EPoS Contribution
EPoS Contribution
Observations of Binary Stars

Rainer Koehler
U Vienna, Vienna, AT
Binary stars are everywhere. The high frequency of binaries in regions like Taurus-Auriga proves that they must form early in the star- formation process. On the other hand, the binary frequency of low-mass stars in the Orion Nebula Cluster is much lower. In fact, every star- forming region that has been surveyed for binaries appears to be different with respect to binary frequency or separation distribution. However, when we try to deduce the initial binary frequency resulting from the initial star-forming process, we have to take into account that many binaries are destroyed in dense regions like clusters. It is not clear whether dynamical interactions are enough to explain the differences between Taurus-Auriga and Orion, or whether there was a difference in the environmental conditions that resulted in less binaries forming initially. Therefore, we do not know whether the archetype of binary formation is that all stars form in binaries, or if binaries form differently in every region. I will discuss these issues and observations that might help to solve them.
Caption: Examples for binary period distributions in a number of star-forming regions.
Ch. Ackerl, U Vienna, AT
T. Ratzka, U Graz, AT
Suggested Session: Multiplicity