Eclipsing binary systems

- These are binary systems with orbital planes so close to the observer's line of sight (the inclination i of the orbital plane to the plane orthogonal to the line of sight is close to 90 deg) that both components (or one of them) periodically eclipse each other. Consequently, the observer finds changes of the apparent combined brightness of the system with the period coincident with that of the components' orbital motion. GCVS

Table 7.1. Eclipsing variable stars arranged in alphabetical order by designation ition

Designation (and subclasses)

Algol type EA AlgoUype eclipsing system ft lyr type EB p Lyrae-type eclipsing system

Planetary eclipsing type EP Stars showing eclipses of their planets

W UMa type EW W Ursae Majoris-type eclipsing variobles

RS Canum Venaticorum RS RS Canum Venaticorum-type systems

- additional classification according to the component's physical characteristics

GS one or two giant components

PN one component is the nucleus of a planetary nebit

RS RS CVn system

WD systems with a white dwarf component

WR systems with a Wolf-Rayet component

- additional classification based on the degree of filling of inner Roche lobes

AR AR Lac-type detached system D detached systems with components not filling their inner Roche lobes DM detached main sequence system DS detached system with a subgiant DW detached system like W UMa systems K contact system with both components filling the inner critical surfaces KE contact system/early spectral type KW contact system of late spectral type SD semidetached system in which the surface of the less massive component is cbse to its inner Roche lobe.

Note. The combination of the above three classification systems for eclipsing binaries results in the assignment of multiple classifications for object types. These are separated by a solidus ("/") in 1ยป data field. Examples are: E/DM, EA/DS/RS, EB/WR, EW/KW, etc.

This is the catch-all category for eclipsing binary stars. When the characteristics of the light curve are sufficiently ambiguous, the star will generally be placed within this group. If you're looking for an interesting project, this is a good place to start. Obviously, these stars belong to some classification type. Your mission, if you decide to accept it, is to find out which ones, develop the data to prove it, and then to provide your findings to the world.

You might begin such a project by examining the GCVS, looking for those stars visible from your latitude. Then determine which season they will be in a position to be observed. Remember, the best time to observe a star is when it transits. Eventually, check some research literature, perhaps the Information Bulletins on Variable Stars or the Astrophysical Data Service. Both of these resources will be described in Chapters 10 and 11. Check the literature to see if anyone else has conducted some research regarding the stars that you've chosen. There is no need to repeat someone else's efforts without good cause and you might find some information that will assist you in your research. After you've taken these basic steps, develop a detailed observing program. Keep good notes, be persistent and patient. You'll be surprised at what you can find.

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