Spectroscopic Binary Stars

A surprisingly large fraction of the stars are in binary or multiple star systems. Sometimes the binary stars are obviously separated, like 61-Cygni in the close neighborhood of the Sun. They are called "visual binaries". Others can be detected from periodic variations in luminosity associated with the eclipsing of one star by the other. Still other can be detected from the overlapping of different kinds of spectra. Modern interferometric measurements have added to our ability to distinguish and study binary stars.

This image adapted from the Australia Telescope National Facility, see Ref.

Binary stars can be detected from the red shift of the spectrum of one star while the other is blue-shifted.

Binary orbits can contribute to the measurement of the masses of different kinds of stars that appear in such systems.

Eclipsing Binary Stars

A surprisingly large fraction of the stars are in binary or multiple star systems. Sometimes the binary stars are obviously separated, like 61-Cygni in the close neighborhood of the Sun. Others can be detected from periodic variations in luminosity associated with the eclipsing of one star by the other. Still other can be detected from the overlapping of different kinds of spectra. Modern interferometric measurements have added to our ability to distinguish and study binary stars.

This image accessed from the Australia Telescope National Facility, see Ref. Image credit ESA

The light curve of the eclipsing binary star system HIP59683 shows the change in apparent magnitude.

Note that the apparent brightness is greater for a lower value of the apparent magnitude so the dips in the curve represent lower brightness. The Primary Eclipse shown gives a magnitude change of about 0.7 , which is about 1/2 the intensity. The primary eclipse represents the eclipsing of the hotter star by the cooler star (see Ref for simulation of light curves).

Binary orbits can contribute to the measurement of the masses of different kinds of stars that appear in such systems.