Theoret ica l B a c k g r o u n d The procedure bisect is designed to replace the procedures tridibi I and 2 given in ES]. All three procedures are based essentially on the following theorem. Given a symmetric tridiagonal matrix with diagonal elements q to cn and off-diagonal elements b, to b, (with b 1 set equal to zero for completeness) and b i 4=0, then for any number 2 let the sequence Po (...

We report XMM-Newton observations of the eclipsing binary Algol A (B8V) and B (K2III). The XMM-Newton data cover the phase interval 0.35 – 0.58, i.e., specifically the time of optical secondary minimum, when the X-ray dark B-type star occults a major fraction of the X-ray bright K-type star. During the eclipse a flare was observed with complete light curve coverage. The decay part of the flare ...

The Ancient Egyptians wrote Calendars of Lucky and Unlucky Days that assigned astronomically influenced prognoses for each day of the year. The best preserved of these calendars is the Cairo Calendar (hereafter CC) dated to 1244-1163 B.C. We have presented evidence that the 2.85 days period in the lucky prognoses of CC is equal to that of the eclipsing binary Algol during this historical era. W...

We report dual circular polarization VLBA observations of Algol made at orbital phases 0.22{0.30 using a diierential phase referencing technique. The ux density of Algol varied from 10{20 mJy during the observations. The radio maps show a double-lobe source separated by 1.6 mas (1.4 times the K star diameter). Although the total emission is only weakly circularly polarized, the individual lobes...