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Astr384 Class Projects, Spring 2008

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PPM 706067 , Jessie Taylor and John VanderHeide

PPM 706067


The second star to the right is PPM 706067, an eclipsing binary star system. The Calvin-Rehoboth telescope has been intensively studying this system since 2005, devoting hours of observing time to this star. This thorough surveillance is warranted by the intrinsically interesting properties of eclipsing binary systems as well as some of the exciting weirdness of PPM 706067, itself.

Astronomy is different from many other branches of physics in that we cannot set up experiments; all we can do is observe what nature chooses to show us. This motivates astronomers to come up with creative ways of testing and confirming theories. Observing eclipsing binary stars is one such way.
Using the blackbody spectrum, we can determine the temperature of any star. However, for most stars, we have no simple way of determining mass; thus, it is more challenging to study how mass and temperature relate. Binary stars solve this problem. A binary star system is a pair of stars that orbit around their common center of mass. The gravitational interaction of the stars causes this orbiting, and, as the strength of gravity depends on mass, we now have a way of studying the masses of the two stars.

Eclipsing binary stars are even more useful than simple binary stars. They pass in front of each other in our plane of view.  This allows us to indirectly study and map the surface of the stars, something we have relatively few opportunities to do. The only star whose surface we can see is the sun; every other star is so far away that appear point-like and thus we cannot differentiate features on its surface. This poses a problem as we wish to understand the surface of stars. While we can suggest theories merely from observing the sun, we need to study the surface of other stars to really develop a robust theory. Eclipsing binary stars give us the necessary other objects to complete our data set.

Suppose one of the stars in the binary system had some brighter spots on it. As that star is eclipsed, those bright spots get covered up. During the eclipse we expect the system to get steadily dimmer as one start is completely covered by the other. However, when the bright spots are covered we lose more light than we would expect to lose. Thus, we know that bright spots are located in the area just eclipsed. Similarly, as the star moves out from being eclipsed, when the bright spots are uncovered we get more light than we would expect. Thus, we know the bright spots are along the area just uncovered. Combining both these pieces of information, we can locate the spots.

Since PPM 706067 is an eclipsing binary star system, it is worth studying merely to characterize it in this way. In addition, we have a special interest in PPM 706067 because it was discovered to be an eclipsing binary by one of us (John VanderHeide). In 2005, while searching for extra-solar planets, in conjunction with the University of Florida, John discovered his reference star, PPM 706067, to be variable. Further study revealed it to be an eclipsing binary system. As far as we know, we are the first people to recognize it as an eclipsing system. One of the few references to it in the literature, F, K and G Stars in the Rosat All-Sky Survey, identifies PPM 706067 as a strong x-ray source, one of few x-ray sources that are also eclipsing binary systems, further piquing our interest in the star.

Basic Properties

Further Study

X-Ray Data