XMM-Newton and the VLA simultaneously observed the eclipsing Algol-type binary \object RZ Cassiopeiae in August 2003 .
The secondary eclipse ( K3 IV companion behind the A3 V primary ) was placed at the center of the 15-hour radio campaign , while the X-ray satellite monitored a full 1.2-day orbital period .
We present results of the X-ray and radio campaigns .
The X-ray light curve shows significant modulation probably related to rotational modulation and active region evolution , and even small flares .
However , the X-ray eclipse is not deep , implying that the coronal X-ray emitting material is spatially extended .
The Reflection Grating Spectrometer ( RGS ) spectrum shows a variety of bright emission lines from Fe , Ne , O , N. A strong [ C/N ] depletion probably reflects the surface composition of the secondary which fills its Roche lobe and loses material onto the primary .
The O vii He-like triplet reflects a low forbidden-to-intercombination ratio ; while it generally suggests high electron densities , the ratio is here modified by photoexcitation by the strong UV flux of the primary A3 V star .
The radio light curve shows no similarity to the X-ray light curve .
The eclipse timings are different , and the radio flux increased while the X-ray flux decreased .
The radio spectral slope is shallow ( \alpha = 0 - 1 ) .