| 其他摘要 | Stellar magnetic activity phenomena, similar to those of the Sun, such as starspots, chromospheric plages and °ares, are continuously studied since 1950s. Since open clusters present various advantages, for instance, their members have the same age, initial chemical abundance, distance and hence interstellar reddening, meanwhile, open clusters are ideally suited for performing CCD's en-semble photometric observation. There are lots of low mass stars with rapid rotation in young open clusters. According to the dynamo mechanism of stellar magnetic activity, young open clusters become the ideal place to study stellar activities. However, the active phenomena caused by the magnetic ¯elds are not understood well for the low mass members of open clusters. In order to search for variable stars with magnetic activity and know the stellar magnetic activity better, we have observed and studied several open clusters, e.g., NGC1348.For NGC1348, on the basis of CCD's multi-color photometry obtained in Jan. 2008, we found a new variable star (GSC2.3-NCB0032066) with variation amplitude 0.3 mag in R band. By using PDM method, we derived its period P = 0:3469 days. Additionally, we found its e®ective temperature is about 5300 K, which indicates a late G star or early K star. Based on these features men-tioned above, it seems that this star is a magnetically active candidate. Conse-quently, we obtained its spectroscopic data in Nov. 2008. Unfortunately, these spectra including Ca iiHK and H¯ lines cannot use to indicate its chromospheric activity due to the low signal to noise ratio. So, this star needs further observa-tion. In Nov. 2008, we made simultaneous photometric and spectroscopic obser-vations for a spotted G dwarf AP149. We have reconstructed the observed light curves with two spots by means of light curve modeling technique, and foundthat the active regions have shifted oppositely along longitude on a time scale of one day. In addition, we utilized other observations to discuss the evolution of active regions in photosphere. We found that AP149 is active not only on a long time scale but also on a short time scale, though we cannot derive the active cycle on the basis of these data. The pure chromospherical emissions for Ca iiHK and H¯ lines have been derived by using the spectra subtraction technique. The variation of Ca iiHK lines' excess emission shows that the spot regions are cor-related spatially with the active regions in chromosphere. However, the H¯ line is probably contaminated by prominence emission, there is no evidence of rota- tional modulation for this line. |
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