the system, which maybe result from the strong optical flare happened in Sept. 2000. The chromospheric activity of II Peg is very strong, and exhibits an obvious rotational modulation phenomenon. The optical flare is happened In every rotational period, and it is through each layer of the chromosphere. The photospheric activity of II Peg is related to the chromospheric activity, and the optical flare is corresponding to the spot active region in spiral structure. This has told us that the photospheric activity and chromospheric activity origin from the same magnetic flux tube. The main spot features of UX Ari are distributed in high-latitude, middle-latitude, and low-latitude regions in 2000. The features in high-latitude and middle-latitude regions are long-terra phenomena. Its chromospheric activity is strong, shows the rotational modulation feature. The stronger chromospheric activities happened in the quadratures maybe result from the coupling between itself of the chromospheric activity and mass transfer between the two components. The spot active regions of UX Ari are corresponding to the areas with stronger chromospheric activities in spiral structure, and they should be two kinds of active events linked by the same magnetic flux tube.In the final section of the thesis, we have made a prospect to the research topics of this field in future, and emphasized several subjects with large potential. Considering our present research status, a long-term project is proposed according to our practicality.