EUVE Observations of Algol

The EUVE satellite spectrometers observed the prototype eclipsing binary Algol over nearly 1.5 orbital periods. Effective exposure times were 100 ksec and 89 ksec in the short wave (70-180 Angstroms) and medium wave (140-370 Angstroms) channels. High temperature (up to 20 MK) Fe XVI-XXIV emission lines are clearly detected in the overall spectrum. In addition, a quiescent continuum is present which increases towards shorter wavelengths. Using synthesized spectra of optically thin line and continuum emission folded through the instrumental response, we have examined constraints on the [Fe/H] coronal abundance in Algol. We find that the coronal Fe is underabundant by factors of ~2--4 relative to solar photospheric values, unless an unreasonably large quantity of coronal plasma at T > 30 MK is present in the quiescent spectrum. The latter possibility is, however, inconsistent with available X-ray data. Lightcurves of the high temperature EUV lines compared to line emission at He II 304 A show considerable differences, with much deeper minima present in the He II line during both primary and secondary eclipses. Toward the end of the observation a moderate flare lasting ~ 6 hours was detected in the high temperature Fe emission lines. This work was supported in part by NASA Contract NAS5-32492 and by the Lockheed Independent Research Program.