The Thuringian State Observatory is developing a blue-sensitive spectrograph to observe faint hot subdwarf B stars. They shine mainly in blue and ultraviolet light (UV). The Tautenburg Faint Object Spectrograph (TauFOS) is operated at the Nasmyth focus of the Alfred Jensch Telescope.
The transmission path of the light from the Nasmyth focus to the spectrograph is modernized with a glass fibre coupling. For this purpose, a new interface between the telescope focus and glass fiber is being developed - a so-called telescope front end. A glass fiber coupling is more efficient than the previously used setup, as it allows much more light from the telescope to reach the instrument. With a second fiber, a calibration lamp can be recorded simultaneously with the observations of the star spectrum.
Scientific Background
Close binary stars interact with each other during their lifetime, often on the red giant branch, when the radius of the star increases a hundredfold. The material around the star is then no longer completely gravitationally bound. A stable or unstable mass transfer to the companion takes place. The envelope of one star is transferred to the other, which has a major influence on the further development of the star.
Hot subdwarf B stars (sdB) are evolved stars that are in the helium-burning phase but have lost most of their envelope through mass transfer to a close companion. Therefore, they are perfectly suited to study this very short phase of mass transfer and other interaction phenomena. They show both photometric and spectroscopic variations. Since hot subdwarf B stars are both faint and hot, and therefore emit most of their energy in the UV, a blue-sensitive spectrograph with intermediate spectral resolution is needed to obtain enough signal to study their spectroscopic variations.
Veronika Schaffenroth, staff astronomer at the Thuringian Observatory, will use the Tautenburg Faint Object Spectrograph for her research.