* Astronomy

Blobrana · L

RE: Algol

Blobrana · L

Title: Imaging the Algol Triple System in H Band with the CHARA Interferometer
Authors: F. Baron, J. D. Monnier, E. Pedretti, M. Zhao, G. Schaefer, R. Parks, X. Che, N. Thureau, T. A. ten Brummelaar, H.A. McAlister, S.T. Ridgway, C. Farrington, J. Sturmann, L. Sturmann, N. Turner

Algol (Beta Per) is an extensively studied hierarchical triple system whose inner pair is a prototype semi-detached binary with mass transfer occurring from the main-sequence primary to the sub-giant secondary. We present here the results of our Algol observations made between 2006 and 2010 at the CHARA interferometer with the Michigan Infrared Combiner in the H band. The use of four telescopes with long baselines allows us to achieve better than 0.5 mas resolution and to unambiguously resolve the three stars. The inner and outer orbital elements, as well as the angular sizes and mass ratios for the three components are determined independently from previous studies. We report a significantly improved orbit for the inner stellar pair with the consequence of a 15% change in the primary mass compared to previous studies. We also determine the mutual inclination of the orbits to be much closer to perpendicularity than previously established. State-of-the-art image reconstruction algorithms are used to image the full triple system. In particular an image sequence of 55 distinct phases of the inner pair orbit is reconstructed, clearly showing the Roche-lobe-filling secondary revolving around the primary, with several epochs corresponding to the primary and secondary eclipses.

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Blobrana · L

Title: Did the ancient Egyptians record the period of the eclipsing binary Algol - the Raging one?
Authors: L. Jetsu, S. Porceddu, J. Lyytinen, P. Kajatkari, J. Lehtinen, T. Markkanen, J. Toivari-Viitala

The eclipses in binary stars give precise information of orbital period changes. Goodricke discovered the 2.867 days period in the eclipses of Algol in the year 1783. The irregular orbital period changes of this longest known eclipsing binary continue to puzzle astronomers. The mass transfer between the two members of this binary should cause a long-term increase of the orbital period, but observations over two centuries have not confirmed this effect. Here, we present evidence indicating that the period of Algol was 2.850 days three millenia ago. For religious reasons, the ancient Egyptians have recorded this period into the Cairo Calendar, which describes the repetitive changes of the Raging one. Cairo Calendar may be the oldest preserved historical document of the discovery of a variable star.

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Blobrana · L

Algol is at minima at 09:20 UT, 9th April, 2012.

Blobrana · L

Algol is at minima at 22:00 UT, 28th March, 2012.

Blobrana · L

Algol is at minima at 11:00 UT, 17th March, 2012.

Blobrana · L

Algol is at minima at 14:00 UT, 14th March, 2012.

Blobrana · L

Algol is at minima at 17:00 UT, 11th March, 2012

Blobrana · L

Algol is at minimum brightness at 20:30 UT, 8th March, 2012.

Blobrana · L

Algol is at minimum brightness at 22:30 UT, 5th March, 2012.