Soft X - ray emissions of highly charged Si VII – Si XII in cool star – Procyon

Different observation data for cool star—Procyon (Obs IDs of 63, 1461 and 1224) available from Chandra Data Public Archive were co-added and analyzed. Emissivities of emission lines of highly charged silicon ions (Si VII–Si XII) were calculated over temperatures by adopting the published data of Liang et al. (2007, Atom. Data and Nucl. Data Tables, 93, 375). Using the emission measure derived by Raassen et al. (2002, A&A, 389, 228), the theoretical line fluxes are predicted, and the theoretical spectra are constructed by assuming the Gaussian profile with instrumental broadening (0.06 Å ). By detailed comparison between observation and predictions, several emissions lines are identified firstly such as emissions at 43.663 Å (Si XI), 45.550 Å (Si XII), 46.179 Å (Si VIII), 50.874 Å (Si X), 64.668 Å (Si IX), and 73.189 Å (Si VII) etc. Several emission lines are re-assigned in this work, such as the emission line at 52.594 Å to Si X (52.612 Å ), at 69.641 Å to the blending of Si VII (69.632 Å ) and Si VIII (69.664 Å ) lines, as well as at 70.050 Å to Si VII (70.027 Å ). The prediction reveals the large discrepancies between the 3s–2p line (63.715 Å ) versus 3d–2p line (61.012 Å ) again for lower charge stage Si VIII. Solar flare observation is also added for the assessment of present calculation. Different assignments for some lines between Procyon and solar flare, have been found to be due to the hotter emitter in Sun than in Procyon coronae.