Cool Stars 14 - Submitted Abstract # 223
This version created on 05 October 2006

Analysis of magnetic activity of F to M main sequence from IUE
observations


Andrea P. Buccino, IAFE-CONICET
Pablo J. D. Mauas, IAFE-CONICET

The International Ultraviolet Explorer provides a dense UV spectra
database from 1978 to 1995.  Moreover, the UV Mg II h and k lines (at
279.6 and 280.3 nm) are, analogous to Ca II H and K lines, good
indicators of the thermal structure of stellar atmospheres.
Therefore, one of the purposes of this work is to be able to use IUE
observations of Mg II and visible observations of Ca II jointly and so
extend in time the registry of activity of stars.  First, we obtained
a colour dependent linear relationship between IUE Mg II h+k line core
surface flux and Mount Wilson Ca II H+K index (S) for a set of nearly
simultaneous observations of a sample of 21 F5-K3 main sequence stars.
From this calibration, we built a catalog of Ca II indexes for all the
F, G, K and M main sequence stars with high resolution IUE spectra.
Secondly, from these results, we obtained a Mount Wilson index for IUE
low resolution spectra.  Finally, for the most observed main sequence
stars, we anlayzed the stellar activity behaviour using the Mount
Wilson index S obtained in this work, together with the one obtained
by from CTIO spectra, thus spanning a time interval between 1978 and
1996.

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