E.F. Guinan, M. Güdel, P. Etzel, A.O. Benz, R. Mewe, J. Kaastra, S.L. Skinner
The bright, young F0 V star 47 Cas has been recognized as an unusual source of magnetic activity. It displays very strong coronal emissions in X-Rays and microwaves, strong and long-lasting flares in radio emission, strong chromospheric and transition-region emission lines, and rapid rotation as seen in optical (photospheric) lines. 47 Cas is important to magnetic dynamo theories because it is located near the boundary in the HR diagram where the convective envelopes become vary shallow, a boundary that separates coronal/chromospheric stars from stars with no or little magnetic activity. At the same time, its space motions suggest a very low kinematic age and point at a possible membership in the Pleiades Moving Group.
We present the results of a number of recent observing campaigns on 47 Cas. These include data from ground-based observatories such as the VLA and the optical instruments and satellites such as ROSAT, ASCA, EUVE, SAX, the Hubble Space Telescope, and the IUE. Special emphasis will be given to discussing (i) the X-Ray structuring of its very active corona in terms of its emission measure distribution and elemental abundances; (ii) IUE and HST data; (iii) fundamental parameters (v sin i, radial velocity, rotation period, distance, age) deduced from new optical spectroscopy data and catalog information; and (iv) flare processes evidenced in radio observations. We attempt to construct a rough synopsis of our knowledge on this critical star and in particular discuss evidence for or against the presence of an unidentified, cooler companion to the F0 star that might be responsible for the observed magnetic activity.
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